Rca ant751
 

Fascinating classroom lecture today, Professor rabbit73!

I've written down your "experiential fix" of the stripped screw for future use when necessary. Thanks for the tip!

Now I'm beginning to see how the mysteries of antenna theory work in real time from your analysis. Still I'm a bit awe struck, to say the least.

It will be interesting to see Adtech's field testing of GEs latest antennas in comparison to the similar RCA (AKA ANT705Z) that JOEAZ mentioned in his post. IMHO, the plastic used on both these antennas and similar others probably are UV resistant and will give at least a few years of use even in harsh desert environments. But mileage may vary in each individual situation.

I'm guessing that other antennas on the market today which are using built in baluns like this GE 34792 are of similar circuit design. This should be informative for those who end up using them at their locations, or who might have to open the board up in case possible circuitry issues. Your provided information has been very helpful here.

Thanks, as always, Professor rabbit73 for your yeomans efforts! Much appreciated!!

The tests that I have made so far tell how well the antennas work indoors with my signals, but I have been searching for a test method that would give a more accurate indication of relative antenna gain.

I have settled on an Antennas Direct DB2E antenna and a Blonder Tongue HAVM-1UA Frequency Agile Modulator for a stable transmitted test signal.

I read about the antenna test measurements done by Kent Britain (WA5VJB). He has made measurements with the test antennas at ground level and above ground level. When the antennas are elevated, the receiving antenna picks up the direct signal and a signal reflected from the ground. I tried it both ways. The ground level signals level are much weaker, but the gain difference between antennas is about the same, so I used elevated antenna measurements. Kent was making measurements at microwave frequencies with horn antennas, see p. 5:
http://www.wa5vjb.com/references/Ant...0Notes-keb.pdf

http://forum.tvfool.com/attachment.p...1&d=1495302313

http://forum.tvfool.com/attachment.p...1&d=1495302313

First I did a comparison between the antennas elevated on tables and on the floor. The HAVM is only for UHF:

Rca ant751
 

Rabbit73, we really do owe you overtime wages for your continued testing results in this thread! Retired or not, I sure respect your life long experience in this technical field of TV antennas, et al. I'm back in your class sitting in the front row, no less.

And I wish there was some way we could repay you for all your very kind help on TV Fool. Like the best of my past teachers, you not only teach us students through narrative, but "show" us exactly what you're talking about with pictures, or rather, photos.

I just wish there was some way I could have say, Antennas Direct for example, send you an antenna or supplies of your choosing if I called them and placed the order. As long as they had a secure address I'd be willing to step up to the bar and pay the tab. LOL!

Anyway, it looks like the GE Outdoor has the edge with your testing so far. Interesting. And the AD DB2E looks like a very good antenna which could rival the GEs. With the VHF add on kit from AD, I'm toying with the possiblity buying one to see how well it would pick up signals in my area. Hmmm.....

Well, your loyal student is ready for his next lesson professor! Thanks so much again! BTW, very interesting article you linked from Kent Britain (WA5VJB). I have not heard about him before, but you can always count on the hams to come through!

Kent writes an antenna column for CQ Magazine (amateur radio). He is the creator of the "Cheap Yagi" antenna. If you Google it:
https://www.google.com/#q=cheap+yagi&spf=1495326554715

This is his website:
http://www.wa5vjb.com/index.html

He did a version for TV reception:
http://www.wa5vjb.com/references/CheapYagi4HDTV.pdf

If you look at Figure 6 of that article, you will see an analog TV signal. That is what my HAVM modulator puts out. I am using the video carrier as a test signal.

Rca ant751
 

OMG, rabbit73!

I'm just a kid in a candy store!

Now, to the homework.....circuit board antennas.....easy build it yourself yagis.....I'm down with it for the rest of the weekend.....:) P.S. I'm fascinated by your test equipment!

The next test that I did was to compare the GE PRO, ANT 751R, and the ANT 7511.

Conclusions:

The GE PRO 29884 antenna is the best of the 3 antennas for my indoor location. The RCA ANT 751R is a close second. The RCA ANT 7511 is third. The RCA design change has sacrificed considerable UHF gain.

