Topband: FT8 on 160m

[Roger Parsons]

As we all know, CQWW produces huge activity on all HF bands. This year I was hearing stations up to well above 1850kHz. I have found that trying to run Europe is often more productive in the 1840-1850 segment, presumably because it is less crowded than lower in frequency. 


Late in the contest I started to CQ on about 1842kHz, and after a while, and several QSOs, was told (on CW): "Please QSY. 1840 is reserved for FT8. Good luck in the contest." Ignoring the fact that nobody has a reserved frequency on any band, I thought OK, don't want to upset anybody, and moved to 1842.9kHz. Shortly, the same message arrived.

My (probably incorrect) understanding is that FT8 stations are using USB with a carrier frequency of 1840kHz. So a CW station on 1842.9 should be out of their passband. I did listen carefully and could not hear any FT8 transmissions above 1842.2. (I have multiple receive antennas in a very quiet location.)

I believe that FT8 transmissions in principle use a microscopic bandwidth, but it appears they actually need a wide clear channel.

Yes? No?

73 Roger
VE3ZI