External LNB power with the MiniTiouner question please?

[Basil]

I assume if I do NOT jumper either J3 or J4 on the MiniTiouner I am OK supplying my LNB with 12V from an external Bias T with the Bias T after the LNB feed to the MiniTiouner? In other words I do not need to use the 12V from the MiniTiouner to the LNB? Just wanted to be sure that's OK, I think it should be. Thanks.

[radiogareth]

That's what I have done/do, not least during my 2 years of using my MT I have 'lost' the internal inductors to magic smoke (DC short-circuit aerials usually being the cause...).
Gareth

[Basil]

Thanks, that's set now, but no decode. I am trying for the Oscar 100 wide band DATV beacon, my set up receives SSB from the sat fine, but I am struggling to decode the DATV beacon. The software is a bit daunting on first experience. I have put a screenshot of what i am using on my web server if I can't attach it here. My Bulls Eye LNB has a LO of 9750. I have rotated the LNB 90 degrees from the SSB receive position. Thanks Gareth
http://www.chriswilson.tv/minitioune.jpg

[m1cdq]

NB on transponder is vertical 12v lnb supply WB is Horizontal is 18v lnb supply

[Basil]

I am supplying an external 12V and rotating the LNB 90 degrees from where the best SNR was for SSB. Do I need to do anything else with the MiniTioune software, I have no jumpers on the LNB A and B pins on the MiniTiouner? Thanks for the reply.

[g4hiz]

Basil,

just one thought. Check that you are connected to the LNA A input of the MiniTiouner (furthest from PCB).

Jen

[g0mjw]

What Jen said - plus how big is your dish?

Mike

[Basil]

Definitely on the correct (A) socket, and the dish is 1.8 meter prime focus with a Bulls Eye LNB turned 90 degrees (tried 90 clock and anticlockwise) from where max signal is shown on Oscar 100 SSB, which works fine into a Pluto and an RTL dongle.

I am not all sure if it's not something to do with frequency offset, but how that works in the Frequency in kHz -- Adapt Frequency box I have no idea. I have fiddled blindly around and not much seems to occur, to be honest.

My other thought is maybe this laptop is underpowered, Windows 7 64 bit Task Manager shows a lot of CPU time quite often (over 75%). Thanks for the ideas, not getting anywhere fast at the moment. The self test programmes in the MiniTioune software all show good.

[G4KLB]

Hi Basil,

I couldn't read the settings on your picture, so this is what I have.
LNB voltage settings don't matter as you have a bias tee and have turned the LNB 90 degrees.
You cant be far off now.

This is also a Bullseye LNB on a 1.2M dish.

qo100.jpg (407.68 KiB) Viewed 6573 times

[g0mjw]

What is the level of the NB transponder noise floor relative to adjacent clear spectrum below? With a 1.8m dish it should be 9dB or so, but it's possible to lose 10 dB easily with the narrow beamwidth of a large dish such that the SSB signals are still OK but the DATV ones are not.

If you could post a spectrum analyser or SDR plot of the LNB output it would help. In the old days it wasn't reasonable to expect someone to have a spectrum analyser but Lime/Pluto SDRs and the TinySA have really changed that.

Failing a spectrum analyser, the Scan and Tioune software can do something similar using the Minitiouner.

Mike