Some Antenna Photos and Tests
 

Tests were conducted in 2011 to evaluate performance of some TV antennas.

The tests involved a signal source feeding a CM-4228 at ~45 ft AGL radiating to antenna under test located ~150 feet distant at ~level height to source antenna.

The signal source was a homebrew signal synthesizer, remotely controlled at the receiving location by a notebook PC.

Received signals from the test antenna were measured using a homebrew wideband power meter with digital readout and logged into an Excel spreadsheet.

The test frequencies were chosen to represent channels that might be of personal interest.

This location is rural, the only UHF strong signal is at Channel 14; the frequency band was omitted from the tests.

The last image below shows results from comparing four antennas:

- Channel Master 4228 (the most common of the older versions)
- Channel Master 4251
- Antennacraft P7
- Antennacraft SuperG 1483 (the stacked Hooverman version)

http://forum.tvfool.com/attachment.p...5&d=1364921502

http://forum.tvfool.com/attachment.p...7&d=1364923084

http://forum.tvfool.com/attachment.p...4&d=1364921475

The decibel scale is relative for a comparison between the units.

Caveats:

Each antenna was installed at the test mast for a few days while several preamps were individually tested with that particular antenna. So, each antenna was measured days apart from others.

There may be some SWR effects in the antenna gain patterns, affecting each antenna differently.

Comments:

In general, testing against distant weak TV signals was consistent with the measured results. CM-4251 was best on upper UHF. P7 performed well on mid UHF channels. SuperG 1483 was comparably good on mid-20 range channels.

Attachment 496

Are the signal source and/or power meter proprietary works? Or can you share details of those with us also?

Thanks for the work, and willingness to share it with us.


Oh, nice towers. :)

Thank you GroundUrMast, for your kind words.

No, not proprietary. Yes, can provide some details.

The synthesizer is based on IC Silicon Devices SI570. PDF available here:

http://www.silabs.com/support%20docu...docs/si570.pdf

The version (BBB) that covers range from about 10 MHz up to about 950 MHz was used.

Some kits containing major parts of the circuitry and components are available from SDR hobbyist groups. SDR=Software Defined Radio

http://en.wikipedia.org/wiki/Software-defined_radio

SDR-Kits were used in this particular synthesizer.

http://sdr-kits.net/QRP2000_Description.html

The components are not complicated to assemble, nearly all were thru-hole. The synthesizer IC is SMD (surface mount).

One should have output attenuators, power supply, metal housing, and filters. Other modifications and items are useful, but with these become quite useful. USB power can be used when near such, otherwise wall wart with additional filtering can be used.

The controller for the synthesizer chip is USB based.

Software to control the synthesizer from PC can be obtained on the web.

For remote control one can use USB to LAN adapters at each end of the circuit, then use whatever LAN devices one desires in between.

In this case, for remote control, ~165 feet of Ethernet LAN CAT5e cable was used, probably beyond specifications without repeaters, but worked fine. To reach greater distances, one could probably use wireless game bridges, or something similar.

The wideband power meter is based on Linear Technology LT5534 integrated circuit.

http://www.linear.com/product/LT5534

Haven't seen a kit of parts for such.

Manufacturer provides a good reference design. Found a PCB made for another similar part and adapted it. It is all SMD.

For accurate results, one should provide for a matching circuit on the input. Resistive pad matching at input combined with ~ 10-20DB fixed attenuation provides a reasonably low SWR. Can use ordinary DMM for digital readout.

Need: power supply, metal housing, and external attenuators.

Below is an image taken in 2011 around the time of the preceding test. The workbench is behind that window, inside the building next to the receiving antenna mast.

http://forum.tvfool.com/attachment.p...8&d=1365093205

Shown on part of the workbench, among cables, planks, and bricks; from top to bottom, left to right:

- Some version of Research Communication preamp (loose)
- Blonder Tongue FSM-11 signal strength meter with brick
- Antennacraft preamp power supply (loose)
- Signal synthesizer (in aluminum case)
- Half Wave Loop balun
- DMM (Red)
- HP notebook computer
- Holland Splitter
- Various fixed attenuators (in-line)
- Another Research Communications preamp (in-line)
- Power Inserter (in-line)
- Winegard Power Inserter (loose)
- Fixed attenuator (Red, in-line)
- Wideband power detector (blue aluminum case)
- Some version Winegard preamp
- Channel Master preamp (loose)


Thank you.

The near tower has the transmitting CM-4228. Hard to see, it is mounted directly behind the CM-4251. The tower and that particular CM4251 have stood for more than 40 years.

.

tripelo,

I finally got cleared to post. As I mentioned last week, I’ve contacted Antenna Craft to see if they will sell me a Super G and what it will cost with shipping. Still haven’t heard back from them yet so I'll probably try to give them a call.

Again, thanks for pointing me to this most interesting information. You do have an envious test setup.

Very interesting.

That was a good idea to contact Antennacraft. Maybe we can learn something from it. Curious as to what Antennacraft's response will be.

-----------------------

Pete, thank you for the compliments.

Just chatted with a rep at www.summitsource.com she said both the sigle and stacked version are in stock there.

Super G 1483
 

The problem isn't availability, its paying for the excessive shipping weight.

When I went to the Summit Source web site to order it, in addition to the $109.95 for the antenna, they want $76.88 for ground shipping. That brings the total to $186.83!

They list two different weights, one for the United States Postal Service @ “37 lbs, 11.62 oz”, and a second for UPS / FedEx @ “(2 x 37.72575 lbs)”.

I contacted Antennacraft to ask about the weight and they said "We pack the Super G1483's 2 per box when they leave our facility. The weight for a 2 pack is 8.5#'s. So each antenna would weigh approximately 4.3#'s each.”

I then talked to Erick @ Summit Source and he confirmed that even though the AntennaCraft shipping weight for a box of two Super G1483's was only 8.5 lbs the Summit Source computer takes into account dimensional weight and ground shipping would cost me $76.88.

I think before I shell out $186.83 to try one of the commercially available Hoverman designs it might be prudent to cost out building one of the more versatile Grey-Hoverman designs.

Mid 1960's VHF Antenna
 

No intention to divert from other antennas and tests, or other related.

Took down an antenna this morning and thought it (or the story) may be interesting to someone.

It's a Log-V antenna, VHF (low and high), maybe FM.

It was located at an apartment complex and appeared to be a potential hazard to those who lived there. From the ground, the antenna looked to be in good shape (see photo). Realizing that the antenna might soon be lost to wind, an inquiry was made and the responsible people were glad to have it removed.

http://forum.tvfool.com/attachment.p...5&d=1365875492

The antenna originally had four guy wires that had long since broken. The guy wire remnants were so degraded that flexing a couple of times, they crumbled.

http://forum.tvfool.com/attachment.p...6&d=1365875520

.

