[hpsdr] Observations on JanOz-163 SDR-1000 combination

[Ahti Aintila]

Hi Phil,

After a successful start-up of the Janus/Ozy and SDR-1000 combination,
I strongly agree with you that for the best use of the available
dynamic range, the excessive hardware gain of the SRD-1000 has to be
reduced. Setting the gain of the INA163 amplifier down to 0 dB is not
the right solution due to the high internal noise of that amplifier at
low gains. The obvious way might be that we simply bypass the
amplifier and take the differential I- and Q-signal straight from the
sampling capacitors as you have suggested already a couple of years
ago.

I am going to try that, but unfortunately due to my one month holiday
trip to Malaysia, I possibly can do that earliest in July. It is also
possible that I will "steal" the DDS and RF signals out of the
SDR-1000 and use an outside QSD/ISD circuit directly plugged to the
Janus P3 header as you suggested.

The reason that I didn't see any improvement of the dynamic range when
connected to Janus/Ozy, may be that I'm already more than three years
using WaveTerminal 192X as my sound card. As you well know, it has the
excellent low noise AK5394A ADC. The only problems with it have been
that it has two input channels only, not been supported by FlexRadio
and the worst - it has the unnecessary -14 dB attenuator. Maybe, now
that I dont need the WaveTerminal for my daily SDR-1000 companion, I
possibly take the risk and modify the internal attenuating "amplifier"
to a 0 dB buffer.

73, Ahti OH2RZ