Now you see it, now you don't

Squire Dustin · 06-22-2009, 09:03 AM

I thought I was all set for the transition. I live in central Mass in zip 01473. I have a 6' boom UHF Yagi in the attic on a rotor, amplifier and a 4-way distribution amplifier, 2 converter boxes feeding analog TV's and a Samsung tuner feeding an HDTV monitor. All wiring is RG6 coax. When the transition occurred, this rig received 21 channels from Boston, Providence, Manchester most with signal strengths of 50 to 70%. After a couple of days, I started to experience signal drops on most of the channels, some to complete zero. At the worst, only a couple of channels are usable, 44 (WGBX Boston) and 50 (WZMY Nashua). After a few hours, the signals all come back, This effect is identical on both converter boxes and the tuner.

I have checked the cables for continuity, replaced the amps one at a time and even ran a direct connection from the antenna to one of the converters with no amps in the line.

I looks like it might be some sort of multi-path or intermittent interference problem, but I am out of my field when it comes to RF propagation.

I can't think of anything else to try, so suggestions would be appreciated.

Piggie · 06-22-2009, 12:37 PM

Dustin, if I may call you that, to TV Fool put in the height of your antenna and address. And I will take a look.

I know there have been a LOT of stations in your area that have changed things like channel, some moving to VHF which could be a great deal of your problem.

Trip knows a lot about who is doing what in that area, and he probably will read this.

But there is proabably a great chance you will need to add a VHF or replace your antenna with a combo VHF/UHF.

A LOT of people that were digitally ready until one or more of their locals moved to VHF. I call this the "Hidden Transition" because it was digital to digital and not mandated by the FCC to inform the public. But why wouldn't a station want to inform viewer because few of them bothered. Part of the snafu we call the digital transition.

If it makes you feel any better you can watch the movie I made about it.
http://www.dtvusaforum.com/everythin...html#post18763

DTVuser2009 · 06-22-2009, 01:01 PM

The only VHF one i have currently is WEHT ABC 25.1, and RTV 25.2. those won't come in at all during the day (0% flat dead) but after dark, it's upwards of 73-80%. somehow it must have something to do with that Tropo ducting as i usually get two or three 'new' ones that are gone the next day. they're different; the same 'new' channels are never exact, they could be from Illinois, or Tennessee, or east of my location. it's never exact. but when it happens i lose or gain some of my normal ones too. odd.

Don_M · 06-22-2009, 01:22 PM

Looked at a ZIP code-based report to get a general idea of the situation. This is hill country we're talking about, so a location-specific report, either by street address or coordinates, is especially crucial for your situation. In the meantime, here are some very general ideas:

VHF stations are 7, Boston; 9 Manchester, NH; 10, Norwell, MA; 11, Manchester; and 13, Providence RI. Manchester (9) is the nearest at 35 miles, and most others are between 50-60 miles. This is fringe reception, where a UHF Yagi simply won't cut it for channels 7-13. The best add-on VHF-high antenna you can get at reasonable cost would be the Winegard YA-1713. If a single, all-channel replacement is more to your liking, you're a good candidate for the Winegard HD-7698P.

What make and model pre-amp are you using, Dustin? The two strong stations nearby -- WUNI 27.1 (RF 29, noise factor 58.2 dB) and WUTF 66.1 (RF 27, NF 52.8 dB) -- are just strong enough that, together, they would probably overload most full-power pre-amps. Too much signal is just as bad as not having enough. When you pulled out all the pre-amps, you experienced the "not enough" part.

For a similar reason, the distribution amp is, to be honest, overkill. Few homeowners need more than one or the other, and you're definitely in pre-amp country. Have you tried the system by replacing the distribution amp with a splitter, and just running the pre-amp? (I know you said you had "replaced the amps one at a time," but that might mean something else.)

Trip · 06-22-2009, 01:37 PM

At what time of day do your signal drops occur?

- Trip

Piggie · 06-22-2009, 02:34 PM

wow has it been a busy day here, thanks to those helping answering things.

staticMHZ · 06-22-2009, 03:16 PM

I live in the same market as you dustin, WHDH has temporarily turned on it's old UHF channel 42 DT transmitter for the time being while they work out the bugs on the VHF side. So if you can't get 7 to come in, try channel 42.

Squire Dustin · 06-27-2009, 03:09 PM

Thanks to everyone who responded for the useful information.

I probably tried to simplify the situation in my original post, and led some down the wrong path.

I know that after the transition, some of the stations which were on UHF migrated to the upper VHF band. In this area channels 7, 9, and 11 are the ones I am aware of. Since I was on the fringe area for analog TV, there was a VHF antenna in my attic (not on the rotor) which I left pointed to Boston and fed into the distribution system through a combiner. Channel 7's signal is solid, 9 and 11 are marginal since they are in Manchester, NH and the antenna is pointed at Boston.

Yes, I am in a hilly area but fortunately I am on the top of a hill. I can see Boston buildings from my roof.

Thanks for those who mentioned tvfool. That has been the best source of information that I have seen on the internet on available channels, direction and expected signal.

When I was trying to characterize the signal loss problem, I tried every configuration including directly from the UHF antenna to one of my converter boxes with no splitters, combiners or amps at all. I did lose some of the weaker channels with this configuration, but basically I had the same work-for-a-while, die-for-a-while operation that I described in my original post.

As to correlation with a time of day, there was not an exact one. Signals would be good from a few hours to a couple of days and then go out for a few hours to a couple of days. The majority of the time they seemed to die around 9-10pm and come back in mid morning.

As Murphy's law would have it, everything has been working fine for the last week. Weaker channels come in sometimes and sometimes don't as is to be expected, but the stronger ones are always there.

Possible causes that I have thought of include:

1) Multipath effects with sometimes re-enforcing, sometimes canceling,
2) A strong interfering signal on a close frequency causing saturation of the pre-amps.
3) Some signal fiddling by the stations while kinks were being worked out of the system.

If anyone has any suggestions of other things to try if another major signal dropout occurs, let me know.

Thanks again to all who responded.