Turned out, the antenna is in good shape. Whoever designed and built it, made it to last. Element-to-boom support is very sturdy. All the elements folded back to the boom perfectly, no insulator was cracked. On the ground, the gold anodizing is still visible.

The antenna could be vintage mid-1960s. Certain features in the construction point to early times. Mid 60's is about the earliest date that Log-V antennas were available, and was probably about the time the apartment complex was constructed. Could be a Radio Shack antenna. Seems that during the 60s, Radio Shack marketed several major brands; Finco, Channel Master, JFD, and others.

If anyone has clues to it's origin, please post.

Anyhow, back to regular program.

.

tripelo,

Great find. Wish I could find an old Channel Master 4251 that someone wanted removed.

I got started last summer playing with a 40+ year old Channel Master 4228. If it had received CBS on channel 43 (2.1) as well as it received NBC channel 36 (4.1) I probably wouldn’t have built my new system using a 91XG and an AntennaCraft Y10-7-13. Now, the 91XG always gets CBS but rarely gets NBC and the CM-4228 always gets NBC but rarely gets CBS. Go figure! I have them connected through a coax switch in the garage so I can switch between them when needed.

It would be interesting if you could compare this old LPA to some of the current crop of VHF High antennas like the Winegard YA-1713 or the AntennaCraft Y10-7-13 Yagi Antennas.

Enjoy.

Yes, hope you can find such. Was the CM-4251 popular in California?

You have some nice antennas.

Interesting that you have found such a difference between the antennas. As you probably know, for the 91XG, its directivity (gain) increases with frequency, whereas the 4228 has relatively flat gain characteristic from around channel 20 or so, through channel 51. Unless there is some other factor, the 42 MHz difference between the two channels means quite a lot for the 91XG.

Would be interesting to see the TVfool predictions for your antenna locations, can you post them?

Seem like a workable solution.

Yes, good thinking. That would be quite interesting.

Maybe that could be feasible. Right now, the Log Periodic is here in suburb Dallas, and the good antenna range is in KY. The LP is too long to ship by conventional means. And, probably the most interesting antennas (that I have) to compare against the LP are also located in KY.

Although, have done antenna comparisons at both locations (KY and here).

Such a test would be interesting and worth some thought and effort.

Mid 1960's VHF Antenna, FinCo CS-V10
 

The vintage antenna (previous post) is a Finco CS-V10.

http://forum.tvfool.com/attachment.p...0&d=1366051673

The image is from: Popular Science 1967

It is covered by Finco patent No.3,427,659.

FISHBONE TYPE ARRAY WITH DIPOLE SPACING INCREASING TOWARDS THE SMALLER END

The patent describes Finco’s discovery that log periodic dipole antennas could achieve greater gain for TV frequencies if the element spacing was tapered somewhat wider towards the front. Previous thought was either; logramithic spacing which tapered smaller spacing towards the front, or uniform spacing.

In the patent, an example antenna lists dimensions and increased gain values. The dimensions given in the example match those measured on this CS-V10 antenna.

The patent was originated in 1964 and issued in 1968.

Interesting in this same time period , The University of Illinois (holder of the log periodic patent) was in litigation with several TV antenna manufacturers, of which Finco (Finney) was one.

tripelo,

here you go:
http://www.tvfool.com/?option=com_wr...1dda169109ca5c

FM Fool shows 99.9 MHz @ -13.4 & 91.9 @ -26.9

I've got to run to the Dentist

High Dynamic Range
 

Initial thought:

You cannot receive Channel 43 very well because it isn’t there (that is; in the TVfool table)! :)

Then, after eliminating analog channels from the table, channel 43 shows.

That’s a difficult situation to receive such a weak signal in the presence of very strong signals.

--------------------
2nd thought:

When applied to your area, TVfool signal prediction algorithms (presumably based on Longley-Rice model) must not be as accurate as they usually seem to be.

1. It’s unlikely that an ordinary TV receiver can simultaneously process signals having a dynamic range of 106.5 dB (difference between KVCR, -15.6 and KCBS, 122.1).

Then, recalling that you used a notch filter to essentially remove KVCR, obviously improving the dynamic range situation, tho still very challenging for an ordinary TV receiver.

That’s not to mention the complications of two FM stations at –13.4 and –26.9 dBm, plus some more moderately strong TV stations.

2. The available antenna gain is insufficient to compensate for a noise margin of -22 dB.

-------------------
For many, receiving KNBC, at predicted noise margin =-16.8 dB, would be a challenge.

Do you receive both KNBC channel 36 (-107.7 dBm) and KCBS Channel 43 (-112.9 dBm) on their assigned antennas throughout the day (say most of 24 hours)?

-------------------

Regardless the accuracy of TVfool predictions for your particular location, you undoubtedly have a situation that challenges the dynamic range of amplifiers and tuners.

Pete, you have an interesting situation. From reading in other forums, you have worked out a good approach toward solving the problem (filters, high dynamic range drop amplifiers, and such).

tripelo,

We’ve had the Time Warner’s “Everything” package for years (my wife even got me the Playboy channel) so OTA is mostly a hobby. I originally started just trying to see what I could get with a 40 year old Channel Master CM-4228 8-Bay Bow Tie. After receiving both VHF & UHF channels from LA & San Diego I decided to see how much I could improve my reception. Things just kind of grew from there.

I am not currently using the Channel Plus NF-471 notch filter.

My original plan was to use a Winegard AP-2870 pre-amp. with separate VHF & UHF inputs. I tried the Channel Plus NF-471 55 dB channel 26 (KVCR) notch filter in-line with the UHF input to the 2870 but the amp. overloaded so badly that I almost didn’t get anything. I also tried both antennas into a UVSJ, through the notch filter and into my Winegard HDP-269 with basically the same result. The PCT MA2-M’s don’t seem to overload, even without the notch filter.

A pictorial of my new antenna array setup can be found @:
http://www.digitalhome.ca/forum/show...t=42426&page=7
(Post # 3348).

The CM-4228 is on a push-up mast with a rotor and is using the HDP-269. I have the coax from the tower array and the HDP-269 going into a coax switch in the garage, the output of which feeds my PCT MA2-4P distribution amp.

Channel 2 seems quite reliable on the new array, but the array rarely gets channel 4. By the same token, the old 8-Bay always gets channel 4 but almost never can hold channel 2. A lot of the one hour shows my wife & I like are on CBS (Ch. 2.1) so when the 8-Bay couldn’t pull it in I was motivated to come up with a better solution. To that end my new setup does what I wanted. I’m just not sure what the mechanism is that prevents the new array from getting NBC (channel 4.1). For the most part, the SNR between the two antennas is within 2-3 pts. with the 91XG higher in a little over half the cases. It could be as simple as it has better response on RF 43 (2.1) than the 4228 and the 4228 has better response on RF 36 (4.1).

