Help with one VHF Channel
 

I have a second-hand Radio Shack VU-75XR about 20 feet up. HERE is my report. I first tried it at 15 feet and barely received WCHS and WOWK. I added 10 feet of mast and lost those 2 completely. I lowered it to 20 ft. and still no joy. I'm using an RCA matching transformer. Could that could be hurting a little? If it proves impossible to receive WCHS, is there a way to optimize the VHF portion for one channel? WOWK is VHF 13.

Welcome, Chris:

Please post the link to your tvfool report. I see "HERE" but nothing happens if I try to click on it.

I see a report on your previous thread. Is that still accurate, or have you moved? It would have been better to add your new question to that thread for background information, instead of starting a new thread.

previous thread
Why can't I receive this station?
http://forum.tvfool.com/showthread.php?t=15444

old report:
http://www.tvfool.com/?option=com_wr...f1f05778a90214

Matching transformer or preamp? If it is a preamp, what model is it?

It's just a matching transformer. I fixed the link to my report,

I did some testing today. I tried an indoor matching transformer that I believe is good and got the same results. I swapped coax also. While I was out there, I took a picture looking the direction of most of the stations. The antenna is higher than the huge bush by the sidewalk. The hill is probably my biggest issue. I believe the tower across the street is the college TV station uplink. Another possible concern is the local FM station. It's not very powerful but a cheap radio will pick it up all the way across the dial.

As for the antenna, is there a way to modify the VHF section so it works better on channel 13? I believe 13 inch elements would be a half-wave dipole. The live elements on the antenna are 6, 26, 38, and 48 inches. That's not exact because its cold and dark out but close. It seems to me that with 13 being the lowest channel, I don't need any elements longer than 13 inches.

To pick up channel 13 I'd get a HLSJ to filter out the FM stations. The local college station is 50 KW from .8 miles away which will cause fundamental overload. Yet there is a second FM station at on 107.1 at .9 miles that will also overload the tuner in the TV set which creates an internal second harmonic within channel 13.

Tower Guy is correct. You have some very strong FM stations that most likely are causing interference to TV reception. The HLSJ can be used as an effective FM filter. It will block signals below TV channel 7, including the FM band. Use the High and common ports and insert it in the coax line from the antenna.
http://www.solidsignal.com/pview.asp?p=zhlsj

http://www.atvresearch.com/hlsjvhfba...-combiner.aspx

http://www.nsccom.com/hlsj.aspx

Here is an FM signal report based on your short coordinates as showing on your tvfool report:
http://www.fmfool.com/modeling/tmp/a...7/Radar-FM.png

Here is a report based on where I think you were standing when you took the photo:
http://www.fmfool.com/modeling/tmp/2...f/Radar-FM.png
To keep the strong signals from causing interference, you should ground the coax with a grounding block connected to the house electrical system ground.

http://forum.tvfool.com/attachment.p...9&d=1441917363

If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.

You don't need to modify the antenna for channel 13. It's as good as it will ever be for 13. If you need more gain for channel 13, you should use an antenna with more gain.

Channel 13 is 210 to 216 MHz; center frequency 213 MHz. A half wave dipole is 5540/freq in MHz, with the answer in inches.
5540/213 = 26 inches for a half wave dipole

VU-75XR VHF/UHF/FM Antenna (150-2151)
Specifications Faxback Doc. # 38046
Average Gain
Low Band VHF 2-6: ...................... 2.8 dB
High Band VHF: 7-13..................... 5.8 dB
UHF Band: .................................... 5.6 dB
FM Band: 88-108 MHz................... -0.8 dB
Median Av. F/B Ratio
VHF Low Band: .................. 8.0
VHF High Band: ................. 9.0
UHF: ............................... 15.0
FM: ................................... 6.0
Average Half-Power Beam Width
Chan. 2 - 6: ................. 69 degrees
Chan. 7 - 13: ............... 49 degrees
UHF*: ......................... 54 degrees
FM: ............................. 72 degrees
* At Chan. 30 (566 MHz)

http://forum.tvfool.com/attachment.p...5&d=1459996934

I didn't know WOUL was that close! I think the tower in the distance is theirs. That means it's directly in line with all of the TV stations we want. I guess we are all supposed to support our poor starving (Time Warner) cable company.