I have a little more confidence in these measurements, but there are reflections that will introduce errors. I miss my outdoor range with stable LOS signals.

So am I. Making antenna measurements is one of my favorite things.

You don't need a lot of expensive equipment. With just a variable attenuator and a TV, you can measure margin to dropout of the signal. The simplified form is shown in my signature link.

http://forum.tvfool.com/attachment.p...5&d=1477146996

Rca ant751
 

I too, wish you still had your outdoor set up rabbit73. But your most recent test results probably would be similar out of doors, is my amateur guess.

Still, what you have shown here on this thread with the indoor equipment used, more than justifies my nomination of you as, THE DEAN OF TV FOOL.

And you just cannot take away certain vital elements in a TV antenna as RCA has done with their stripped down version 7511, without compromising overall gain. I'm fairly certain someone with a good understanding of physics, math and electronics would agree with me??? I'm still in undergraduate school as far as those subjects go.

But as far as everyday reception goes, RCA dropped the ball on a very good antenna with their newest version 7511. Fortunately, us OTA fans out here in the hinterlands have other choices going forward. And your help with this issue has been exceptional, rabbit73! THANK YOU!!

I finally should be able to upload a summary plot of the relative boresite reception of a number of small Yagi/LPDA antennas from my testing earlier this month.

A few notes to ponder while you're waiting:

1. I'm not terribly happy with the quality of the data gathered. I identified, after the fact, a number of things that need improvement in my process including an huge signal "suck-out" (it will be painfully obvious) in the middle of the UHF band, probably due to an unwanted signal reflection or a fault with a cable or the transmitting antenna. I didn't find it until the range was broken down and I started pulling data into Excel for plotting. Since the anomaly is present for all of the antennas tested, it's still an equal playing field.

2. I did not have the opportunity to normalize the spectrum analyzer to the tracking generator (impractical), either before each measurement was made or via a correction file in the post-processing (didn't think of it) in order to smooth tracking generator non-linearities (up to +/- 2dB over sweep span) and other fast-changing (frequency-wise) impairments. If you know how to easily implement weighted average smoothing in Excel 2007, I'd be interested.... It would really clean up the presentation of the data.

The plot to be posted, once I finish tweaking it in the morning, is fairly congested with the data for seven antennas overlaid using Excel's default coloring scheme (ugh!). I haven't gotten around to changing the line style and color for better legibility and probably won't since this plot is a one-off from my normal analysis which normally compares ten different readings for each antenna done in a two-up comparison (Antenna A vs Antenna B).

I will say there are some interesting results to be seen. ;)

Rca ant751
 

Thanks for sticking with this thread, ADTech!

Even though your testing is not under optimal conditions and rabbit73s too, both of you are probably doing ground breaking research here. I have found very little results for these type of antennas anywhere on the Net. Perhaps there are posts somewhere, but I have not seen any. If someone reading this thread can illuminate us here, I would certainly appreciate it.

Anyway, anxious for your test results ADTech!:)

I did one final test in this indoor series, which is to compare the GE Attic Antenna with the AD DB2E, using the GE Pro as a source antenna.

The Antennas Direct DB2E wins.

Rca ant751
 

Thank you, Dean rabbit73!

Looks like AD DB2E more sensitive or gain than GE Attic on UHF channels you tested. Of course, you would have to add a VHF kit to use as all around antenna, whereas GE already equipped with VHF dipole. Also, cost comparison, GE is less. Something to certainly consider.

I can only speak for me, but all your testing here as educated me immensely in what to look for in good antenna reception. I cannot thank you enough for the information. As I previously mentioned, not much out there to judge these antennas nowadays.

Not much difference; the DB2E was on sale.
http://www.solidsignal.com/pview.asp...u=853748001408

Yes, you are correct.

That is my next project; channel 13 ABC is weaker because the folded dipole doesn't have much gain, and a reflector is needed for VHF because of multipath reflections.

It will be difficult because VHF-High antennas are about 3x the size of UHF antennas.

