Gary
I strongly suggest using an outboard DSP filter on the audio. The Flex
radios are great receivers and will bring in signals at the noise level,
but once you get to the noise level you can use a DSP audio processor to
help reduce the background hiss. I use a BHI NEIM1031 unit that is very
effective in reducing the background hiss. The same unit is marketed in
the US by GAP under the "Hear It" brand name. I also use a audio
intelligibility enhancer AIE in line with the BHI and this enhancer is a
two stage shelf filter that boosts the high frequencies. The BHI has a
tendency to roll off some of the high frequencies and the AIE restores
the clarity of the speech. It was originally designed by Hal Kennedy
N4GG as a hearing compensation unit for aging ears. The plans are in
the 2011 ARRL Handbook, page 24.36. I purchased the board from Far
Circuits, built the unit and put it in a small Hammond metal box. It
provides two levels of boost 3dB and 6dB. When used in conjunction with
the BHI it is very effective in digging signals out of the noise floor.
My interests lie in weak signal work on 2m and 70 SSB.
Terry
On 29/02/2012 15:01, GARY HUBER wrote:
After reading through the latest White Paper
at<http://support.flexradio.com/Downloads.aspx?fr=1> and setting the AGC-T of
my FLEX-1500 at the noise threshold or slightly below it and with the AGC in Fast are
there any other settings that can be changed to improve the readability of a signal
which is “in the noise” when the noise floor is at –115 dBm and external noise has
been reduced through antenna selection or noise cancellation (180 degree reversal).
Are there any recommendations for changes on the DSP; Options, Image Rejection.
or AGC/ALC tab or the Audio; Primary tab to improve the received audio?
The computer running PSDR is an AMD Phenom II 970 Quad-Core running at 3.5 GHz
with 8 GB RAM and with a Sound Blaster audio adapter.
73 ES DX,
Gary -- AB9M
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