I'll try the HLSJ and try to find a ground. The power lines are on the opposite corner of the house but there might be a copper water pipe. The FM stations would also explain why I can't use an amplifier at all. The Radio Shack amp even has an FM trap but that doesn't work. That same amp helped with rabbit ears.

Back to the antenna, a half wave dipole on CH 13 is 26 inches total, right? That's 13 inches per element, right? That would make this one a full wave at 13 if the elements are 26 inches each and 52 total, right?

Thanks for everyone's help. I'll update with progress.

If you don't find a good ground for the coax shield using a grounding block, the FM signals can get directly into the TV cabinet, bypassing the FM filter. The FM signals are so strong that even with a good ground you might need two HLSJs in series.

Folded Dipole

http://forum.tvfool.com/attachment.p...1&d=1486829832

The FM stations would overload a preamp, but you could put the filter(s) between the antenna and the input of the preamp. However, your strongest TV signal WKAS would also overload most preamps and the TV tuner after it.

It is possible to buy a custom filter (expensive) that would attenuate WKAS so that you could use a preamp for the very weak WCHS. Without that custom single channel bandstop filter for real channel 26 to make WKAS weaker, all you can do is use an antenna with more gain for WCHS.

So, you have three issues that are making TV reception difficult.
1. Very strong FM signal interference
2. A very strong TV signal WKAS, that limits your use of a preamp to help you with WCHS ABC.
3. The hill, that makes your desired signals weaker from that direction.

http://forum.tvfool.com/attachment.p...3&d=1459994634

Here is a close up of the WCHS coverage map for your area. Where there is red, the signal is weak. Where there is no color, it is even weaker, which is why WCHS has a NM of -11.1 dB. Any channel with a Noise Margin of less than -10 dB is difficult to receive. If you are able to receive them, you have an excellent antenna system, your tvfool report is wrong, or they have been enhanced by Tropospheric Propagation.

http://forum.tvfool.com/attachment.p...4&d=1459995010

WOWK also has to make it over the hill, but VHF signals can do it better than UHF signals.

The design of the VU75 is of a different type than you're referring to.

Before I forget, thanks for the photo; it helped a lot.

I think you have a good chance of getting WOWK with your antenna, if you use an FM filter and ground the coax.

Ant > coax > grounding block > coax > HLSJ or 2 > coax > TV

If that works, I have some ideas to try for WCHS; let me know.

Wow, thank you. That coverage map helps a lot. Where do I find that for other channels?

Would it be OK to ground the HLSJ and omit the grounding block to avoid another connection? I only ordered one HLSJ so I'll see how it does first. I don't think I'll find one locally. I do have a grounding block.

I found this diagramon my antenna. It seems to have more gain on higher VHF channels so that's good.

Guess I'll be waiting patiently by the mailbox.

It's a little involved. I'll take you through it for WOWK step-by-step:
http://www.rabbitears.info/
First Section, Web Listings
Type wowk in Find: Call Sign box and click Search which will take you here:
http://www.rabbitears.info/market.ph...&callsign=wowk
Digital TV Market Listing for WOWK
scroll down to WOWK
click on Technical Data and Screencaps in yellow band which will expand the yellow band
click on RabbitEars TV Query which will take you here:
http://www.rabbitears.info/tvq.php?r...ms&facid=23342
RabbitEars TV Query for WOWK
WOWK-TV - HUNTINGTON, WV, US - Main Listing
scroll down to Area: and click on Longley-Rice Coverage Map which will take you here:
http://www.rabbitears.info/contour.p...=2001528&map=Y
Coverage Maps
WOWK-TV (13-1) BLANK-0000003187
Look for Ashland; it is half way out from the center of the circle toward 9 o'clock
zoom in on Ashland
Ironton is NNW of Ashland
Your location is just SW of where 141 meets 52
You will see more signal color in your area because WOWK is stronger than WCHS but there is a dead zone around S 10th and Adams St near the Holiday Inn

http://forum.tvfool.com/attachment.p...6&d=1460052307

Keep in mind that field measurements are made for the contour circles, but the color patches are the result off the Longley-Rice computer simulation which gives an impression of greater accuracy than what actually exists. Your tuner will tell you the truth, especially with 2Edge signals.
It would work, but it doesn't meet NEC requirements, if you care about that.
Yes, the pattern shows more gain on VHF-High than on VHF-Low, which agrees with the specs.

