unstable lnb?

[truckracer]

Just wondering if you all think my lnb is destabilizing in cold weather?
Ku is still good across the entire arc. C band now that it's cold as crap here is down quite a bit with signal quality jumping up and down a lot.
FTA and 4 dtv is suffering. even w5 has some tp's down to 85% quality on the dsr 905. that bird is always pinned on 99% every channel.

I have another lnb but its less than 30 outside now i think.

 

[Anole]

few ideas:

Is there anything you could warm the C-lnb with to prove this theory?
- Electric socks?
- hair drier?
- one of those hot packs for sore muscles?

I had a chat with Turbosat last week about upgrading his lizard hotel (DirecWay lnb housing) with two tail light bulbs in series, to provide warmth for the residents.
For your LNB: twelve volts through two bulbs; warm orange glow; maybe some foam cups for insulation?

Ta hell with buying a new cold-stable LNB if warmin' yours makes ya happy. -

BUT, first check your cables, your coax connectors, and any switches.
Maybe you lost power to 'em??

 

[truckracer]

i put the norsat 8115 on and signals shot to the moon.
The cheap lnb was giving up @ 21 degrees F.
I do like the idea of a couple 12 volt bulbs on a 1 amp walwart idea. Cheap to make and easy to do. You could even go a hair further by going to your local hvac supply and buying a "freeze stat". A thermostat used for heat pumps to detect freezing temperatures that will turn on the good old electric resistance heater strips. You could wire that inline with one of your leads to turn on the bulbs in freezing weather.

 

[B.J.]

An LNB shouldn't become that unstable with cold temperatures, although LO freq drift will occur.
However if there are hardware defects in the LNB, the cold weather can trigger problems. I had one LNB once that worked fine for a few years at cold temperatures, but then began to give me problems. What it would do, was when the temperatures started to drop, the LNB would go into oscillation, and there would be a strong birdie freq that would appear in the spectrum and as the temperature dropped it would one by one knock out each channel. This was back in the analog days, and my TV screen would go black on one channel at a time only, and the signal reading would be pegged high. I found that if I'd unplug the receiver for a few seconds and turn it back on, everything would be OK again.
THis occurred every evening as the temperature dropped from about 15 degrees down to 5 or 10 deg F. Once the temperature had dropped down to below 5, everything was fine. I lived with this for several years, then got a new LNB, and never saw the behavior again.
Anyway, if your LNB gets unstable with low temperatures, I think it's a defective LNB. On the other hand, most moderate cost LNBs will drift up to 2 MHz at low temperature, and some receivers will have problems tracking the frequency difference.
The DCII receivers will usually start out using the expected frequency for a signal, but will eventually generate a freq offset that will allow it to be stable.
I'd suggest leaving it on one of the problem channels for several minutes to see if it gets more stable, then switch channels and come back. If it is unstable again, then it might just be an lnb freq drift issue, not an instability issue.
I used to have problems with the narrow SR PBS DCII channels when the temperatures got cold, because my LNB would drift off freq, but if I left the receiver on that channel for a while, it would eventually stabilize.

 

[JAS]

An LNB shouldn't become that unstable with cold temperatures, although LO freq drift will occur.

BJ

Could this cause the loss of -S2 signals on KU? When the temp drops below 20 degrees f . I am loosing all my -S2 signals. Even the ones that are normally in the high % quality range i.e. 90% and above. -S signals are ok and do not appear to not to change in quality or signal levels.

I believe the LNB is a Chaparral degree unknown (all information gone. I can see the tag but all the printing is gone) just about 20 years old.

Thanks

 

[truckracer]

it very well could be. i had an lnbf that would not want to change polarity when it got real cold. I have had diseqc switches that would work right cold too. cold weather can do wierd stuff to this equipment.

 

[JAS]

It's -5 f this morning and now all KU signals are gone. Time for a new LNB I guess.