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LF: CW-R and IF shift

To: [email protected]
Subject: LF: CW-R and IF shift
From: "Vernall" <[email protected]>
Date: Sun, 16 Jan 2005 11:41:25 +1300
References: <[email protected]> <006901c4fa2c$fc275e40$0702a8c0@parissn2> <[email protected]> <001101c4faf8$ec28b260$53c9c354@pc2> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Alberto, Wolf and others,

I concur completely with what Wolf has said. Both Yaesu and Kenwood (and I suspect Icom too) have the
rig switched to USB when using CW.

No, it seems Icom designs use LSB for the "CW" mode. Certainly the Icom IC-R75 needs to use CW-R to faithfully translate the RF FSK to AFSK.

It is easy to test a receiver, by using a signal generator as a test signal. Leave the receiver tuning alone and adjust the frequency of the signal generator, and it soon becomes apparent whether CW or CW-R setting is appropriate for the data mode of interest. It is mentally more challenging to use an existing carrier (or a fixed frequency signal generator) and tune the receiver to observe the change in sidetone, as that activity involves an "apparent reverse effect".

Receivers with IF shift can slew the narrow IF passband (of a so-called CW filter) to the appropriate IF centre frequency for a data mode such as Jason. On receivers that have no readout of IF shift, it is a bit more tricky to set it for receiving a DX signal, as the desired signal (as detected and sent to the loudspeaker) may not be audible in the noise, in which case it is essential to pre-set the dial frequency and IF shift to be right on the expected frequency to be received.

73, Bob ZL2CA



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