I was thinking earlier that I wish I had a Spectrum Analyzer. Then I wondered if anything would show up on an oscilloscope. It did and this should not be happening. That's 10 cycles marked so it's really showing 107MHz. But look at the voltage. That is straight off the coax.

0.433Vpp = 0.153Vrms = 153mVrms :eek:

That is a lot of RF voltage coming from your antenna!

Or as Mr. Spock would say, "Fascinating!"

Thanks for making the test; good detective work. I also wish you had a spectrum analyzer, to confirm the frequency and check for other possible interference like cell phone transmitters from above TV CH 51.

That is waaaaay too much. It does look like it is coming from WLRX, but why not from WOUL-FM that is 15 dB stronger at +4dBm; they are both in about the same direction? Maybe it has something to do with the gain curve of your antenna. The specs say FM band gain -0.8 dB.

So, 153mVrms = -5.1 dBm in a 75 ohm system; about what you would expect after looking at your FM signal report:
http://www.fmfool.com/modeling/tmp/2...f/Radar-FM.png

You are getting the experience now. Maybe you can borrow a spectrum analyzer if you have ham friends. If you do borrow a SA, be careful not to blow out the front end with that hot signal. Look at the analyzer specs and use an attenuator if necessary.

from this original post:
http://www.digitalhome.ca/forum/186-...ml#post1307146

If K4ERO was able to operate a ham station at HCJB and receive signals, I think your chances of receiving at least WOWK are good with the right filters and a good ground.

There are some tests you can do with your 'scope now. Insert a HLSJ, high and common ports, in the coax and take more voltage readings. Try it with and without grounding the coax. You can also try inserting a UVSJ (not the MCM UVSJ), high and common ports, which will limit reception to UHF. You should get a reading from WKAS.

WKAS -27.5 dBm + ant gain 5 dB = -22.5 dBm = 0.02 Vrms across 75 ohms = 20mVrms = 56.6 mVpp if your 'scope reads that low at 545 MHz.

My primary TV is a newer CRT with an RCA DTA800B1lL digital converter. I have a Samsung LCD but it needs a board replaced. If I connect the antenna directly to the Samsung, I can receive WOWK and WCHS but with a weak signal. The WCHS signal is only good for a few degrees of antenna rotation but does correspond with WVAH as expected. Is it possible that the Samsung has filters to block the FM band or is the RCA tuner just junk? I'll find out when I get HLSJ. I wish there was a filter I could make just for some tests.

By the way, I am still puzzled as to why I have more problems from the 3100W WLRX than the 50,000W WOUL. I further confirmed the strength by using a C. Crane FM transmitter and my stereo. I can interfere with WOUL 89.1 from 3-4 feet away. The only way I can interfere with WLRX is by electrically touching the antennas. The only reason I can think of is that WLRX has a directional antenna pointed this way.

I received the HLSJ today. I am happy to report that the RCA converter finally detected WCHS. It doesn't receive it clearly but at least I can work on it now. I even got signals through the amplifier and it may be helping a little. I plan to order another HLSJ and try to optimize the signal. If I still have issues, what kind of antenna would be recommended? Not giving up yet.

Glad to hear the HLSJ makes a difference. Is that with the coax grounded?

What is the voltage measurement on the oscilloscope with the HLSJ?
An antenna with more UHF gain for WCHS.
That is the true spirit of an antenna experimenter.

Is WOWK better with the HLSJ? That's why you ordered it.