Tower & CM-1110
 

Pete, have been out of town for a while. Was actually in KY at the main antenna test location, and climbed above the top of the tower a few times. Above the top, to be explained later. :)

Please, feel free to update on your antenna work.

----------------------

In the meantime, this is an image taken in 2009 of the main tower (lower part shown in Post #1) as it has stood since I personally erected/installed in the early 1970's. The tower and antennas were largely ignored all those years, (meaning almost no maintenance), although they reliably provided TV reception for my parents.

The large VHF antenna is a Channel Master Quantum CM-1110.

The plastic bucket lodged in the tower was there temporarily for convenience to hold tools and such. The photo was taken just before the CM-1100 was lowered to the ground.

Since that time in 2009, there have been several different antennas residing above the tower top, or near the top of the tower. Maybe later can show some of the other antenna arrangements.
.

http://forum.tvfool.com/attachment.p...7&d=1369333651

One step forward - Two steps back
 

tripelo,

Good to hear from you.

As I said in my last post, the CM-4228 was on a push-up mast with a rotor and was using the HDP-269. I ordered a Winegard YA-1713 Prostar 1000 10 El. Hi-Band VHF Antenna to go with it.

I thought I would use that combination to test the Winegard pre-amplifiers that overloaded with my tower array.

I installed the YA 1713 above the CM-4228 and ran two new 17’ pieces of RG-6 down the mast, one from the CM-4228 (white) and the other from the YA-1713 (black), so I could experiment with UVSJ's, my HDP-269 and AP-2870, and several cable drop amps I’ve collected without having to lower the mast for each change. In anticipation of testing the pre-amps, I ordered three Antennas Direct FM Band 20 dB traps and two 3 dB & two 6 dB in-line attenuators to go with my Channel Plus 55 dB channel 26 notch filter.

When I got everything hooked-up, the new Winegard YA-1713 wouldn’t receive channels 7 or 13. It is mounted about 30’ south and 6’ lower than my Antenna Craft Y10-7-13.

When it wouldn’t work with my amps., I hooked it directly to the cable that runs to my PCT-MA2-4P distribution amp. and was able to receive 8 (8.1) & 10 (10.1) out of San Diego and 9 (9.1) & 11 (11.1) from LA. I then disconnected the YA-1713 and hooked up my Channel Master CM-4228 to the cable that runs to the PCT-MA2-4P distribution amp. and got a very pixelated channel 7, a fairly solid 9, intermittent 11 and a pretty good 13. All 4 LA stations measured high “Green” on my SNR meter with the Antenna Craft Y10-7-13 switched in (of course it has a +15 dB MA2-M mounted right behind it). Adding an amplifier to the Winegard 1713, at the base of the push-up didn’t improve/add the missing LA stations. It did considerably improve VHF reception from the CM-4228.

Since I only had one 50’ run of RG-6 going from the base of the push-up mast into the garage, I had to get up on the roof to switch antennas. I added a second run (white) so I could route the UHF and VHF signals to a garage coax switch separately. After I got tired of running out to the garage to switch between antennas I added a 4th RG-6 run into my office so I could monitor both push-up antenna signals from the office. That’s kind of where I’m at right now. With no amplifiers in-line, the 4228 actually does better getting channels 7 & 13 than the YA-1713. Mid-band, the YA-1713 does better.

I sent Winegard an email on May 13th to see if they could think of any reason performance would roll off that dramatically at the top & bottom of the YA-1713’s band. So far I haven’t heard back from them. They probably got the email and thought I was nuts!

Solid Signal sent me an email flyer for an 8-Bay “Solid Signal Xtreme Signal HDB8X High Definition Blade 8 Bay Xtreme Antenna (HDB8X)” for $59.99 with $0.05 shipping. It looks to be 2 4-Bays on a swivel with 2-BALUM’s hooked to a combiner. It has the multi-directional feature like the new Antennas Direct DB8e and blade elements similar to the 91XG. For $60.04 delivered I couldn’t resist. They claim a maximum gain of 25 dB when both sides of antenna are parallel, which I believe defies the laws of physics, but if their matching harness arrangement is any good at all, I expect it will perform about as good as any other 8-Bay. They don’t expect to ship them until after 1 June.

Next, I want to pull down the push-up, inspect the YA-1713 and swap the 17’ cables. I’ll probably also try it on my tower and try the Antenna Craft Y10-7-13 on the push-up.

I can’t drop or raise the push-up mast by myself. I have to set a ladder in front of it so I can reach the U-bolt through the upper stand-off bracket. Once I get the U-Bolt off I need somebody to hold it while I move the ladder out of the way so it can be laid horizontal. Going back up, I need somebody to hold it so I can position the ladder and re-install the U-Bolt. There’s a real shortage of people in my neighborhood lining up to climb on a roof to raise & lower antennas! Since I’ll want to try the new 8-Bay anyhow, I’ll probably wait until the HDB8X gets here to do any more YA-1713 testing.

The tower got too heavy to lift, even with help, so now I can lower and raise it by myself with help from a 110 VAC winch. When I have the new patio roof put on I’ll try to figure a way to get winch’s working for the push-up and my other tower.

Take care.

Pete, looked back at your tower array, mentioned in your earlier post.

Direct link to post #3348 here:

http://www.digitalhome.ca/forum/show...postcount=3348

As to why the poor reception of the YA-1713 for VHF compared to the 4228:

Not a lot of suggestions, there are several variables.

The YA-1713 and most antennas have a bit less gain at the band edges (in this case; channel 7 and 13). If there were extra attenuation in the YA-1713 path, then the normal roll-off of the gain vs frequency pattern for the YA-1713 could become more obvious.

As you mentioned, reversing the cables between the CM4228 and the YA-1713 seems a good step.

If you have cables with pre-installed factory connectors, they sometimes cause problems.

The YA-1713 has a snap on balun that could have a problem.

-----------------------

Your thoughts on the new 8-bay (Solid Signal HDB8X) will be interesting. Since it has separate reflectors (not-continuous like the 4228) then it will probably have less response for your VHF signals.

tripelo,

I made up both of the 17’ cables going to the antennas just to simplify testing. Since I still had both white & black rolls of coax, I arbitrarily used white for the UHF run & black for the VHF run. I installed the boot that came with the YA-1713 on the black cable & new Channel Master (PCT) compression connectors on both. I doubt that I have a bad connection on the black cable but that’s why I want to swap them.

The original black cable that runs into the garage is probably 30 years old with crimp on connectors. It is the one I originally used to compare both antennas so I’m pretty sure it is still Ok. The “new” cable I pulled is a 50’ “factory” Magnavox M61210 roll of white RG-6 with molded ends that my son gave me. I have swapped the antenna feeds between both of the garage runs and can’t tell any difference so I’m pretty sure both of those are Ok.