Rca ant751
 

That's a very tempting price.....sold I think!

I would be interested in your VHF findings when you're able to post, professor rabbit73.

Thanks!

As promised yesterday, I've attached the mentioned plot.

A couple of additional notes:

1) I added black vertical lines to denote the boundaries of the current high HF and UHF bands.

2) Low VHF reception was not a factor in this data collection effort.

3) The RCA751R was purchased at a local Menard's in late 2015.

4) The RCA 7511 and 705Z were purchased from a local Walmart less than a month ago.

5) The Winegard HD7000R was purchased from an online seller this spring. It is the newest (known) version that includes the low-VHF conversion kit which was not installed for this testing.

6. The GE 30741 was purchased about a year ago at a local Walmart.

7. The CM3010 was purchased directly from CM's web store last summer. COMMENT: This antenna fared so poorly against the rest of the pack that I suspect that it may have a faulty balun. The alternative interpretation is obvious.

8. The identical physical layout, cabling, test equipment configuration, and data collection procedures were used for each antenna to the best of my knowledge and ability.

9. Boresite reception as a basis for a relative antenna performance comparison is only one of the possible tests that can be performed to characterize any given antenna. Polar patterns are probably a more instructive characterization as they identify the additional parameters of F/B ratio, F/R ratio, beam width, as well as major and minor lobes, if any. They are not included in this posting for various reasons including several deficiencies that I identified post-testing and I'd prefer not to have to address.

http://forum.tvfool.com/attachment.p...4&d=1495639678

Observations:

By virtue of it's UHF reflectors, the RCA705Z offered the best UHF performance of this cohort. It's VHF performance, however, was hindered by its single folded dipole element when compared to its stablemates. Now, if they tacked that UHF front end onto the VHF section of the 75XX, it would be an interesting combo for close-in work. It also probably would not end up on the shelf at Walmart due to the resulting larger package size, IMHO.

The other two RCAs and the WG (all three are manufactured by WG) are based on the same original design and are all very similar in performance with some observable minor differences. FWIW, it would be my opinion that the casual antenna user would probably never note any difference unless they happened to be right on the edge of reception for a station using a channel where a difference in reception can be discerned from the attached plot. YMMV.

If I think of more comments later, I will append them below this line.

Cheers!

Wondering what kind of polarization did you use? How much of a factor
would the polarization play in your tests??

Everything (TX & RX antennas) was horizontally polarized since that is the de-facto standard for North American TV broadcasting as well as the design of all of the tested antennas. I could just as readily, with a bit of hardware modification, have rotated everything 90° but it would have had little to no impact on the recorded results except possibly for ground reflection influence.

Not sure what detail you're inquiring about, but I can say that from prior experience, that if I cross-polarize one of the antennas, there's usually a penalty of 20 dB or more.

I asked because one of the translators we view uses circular polarization,
I have been told. Supposedly, circular polarization is somewhat better
with mountains and hills. That translator is most always a challenge to
receive over all the others.

Rca ant751
 

Wow, VERY INTERESTING results ADTech!

I'm still pondering your graph. But I do have a question first before proceeding with perhaps a few other comments.

Is there a way to figure out the overall gain of the antennas you tested for their VHF High/UHF and FB numbers? Sometimes on various antenna web sites you will see numbers like 5/7 for VHF/UHF gain and 12 FB. Perhaps a mathematical formula or even something less technical? Pardon me if I'm not asking the question in the correct way. I'm still very much learning about the technical side of TV antenna reception. But TV Fool has really helped me in this regard.

Thanks so much again for your results. This will be quite useful for me in evaluating possible future antenna purchases.

In my opinion circular polarization is worse with mountains than H pol only. This is because the V pol reflects more than the Hpol. This multipath is the bane of 8VSB.

ATSC 3.0 will do better with multipath and circular polarization than 8 VSB.

I've never heard of CP or EP being useful for that purpose. I've always heard that it helped with indoor antennas or mobile-type reception devices (which didn't pan out under ATSC 1.0).

What are the call letters of that translator?