No, I didn't get to that yet

Not an exact measurement but 17mV P-P

Not picking it up at all right now. I'm going to try raising and lowering the antenna again as well as moving it around a few feet. The cold, wet weather probably isn't helping.

OK, the HLSJ is blocking channel 13. I don't understand. It's a Skywalker SKY26802. Mine passes DC on the Hi side but is otherwise the same. If anything, I would be afraid of it blocking UHF but it doesn't. Sound like it's defective?

If you are using the high and common ports and it blocks 13, they sent you the wrong thing or it is defective.

It doesn't need to be power passing if it is between the antenna and the input of a preamp if you use one.

I have never been impressed with that brand; why didn't you buy one that I suggested?

A good HLSJ doesn't block UHF coming in the high port.

http://forum.tvfool.com/attachment.p...0&d=1447018218

http://forum.tvfool.com/attachment.p...1&d=1447018564

I only had a few bucks in PayPal so I got the cheapest on Ebay. Who has the best shipping prices for a small item like this?

Do you happen to know what is inside an HLSJ? I found this thread on FM Traps. I'm just curious. I could probably make one, or at least the high-pass half. I'm trying an FM trap now.

What good is cheap shipping if you got the wrong thing?

What FM trap are you trying?

Not much at all, lol. I didn't realize you were recommending that particular brand. I do plan on getting a couple of them as soon as I can.

The one from MCM with the nice pictures and schematic in the thread. I didn't make a PCB. I just built it into a metal RF box from an old satellite receiver. I can't fine tune it without proper equipment but it works well enough to confirm that this HLSJ is not working properly. WOWK has a strong signal with some dropouts and WCHS has a weaker signal but about the same performance. I even pulled in WLPX, ION with the antenna aimed for WOWK. That's way down on the list. I was actually able to connect an amplifier without overloading it and it seems to help the RCA tuner a little.

Good test to confirm that your HLSJ is NOT doing what it should.

The original MCM FM filter is a good one, but is hard to find now.
http://www.amazon.com/In-Line-Trap-N.../dp/B00EIAFHLK

Radio Shack discontinued their FM trap and Antennas Direct is running low on stock, and will not be replaced. Even HLSJs are getting hard to find. All that will be left is DIY or custom built.
https://www.google.com/?gws_rd=ssl#q...ematic+diagram

The Radio Shack FM filter has poor attenuation at the 88 MHz end to protect TV channel 6, but good attenuation at the 108 MHz end. The AD filter is just the opposite. Neither one would be good for you because you have strong signals at both ends.

http://forum.tvfool.com/attachment.p...0&d=1441159109

Your test results sound like you are on the right track.

Rabbit73, I think I was editing when you sent that last post. I added a picture (wish I could show the picture or a thumbnail.
What I'm hoping to find out is I can raise the antenna higher now. I think maybe the FM interference was increasing with antenna height also and overloading the tuner.

Thanks everyone. I'll post updates when I find out.

I can display it for you; nice job, chris.

http://forum.tvfool.com/attachment.p...0&d=1460398508

This is what the MCM FM Trap looks like inside:

http://forum.tvfool.com/attachment.p...1&d=1460417400

diagram

http://forum.tvfool.com/attachment.p...2&d=1460417425

Inside is a low pass filter and a high pass filter, just as there is inside a UVSJ, but for different frequencies. The general term for these filters is a diplexer. All UVSJs are diplexers, but not all diplexers are UVSJs.

Here is a DIY 5-pole Diplexer, AKA UVSJ:

http://forum.tvfool.com/attachment.p...4&d=1460419288

DIY photos
http://www.is0grb.it/duplexer/

DIY 3-pole HLSJ; 5-pole would be better:

http://forum.tvfool.com/attachment.p...5&d=1460422427

source:
http://www.electro-tech-online.com/t...ircuit.122182/
post #12
http://www.electro-tech-online.com/t.../#post-1008775

Thanks for the information. I looked inside the HLSJ I got and the component values are more consistent with UHF/VHF splitter. I left the low side alone and put a 5 pole chebyshev on the high side. 160 MHz gave me convenient values.