The 4 cables from the garage to my office are new RG-6 runs with compression connectors that are routed between the downstairs ceiling and the upstairs flooring through PVC conduit, then down through the office wall to a metal plate with 4 F-81 barrels.

The YA-1713 balum looked like it could install either of two ways so I checked online with Winegard and found that it didn’t make any difference. I didn’t pay a lot of attention to it but as near as I remember it just looked like a clip-on microstrip line matching transformer. It should have been foolproof. If I can get it apart without destroying the plastic housing I’ll inspect it for any signs of damage or missing parts.

I think the most informative test will be dropping the tower and swapping the VHF antenna locations. That will put the YA-1713 in a known good signal location with plenty of amplifier gain and all new end-to-end proven cables.

Of course I want to compare the HDB8X to my 40 year old Channel Master CM-4228. That may not sound fair, but last summer I compared the 4228 to a brand new 91XG and in the same location both antennas provided about the same SNR +/- ~1 dB on most channels. I also want to see how it does on channel 36 (4.1 NBC) & channel 43 (2.1 CBS) since the 91XG has trouble with NBC & the 4228 has trouble with CBS (from the same location).

My San Diego UHF stations arrive from ~169 deg. and seem pretty strong. One of the things I also want to try with the HDB8X is pointing one panel towards San Diego and the other towards LA (292 deg.) and see how the 4-Bays do through the combiner and/or individually. That’s assuming that they will swivel through 123 deg. Fortunately, I have the rotors so if I don’t get the angle set to exactly 123 deg. I can “bump” align each panel for best signal.

I’ll be waiting to hear how you climbed “above the top of the tower”.

Tower & Vertically Stacked YA-1713's
 

Pete, you have an extensive cabling arrangement.

Your idea of swapping antenna positions is a good one. Vertical signal layering can cause a substantial signal strength variation over relatively short distance when antennas are relatively close to ground (in terms of wavelength).

About the Winegard balun. It can be installed either way, phase relationship flips with balun reversal, matters not much on single antennas. For stacking, to maintain phase relationship, one must take this into consideration.

Antenna rotators can be very useful tools in troubleshooting.

--------------------------------

'Above the top' will be easier explained after a few more photos.

--------------------------------

This is a photo of the antennas that replaced the CM-1110.

.

http://forum.tvfool.com/attachment.p...8&d=1369571323

.


The only objective of the VHF antennas was to better receive WKYT (at that time RF channel 13), 74 miles distant, 2-edge diffraction according to TVfool.

The configuration:

- Two Winegard YA-1713, stacked
- Combiner; Winegard CC-7870
- Spacing; 43 inches (was varied +/- 18 inches while watching Signal Meter)
- Mast length; 10.5 feet, ~ 7.5 feet above tower.
(Made from heavy duty top fence rail (SS-20, ~1 & 3/8 inch outer diameter)

- Channel Master antenna rotator moved inside tower for stability.
- Final Preamp, Channel Master CM-7777 (original), a WG-3700 was tested
- All cables RG-6, custom installed connectors.

In 2010, WKYT changed RF channels from VHF 13 to UHF 36, so the YA-1713s were not of much use after that.

The configuration stayed in place for approximately a year, until ~mid 2010.

.

Early Channel Master 8-bay
 

The following image shows an 8-bay antenna that was purchased in 1970. Pretty sure it is Channel Master, probably a precedent to the popular ’original’ CM-4228. The physical dimensions and construction are different. Note the differing transmission line feeding the right and left 4-bays, it extends downward. The antenna demonstrated about 0.5 dB better gain on low to mid UHF channels than the popular ‘original’ CM-4228. No comparison was made for upper channels.

That antenna was hit by a tornado in 1971, breaking a whisker (upper right). The tornado destroyed surrounding buildings, along with the tower and other antennas on it.

Note: People lost their lives and many homes were destroyed in that tornado.

The 8-bay whisker was repaired and it was placed in storage until 2010.

http://forum.tvfool.com/attachment.p...9&d=1370105543

Mid 2010, the antenna was installed to receive channel 22 WCTE at 65 miles distant. At that time WCTE was transmitting 57 kW ERP. TVfool showed the path diffraction as 2edge.

http://forum.tvfool.com/attachment.p...0&d=1370105556

For convenience and shorter preamp feed length, the 8-bay was mounted upside down.

The preamp was the UHF section of the CM-7777 (VHF portion in use for Yagis), using an 'inside' balun (with silicone waterproofing).

The Yagis and the CM-4251 already had their separate cables and were combined with UVSJ behind the TV. So, behind the TV, the 8-bay channel 22 signal was separated from CM-7777 coax with another UVSJ, then added back to CM-4251 UHF signals via a Channel Master Jointenna.

Although the reception was very good for WCTE, channel 22, this antenna configuration lasted only a few months.

.

tripelo,

Until you pointed out the feed line configuration, I thought it looked just like my "original" CM-4228. It appears that the "original" CM-4228 is a design evolution of this model?

Solid Signal notified me that my HDB8X shipped on the 30th. It was originally scheduled for delivery on Wednesday, but now FedEx tracking is saying it could be delayed because of the storms and tornados. It’s been sitting in PERRYSBURG, OH since 4:37 AM Friday morning.

Yes Pete, it appears so.

Since your comment, I looked at a 1973 Channel Master catalog, it shows the 4228 as is commonly known. So, guess the design change occurred before 1973.

Some of the story behind it:

When the antenna was purchased, I was working as a technician at a regional TV repair & Motorola 2-Way radio service center. That business only handled Channel Master TV antennas. And, I thought it was a Channel Master antenna.

Last year, a long-time retired TV antenna installer was at my shop (garage in the earlier photo). Inside on one wall, were six 8-bays hanging side-by-side.

Without providing any information, I asked the experienced TV antenna man to identify the antennas.

He identified all the 8-bays.

He pointed out:

- Four of the 'original' CM-4228s,
- One 8-bay was copy of a 4228 made at a regional factory, and
- This particular 8-bay antenna as an old Channel Master antenna.

So, if it looks like a ..., quacks like a ... it must be...

Yes, saw your comments in a neighboring thread:

http://forum.tvfool.com/showthread.php?t=2288

You may have the earliest reports on it.

Will be quite interested in your assessment of the antenna.

Jerrold/Wade VIP-306 for VHF-11
 

Previously mentioned was that the stacked YA-1713’s on the main tower were not much use after WKYT moved from Channel 13 to Channel 36. Then, it was realized that for part of the time, a Louisville KY VHF station could be received and was occasionally watchable. The station:

WBNA (ION) Channel 8, 24.5 kW, at ~80 miles, TVfool Noise Margin -7.0 dB

And also interesting, for short periods of times, Louisville’s WHAS channel 11 (16.4 kW, at 101 miles) could be received, but was not actually watchable.

