VIP722 Modulator Quirk(?)

[kenalpine]

I have a 722 whose modulator output feeds an RG-6 network throughout the house. Initial setup was rcvr 1 on channel 21 and rcvr 2 on channel 25. All looked fine except the ch 21 signal on a 7" LCD TV in the kitchen was snowy. I assumed it was due to using about 25 feet of microphone cable as a feed, so I finally replaced it with RG-6. No improvement (!). For the first time I tuned up to ch 25 when rcvr 2 was on and the picture was great. Hmm... So I reprogrammed the rcvr 1 modulator up to ch 40 and, shazam, the picture was great. I guess the moral is if you get inadequate signal quality from the modulator signal, go to a higher channel. BTW, there was no evidence of crosstalk from ch 25 onto the ch 21 signal, just a lousy signal. Wonder why?

 

[dishrich]

You might have a local OTA ch 21 that's overpowering the mod signal...

 

[kenalpine]

VIP722 Modulator Quirk

Nope. Nearest OTA is 28 which would pooch 25 more than 21 were it true. Also no OTA antennas feed the RG-6 net. BTW, a set of old rabbit ears nailed under the eaves gives clean digital signals from 65+ miles away on my Sony XBR! Digital is cool!

 

[Agonizing Fury]

Nope. Nearest OTA is 28 which would pooch 25 more than 21 were it true. Also no OTA antennas feed the RG-6 net. BTW, a set of old rabbit ears nailed under the eaves gives clean digital signals from 65+ miles away on my Sony XBR! Digital is cool!

If your location for sateliteguys is correct (Montrose CO), there is indeed a broadcast on channel 21. It is located 21.0 miles from the center of the city of Montrose. You can see what channel each station is using at TVfool.com Here is the info on that particular station.

Transmitter Profile Detail

K21JK-D (Digital)

Channel: 21
Network:
Maximum ERP: 13.000 kW
Coordinates: 38.315266 -108.196466

 

[Tyralak]

Exactly why I don't use 73 around here in most places. There's some PBS station that likes to bleed over into it. 60 Works great most of the time, and is far easier to rememebr to most customers. (73 sounds about as random as you can get to a new customer. Round numbers are easier for them to remember.)

 

[kenalpine]

Thanks for the reply re: ch 21. When I auto scan with several TV's with OTA antennas many signals pop up but not 21. Using the TVFool.com coordinates in Google Earth I see that the location is on the western slope far side of a 9,000 foot mesa so I take TVFool's definition of LOS with a grain of salt. I wonder if TVFool's algorithms incorporate intervening terrain? Anyway, it is good to learn that OTA signals may bleed in to even a 'closed' coax network.

 

[Fredinva]

Actually, the lower air channels (21, 22, 23, 24) put out a better modulated signal than the default of ch60.
as info, air 22 is almost the identical frequencty as cable 73.

fred

 

[Tyralak]

Actually, the lower air channels (21, 22, 23, 24) put out a better modulated signal than the default of ch60.
as info, air 22 is almost the identical frequencty as cable 73.

fred

60 is 116 air, but as I said, around here 73 (air 22) is too close to a another station and gets interference.

 

[dishrich]

Anyway, it is good to learn that OTA signals may bleed in to even a 'closed' coax network.

Absolutely - regardless if the OTA signals are analog OR digital, they can definitely cause problems, even on CATV systems. Many systems either DON'T use the same ch's as any nearby OTA transmitters, or use them for maybe "unimportant" channels, due to OTA ingress into those "closed" systems. (particularly on ch's 2-13) Your modulation system is no different...

In my case, I can NOT use CATV ch 94 as an in-house ch, due to having BOTH strong OTA UHF ch 42 & 44 DT signals getting into the system, so I just skipped it on my 9 ch modulated system.

 

[TheKrell]

I wonder if TVFool's algorithms incorporate intervening terrain?

Supposedly yes.

The signal strength from each of the broadcasts is analyzed for your location using 3D propagation modeling algorithms, and the results are summarized in the plot and table. Transmitter power, terrain obstructions, Earth curvature, and your antenna height (if specified) are already factored into the report.