Part Values
Part Chebyshev 0.1 DB
L1 0.048 uH
L2 0.048 uH
C1 10.19 pF
C2 5.92 pF
C3 10.19 pF

http://forum.tvfool.com/attachment.p...0&d=1460598659
http://forum.tvfool.com/attachment.p...1&d=1460601448

I'm not sure where to go from here. I can buy 2 HLSJ's to replace my homemade FM trap and modified HLSJ but I don't think it will matter . What works best is to have a filter, amplifier, and then a second filter. The amp is a RS 15-1108 that is supposed to have an outdoor amp, which I don't have. I'm still thinking of buying a better outdoor matching transformer. I can get all the channels I want on the RCA converter box but not without moving the antenna a few degrees. The strange part is that the direction doesn't correspond with the report. I'm going to use virtual channel numbers for a minute. If I have the antenna pointed at 3,13, and 29, I have to turn it counter clockwise to get 8 and 11. They should be clockwise. Channels 3 and 30 actually have 2 strong points. Raising the antenna higher decreases the weak signals. This still doesn't make sense unless the roof is acting as a reflector.

So, what is an easy way to rotate an antenna without digging it into the ground while rotating? Put it in a bigger pipe? I can reach it through an open window. If I added a second antenna, can I just use a splitter in reverse or do I need to separate the frequencies?

Please limit the width of your photos to about 800 pixels. I have a hard time reading your posts when they are so wide.Don't make any more tests until you ground the coax with a grounding block; you are wasting your time and money.
You are wasting your time with that, too. The outdoor part is the preamp; the indoor part is only an attenuator and power supply. Even if you had both parts, it wouldn't be the right amp for you. If you must use an amp, it should be one that is resistant to overload.
That means that you are on the edge of the "Digital Cliff: with barely enough signal for the weak ones because of the overload from the strong ones that raises the noise floor from spurious signals created by IMD.
I think that is because of the FM interference and WKAS. There is less overload when you turn away from them.
It could be a reflection off the roof or it could be it is making the FM signals and WKAS stronger.
Use the "Armstrong Rotator." Clamp a ViceGrip wrench to the mast and rotate it by hand. Setting the base of the mast on something hard and holding it in place with a wall bracket or U bolt would help.
No, you already have enough complications; don't add another one.

Thanks. I looked for a ground and didn't find anything close. The fence post wouldn't be very good so I guess I'll have to get a ground rod. On the bright side, I found some additional mast so I could easily go to 30 feet. I would be worried at anything higher because guy wires are not possible here.

One time I did a test setup with the antenna and preamp connected to a 4-way splitter and then to two converter boxes, two 8-inch monitors, a Sony 22-inch LCD TV, and signal level meter. This was a temporary setup to compare the sensitivity of the tuners using a step attenuator to bring the signals to the digital cliff. The antenna coax was not grounded.

When I touched the coax and the metal strip on the edge of the counter I felt a mild shock. I investigated further and found that what I felt was the sum of the leakage currents from all of those AC operated devices. The leakage current measured about 200 uA; not a dangerous amount but enough to be felt.

I connected a wire only to the grounding pin of a 3-wire plug (no connection to the other pins), connected the other end of the wire to the splitter case, and inserted the plug into a properly wired 3-wire outlet. This connected the coax shield to the house electrical system ground. The leakage current then measured zero.

So, I'm very particular about grounding the coax shield to the house electrical system ground with a grounding block for personal electrical safety AND to reject interference.

Case history:
http://www.digitalhome.ca/forum/81-o...ml#post1457594
http://www.digitalhome.ca/forum/81-o...ml#post1457668

I don't disagree with you on grounding, as I have a background in electronics and measurement. I just haven't found one yet. As a matter of fact, I found more problems. I did some checking with my multimeter and there is 60 VAC between my PC case and the LCD TV. Both are plugged in to different 3 prong outlets. There is no ground wire on either outlet. This is a very old house.

I'm hoping I will find a cold water pipe just inside the basement by the antenna. Hopefully, that's how the electric service is grounded. I'll ground the coax and mast and then see about the rest.

