Another 'Wonderful' Evening in DTVland - NOT!

[landtuna]

It's 8PM in Phoenix and we're having wind. 25 MPH with occasional gusts to 35. No dust, fog, rain, low hanging clouds or other RF-debilitating obstructions.

I'm trying to watch C(BS) 5 (RF in the UHF range) and audio is getting pasted constantly with occasional video drop-outs as well. Goes from slightly watchable to not watchable.

I wasn't aware plain old wind was an enemy of DTV in addition to all the others.

Wonderful! Just fookin' wonderful!

 

[pabsungenis]

Make sure your antenna is properly mounted. The wind might be blowing it out of alignment.

 

[kenglish]

Can't you just get Mexican channels in analog for a few more years?

Seriously, though, I wonder what is REALLY affecting the signals:

Could it be vibration of the antenna, affecting the connections between the elements? (How old is the antenna?)
Could it be static discharges, which might be minimized by better grounding?
Are trees blowing in and out of the path of the antenna signal? (Or, affecting the bounced multi-path signals?)
Are winds affecting power lines nearby, causing some intermittent arcing or noise?

Lots of stuff for us all (viewers, FCC, engineers, antenna technicians) to think about.

 

[dhett]

Can't you just get Mexican channels in analog for a few more years?

Seriously, though, I wonder what is REALLY affecting the signals:

Could it be vibration of the antenna, affecting the connections between the elements? (How old is the antenna?)
Could it be static discharges, which might be minimized by better grounding?
Are trees blowing in and out of the path of the antenna signal? (Or, affecting the bounced multi-path signals?)
Are winds affecting power lines nearby, causing some intermittent arcing or noise?

Lots of stuff for us all (viewers, FCC, engineers, antenna technicians) to think about.

I live a few miles from landtuna and was experiencing problems as well. I have indoor antennas only. My problems were also on KAET and KPNX, both RF VHF stations, as well as KPHO, an RF UHF station. The problems were severe - complete loss of signal for both KPHO and KPNX - but they were for a short duration, no more than 5 minutes. Otherwise, it was just occasional pixelation.

 

[firepoint525]

Advice, and a question.

First, the advice: don't use your microwave oven while watching DTV. It will cause the signal to freeze up and pixilate, on channels that don't normally do that. I'm not sure why that is. But once the microwave stops, the TV signal returns to normal. Not sure why that is. If you don't mind the momentary interruption of your DTV signal, go ahead and use your microwave. But if you are using your microwave while you are experiencing disruptions, that may be the reason why.

Now the question: why can't I get channel 58 on my DTV? I actually could get them before the DTV transition in June, but I can't now. Also, my reception on channel 30 remains marginal. Not sure why for either of those. There were also a number of other minor UHF channels that I could receive on DTV prior to the changeover, like preaching channels, etc., but I can't even receive those now. My scanner only stops on the major stations now. I can get some VHF channels now, better than I could right before June 12, but I was never sure why that was, either. They had a DTV presence prior to June 12th, but their signal is better now. (Fortunately, the channels that I cannot receive, or receive very well, (channels 30 and 58) are channels that I likely would not watch very much anyway.)

 

[willcail]

I can use my microwave and watch DTV just fine. I have zero reception issues when it comes to DTV. It comes down to one simple thing if you don't want to invest in a new antenna, coaxial cable and an amplifier then you shouldn't complain. If you think sticking a wire coat hanger to the RF port of a DTV to get perfect reception then you are wrong. I have a simple RCA amplified indoor antenna and getting perfect DTV reception. I'm glad that analog TV is dead. I can sum up Analog poor reception, poor audio. WDEM CD comes in clearer at 1.05 KW ERP than WCLL CA and W23BZ both low power analog stations that have a higher ERP. If you don' want to fix your DTV issues then don't complain. If your local DT stations broadcasting on the VHF band then you need to contact them to see if they are willing to put in applications to move their digital signals to the UHF band. Quit complaining do something about it.

