TV Fool

TV Fool (http://forum.tvfool.com/index.php)
-   Help With Reception (http://forum.tvfool.com/forumdisplay.php?f=7)
-   -   Channel moved to VHF low (http://forum.tvfool.com/showthread.php?t=16652)

custom1 8-Aug-2019 2:40 PM

Channel moved to VHF low
 
My local PBS station WQED moved to VHF low 4. I have an RCA antenna ANT3037x in the attic. When WQED changed Freq I lost them all together. Yes I did the rescan. I went in the attic to try some adjusting of the antenna and found the box it came in and realized I never added the VHF low kit as I never needed it before. So I added the extensions. Now I can get the tvs to recognize the channel but it is all pixelated. I am also running an RCA amp #2R43GM on the case. And a powered splitter Channel Master #CM-3414. I Don't want to move the antenna outside if I don't have to. I am in Mammoth Pa and the station is in Pittsburgh.

So my question is, is there an antenna that would be better at picking up the VHF low band. Or an amp that is better suited for VHF low. Also when I do the signal report I don't see WQED listed.

http://www.tvfool.com/?option=com_wr...90382cb76312f5

GroundUrMast 8-Aug-2019 6:19 PM

There are a number of large all channel antennas still available. Winegard, Channel Master and RCA being at the top of my list. Be careful to compare the available space vs. the antenna dimensions.

The following models all have more VHF elements than your current antenna;
HD8200U (168.25" boom)
Advantage 60 (113" boom)
Advantage 100 (152" boom)
ANT3038E (150" boom)

I respect your preference to avoid outdoor mounting but reception of low-VHF, especially on the lowest channels is affected by significantly more interference than the UHF band. Often the sources of interference are right there inside your home, including the various electronics embedded in daily life. An antenna in the attic is partially blocked by the roof system and it's closer to the sources of interference.

I would suggest experimenting with outdoor reception at 5 to 10 feet above the roof peak.

GroundUrMast 8-Aug-2019 6:24 PM

I am an unpaid volunteer here at TVFool. I honestly don't know any details re. the size of their staff and have to assume they simply have limited resources for keeping the database 100% current.

I've taken the liberty to run a search at rabbitears.info based on an approximation of your location:

https://www.rabbitears.info/searchma...&study_id=3450

The terrain profile produced suggests you have a 2-edge path from WQED to you. https://www.rabbitears.info/search_t...0&scrnhgt=1032 That further complicates reception reliability... Added mounting height being the obvious recommendation.

custom1 9-Aug-2019 2:10 PM

Thanks for the info. Are there any links to specs on these and my current antenna? If I could find info on gain in the VHF low band for each it would help me pick another antenna to try. I am really trying to stay in the attic.

Also not sure what 2-edge actually means. Probably line of site...topography?

GroundUrMast 9-Aug-2019 3:33 PM

Winegard and Channel Master post useful information on their public websites:
http://www.winegarddirect.com/viewit...HD8200U)&post=
https://www.channelmaster.com/Digita..._p/cm-2018.htm

RCA does not choose to share much specifications. http://forum.tvfool.com/showthread.php?t=16650 That leaves one to estimate based on similar designs from other brands which do publish useful data.

You're correct, 2-edge is a term that describes the number of terrain obstructions a signal path has. LOS (line of sight) is ideal, 1-edge means the signal has to refract (bend) over one piece of terrain in order to have a path to the receiving location. Beyond 2-edge the term tropospheric is used because the majority of any signal at the receiving location likely is the result of reflection off of the upper atmosphere's tropospheric layer. Of course, a line of sight path is much preferred for reliable reception... Tropo is quite variable and therefor the least ideal signal path.

custom1 9-Aug-2019 6:13 PM

Doing a little more research I found that channel 4 is at 69MHZ. Dabbling in antenna theory, if I was to modify an element or two on my current antenna what would be the ideal length they should be for that frequency? Or is there more to it than that? A full wavelength is 14.25 feet. These other antennas state db gain compared to a dipole. Is each company using the same length dipole for the testing?

