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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