 

[firepoint525]

Not sure who that was aimed at, but I'll respond. I have an outdoor antenna. And the microwave thing is only temporary, and something I can control, so I don't worry about it.

Why would I want my VHFs to move to UHF? The VHF channels come in better than the UHFs! The only UHF that doesn't drop out is channel 17.

As for writing to my local TV stations requesting changes, I've done that, too. I wrote to one, asking them to make their (previously) cable-only channel available as a sub-channel of their regular channel, since they carried emergency weather information on that extra channel last spring, while their primary channel was in March madness. They wrote back saying they had plans to do so by the end of this year, but I'm pleased to report that they've already done that!

 

[landtuna]

Seriously, though, I wonder what is REALLY affecting the signals:

I'll try to explain my setup but agree with dhett's post above about the symtoms.

Could it be vibration of the antenna, affecting the connections between the elements? (How old is the antenna?)

No. Antenna is anchored firmly. The longer VHF elements cannot move more than a few millimeters at the ends and don't seem to vibrate at all. The antenna is in a sheltered area which is not affected by any but the strongest winds. Also, the problem last evening was worse on UHF (RF17) than VHF.

The antenna is about ten years old but until six months ago had lived its whole life in an attic. The connections between the elements are good and the plastic insulators are not cracked or otherwise damaged. Coax is new.

Could it be static discharges, which might be minimized by better grounding?

Not sure on this one as I never had any issues with the analog signal. I'll try a stronger ground and see if that improves the reception.

Are trees blowing in and out of the path of the antenna signal? (Or, affecting the bounced multi-path signals?)

There are two mature pine trees on the margins of line-of-sight to the towers but they don't move into the signal path. But while I was experiencing this signal drop-out I also check two other TV's which have inside antennas and they were having nearly identical issues. Since I've seen this condition before under similar circumstances I'm also thinking it might be the wind on top of the tower location instead of down here in the flatlands but it never was a problem with their analog signals (VHF or UHF) before. Just noticed it after the DTV transition.

Are winds affecting power lines nearby, causing some intermittent arcing or noise?

All utilities are underground here.

Lots of stuff for us all (viewers, FCC, engineers, antenna technicians) to think about.

One of my navy chief radioman told me once that antenna propagation was pure magic. I'm beginning to believe him.

 

[fybush]

A question I've asked landtuna before, and I don't recall getting an answer: is it possible your setup, which sounds like a textbook one, is giving your receivers too much RF?

Because that's another way DTV differs from analog - while the more RF you give an analog receiver just makes it stronger, too much RF into a DTV receiver can cause exactly the symptoms landtuna is describing. And a rooftop antenna just a few miles away from the mighty blast of RF coming off South Mountain is presenting a heck of a lot of RF to your receiver input.

I'm in an even worse situation here in Rochester: I'm 4300 feet away from the hilltop (barely a bump on the landscape compared to South Mt.) that has all our TVs, and when I aim my rooftop antenna directly at the towers, I lose the signal completely...

...unless...

...I do some attenuation on the signal before it hits my receiver. Channel Master and others - even Radio Shack, I think - sell simple in-line variable signal attenuators that are both cheap and very effective. I'd be very curious to see if one of those solves landtuna's woes.

For whatever it's worth, my most recent Phoenix DTV experience was in early April, in a second-floor hotel room in downtown Scottsdale. With an unamplified antenna (Terk HDTVi) in the middle of the room, I had rock-solid reception of all the full-power signals on South Mountain, and nearly flawless reception of the LPTV digitals. This was before some of those signals went back to VHF, so I realize that the landscape is somewhat different now from what I experienced in the spring.

 

[landtuna]

A question I've asked landtuna before, and I don't recall getting an answer: is it possible your setup, which sounds like a textbook one, is giving your receivers too much RF?

Hmmmm.....I thought I'd responded to that question before but maybe not.