The signal goodness indication on a CM-7000 DTV converter was calibrated using a Signal Level Meter (~1.5 dB per each 10% indication for channel 11). This calibration of CM-7000 was used to help evaluate the two stations’ signals, hoping to make antenna changes for potentially better reception. For several weeks, reception of these two stations was checked daily.

An additional two YA-1713’s were purchased for possibility of a installing a quad stacked arrangement of YA-1713’s.

Analysis of signal data suggested:

An additional gain of 7 dB, above that provided by the stacked YA-1713’s, may be required for reliable reception of WHAS-11.

This required amount of increased gain (7 dB) essentially ruled out a quad stack of YA-1713’s.

A quad stack of YA-1713s (2 horizontal, vertically stacked above 2 horizontal, or even a diamond stacked quad) would at best provide ~3dB gain above a dual stack.

At the time, the highest gain for commercially available VHF antenna was Jerrold/Wade VIP-306 (specified gain of 12 dB on Channel 11). The VIP-307 version had a bit more gain but was no longer available.

That VIP-306 gain listing was dBd. In the late 1960's when the VIP series were designed, computer simulation (dBi) was virtually non-existant. So dB values were commonly provided in dB, as actually measured, with respect to a dipole (dBd).

A pair of VIP-306’s was purchased for evaluation and potentially for stacking.

Below, is an image of a single VIP-306 installed at the test location, aimed towards the main tower.

http://forum.tvfool.com/attachment.p...4&d=1370511504


Over the next few weeks, other VHF antenna configurations were mounted on the test mast and reception observed.

.

Longer Reinforced Mast
 

If higher gain antennas were to occupy the top position on the tower, then a taller mast may be required. For maximum stacking gain, individual antennas with higher gain require increased stack spacing. At that time, the existing mast was 10.5 feet of SS-20 (heavy duty), 1 & 3/8 inch outer diameter top fence rail.

Realizing that if a longer mast was ever bent by wind force, with unreachable antennas installed, it might be difficult to remove.

To maintain highest rigidity and minimize weight, a mast was configured of three parts:

· Full-length Outer – 15.5 feet of SS-20, 1 & 3/8 inch outer diameter
· Inner – 10 feet of Schedule 40, 1.064 inch outer diameter
· Lower-Outer - 6.5 feet EMT, 1.5 inch outer diameter.

The mast thickness were:

· Bottom portion was 3 pipes thick (EMT, SS-20, & Sch 40)
· Mid-section was 2 pipes thick (SS-20 & Sch 40)
· Top portion consisted of one pipe (SS-20)

The Inner was positioned inside the Full-length Outer, such that it did not reach the top ~ 4.5 feet. In other words, the top 4.5 feet consisted of only the SS-20 pipe. Also, the Inner pipe did not extend all the way to the mast bottom, but there was pipe overlap inside the tower.

The Lower Outer (EMT) was positioned to reinforce the lower part of the mast, up to ~ 4 feet above the tower top.

The Full-length and the Inner mast were assembled with stainless steel screws. The Lower-outer was to be added after the assembly was in place. The assembled mast (without antennas) weighed 35 pounds.

A sort of a ‘gin pole’ (lightweight pipe with upper loop) was temporarily fastened to the tower top as an aid during installation. The top end of mast was fed up through the loop to help balance and stabilize it during installation (especially with air movement). This additional stability was probably most critical when inserting the lower end of mast into the tower top.

Below is an image of the mast on the tower without the Lower-Outer portion. Later when antennas and the Lower-Outer mast portion were installed, the mast was raised a bit higher. The install support ‘gin pole’, is also shown but was later removed.

http://forum.tvfool.com/attachment.p...8&d=1371132108

tripelo,

Very interesting account. I especially enjoy seeing all the earlier antenna designs. It’s a shame that the superior ones like the Channel Master 4251 are no longer available. It is even more of a shame that proven designs like the CM-4228 have been cheapened and redesigned for shipping cost rather than performance. You’ve obviously been doing this a long time and have a wealth of practical experience. Are you still working in the field?

I got the Condo turned over to my property manager on Tuesday so I was able to try your panel isolation suggestions yesterday. I’ll talk to that in the other thread.

You probably can appreciate the innovations exhibited in those antennas.

Yes.

Thanks Pete, not working in TV related field, you might call it an avocation.

Very early – Interest in TV antennas led to electronics, then amateur radio (call WB4LXU).

Career years - Hardware design and systems engineer for two corporations (Texas Instruments and Raytheon).

Recent years - Main interest is in molecular biology and aging research.

-------------------

Pete, seems you have quite a lot of practical knowledge, maybe you worked in a related field?


OK, seems like your condo could have been some work, but having such in California seems good.

Yes, the other thread: http://forum.tvfool.com/showthread.php?t=2288&page=1

Custom Corner Reflector
 

The Channel Master 8-bay coupled through a CM-7777 and a Join-tenna provided reliable reception of WCTE-22 (~ 65 miles distant in Tennessee).

It was noticed that Channel 23 WPXK, also in Tennessee, might also be receivable. WPXK-23 is separated by about 54 degrees in azimuth from WCTE-22. If both stations were receivable, they could probably be accommodated by the single existing Join-tenna.

In addition, a third station Tennessee station, WBXX-20 located in azimuth between WCTE-22 and WPXK-23. If channels 22 and 23 were receivable, then due to higher signal strength of WBXX-20, it might be pushed through the same Join-tenna.

At distances of 65-75 miles, the TVfool noise margin levels and azimuth angles were:

Note: WBXX-20, in azimuth, lies between the weaker stations & closer in angle to WPXK-23.

A wide-beamwidth antenna with moderate gain could be a solution. Some candidates:

· Channel Master CM-4221
· Antennas Direct ClearStream C2
· Custom corner reflector (CR)

Another option could have been something like an Antennas Direct ClearStream C4 or Winegard HD-8800 with:

· Relative phase of right–left (RL) feed lines reversed
· RL Bay spacing optimized for split-beam lobes at 54 degrees separation

Some features of a custom CR antenna were appealing, one of which was it could be optimized for narrow range of channels around channel 22.

First, a CR backbone was retrieved from a scrap Antennacraft all-channel antenna. Then reflector elements were scrounged. Shorter reflector elements can yield wide beamwidth, but compromise some gain. For a few reasons, a moderately short reflector length of 16” was selected. The driven element was made from longer trimmed-to-length elements and supported by recycled insulators.

