Hi Dave,

I do not have any intention to hijack your mail but I hope you allow me to 
state again that we should not concede "signal would drop around 12dB when 3 
channels were used" as weak signal favorites.

By my simple spread sheet calculation, we can achieve 4-3dB degradation range 
at 5 channels maintaining symbol length longer than 64mS, which is sufficient 
for multi-path interference guard under shortwave ionospheric propagation 
model, with simple single carrier TDM frame architecture. Keep in mind that 
RTTY or PSK31 symbol length is around 22mS - 32mS. Thus, I do not see any 
significant reasons to adopt FDM frame architecture.

Regards,

take

de JA5AEA

On 5/13/2018 1:53 AM, David Birnbaum wrote:
Hi Joe

Bands were not helpful this morning, but I did notice something that might be 
important.

Aside from the QSB there appears to be some variation in your transmitted 
signal even if only one frequency is being used.  I would see K1JT call CQ and 
then the response with a RR73; K2xxx -yy <K1JT> response would be down about 3 
dB.  I did see that the signal would drop around 12 dB when 3 channels were 
being used by the Fox which is expected but I did not expect to see a response 
with a single channel being down relative to a CQ.

dave
k2lyv



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