25-10-2016, 08:45 PM
You will eventualy need a vk3hz riglock pll to fix the 9100 drift, but get going first and sort that out later.
Here i had a close lightning strike last friday eve, so have been putting the station through its paces to confirm if all is well.
Without moon to get echos from, and no sun (night time) the next best thing for receiver testing is to compare the noise from cold sky with the noise from a 50 ohm termnation.
With the dish pointed up into the night sky it just requires the 24 volts to be turned on and off to the transco sma relay at the rx feedpoint of the septum to switch between them.
The G4DDK vlna2+ is connected to the centre sma socket of the relay , with the septum on the NO port and the 50 ohm sma terminator on the NC port.
On receive the relay is powered up, so is the G4DDK separately, and its easy to drop power to the relay only.
Reduce (wind backwards) the RF gain of the IC910h so the Smeter shows S9. This prevents the agc from affecting readings.
I had measured 5.2dB difference prior to the storm. Now i measure just under 1dB using Owen Duffys NFM program.
The dural beacon 200kms away over the mountains is only just visible.
So, the vlna is working but at reduced gain. I swapped it for an older G4DDK lna version and saw an improvement to 4.8dB.
Dural beacon is more pronounced on the waterfall now, and barely audible using a BHI dsp audio processor.
With gain back to full on the IC910h i see 2 S points difference from cold sky to the 'hot' 50 ohm termination.
So, some diagnosis showed the biasing screwed up on the atf54143. Replacing it got the voltages back to normal.
These noise measurements can be improved with optimisation of the front end coils and the fet bias.
I hope this info has been of some use to you, how to test and optimise your feedpoint LNA without sun noise.
73 Dave
Here i had a close lightning strike last friday eve, so have been putting the station through its paces to confirm if all is well.
Without moon to get echos from, and no sun (night time) the next best thing for receiver testing is to compare the noise from cold sky with the noise from a 50 ohm termnation.
With the dish pointed up into the night sky it just requires the 24 volts to be turned on and off to the transco sma relay at the rx feedpoint of the septum to switch between them.
The G4DDK vlna2+ is connected to the centre sma socket of the relay , with the septum on the NO port and the 50 ohm sma terminator on the NC port.
On receive the relay is powered up, so is the G4DDK separately, and its easy to drop power to the relay only.
Reduce (wind backwards) the RF gain of the IC910h so the Smeter shows S9. This prevents the agc from affecting readings.
I had measured 5.2dB difference prior to the storm. Now i measure just under 1dB using Owen Duffys NFM program.
The dural beacon 200kms away over the mountains is only just visible.
So, the vlna is working but at reduced gain. I swapped it for an older G4DDK lna version and saw an improvement to 4.8dB.
Dural beacon is more pronounced on the waterfall now, and barely audible using a BHI dsp audio processor.
With gain back to full on the IC910h i see 2 S points difference from cold sky to the 'hot' 50 ohm termination.
So, some diagnosis showed the biasing screwed up on the atf54143. Replacing it got the voltages back to normal.
These noise measurements can be improved with optimisation of the front end coils and the fet bias.
I hope this info has been of some use to you, how to test and optimise your feedpoint LNA without sun noise.
73 Dave