When the prototype was assembled, it was simulated in a computer model using Arie Voor’s 4NEC2 software. One objective was to get every tenth of dB gain while maintaining a good match to 300 Ohms. Since wide-beamwidth antennas usually have only moderate gain, then in this case it was important to have a good impedance match to optimize efficiency.

The prototype was tested with three preamps:

· CM-7777 with low loss balun
· CM-0264 (internal balun)
· Blonder Tongue Vaulter III (internal balun)

The image below shows the prototype and a couple of preamps on the test mast.

http://forum.tvfool.com/attachment.p...2&d=1371920415

The main variables in optimization with 4NEC2 software were:

· Driven element length,
· Position of driven element relative to apex
· Position of reflector elements near apex

After a few rounds of optimization; computer simulations, trimming, and on-the-mast testing, the CM-0264 was chosen as the preamplifier. The final tweak on the main tower was trimming the transmission line between the CR and the preamplifier for maximum signal.

The image below shows the installed corner reflector on the main tower. Most obvious change in the two photos is the position of the two reflector elements near the apex.

http://forum.tvfool.com/attachment.p...3&d=1371920423

With antenna direction at a compromise between the two weaker signals, the signal strength was not high on either of them. Fortunately, for all three signals being 1-Edge diffraction, their signal strengths were relatively stable, especially considering the distance of 65-75 miles. In normal viewing, no TV image dropouts have been seen or reported. Image dropouts have been seen when severe thunderstorms were between the stations and the receiving location.

A CM-0264 preamplifier was modified to replace its internal balun with an internal half-wave coaxial loop balun. In tests, the modified CM-0264 yielded ~1dB more S/N margin for all three stations. It has not been installed.

Early in 2011, WCTE-22 increased power to 200 kW (from 57 kW). This power increase allowed a re-positioning of the antenna in azimuth, with improved signal strength levels for all three stations.

.

tripelo

You outline an interesting design scenario. Did you ever implement the coax balun? From what I’ve read, coax balun’s have a very narrow bandwidth so I would have thought even 24 MHz (ch. 20 -23) might be too wide? Or, did you wind one on a toroid core?

I scavenged a VHF/UHF combo antenna from a rental house I own when one set of tenants moved out. It has a CR in front of the VHF portion so who knows what that might turn into one day.

I assume you weren’t in Dallas when you did this?

Balun
 

Thanks Pete.

Yes, a CM-0264 was physically modified to remove the internal balun and replace it with an internal coaxial half-wave loop balun.

Two types of lab tests were performed:

1. Gain vs. frequency response (dB)- Results before and after the modifications were compared.
2. Post-detection S/N (dB)- Using off-the-air DTV signals, both the modified and an unmodified CM-0264 were measured and compared.

No, the modified preamp has not been installed on the main tower.

Depending on how one defines bandwidth, a half wave loop could be considered to have narrow bandwidth relative to ferrite core baluns. However, for use in TV reception the half wave loop balun has a fairly wide usable frequency range. The losses of a half wave balun depend, as does a ferrite core balun, on design and construction. If one considers usable bandwidth to be when signal loss of a half wave balun is comparable to that of a conventional balun, then it probably has a usable bandwidth approximately equal to the current UHF band (Channels 14 –51).

It may be instinctive to think of functions that require specific wavelengths of coax to be narrow in bandwidth. This thinking could arise because such coaxial items can be a specific length (in terms of wavelength) at only one frequency. Only one frequency, that does seem narrow :)

The above is true if the objective depends on signal cancellation (e.g. notch or trap filters). For signals to nearly cancel, the amplitudes must be near exact and the phase relationship (wavelength-related) must be nearly exact.

But, the function of a half wave loop balun depends not on signal cancellation (subtraction, or out-of-phase condition) but instead utilizes in-phase signal addition. The half-wave delay (180 degrees) of a loop balun attempts to align (in phase) the normally out-of-phase signals of the left and right halves of a dipole antenna.

Even if their phase and amplitudes are not perfectly aligned, signals (vectors) can add with relatively small loss. When adding misaligned signals there is loss, but over a usable range the losses increase somewhat gradually as the misalignments worsen.

The main losses (in no particular order) associated with half-wave loop baluns:

1. Phase alignment Loss (Imperfect 180 degree delay)
2. Amplitude Loss (Normal coaxial attenuation for the half-wave section)
3. Impedance mismatch (Resulting from impedance transformation of non half-wave section)

Bottom line: Over much the UHF band (470-698 MHz), a well designed half wave loop balun can have lower signal losses than a ferrite-core balun and can at worst (near band edges) be comparable to good commercial ferrite core baluns.

Not in this particular case. It is essentially open-air loop, in close proximity to PCB plane and plastic housing.

Having wound many ferrite core baluns for VHF and UHF, winding twisted-pair on a 2-hole ferrite core could be an alternative, especially if coverage of channels at both both band-edges (near channels 14 and 51) is required.

Yes. you may find a good use for it.

All the antenna work, discussed so far, was done in KY.

The preamp modification (balun related) and testing was done in Dallas.

The modified preamp is now stored in KY.
.

Test Transmitter - Crystal Oscillator
 

Returning to VHF antenna tests, recall that an objective was to receive WBNA-8 and WHAS-11 from Louisville KY at distances of 70 and 101 miles. A project was initiated to determine if an antenna arrangement could make such reception possible.

TVfool report (both stations listed as 2-Edge):

A few antennas were compared at the test mast location (garage); Jerrold/Wade VIP-306, Channel Master Crossfire CM-3610, stacked pair of Winegard YA-1713, and a channel-cut Wade antenna.

Other high gain antennas were available, but only single units. It became fairly clear that no single antenna would suffice.

WHAS was listed as 2-edge and at the test site the signal was almost continuously variable. The actual signal strength, on an analog meter, fluctuated ~15 dB within something like 30 to 45 seconds. Portions of the WHAS 6 MHz spectrum varied independently.

The signal variation was such that antenna gain differences of maybe 1 or 2 dB were not visible.

It became apparent that, at this location, there were no commercial VHF signals strong enough or stable enough for definitive signal evaluation. Actually, there were no closer or stronger VHF signals at all. A local signal source was needed.

At the time in 2010, the signal synthesizer discussed in earlier post had not been constructed. So, a 20 MHz crystal oscillator was built to use as a VHF transmitter. The 9th and 10th harmonic of the crystal frequency provided test signals for channel 8 (180-186 MHz) and Channel 11 (198-204 MHz). The signals from the crystal oscillator were fed to a transmitting antenna at the main tower.

The transmitting antenna was a portion of a YA-1713 mounted on reverse side of CM-4251 on the main tower. It was fed by coax from the crystal oscillator located on the ground. The transmit antenna was aimed toward the test mast (at the garage). The signal was then received by the antenna-under-test mounted at the test mast location. Height of receiving test antenna was adjusted to be ~ level with the transmit antenna (~45 ft. AGL).