In my opinion, I don't think the signal is overpowering the receiver. The symptoms I described last night occurred only during moderate winds. Normally the signals piped in from the big outside antenna are fine. I could see the beacons on the towers clearly during this time so no noticeable dust was in the air. Later, when it rained quite hard the signals were unaffected. Just happened during the wind.

I'm in an even worse situation here in Rochester:

I used to live in Greece, near Long Pond, back in the mid-70's. Rochester has more railroad tracks than I've ever seen anywhere. Perhaps they serve as a wave guide for you. <g>

...I do some attenuation on the signal before it hits my receiver. Channel Master and others - even Radio Shack, I think - sell simple in-line variable signal attenuators that are both cheap and very effective. I'd be very curious to see if one of those solves landtuna's woes.

I have an adjustable attenuator but it didn't seem to make a difference.

For whatever it's worth, my most recent Phoenix DTV experience was in early April, in a second-floor hotel room in downtown Scottsdale. With an unamplified antenna (Terk HDTVi) in the middle of the room, I had rock-solid reception of all the full-power signals on South Mountain, and nearly flawless reception of the LPTV digitals. This was before some of those signals went back to VHF, so I realize that the landscape is somewhat different now from what I experienced in the spring.

I am directly east of the towers and you would have been northeast in downtown Snottsdale but I wouldn't think that would make all that much difference. I do get most of the LPTV sigs OK here although I don't watch any of them on a regular basis so can't tell you if they are reliable over time. The three VHF signals have been prone to drop-outs since their return from UHF in June. RF-8 is the worst then 12 then 10. I had no reception issues at all with those three when they were UHF. The only FP UHF that I have problems with, and usually only just before sunset (when the sun is setting directly behind the towers) is 27. It will be interesting to see if that problem goes away during winter (when the sun is much further to the south).

 

[KeithE4]

A question I've asked landtuna before, and I don't recall getting an answer: is it possible your setup, which sounds like a textbook one, is giving your receivers too much RF?

Because that's another way DTV differs from analog - while the more RF you give an analog receiver just makes it stronger, too much RF into a DTV receiver can cause exactly the symptoms landtuna is describing. And a rooftop antenna just a few miles away from the mighty blast of RF coming off South Mountain is presenting a heck of a lot of RF to your receiver input.

Speaking of too much RF, could the dozen 100 kW FM stations be overloading your converter? The second harmonics of the FM stations are in the high-VHF TV band, specifically from 176 to 216 MHz. While the stations probably aren't generating harmonics directly from their transmitters, intermod products could be produced in the VHF-Hi band. If your converter has poor front-end selectivity (and I'm guessing my el-cheapo converter box does), this could happen in areas with strong FM signals.

 

[fybush]

Speaking of too much RF, could the dozen 100 kW FM stations be overloading your converter? The second harmonics of the FM stations are in the high-VHF TV band, specifically from 176 to 216 MHz. While the stations probably aren't generating harmonics directly from their transmitters, intermod products could be produced in the VHF-Hi band. If your converter has poor front-end selectivity (and I'm guessing my el-cheapo converter box does), this could happen in areas with strong FM signals.

This is an excellent suggestion...and surely worth a few bucks for a cheap FM trap ahead of the DTV tuner to see if it makes any difference.

 

[landtuna]

Speaking of too much RF, could the dozen 100 kW FM stations be overloading your converter? The second harmonics of the FM stations are in the high-VHF TV band, specifically from 176 to 216 MHz. While the stations probably aren't generating harmonics directly from their transmitters, intermod products could be produced in the VHF-Hi band. If your converter has poor front-end selectivity (and I'm guessing my el-cheapo converter box does), this could happen in areas with strong FM signals.

This is an excellent suggestion...and surely worth a few bucks for a cheap FM trap ahead of the DTV tuner to see if it makes any difference.

Good suggestions but I'm already running an FM trap on the antenna (it isn't used for FM but does have FM elements). Also, remember that the drop-out issue doesn't happen all the time so there is something intermittent apparently causing it.

