Re: Prevent receive frequency from moving #FT8


Martin G0HDB
 

On Sat, Apr 10, 2021 at 11:20 PM, Ed wrote:
Many times the sending FT8 station is strong with lots of stations trying to contact him, some with overpowering RF signals, thus lots of QRM - just look at the waterfall. All the strong signals make it hard to break through the QRM and contact the CQing station.
 
Sorry Ed, I still can't see what you're trying to achieve by moving your Rx frequency away from the Tx frequency of the CQ'ing station you want to contact.

If you see a station calling CQ and you want to work him, but you're also getting decodes and hence QRM from other stations transmitting at the same time as the CQ'ing 'station of interest', then the QRM won't (in most cases) be being caused by other stations also trying to contact the CQ'ing station.  Moving your Rx frequency away from the Tx frequency of the CQ'ing station won't, as far as I can see, confer you any advantage whatsoever when trying to decode the signal from the CQ'ing station amidst the QRM - the QRM to the CQ'ing station will still be present no matter where your Rx frequency is set.

Anyone else trying to contact the CQ'ing 'station of interest' would, or should, be transmitting at the same time as you and so they wouldn't be the source of the QRM you observe during your periods of Rx'ing when you're trying to copy the CQ'ing station. 

I agree that at certain times of day/night on some bands, eg. 20m and 40m, the waterfall does get extremely crowded and it can be difficult to find an apparently-clear slot in which to transmit, but moving your Rx frequency away from the Tx frequency of the station you want to work won't have any effect whatsoever on that - your transmission will still be competing with all the others on the band irrespective of who they're trying to work.  This situation is no different to what has happened with other modes, eg. CW and SSB, for many decades - there can be many people calling a 'station of interest' and thus creating a pileup.  In such scenarios you wouldn't consider moving your Rx frequency away from the Tx frequency of the 'station of interest'...  :-)

As for the power levels being used for the JT/FT modes, the modes aren't QRP modes but are weak-signal modes so it's entirely permissible to use whatever power might be necessary to achieve a QSO with a CQ'ing 'station of interest'.  If such a station is giving decodes of say -18dB at your QTH then it's quite possible that the station will be at a similarly low level at other QTH's both near you and at some distance from you so the stations at those other QTH's might have decided to use say 300-400W (or more!) in order to achieve a QSO with the CQ'ing 'station of interest'.  The signals from the stations at those other QTH's might seem very strong to you but that doesn't mean they will be with the CQ'ing 'station of interest'.  Again, it has always been the case that nearby stations can seem excessively strong to you but that in itself doesn't mean they're using excessive power - they're (hopefully!) only using the power needed to achieve a QSO with the wanted station.

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Martin G0HDB

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