GroundUrMast 9-Aug-2019 6:48 PM

There are many dipole antenna calculators available on the web... Ex. http://www.westmountainradio.com/ant...p?frequency=69

I also found this calculator that designs multi-element Yagi style antennas.: https://www.changpuak.ch/electronics...enna_DL6WU.php

Here is the output for a 5 element antenna cut for 69 MHz;

Code:

https://www.changpuak.ch/electronics/yagi_uda_antenna.php
Javascript Version 12.01.2014, based on Rothammel / DL6WU
-------------------------------------------------------------
Frequency    :  69  MHz
Wavelength    :  4348  mm
Rod Diameter  :  16  mm
Boom Diameter :  25  mm
Boom Length  :  3119  mm
d/lambda      :  0.004    ( min.: 0.002 , max.: 0.01 )
D/lambda      :  0.010    ( min.: 0.01 , max.: 0.05 )
Elements      :  5
Gain          :  7.99 dBd (approx.)
-------------------------------------------------------------
Reflector Length  : 2110 mm
Reflector Position :  0 mm
-------------------------------------------------------------
Dipole Position    : 1043 mm
-------------------------------------------------------------
Director #1 Position : 1370 mm ,  Length : 1991 mm
Distance Dipole - Dir. #1 : 326 mm
-------------------------------------------------------------
Director #2 Position : 2152 mm ,  Length : 1972 mm
Distance Dir. #1 - Dir. #2 : 783 mm
-------------------------------------------------------------
Director #3 Position : 3087 mm ,  Length : 1955 mm
Distance Dir. #2 - Dir. #3 : 935 mm
-------------------------------------------------------------
Directors / Parasitics are not isolated.
The length has been increased to compensate for that.

Given that the boom length is more than 10 feet, I ran another calculation looking for a frequency that allowed for use of a boom not longer than 10 feet. Here's what I came up with;

Code:

https://www.changpuak.ch/electronics/yagi_uda_antenna.php
Javascript Version 12.01.2014, based on Rothammel / DL6WU
-------------------------------------------------------------
Frequency    :  70.6  MHz
Wavelength    :  4249  mm
Rod Diameter  :  16  mm
Boom Diameter :  25  mm
Boom Length  :  3049  mm
d/lambda      :  0.004    ( min.: 0.002 , max.: 0.01 )
D/lambda      :  0.010    ( min.: 0.01 , max.: 0.05 )
Elements      :  5
Gain          :  7.99 dBd (approx.)
-------------------------------------------------------------
Reflector Length  : 2062 mm
Reflector Position :  0 mm
-------------------------------------------------------------
Dipole Position    : 1020 mm
-------------------------------------------------------------
Director #1 Position : 1339 mm ,  Length : 1946 mm
Distance Dipole - Dir. #1 : 319 mm
-------------------------------------------------------------
Director #2 Position : 2103 mm ,  Length : 1928 mm
Distance Dir. #1 - Dir. #2 : 765 mm
-------------------------------------------------------------
Director #3 Position : 3017 mm ,  Length : 1911 mm
Distance Dir. #2 - Dir. #3 : 914 mm
-------------------------------------------------------------
Directors / Parasitics are not isolated.
The length has been increased to compensate for that.

...pretty close to the center frequency of real channel 4.

custom1 10-Aug-2019 2:41 PM

Wow lots of things to study. And everything in mm...Yea. I am an old American with a carpenters rule. LOL I will have to convert to English measure. I wasn't going to build a whole antenna just modify or add a few elements to the correct length and see if I get lucky. Lots of good info there to get ideas from tho. I have another old antenna to cannibalize parts from. Thanks

GroundUrMast 10-Aug-2019 3:11 PM

As far as metric/imperial conversion is concerned, I rely on the fact that exactly 25.4 mm = 1 inch... And there are plenty of online conversion calculators.

I expect that for the near future at least, one will need to build their own if they need a moderate to high performance Low-VHF antenna. I can hope that one or more manufacturers will see a market develop due to the repack but I'm not holding my breath.

rabbit73 10-Aug-2019 7:02 PM

3 Attachment(s)
GroundUrMast gave you a link above that shows the terrain profile for the WQED signal. This is another profile using different software:

https://forum.tvfool.com/attachment....9&d=1565483696

The Longley-Rice coverage map for WQED on channel 4 looks like it might put you in the yellow, which is encouraging:

https://forum.tvfool.com/attachment....7&d=1565463672

This is the link to the full coverage map;
https://www.rabbitears.info/contour....5&site=1&map=Y

Quote:

Originally Posted by custom1 (Post 61993)
I am also running an RCA amp #2R43GM on the case......Or an amp that is better suited for VHF low.

