OTA tuner question

[gregftlaud]

i have the hd tivo and for the last few days a couple of my ota local hd channels 7-1 wsvn and 10-1 wplg have been acting funny on my ota tuners. tuner 1 picks up those channels at about 7 points higher than tuner 2. and since the signal strengths are in the upper 60's and 70's this can sometimes make a big difference with dropouts. on the other digital channels nbc, fox, wb, upn both tuners have almost exactly the same signal strength give or take 1 point.

7-1 and 10-1.... the channels the big difference are on...just also happen to be vhf also.

anyone else ever notice significant signal differences on ota channels between the two tuners?

what could cause this?

greg

[JimSpence]

Exactly what frequencies are being used? Your 7-1 and 10-1 may not be VHF at all.

[gregftlaud]

frequencies 8 and 9

also....could this be a problem with the diplexor that splits out the ota and satellite signal into my tivo even though some channels dont have a problem at all? i notice when i jiggle my diplexor around i lose the satellite feed on it and then the ota antenna signal meter goes haywire ...jiggle some more things come back but still those ota signal differences remain. all cables are screwed in tightly. tried a different cable going into antenna feed...still the same.

greg

[gregftlaud]

hmmm

[JimSpence]

I would check all cable connectors and try a different diplexer.

[gregftlaud]

ok guess i'll look for one at radio shack

[TyroneShoes]

i have the hd tivo and for the last few days a couple of my ota local hd channels 7-1 wsvn and 10-1 wplg have been acting funny on my ota tuners. tuner 1 picks up those channels at about 7 points higher than tuner 2. and since the signal strengths are in the upper 60's and 70's this can sometimes make a big difference with dropouts. on the other digital channels nbc, fox, wb, upn both tuners have almost exactly the same signal strength give or take 1 point.

...anyone else ever notice significant signal differences on ota channels between the two tuners?

what could cause this?

greg
If you have a reading in the 60's, you can expect a dropout every hour or so, maybe even more frequently. That is normal. If in the 80's or 90's, you will see far fewer dropouts, maybe once a day. But a reading of 100 does not mean you will never see an occasional dropout. That is simply the way digital reception degrades. Rather than a constant minor degradation which will cause a noisy picture in NTSC delivery, digital degrades abruptly and severely, but there is a large margin of error before there is any degradation at all, during which PQ remains perfect. Still, the higher the reading, the less frequent the disruptions.

It is well-documented that the Tivo ATSC tuner will show different readings on the two tuners if there is a less-than-optimal signal. Your Tivo has an active distribution amp that distributes each received 8VSB carrier to two separate tuners. While they are identical and the paths to them are very similar, due to the nature of how the signal metering works, which is to display a ratio of succesfully decoded bits vs. unsuccessfully decoded bits, the readings can vary somewhat, mostly due to VSWR issues (reflected signal is tolerated poorly in 8VSB reception, whether the reflection is from a skyscraper or within the internal wiring of the STB or the antenna system).

It sounds like you have marginal reception on the two channels that are giving you problems. Searching this forum is a good place to find answers about dealing with those kinds of problems.

[gregftlaud]

ok, but i've had this setup for 1.5 yrs and never have seen this situation where the two tuners are getting such a different signal. nothing in my setup has changed.

in addition. the signals on the 7-1 and 10-1 on the 1st tuner are both almost 70 but on the 2nd tuner drop to the upper 50's to very low 60's which is a huge difference maker. signal is locked when u get 70 but upper 50's to low 60's well u get frequent dropouts.

i just find it very funny that both these channels are vhf and ALL the uhf frequency channels come in at a solid 90 with the 1st and 2nd tuner only being different by a point or two.

i know in the avsforum others in my area seem to have a hard time pulling in these channels but i never have......and i'm wondering if this DOES have something to do with them being vhf. i have read elsewhere vhf is harder to pull in on the hd tivo....not sure about other receivers.

so before i go out and spend money what do u suggest i do??

i have switched out wires made sure connections are tight but nothing seems to help this signal fluctuation on channels 7-1 and 10-1 (frequencies 8 and 9). i know it's not my tivo otherwise all other channels/frequencies would have the same tuner differences. i'm pretty sure that's it isnt my wires considering like i said i have made no changes to the setup since june 2004 when i upgraded to hd.

questions/possible causes------yes or no----

1. power cables/power strips cause interference in ota signals?
2. wireless phone jacks cause interference in ota signals?
3. diplexer going bad??
4. just a fluke??
5. other??

thanks for ur help

greg

[gregftlaud]

bump

[TyroneShoes]

1. doubt it

2. doubt it

3. doubt it...usually when a diplexor goes bad the performance of the filter degrades, meaning that the highest OTA channels would be the ones with signals dropping down.

4. doubt it. The inconsistent readings are normal when you have less-than-optimal signal. It doesn't seem that it should be that way, but that's the way it is.

5. If there are strong FM's coming from the same location, which is common, an FM trap can help by preventing the tuner from being swamped (especially if you are using an antenna that spans VHF). 10 bucks at RatShack. Pick one up when you go there to get that variable attenuator. Take back what you don't end up using and get a refund.

Other than that, one way or another, you either have too low a signal, too high a signal, or too much interference. You're in the right place to get answers. Search is your friend.

[gregftlaud]

so go get an fm trap...along with the in line ampflier...ok

to answer your question in my other post...i'm only like 10 miles away from the transmitter "farm". i get a solid 90 on all the channels that are on uhf frequencies....but the one i am having problems with 7-1 wsvn is on vhf frequency.

all the transmitters are in exactly the same area no more than 1 mile apart and no more than 6 degrees difference on my compass....raning from 198 degrees to 204 degrees. in fact another channel on the same compass direction as 7-1 i pick up near 90 on my signal meter......a uhf frequency though. not sure if vhf / uhf is different in terms of locking a signal.

also, i'm using a vhf/uhf antenna dtv installed with my hd setup. it looks like a square wire mesh/fence looking thing with i think two long x shaped pieces of metal on the top and bottom.

greg