Newbie LNB / POTY questions please?

[Basil]

I am bringing an old 1.8 metre prime focus spun aluminium alloy dish out of storage and want to use it to access the QO-100 satellite. Initially for RX and TX of SSB stuff here in the Midlands UK. But I want to future proof the whole installation with a view to adding wide band ATV as an option. I intend to initially buy a Pluto SDR, and have it in a weatherproof box by the dish, with it's own power supplies and feed the Windows 7 64 bit dedicated PC in the shack via a hard wired LAN. Is there any potential issue with doing this to reduce co-ax feeder lengths? For TX I am thinking of one of the Bulgarian 20W amps with a pre amp between it and the Pluto with a Bias T Am I right in thinking that I can pay a premium for an LNB already configured for a GPS locked reference signal?



Now this was a quality dish in its day , but it's now old... The LNB was used for general satellite stuff some years ago at my old house. I am initially looking for thoughts and recommendations for which LNB to buy that's currently available. Ideally I would like to lock the LNB to GPS. I have Trimble Thunderbolt but it's 10MHz. I also have a Ublox NEO-M8T-0-10 GPS unit which will output two user defined frequencies, GPS locked.


I am not averse to buying a Leo Bodnar GPS however. I also want to mount the POTY antenna for TX on the same dish, at the same time. Rather than try and explain the current LNB mounting verbally I felt it much better to upload a zip file of some photos to my server for viewing. I have a small machine shop as I am in the motor race game, so I could make some simple constructions for mounting the new LNB / POTY.

The photos are at http://www.chriswilson.tv/satellite/satellite.zip


Looking forward to any advice as I want to put the 4 inch tube in for the dish and get it mounted before the wife changes her mind As I said, I am in the UK as regards buying an LNB. Thanks for reading and for any replies. 2E0ILY

[G4FKK]

Hi Basil,

I'm probably not the best qualified person to answer some of your questions as I appear to get 2dB less MER on the DATV beacon than anyone else with a 1.1m OS dish! However, a few things I've done/noticed after a year or so on the WB transponder:-

I modified a 4-port Octagon PLL LNB as per the wiki...https://wiki.batc.org.uk/Es%27hail-2_LN ... ctagon_LNB
I then used an NEO7 to generate a GPS locked 25MHz signal by locking a 10MHz OCXO to 10kHz generated by the NE07, which clocked an si5351 fractional synthesiser. This worked quite well but then I obtained a Leo Bodnar which, when I used it to drive the LNB, gave me an extra 2dB of MER. I'm not sure whether this is down to signal level or phase noise - or both; but see the note regarding phase noise at the end of the LNB mod page on the wiki as above.

With regard to remoting the Pluto: I have done this successfully using an OTG adapter on the USB data socket with a 5V PSU plugged into the right-hand USB socket. I found though that the Pluto became more prone to disconnecting itself even with the earth modification carried out
https://www.f5uii.net/en/transmit-datv- ... lutodvb/4/
I believe others have had no problems and some more research on OTG adapters would probably help.

There are others in BATC with much more knowledge regarding all this stuff so hopefully you'll get a few more replies in due course.

All the best and hope to see you on QO100 soon,

Martin - G4FKK

[Basil]

Thanks very much indeed Martin for the detailed and most helpful reply, which is much appreciated. I have been trying to catch you on 1942kHz to thank you in person, but have not heard you recently. I have bought a dual output Leo Bodnar GPSDO which is something I have had an eye on for a while, so we'll see how it goes. The latest D version of the Pluto SDR has an on board connector for an external reference oscillator, needless to say when my Pluto arrived recently it was a Rev B... If anyone knows of a source for a known Rev D Pluto I would be most interested. Thanks again Martin.

Best regards Chris Wilson 2E0ILY