Edit: I see TG chimed in while I was typing. His perspective on that subject should carry more weight since he works on the transmit side of the broadcast system.

With the data as previously presented, no. The comparable data from a reference antenna of known characteristics would need to have been included so that the mathematical comparisons could be done. See image and discussion following.

F/B ratio could be measured by performing the same set of measurements with AUT aimed 180° opposite boresite. I didn't make that particular measurement using the linear frequency sweep procedure plotted above although I did do 360° rotational patterns which would discern this behavior though for specific frequency cuts.

Here's a sample that compares the RCA7511 to our clip-on VHF module which is tuned to 195 MHz, the center of the high-VHF band. See notes following.

http://forum.tvfool.com/attachment.p...1&d=1495723497

Notes:
1) A hardware failure in my circuit that synchronizes the SA sweep to the rotor's start of rotation forced me to manually trigger the SA sweep using a manually activated micro-switch in conjunction with activating the rotor. Consequently, the data may be easily skewed by as much as a second or two (7.5-15 degrees). Kindly overlook this shortcoming, it's particularly noticeable in the 7511's pattern.
2) The data was normalized so that the maximum point in the paired data set was set to "0" and the rest of the data was adjusted by the same amount for the purposes of this comparison. Using Excel, there are, of course, a good number of possible data display methods possible, this happens to be the one I chose as I attempt to enhance my feeble Excel and VBA skills. ;)
3) The VHF module, if balun and insertion loss adjustments were included (they aren't at this point) would be about as close to a reference dipole as a no-budget measurement effort could produce. I may explore this later and then compare it to the BicoLOG just to see how close they are to each other. In the meantime, I'd assume a 1 dB insertion loss @195 MHz and that will get you better than in the ballpark (probably into the infield) for an estimate.
4) Using the above described F/B definition, the F/B of the dipole is measured a almost zero, the 7511 is measured at about 15 dB.
5) Using the above described gain definition and including the estimated insertion losses, I'd estimate that the forward gain of this antenna, as tested, is ~ 5 dBd (7.15 dBi) at 195 MHz.

I spoke to an engineer for Arizona PBS, KAET, several years ago
while at the summit of Mingus Mtn. I mentioned that his
translator, K42AC, was harder to receive than the others on
Mingus. He told me that the signal was directed away from
Prescott and Prescott Valley and that they were using
circular polarization. He then told me to tilt the 4 Bay antennas
from an "X" to a "+" which he said would help. It did help
but not much..... It continues to be hard to receive through
much of the area.

K42AC shares a Jampro JA/LS-8 with K38AI and K40DD up on Mingus Mtn and the antenna is H-POL only, none of them are licensed for any vertical component in their signal. Their antenna is, however, highly directional to the east-northeast with a good amount of electrical down tilt (3°). K42AC, however, maxes out at only 5 KW ERP along its maximum strength signal path compared to 12-15 KW for the other two stations on the antenna. The worst case, if one were situated in one of the weakest nulls, would be that only 920 watts might be sent in that direction. By contrast, K38AI peaks out at 15 kW with a minimum of 2.65 KW in its deepest null.

I suspect the much lower ERP and the directional antenna are the root cause for the difficulty in receiving K42AC as compared with its neighbors, depending o the relative direction and distance of the receiving location relative to Mingus Mtn. The weaker UHF signal of K42AC will be much less capable of diffracting to lower elevations where terrain is an issue or even for simple longer distance locations, even with LOS.

My interpretation, based on the antenna patterns and the City of License for each facility, is that KAET intends K42AC to cover the Cottonwood side of Mingus Mtn and for K43LW, located on Mt Francis, to cover the Prescott side.

K42AC is located on the Northeast side of the mountain with a short tower that doesn't see over the peak. Prescott is Southwest of the transmitter. There are shadows and weak signals in Prescott.
http://www.tvfool.com/?option=com_wr...q=call%3dK42ac

The use of circular polarization may not play a role with your spotty reception of K42AC.