The above arrangement provided stable signals for use in gain comparisons between candidate VHF antennas.

The image below shows the upper-VHF transmit test antenna.

http://forum.tvfool.com/attachment.p...2&d=1372886021

Later, a crystal oscillator was built that could have provided UHF signals, but it was determined that a synthesizer was a better solution.

The crystal oscillator was used as a reference transmitter in tests throughout 2010, until the synthesizer was constructed in early 2011.

.

tripelo,

Do you remember how far apart you mounted the Winegard YA-1713’s in post 20?

I made a Home Depot run this afternoon & bought a 10½’ chain link fence top rail. I’ll try it in the Radio Shack rotor & see if I can spread out the Cushcraft A147-20T and the Winegard YA-1713. It’s been 97 deg. here all afternoon so trying to stay off the roof & out of the hot sun. Maybe tomorrow or Friday?

You just have to keep showing me pictures of those beautiful CM-4251’s don’t you.

Looking forward to the rest of the VHF High story

Tripelo.

Do you make your own clamps for the tower verticals, or is there something commercially available.
I have used clamps from my drum rack, but don't trust them for durability.
A picture would be nice, if you're able to provide one.

The YA-1713 were mounted 43 inches apart.

This particular stack spacing provided highest signal strength for Channel 13, it will probably different for other channels. Best spacing will be different for other types of antennas.

Signal strength varies slowly vs stack spacing so stack spacing for gain is not very critical (within a few inches at upper VHF).

The rotor may need a bearing to take side stress of it.

Don't know, maybe something like a NTE TB-105?

Maybe you have something like this already. From the YA-1713 photo, can't be sure how your rotor is mounted.

Guess so, those antennas are a bit different.

Saw someone, located in California, posted a photo of a CM-4251. So guess Channel Master did some marketing there. Maybe you can locate one some day.

Sorry, don't have any photos that I know of. Presently, I am not at the main tower site to take any photos.

Mostly use recycled antenna manufacturer clamps (the ones that come with antennas).

However, a pair of conduit clamps back-to-back makes a pretty good mast-to-mast or mast-to-tower leg clamp for light masts with light antennas. For mast sizes up to about 1 & 3/8 inches, the clamp size, not sure but think, is labeled 1 inch.

This labeling results from pipes being dimensioned according to inside diameter whereas mostly antenna installations are involving outer diameters (tubing convention).

This photo, a generic conduit clamp from the web, represents the type of clamp discussed.

http://forum.tvfool.com/attachment.p...3&d=1372962330

Look for heavy duty clamps, Lowes and Home Depot here don't seem to have the heavier grades. Probably electrical supply or old fashioned hardware store might be good places to find heavy clamps.

Bolt two clamps together, through the hole shown in the left of the image above. A 1/2 inch long, 5/16 inch bolt with two thick washers and a nut works well to hold two clamps back-to-back. If the bolt is much longer than 1/2 inch it will interfere with the masts.

This arrangement has an advantage in that it allows two pipes to be connected regardless or their orientation (horizontal or vertical or some angle).

Almost any mounting using these clamps requires four clamps (two pair). But maybe in a heavier installation more clamps could suffice.

tripelo,

That’s interesting, I assume you derived your measurement through empirical testing for channel 13? Winegard recommends optimum vertical stacking @ .94 wavelengths spacing and minimum @ .6 wavelengths for the lowest receive frequency of a broadband antenna. They published a chart for single channel antennas showing channel 7 @ 48”, 8 @ 46”, 9 @ 44.5”, 10 @ 43.5”, 11 @ 42.25, 12 @ 41” and 13 @ 40” or all at approximately .6 wavelengths.

Right now, it’s just the bare Radio Shack rotor & mast. So far that thing has taken everything I’ve thrown at it, including the big Wilson Shooting Star for several years. My TV tower rotor is an NTE ECG U106 with a TB-105 thrust bearing ~ 2.5’ above it. I had just ordered another TB-105 before I got your post. Great minds?

Boy, those things sure have gone up in price since I bought the first one a few years ago. I think I paid $17.50 + shipping and this one cost me $24.49, so with tax & shipping was $36.48.

Channel Master was one of the premier brands here from the mid 1950’s through the late 70’s or mid 80’s, when it seemed like their antenna quality and customer service really declined. I think I bought my CM-4228 in 72 or 73 when I was stationed in Sacramento, CA. I also still have one of their 300 ohm dual input VHF/UHF antenna amps. with a 75 ohm output. The power supply has a 110 VAC cord and sends AC up the coax to the mast mounted pre-amp. I used its VHF input (through a 300/75 balun) with my FM Yagi up until last year. No idea what the model number is or its specs.

Thanks, Tripelo.
Probably could sweat them together, too.

Yes.

The signal strength of the combined stack was observed on a signal level meter while the lower antenna was moved up and down by approximately +/- 18 inches.

Interesting about Winegard recommendations, in that they list two recommended stacking heights.

In general, the wider spacing (around 1 wavelength) yields higher gain for a given channel.

---------------------------------------

On the stacking gain topic:

In recent years, read several accounts of unsatisfactory experiences with vertical stacking.

Stacking two antennas for gain (horizontally or vertically) requires near equal illumination of both antennas (equal signals). If the two antennas do not receive equal signals, then the situation tends towards the two-antenna situation discussed earlier. The antenna receiving the weak signal tends to load the strong one and either loses signal in the combiner or re-radiates signal.

The above scenario more likely occurs with vertical stacking as compared to horizontal stacking. The sub-optimal effect on vertical stacking is mainly due to layering (signal reflection from ground, or diffraction from an elevated edge). To equalize the received signal in each antenna, it is usually necessary to have them mounted high above ground, so high that layering affects both antennas about the same.

How high is high enough for effective vertical stacking? Don't know, depends.

In many cases, probably high enough that the spacing between the antennas represents only a small fraction of the height above ground (could be 10 wavelengths or more).

Unequal illumination is related to another factor that has a role in producing less than expected gain from vertical stacks. That factor is vertical angle-of-arrival of received signal.

Stacking antennas may have some advantage (space diversity) other than increasing gain.

---------------------------------------

What are your impressions regarding the NTE rotator, compared to the Radio shack rotator?

Interesting that Channel Master was into California that early. Many of the antenna manufacturing companies in those days were sort of regional. Seems as if Channel Master must have had the best (Quality x Performance)/Price ratio of all manufacturers.

Probably about the time when satellite-fed cable was coming on strong.

NTE ECG U-106 Rotor vs Radio Shack 15-1220
 

tripelo,

Quote:

What are your impressions regarding the NTE rotator, compared to the Radio shack rotator?

