On 21/02/2018 20:41, Stephen Hicks, N5AC wrote:
If I understand correctly, the process will be for the fox to transmit
multiple carriers in the 300-900Hz range. If this is the case, have
there been any experiments run that verify that typical PA linearity
will be acceptable? If not, is there a need to for a more linear PA
on the fox side (thinking of IMD)?
Thanks,
Steve
Hi Steve,
the signal is pre-filtered and reduced in amplitude to optimize the IMD
products. Clearly there will still be some IMD as the signal when
replying to multiple hounds simultaneously is not constant envelope.
OTOH the Fox will be the only station transmitting in their T/R period
so even if they were to fill the whole SSB passband with IMD products
there would be no more QRM than an SSB signal and it will not effect the
Hounds at all, and it will be much less than that of an SSB voice
transmission anyway. It should be noted WSJT-X FT8 DXpedition mode is
only intended for high value operations that will justify working on a
dedicated dial frequency away from normal FT8 sub-bands.
Normal linearity requirements for SSB operation will be fine especially
if ALC action is avoided as recommended.
73
Bill
G4WJS.
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