[Elecraft] Filter Recommendations

[Bob McGraw K4TAX]

I agree with Peter in that many hams use too much RX RF Gain and too 
little attenuation.    Per one authority on receiver performance, the 
optimum receiver performance occurs when the no signal band noise is 
about 10 dB above the receiver noise floor. Since we can't adjust the 
receiver noise floor, we can adjust the overall signal coming into the 
receiver by using attenuation and RF gain reduction.  Typically, 160M - 
40M one should expect to run 15 dB to 10 dB attenuation unless you are 
in a super low noise receiving environment.  For higher frequency bands, 
less attenuation and more RF gain is found to be desired.   Still 
maintaining the 10 dB practice regardless of band and antenna and band 
noise.

As example; if your no signal band noise is S-5 or -97 dBm and the 
receiver noise floor is -130 dBm,  thus a difference of 33 dB, then the 
optimum performance will occur with about 15 dB attenuation and 6 to 8 
dB of RF gain reduction.   Or  use 10 dB of attenuation and 12 to 13 dB 
of RF gain reduction.     It will vary from band to band and antenna to 
antenna but will generally be stable across the band for a short period 
of time,  i.e. several hours considering atmospheric activity.  Once 
applied,  you will find signals will pop out of the noise.    Many hams 
believe attenuation is used solely to prevent receiver overload. 
Attenuation can be utilized for a more effective means as well.

73

Bob, K4TAX



On 8/27/2018 9:55 AM, Peter W2IRT wrote:
> I find the best thing for phone contesting is a ton of attenuation and judicious use of RF Gain, combined with narrow bandwidth. No way to get rid of the low-frequency rumble from within the passband, but the combination of the roofing filter, DSP high cut and shift/width will get rid of the high-pitched adjacent noise enough to be reasonably efficient. I still don't like SSB contests, but they're far more survivable with a loaded K3s than they were with previous radios!
>
> ---------------------------------------------
> GO FRC!
> Peter, W2IRT
>
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>