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

Jerry Gaffke
 

Tim,

I'm not convinced. you can't just move the BFO to receive CW.

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.

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 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.

Jerry, KE7ER


On Fri, Jun 15, 2018 at 07:54 am, Tim Gorman wrote:
Jerry,

On Thu, 14 Jun 2018 20:57:48 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:
I'm not sure what you mean about shifting the BFO.
The BFO has nothing to do with transmit.
On receive, it can remain exactly where it was for SSB operation.
The original message says: "The uBITX is on CWU has a 700 Hz sidetone
set (ie offset) then the dial on the uBITX needs to be at 7.029.300
Mhz  so that it is receiving a the Flex with a 700hz audio tone."

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?



And no idea what all the other software releases out there are doing.
Mine is rigged as follows

On transmit the dial shows the frequency of the CW carrier (of
course).

On receive (if RIT is not enabled) it still shows the same operating
frequency in the LCD. However, the VFO is tuned up in frequency by
however many hertz the cw sidetone is set up to be if operating in
LowerSideBand mode, and down in frequency by that many hertz if
UpperSideBand mode.
This is *exactly* what I am saying. You are doing it with the VFO. You
can do it with the BFO as well! It's why my homemade receivers always
had two BFO frequencies. It was easier to shift the BFO oscillator with
a switched-in capacitor than to try and shift the VFO frequency in an
analog vfo!

Apparently the software Michael is using utilizes neither of these
methods.

tim ab0wr

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