Unfortunately, K43LW on Mt Francis, is only 1kw and is severely
hampered by the hills and terrain of Prescott. Additionally, there
is another RF43 on Bill Willaims Mtn about 40 miles away. Many areas
have LOS to Mingus and Williams but not Mt. Francis. That is why it
is imperative to capture K42AC. There is another PBS translator in
Flagstaff on RF14 but it cannot be received because there is also a
translator for KUTP, RF 14 on Mt Francis, here in Prescott.
It is what you could call " A MESS."

I cannot help but wonder if the polarization was changed, if the F.C.C.
database is correct or if the engineer was mistaken.

I'd guess that the engineer was wrong. Perhaps he was thinking about a different facility. The Jampro antenna listed is Hpol only. The FCC application does not mention a CP antenna.

The ability to pick up a signal while your antenna was mounted vertically indicates significant depolarization due to refraction off the mountains.

In mountainous locations antenna height can make a huge difference. You can try moving your antenna up or down to see if reception improves. Scientifically, you can calculate the angle to to the mountain, determine the slope in front of the antenna, and use ray tracing techniques to get a good starting point. I don't know where you live in Prescott, but you may find that an antenna several feet off the ground with nothing in front of the antenna might be better than the roof.

I'm going to go with the engineer either mis-poke or there was a miscommunication. There's nothing in the FCC file that indicates the digital facility was ever anything but what it still is.

I'd expect it's going to get a lot messier as the repack progresses. All of the facilities operating on channel 38 and above must vacate those channels. And, since none of the translators (and other LP-class stations) are even guaranteed a post-repack channel, it's fairly likely that some will disappear completely and that the remaining ones get packed even tighter into the remaining channels, increasing the rate of co-channel and adjacent channel interference. Since this class of operator does not enjoy any interference protection under the rules, the mess will not get better.

[QUOTE=
In mountainous locations antenna height can make a huge difference. You can try moving your antenna up or down to see if reception improves. Scientifically, you can calculate the angle to to the mountain, determine the slope in front of the antenna, and use ray tracing techniques to get a good starting point. I don't know where you live in Prescott, but you may find that an antenna several feet off the ground with nothing in front of the antenna might be better than the roof.[/QUOTE]

Agreed. In some locations I've lost RF13 but received RF22 which
transmit from the same basic location. Moving the antenna a few feet,
I was able to capture RF13, though weakly.

Agreed. I've done some studies and found that in almost every case,
low band VHF will be used. There will be even more co-channel interference.
Invariably, some channels will simply disappear. Trying to find as compact
as possible antenna capable of RF 2-36 or Rf 2-51 is impossible.....

That's because of the physics of the lower frequencies. You can currently get a small Winegard (HD7000R) or a small Channel Master like the CM3016 or CM5016 but they're going to range from rudimentary like the HD7000R or fairly modest for the CM models which are still fairly large (relatively).

Personally, I'd expect the rural translator operators to do like all the majors and avoid low-VHF for the most part unless there's nothing less to pick from. IIRC, the filing window for the LP and translators being displaced is later this year so we'll have to see how it shakes out.

ADTech
I bought two EU385CF for evaluation. I opened the black enclosure, and something didn't look right. I opened the second enclosure and it did look right.

I was able to figure it out, but if someone only purchased sample #1 with the upside down label, it might confuse them.

Sample #1 was sealed at the rear with epoxy; sample #2 with solder and epoxy, so I didn't mess with it.

Since you do QC, I thought you should know. I also called customer service to let them know, but didn't ask for an RMA because I wanted to look inside anyway to add to the AVS UVSJ thread.
http://www.avsforum.com/forum/25-hdt...ombiner-8.html

my post for the Antennas Direct EU385CF-1S UHF/VHF Diplexer (UVSJ):
http://www.avsforum.com/forum/25-hdt...l#post53267506

Thanks for bringing that to my attention. Must have been a Monday morning at the factory!

I couldn't find any relevant tickets in our system. Any chance you received a ticket number?

Sending ticket number in a PM on other forum.

I did some more testing with my GE 34792 Attic Antenna indoors on VHF-High because CH 13 is more difficult to receive than my UHF channels.

