Re: Can't get my uBitX to transmit CW on the Dial frequency

Jerry Gaffke
 

Hmmm.
OK, if we are now talking about moving the BFO to the other side of the 12mhz
crystal filter when switching between lower and upper sindband operation,
we can just agree and stop the discussion.

I was responding to this from post 52029:

> If you are working CW at 7030 then why should you have to set the
> receive frequency to 7.029.300? That just means you need to know
> whether you are in CWL or CWU and do math in your head to know what
> frequency you are actually listening to!
>
> Why not just shift the BFO so the receive frequency can remain showing

> 7030 and you still get your 700hz tone?

Not always totally clear what you are talking about, but my best guess was that
you thought moving the BFO was all that was needed to receive CW instead of SSB.
That could indeed be done in such a way that the CW carrier would create a 700 hz
audio tone, and the LCD display would correctly show the frequency of that carrier.
But I was pointing out that the carrier would be blocked by the 12mhz crystal filter,
and thus just moving the BFO is not optimal.  The rig should do the 700 hz addition
to determine the carrier frequency to be displayed in the LCD, not my head.
I've got other uses for that.

Jerry, KE7ER



On Fri, Jun 15, 2018 at 03:12 pm, Tim Gorman wrote:
Jerry,

On Fri, 15 Jun 2018 11:54:42 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:
Tim,

I'm not convinced. you can't just move the BFO to receive CW.
That's not what is being discussed.


Assume you are receiving an upper sideband phone signal at your 7030
mhz. The crystal filter is only allowing through that upper sideband
energy between roughly 7030.500 khz and 7032.500 khz, any residual
carrier from the transmitter is further suppressed by our 12mhz
crystal filter.
We are talking about changing from CWL to CWU, not from SSB to CW.

Now, assume that remote transmitter switches to a CW transmission at
7030 khz. We are now only interested in the carrier at 7030 khz, but
the crystal filter is not allowing that carrier through.  Does not
matter where we place the bfo, there is simply no signal to hear.
(Assuming our filter is perfect).
The remote transmitter is already sending CW. There is no switching
involved.


The solution is to special case the reception of a CW signal.
When receiving in upper sideband mode, we should have the receiver
tuned for a frequency 700 hz lower than that displayed in the LCD.
And when receiving in upper sideband mode, we should have the
receiver tuned for a frequency 700 hz higher than that displayed in
the LCD. The BFO can stay where it was for SSB phone reception.
We aren't talking about using USB and LSB to receive CW, we are talking
about using the CW mode to receive CW. Since it is a carrier we can
receive either on the upper side of the carrier or on the lower side of
the carrier.

But there is no reason to have to tune to a different indicated
frequency for receive. Just adjust your vfo or your bfo and leave the
indicated receive frequency the same as the transmit frequency. I used
to ue the adjustable BFO in my old RME-4350 to move from one side of
the CW signal to the other to avoid interference.

tim ab0wr

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