No comparison. The Radio Shack 15-1220 is a 5-wire rotor that uses a balanced bridge for exact positioning. In the 50 years I’ve used it; it has never gone out of alignment. It also seems to produce more turning torque. The accompanying control box displays ‘N’ at the top & ‘S’ – ‘S’ at either end of rotation. Being an old flyer, that fits the way I think.

I also have an RCA 10W707S that is almost identical. Motor unit is exactly the same and control box looks identical except it displays ‘S’ at the top and ‘N’ – ‘N’ at either end of rotation. The one drawback is the directional calibration. Tic marks on both rotors are 4.5 deg. apart. When aiming towards a “True” heading, I can visualize the heading with respect to true north and align the knob pretty close. Degrees with respect to true south –not so much. (If I put the RCA in service, I’ll make stick-on labels for the cardinal headings (S-S, W, N, E) to cover the ones silkscreened on the control panel. Other than control panel screening & branding, they really are identical.)

The U-106 is a three wire rotor that uses a timing circuit for calibration. 3-wire rotors use AC synchronous motors that run at a predictable speed, and the control box simply runs the motor for the amount of time needed to turn the antenna from where the controller thinks it is to where the controller wants it to be. Over time, the position error grows.

After moving it to “home” or 00 deg., basically, you rotate it full clockwise (360 deg.), hit a button labeled “Initial” and it memorizes the time it takes to return to 00 or “home”. Unfortunately, it frequently requires recalibration. Since my signals come from four directions, it’s fairly easy to detect when it needs calibration because when I turn the array there is either nothing there or the signals are barely watchable. I probably have as much calibration mileage on the rotor as actual array turning mileage. Sometimes, when the calibration goes off, it won’t fully turn to a true 360 so to get it full clockwise you have to power off, power on with a “reset” turn some more and repeat the process until it visually has the array pointing north. I’ve since read that other folks are experiencing the same calibration issues with other brands of 3-wire rotors. I think AntennaCraft, Centronics, Channel Master, Magnavox, Philips, RCA, Stern and probably others sell this same design under their own labels.

I bought the U-106 because the literature said “Digital display indicates antenna position during operation” & “Pre-set to 12 TV/FM station directions for automatic antenna positioning”. What I didn’t pick up on was that the bearing readout was a 2-digit display. North is 00 or 36, east is 09, south is 18 and west is 27. My street is aligned with True North and my house sits squarely on the lot facing east so visually it’s easy to determine array alignment. Even after a fresh calibration, manually turning the rotor to display “18” can have me pointing somewhere between ~175 & ~185. Fortunately, if you “bump align” for max SNR and memorize the location to a pushbutton it seems to return to that location –at least until it goes out of calibration.

I’ve been tempted to put the RCA on the tower, but then I’d have the new U-106 just sitting in the garage gathering dust. It’s useable, but I couldn’t in good conscience sell it to anybody.

Hello Pete,
The TB-105 support bearing that you ordered is currently out of stock. The vendor will not have anything available until mid September.
Please let me know if you wish to keep your order open or cancel.
Thank You
Tom

Kept order open, so it looks like I don't have to go out in the 100 deg. heat (at least until September).

http://forum.tvfool.com/attachment.p...1&d=1373129246

Found this ad in the Pitsburg Post-Gazette for Friday August 24th 1973. I think I bought mine about 10 years earlier for $29 or $39.

Thanks Pete, for your interesting writeup on the antenna rotators.

Looks like your Radio Shack and RCA rotators are good ones.

Couple of thoughts:

Rotators currently available may be suitable for a single small antenna, but not much more than that.

At present, seems like if one wants a heavy-duty antenna rotator with some accuracy in pointing, one may have to look at rotators marketed to amateur (ham) radio. Likely, the ham radio rotators will cost more than the typical TV rotator.

Half Wave Coaxial Baluns for VHF
 

Recalling the VHF antenna project objective:

To receive WHAS-11 and WBNA-8 located in Louisville KY.

TVfool report (both stations listed as 2-Edge):

Observations over several weeks with the stacked YA-1713 antennas on the main tower, it was determined that an additional gain of 7 dB may be required for reliable reception of WHAS-11.

After testing for a few weeks at the test location (garage) with some high-gain antennas, it seemed like there were few options that could provide 7 dB gain above that obtained with a pair of YA-1713 antennas. A stack-of-two large, either Wade/Jerrold or Channel Master antennas seemed likely to be insufficient, and a quantity of four of such antennas was unavailable.

At about half the length and 1/3 the width, the gain of the channel-cut antenna tested to be within about 2 dB of a single large antenna.

Since it was desired to receive two stations separated in frequency, WHAS-11 and WBNA-8, then using channel-cut antennas for a single channel could be problematic

Fortunately, in this case, a characteristic of Yagi antennas is that gain decreases less rapidly on the low side of the design frequency. Since the design frequency would be weak signal channel (channel 11) and the lower in frequency, channel 8 signal was considerably stronger (not requiring as much gain), then a channel-cut antenna might suffice.

Considering the above information, it seemed a pair of long channel-cut Yagis designed for channel 11 might meet requirements. Since a channel-cut Yagi of about 85 inches in length delivered a gain within ~2dB of a VIP-306 or a CM-3610, then a channel-cut Yagi of 170 inches probably could exceed the performance of either of the larger antennas.

Location: Dallas

In an attempt to maximize signal from such antennas, half-wave coaxial loop baluns were designed.

A small channel-cut Yagi for channel (Wade 5y10s) 10 was purchased for balun design and testing.

http://forum.tvfool.com/attachment.p...6&d=1373568437

At that time, there were 3 VHF stations (Channels 8,9, and 11) in Dallas. The signal paths were line-of-sight and the signals were strong and steady at the Dallas test location. The broadcast DTV signals provided signals for gain comparisons between antenna modifications and balun types.

Several loop baluns were constructed and reception compared to each other, and to commercial baluns (using the small Yagi and broadcast DTV signals).

After suitable half-wave loop balun designs had been constructed. The input impedances of several balun and antenna combinations were quantified. Knowing complex input impedance allows SWR to be calculated. The impedance measurements were performed using a vintage Boonton/HP RX250A The RX250A is capable of accurately measuring complex impedance from 500 kHz to 250 MHz. Measurements confirmed that the three-bar folded dipole had sufficient bandwidth and that a half-wave coaxial balun provided a low SWR match to 75 Ohms.

Half wave baluns were constructed using both RG6 and RG-62 (93 Ohms). In agreement with theory, the RG-62 cable provided the widest bandwidth and best match over channel 8-11 and thus the lowest overall signal loss.

Note: At, or near, the loop half wavelength frequency, loss was less with RG-6 cable. Away from that frequency, losses were less with RG-62.

.