[Elecraft] KPA1500 and FT8

[W0MU Mike Fatchett]

They recommend turning agc off and manually adjusting RF gain.

There is more to the mode than pushing a button and waiting for your 
honor roll DXCC to come in.

W0MU



On 3/4/2018 2:15 PM, Jim Brown wrote:
> On 3/4/2018 11:58 AM, Erik Basilier wrote:
>> The reason seems to be that they have been taught to use a wide 
>> receiver in
>> combination with a sound card, so as to get a panoramic view 
>> including other
>> stations. This lets a strong nearby station control the agc, and affects
>> reception of stations on a range of frequencies.
>
> There is a VERY good reason why WSJT developer, K1JT, advises users to 
> use wide IF bandwidth, and it's NOT the panoramic display. The reason 
> is that filters introduce phase shift in the passband, and phase shift 
> is the enemy of good decoding. The same physics, by the way, applies 
> to other digital modes, including RTTY. Serious RTTY contesters have 
> learned that 500 Hz is a good setting. Our ears may hear off-frequency 
> QRM louder than the signal we're trying to detect, but the decoder 
> does just fine.
>
> This is true of both WSJT and other decoders I use for RTTY. Indeed, 
> even though a strong signal may APPEAR to cover much of the display, 
> if the strong signal is  CLEAN and you have your receive audio levels 
> to the computer set to that the strong signal doesn't overload the 
> computer, the decoder is likely to copy signals that appear to be 
> covered by it. If you consider AGC pumping a problem, simply turn it off.
>
> FWIW, with both FT8 and RTTY, I keep AGC on Slow, and set WSJT-X for 
> an indicated level as high as 50 dB, using the RF Gain. With this 
> setting, if a strong signal reduces gain in the radio, weak signals 
> will still be strong enough at the computer to be decoded. I mostly 
> use WSJT-X on 6M and 160M, but the few times I've gone to FT8 on HF to 
> work a DX trip, I've more than filled the 36 slots in JTAlert. So I 
> guess it's working. :)
>
> 73, Jim K9YC
>
>
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