 

[dhett]

A question I've asked landtuna before, and I don't recall getting an answer: is it possible your setup, which sounds like a textbook one, is giving your receivers too much RF?

Hmmmm.....I thought I'd responded to that question before but maybe not.

In my opinion, I don't think the signal is overpowering the receiver. The symptoms I described last night occurred only during moderate winds. Normally the signals piped in from the big outside antenna are fine. I could see the beacons on the towers clearly during this time so no noticeable dust was in the air. Later, when it rained quite hard the signals were unaffected. Just happened during the wind.

I'm in an even worse situation here in Rochester:

I used to live in Greece, near Long Pond, back in the mid-70's. Rochester has more railroad tracks than I've ever seen anywhere. Perhaps they serve as a wave guide for you. <g>

...I do some attenuation on the signal before it hits my receiver. Channel Master and others - even Radio Shack, I think - sell simple in-line variable signal attenuators that are both cheap and very effective. I'd be very curious to see if one of those solves landtuna's woes.

I have an adjustable attenuator but it didn't seem to make a difference.

For whatever it's worth, my most recent Phoenix DTV experience was in early April, in a second-floor hotel room in downtown Scottsdale. With an unamplified antenna (Terk HDTVi) in the middle of the room, I had rock-solid reception of all the full-power signals on South Mountain, and nearly flawless reception of the LPTV digitals. This was before some of those signals went back to VHF, so I realize that the landscape is somewhat different now from what I experienced in the spring.

I am directly east of the towers and you would have been northeast in downtown Snottsdale but I wouldn't think that would make all that much difference. I do get most of the LPTV sigs OK here although I don't watch any of them on a regular basis so can't tell you if they are reliable over time. The three VHF signals have been prone to drop-outs since their return from UHF in June. RF-8 is the worst then 12 then 10. I had no reception issues at all with those three when they were UHF. The only FP UHF that I have problems with, and usually only just before sunset (when the sun is setting directly behind the towers) is 27. It will be interesting to see if that problem goes away during winter (when the sun is much further to the south).

A need to attenuate the signal is plausible, but I'm going to agree with landtuna, since I experienced the same problems with a set of $10 indoor rabbit ears. I can't imagine those being overloaded, even though I'm closer to the antennas.

Maybe it just affects former Rochesterians.

BTW, 27 is LPTV, not FP. I think we'll just have to wait until they move to 36 to see whether its being caused by an adjacent-channel FP station.

Also, I solved my problems with 45 and most of the problems with 38 after moving my rabbit ears about 4' higher so they're now above the TV.

 

[kenglish]

Speaking of too much RF, could the dozen 100 kW FM stations be overloading your converter? The second harmonics of the FM stations are in the high-VHF TV band, specifically from 176 to 216 MHz. While the stations probably aren't generating harmonics directly from their transmitters, intermod products could be produced in the VHF-Hi band. If your converter has poor front-end selectivity (and I'm guessing my el-cheapo converter box does), this could happen in areas with strong FM signals.

This is an excellent suggestion...and surely worth a few bucks for a cheap FM trap ahead of the DTV tuner to see if it makes any difference.

Be sure that your FM Trap is one designed to attenuate the entire (88-108 MHz) FM Band, not just 95 MHz and up. Those are designed for communities that have a channel 6 to contend with, and they also assume that you won't have strong stations in the low end of the FM band, where the low-powered educational stations used to live exclusively.

Good suggestions but I'm already running an FM trap on the antenna (it isn't used for FM but does have FM elements). Also, remember that the drop-out issue doesn't happen all the time so there is something intermittent apparently causing it.

 

[vchimpanzee]

I've described this in detail on other threads, but I have a problem sim,ilar to the microwave problem.

If the tape gets stuck in a VCR, while it is being poulled out the signal pixillates.

I have experienced pixillation just from pushing the "rewind" button, although with the worst of my VCRs that I still use, I don't do that any more.