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.
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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 Quote:
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It's just a matching transformer. I fixed the link to my report,
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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.
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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 Quote:
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. |
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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. |
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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 Quote:
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. |
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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. |
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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. |
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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. Quote:
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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.
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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 Quote:
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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.
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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? Quote:
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Is WOWK better with the HLSJ? That's why you ordered it. |
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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?
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