Recovered FM Audio

Mark NS9N

What level of signal is needed to hear an FM signal on a Flex Signature Series radio? I am using a new 2 meter transverter with my 6600 and have a noise floor of -125 dBm. I can see signals on the band scope at -115 dBm but can not hear the recovered audio. FM repeaters and simplex signals at -90 dBm are very clear. My question is, at what signal level should I be able to hear the signal audio? 

Rick - W5FCX

Lower the SQL squelch level. You should be able to lower it to hear the noise floor.

Mark NS9N

Thanks Rick, that is the strange part. I have the squelch level at zero and can hear the noise floor. I would think if I could see the signal I should be able to hear recovered audio.

Rick - W5FCX

Very odd.

Mark NS9N

Agreed time to drag the test equipment from the basement lab to the shack on the second floor.

Ken - NM9P

Obviously the detection threshold will be poorer than with SSB, but I never thought it was too bad when listening to FM on the transverter. The squelch response needs a little work — random opening of the squelch, and the hysteresis (sp.) response curve could stand some adjustment — but the decode always seemed to be OK. Though I haven’t done a lot of comparison testing with other rigs.

Stan VA7NF

While we are talking low level FM I find the same things and more.
Low levels are not clear, sometimes going FM rather than NFM helps.
Also as Ken mentioned, random squelch openings - Actually Ken it seems a bit like an old relaxation oscillator in that, as the squelch is raised, the frequency of the random openings are reduced until around 10 when they stop.
What bothers me the most, and ever since pre-release 1, when the panadapter reaches into either the top or bottom of the Second Nyquest zone it jumps into Nyquest zone 1 and only returns when the band is switched into 1st and then back to 2nd.  It should "bounce" off the top or bottom like it does on HF.
I also find the noise level on 2nd Nyquest is higher than expected.  This I have not tried to search out but it drops significantly when the antenna is removed (a 10' vertical co-linear with double shielded RG-6).  When away from 2M (say 158Mhz) it is outside the DEMI low-noise pre-amp range, but the noise doesn't drop, just the signal.  Much better without the DEMI wired in (on or off)
Any other 6700 owner care to reply.  I'm hoping for some good advice on the noise.