BATC Forum

So I installed my dish and set up the LNB down the garden using a RTL dongle and PC - surprisingly easy to align the dish and resolve SSB signals using a Technomate TM1 PLL LNB.

Could easily see the narrow band noise floor.

Then I connected the feeder back to the shack (about 150 feet long) but found I had a high noise floor from exactly 10.483GHz to 10.491MHz about 8MHz bandwidth of noise at a high level - so much so I couldn't see the LNB noise floor - but outside this range everything was fine.

Turns out that above freqs correspond to 734 to 741MHz and are actually TV signals leaking into my system. Winterhill is very strong here and don't even need a TV antenna to get a signal.

Going to install a line amp at the LNB end to overcome the feeder loss and drown out the reverse TVI (I hope) !!

May also shift the LO in the LNB.

Regards Tim

You would be better to shift the LO. The 700 MHz band will soon be used for mobile. Also, use better coax as it should not be getting on even if it is strong.

Mike

Hi,

yes will have to move the LO at some point and the line amp is a quick fix - I hope.

The coax run I'm using is high quality RG8 with a very thick brading so am surprised as much signal leaks in as it does, the same run also carries my LF rx magnetic loop signals - I thought the loop was the culprit but disconnecting had no effect. Indeed just the coax on the ground was enough to cause the problem - very odd but at least I know what the problem is and can do something about it.

Thanks Tim

The line amp did the trick - can now receive the DATV beacon with an MER of 6dB - this is using an 80cm dish and Technomate TM1 LNB.

The narrow band noise floor hump is about 15dB above the LNB noise floor.

I've laid in place a run of RG6 double screened coax which may remove the need to have a line amp in use and will make the injection of a 25MHz reference that much easier.

All in all very satisfied with the signals being received.

Regards Tim