I found a convenient location in the bedroom for the antenna and made some measurements. In this location, CH 13 is picked up by the tuner, but there is picture freeze and many uncorrected errors, not too good:

http://forum.tvfool.com/attachment.p...1&d=1496712910

The signal level meter shows adequate signal strength, but a bad channel scan:

http://forum.tvfool.com/attachment.p...1&d=1496713140

I suspected that multipath reflections were causing a problem and decided to add a reflector element to the VHF folded dipole. A cardboard box is used as a temporary support.

http://forum.tvfool.com/attachment.p...1&d=1496713473

The reflector is 13" behind the VHF dipole and consists of a 24" length of 1" aluminum tubing with a 12" length of 7/8" tubing in each end and clamps. The length has been adjusted to 27.7". I also tried a strip of aluminum foil on a yardstick with the same results:

http://forum.tvfool.com/attachment.p...1&d=1496713915

The reflector improves the reception:

http://forum.tvfool.com/attachment.p...1&d=1496714072

and the scan looks a lot better:

http://forum.tvfool.com/attachment.p...1&d=1496714197

Since the convenient location for the antenna had some problems, I tried other locations in the room. The best location for the signal was in the middle of the room in a high traffic area (of course it was).

http://forum.tvfool.com/attachment.p...1&d=1496715021

No reflector was needed in this location and the reception was excellent:

http://forum.tvfool.com/attachment.p...1&d=1496715151

and the channel scan looks good, with increased signal strength:

http://forum.tvfool.com/attachment.p...1&d=1496715270

The Sadelco DislayMax 800 signal level meter makes 43 measurements across the channel and diplays the average of all readings. If one of the 43 measurements is below -20 dBmV, the meter says "Ur" for under range and doesn't give a reading. The scan covers about 5.3 MHz of the 6 MHz channel.

http://forum.tvfool.com/attachment.p...1&d=1496716036

If the meter is switched to the single frequency mode, it will measure down to -35 dBmV at the center of the channel, but the correction for a digital signal is not added; +6.8 dB IIRC.

http://forum.tvfool.com/attachment.p...6761421http://

The screen on the meter actually shows a dark gray image on a dark green background and doesn't have much contrast. The image looks pretty good on a computer screen, but makes a muddy image on a print.

analog channel:

http://forum.tvfool.com/attachment.p...1&d=1496762257

digital channel:

http://forum.tvfool.com/attachment.p...1&d=1496762257

To make an image that has more contrast and room for notes, I set my digital camera for a B&W image, and then edit in Photo Gallery to increase the contrast.

http://forum.tvfool.com/attachment.p...1&d=1496769065

Photo Gallery will only allow me to increase the contrast one time, AFAIK, so I use Lunapic to increase the contrast 4x more:

http://forum.tvfool.com/attachment.p...9&d=1496715329

Rca ant751
 

You may not have your outdoor antenna testing equipment available anymore, rabbit73, but your indoor results here are AMAZING!

As I'm beginning to understand much better now, indoor antenna set ups are even more complex and perhaps mysterious than their outdoor counterparts. LOS is a bit more straight forward out of doors, or so it seems. But like you previously mentioned, not everybody can put up an outdoor antenna.

If you keep up grading that GE Indoor antenna of yours, you might want to seek a patent, make a ton of money and really retire in a manner you're unaccustomed too--LOL! But necessity is the mother of invention. I'm copying your attachments for possible future inventive use. Ha! Ha!

Thanks for remembering my request here, rabbit73! I appreciate your dedication to this forum. It has been extremely enlightening. BTW, I've been watching your other posts. I'm learning something new every day!

Thank you for your encouraging comments. I also learned a lot about indoor reception from this experiment.

Trip in VA, who runs the rabbitears.info web site and now works for the FCC, had an even more difficult time with reception of local signals. When he was living in Chattanooga he had to put his antenna inside a trash can to reject multipath reflections.

http://forum.tvfool.com/attachment.p...3&d=1470521359

Background information on this technique:

http://www.avsforum.com/forum/25-hdt...l#post21358820

http://forum.tvfool.com/showpost.php...27&postcount=7