Me, too. Measurements are one of my favorite things to do, as you can see from the signature for my posts.
Maybe you have leakage current. You probably don't have a Simpson 229 Leakage Current Tester, but you can build a simple circuit to make tests.
http://www.repairfaq.org/sam/safety.htm#saftes

Manual
http://www.simpsonelectric.com/image...9-2_manual.pdf
You have two 3 prong outlets, and neither one has the socket for the grounding pin of a 3-wire plug connected to ground?:eek:

Please make some leakage current tests soon.

http://www.mdsr.ecri.org/summary/det...px?doc_id=8285

I just realized that I can't find the answer to one of the questions I had early on. WVAH and WCHS appear to be on the same tower. They have the same ERP. Why does WCHS only have half of the signal strength?

Good question. I don't know why; the specs look the same.
http://www.rabbitears.info/tvq.php?r...tems&facid=417
http://www.rabbitears.info/tvq.php?r...ms&facid=71280

The only difference I can see is the frequency of the transmitted signal.

The TV Fool report is consistent with my actual reception, too. I wonder if one antenna is higher on the tower or if the different frequencies propagate differently.

Well, I'm about to give up. I have moved this antenna up, down and even back a few feet. That is about 15 ft. in the picture but I have tried as high as 25 ft. It works better when the antenna is lower than the flue pipe. Some things just don't make sense. When cars go by, the signal changes. WCHS gets lost by lowering it. WOWK and WVAH get lost by raising it. WOWK has a decent signal when it breaks up or cuts out. I'm thinking multipath? Is there anything in the picture that screams "fix me"? If not, what antenna do I need that is reasonably priced?
http://forum.tvfool.com/attachment.p...9&d=1461469415

By the way, I have looked this antenna over a few times and I'm still curious how it works. It looks like an LPDA but I'm not sure. I do know that each of the 3 sets of VHF elements is resonant at 2 frequencies. The first set is a full wave on channel 13 but 1/2 wave around 105 MHz. The third set is 1/2 wave at Channel 2 but a full wave at 108 MHz. It would probably be better for me to have an antenna that is made for UHF and High VHF that is not designed for VHF low at all. There would be less to filter out.

Yes! You need lot more metal in the air and more height to reliably receive the stations shown on the signal report in your first post on this thread. If you are aiming for the stations in the arc from 99 to 108 degrees magnetic, then you need a fair amount of gain for real channel 13 (VHF-Hi) and very high gain for the others (UHF). Even then you may encounter problems with the stations showing negative NM in your report. Some of the others on the board can make better suggestions than me, but if I were in your shoes I would probably try an 8 or 12 element VHF-Hi antenna and a long yagi or 8-bay bowtie for UHF.
Here are a few links to check out:
http://www.mcmelectronics.com/produc...-2475-/30-2475
http://www.mcmelectronics.com/produc...-2476-/30-2476
http://www.mcmelectronics.com/produc...-2370-/30-2370
http://www.mcmelectronics.com/produc...-2430-/30-2430
There are not many choices out there for VHF-Hi antennas, but there are other brands of the UHF antennas you could check out that may have better build quality. You could also look at a combination VHF-Hi/UHF antenna but I think you would be best served with the highest possible gain on UHF that you can get.

That's normal; you are getting a reflection from the car. It's called dynamic multipath.
Yes, you are geting reflections off metal objects like the gutter, awning, and fence that can interfere with or enhance the direct signals. It's called static multipath.
There is no sense in trying another antenna yet until you have done the things needed with this antenna like grounding, filters, and another antenna location.

What is your present connection system?

Ant > grounding block > HLSJ > tuner ? You should get WOWK with that.

Once you have that you can try some experiments with an antenna with more gain, another filter, and a preamp for WCHS.

Ant > UVSJ > NF-471 > preamp > grounding block > power inserter > tuner

The antenna would be a UHF antenna with more gain like the 91XG

The UVSJ blocks FM and VHF-High but passes UHF

The NF-471 Notch Filter blocks UHF channels 24-29 to make 26 much weaker to keep the preamp from being overloaded by 26