That's not a model number for your RCA amp, it's a production code number.
Quote:

So my question is, is there an antenna that would be better at picking up the VHF low band.
A Yagi antenna made with aluminum tubing in your attic would be best if you can't go outside. Second best made with wire might work, but you still have the potential problem of electrical interference on VHF-Low as GroundUrMast mentioned. The indoor noise level for channel 3 at my location is very high. A signal must be at least 15 dB stronger than the noise to be received.

https://i.imgur.com/aAU1EBY.png

This is a 3 element channel 4 wire Yagi for the attic. If it doesn't have enough gain, you will have to build one with more directors using aluminum tubing.

https://forum.tvfool.com/attachment....8&d=1565479964

If a bigger channel 4 Yagi doesn't work, hunt for sources of electrical noise interference using a battery operated portable radio tuned to a clear channel in the AM broadcast band. My experiments with indoor antennas show that an antenna with more gain doesn't always help because it makes the signal AND the noise stronger. This is the portable radio I use to hunt for noise sources:

https://i.imgur.com/tcbmnmI.jpg

FCC interference advice
https://www.fcc.gov/consumers/guides...ephone-signals
Quote:

A simple method of determining the location of electrical interference is by using a portable AM radio tuned to a quiet frequency at the lower end of the dial. You should hear static or a buzzing sound as you get close to the source of the interference. The closer you get, the more intense the static will be.

custom1 11-Aug-2019 1:51 PM

All great info guys. I had no idea the noise would be that big of a deal. I wish the station would have thought more about it when they bid on the new frequency. I had no problem receiving their station for the last 15 years at this location. The only change was their frequency. As far as I know their tower and antenna height stayed the same and I din't change anything on my end. I think they are even running a bit higher power now. As I get time this week I will do some experimenting. May try the outside now that I know more about the noise. An added benefit of moving outside is we may pickup a couple more channels that we have received hit and miss in the past. 61 and 69 with some programming that we liked. I just don't like look of the antenna on the roof and the maintenance out there.

JoeAZ 11-Aug-2019 9:53 PM

Quote:

Originally Posted by custom1 (Post 62023)
All great info guys. I had no idea the noise would be that big of a deal. I wish the station would have thought more about it when they bid on the new frequency. I had no problem receiving their station for the last 15 years at this location. The only change was their frequency. As far as I know their tower and antenna height stayed the same and I din't change anything on my end. I think they are even running a bit higher power now. As I get time this week I will do some experimenting. May try the outside now that I know more about the noise. An added benefit of moving outside is we may pickup a couple more channels that we have received hit and miss in the past. 61 and 69 with some programming that we liked. I just don't like look of the antenna on the roof and the maintenance out there.

WQED did not "bid" on the new frequency. They were assigned that frequency and as such received a windfall of cash to accept low band VHF. They could have chosen to remain on UHF as in the past but apparently wanted or needed the money.......

Tim 11-Aug-2019 9:59 PM

Here is some insight about stations moving to VHF
https://current.org/2017/04/prompted...nd-advantages/

ADTech 12-Aug-2019 2:06 AM

Quote:

WQED did not "bid" on the new frequency.
Well, yeah, sort of, they did.

They threw their hat in the ring and volunteered to got to low-VHF if the price was right in the reverse auction. They didn't know which specific channel they'd end up on, but they intentionally CHOSE to go to low-VHF in return for cash. $9.85 million (plus relocation expenses) to go from high-VHF to low-VHF.

There are a total of 17 stations that participated in the reverse auction in the whole country who moved to low-VHF. WQED has the distinction of being the only of those stations that moved from high-VHF to low-VHF.

custom1 12-Aug-2019 11:46 AM

I didn't know any details about the move. Just heard the word auction and assumed there would be bidding. Either way they decided to move and either didn't know they were going to lose coverage or didn't care.

Tim, That's an interesting article. I was told they were running more power than the old frequency. That is not true. In fact it reads like they might be asking to be able to up their power. ( the article is from 2017 tho) I hope I don't go to the trouble of moving/ modifying my antenna and then they go and up the power later. I could just wait and not have to do anything. I have tried to communicate with them via e-mail and their online form for people having problems receiving them now and I get no real response. I also called. They could have at least given me the details that are in that article. If I knew what they are planning to try it would help me decide what to do on my end. They say in the article that 90 percent of their viewers are cable subscribers. They should realize that number is dropping every day. More people are going to antennas and they are going to lose viewers.

Tower Guy 12-Aug-2019 3:32 PM

Another way to increase the signal on low band VHF is to raise the antenna. This also places the antenna further from interference from inside the house.

Low band VHF seldom needs a preamp, so be careful with using a preamp and a powered splitter. Two amplifiers can easily cause interference due to overload.

Tim 12-Aug-2019 6:20 PM

Quote:

Originally Posted by custom1 (Post 62039)
I have tried to communicate with them via e-mail and their online form for people having problems receiving them now and I get no real response. I also called. They could have at least given me the details that are in that article.

Don't know who you have called there, but have you asked to speak to the chief engineer? That will be your best source for reliable information.


All times are GMT. The time now is 7:58 PM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright © TV Fool, LLC