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CW Transmit Frequency VS Sidetone setting #ubitx #radiuno #ubitxcw #firmware

Tom, wb6b
 

Hi,

I was recently puzzled about why my transmit frequency seemed to be about 1khz low on 80M. I was doing what seemed natural, using the CW key to key up the transmitter into a dummy load and check the signal on another receiver. The frequency of the uBITX when in the receive mode was accurate. 

I noticed this on the original factory firmware, but switched to the CEC because of the additional features it provides, and so I could experiment with more parameters to adjust vs the transmit frequency shift. What I discovered is, as with the factory firmware, the transmit frequency is shifted. With the CEC firmware I was able to determine the transmit frequency shifts by the amount of the sidetone setting. Varying the sidetone setting lowered or raised (depending on the LSB, USB, CWU, CWL setting) the transmit frequency by the same amount. This is only when keying the transmitter with the CW key. PTT for SSB does not seem to be shifted.

Call me old fashioned, but shouldn't the radio transmit on the displayed frequency and any frequency offset to create the tone for CW be done as a receive frequency shift, such as RIT? Maybe the preference has changed.

The CEC firmware has defined settings for the SSB and CW modes, so setting a receive offset in the CW modes would seem like the solution. On the original factory software the solution is not as clear.

Tom, wb6b

Jack Purdum
 

This seemed odd to me, too, but since I'm not an EE type, I simply assumed this was the way it's done and jumped on the bandwagon. I worried about two hams chasing each other right out of the band, but never had problems making contacts.

Jack, W8TEE

On Thursday, May 24, 2018, 5:07:33 AM EDT, Tom, wb6b <wb6b@...> wrote:


Hi,

I was recently puzzled about why my transmit frequency seemed to be about 1khz low on 80M. I was doing what seemed natural, using the CW key to key up the transmitter into a dummy load and check the signal on another receiver. The frequency of the uBITX when in the receive mode was accurate. 

I noticed this on the original factory firmware, but switched to the CEC because of the additional features it provides, and so I could experiment with more parameters to adjust vs the transmit frequency shift. What I discovered is, as with the factory firmware, the transmit frequency is shifted. With the CEC firmware I was able to determine the transmit frequency shifts by the amount of the sidetone setting. Varying the sidetone setting lowered or raised (depending on the LSB, USB, CWU, CWL setting) the transmit frequency by the same amount. This is only when keying the transmitter with the CW key. PTT for SSB does not seem to be shifted.

Call me old fashioned, but shouldn't the radio transmit on the displayed frequency and any frequency offset to create the tone for CW be done as a receive frequency shift, such as RIT? Maybe the preference has changed.

The CEC firmware has defined settings for the SSB and CW modes, so setting a receive offset in the CW modes would seem like the solution. On the original factory software the solution is not as clear.

Tom, wb6b

Allard PE1NWL
 

On Thu, May 24, 2018 at 02:07 am, Tom, wb6b wrote:

Call me old fashioned, but shouldn't the radio transmit on the displayed frequency and any frequency offset to create the tone for CW be done as a receive frequency shift, such as RIT? Maybe the preference has changed.
You are absolutely right. We had similar discussions for the Raduino sketch for BitX40 at the time.
During TX the frequency shouldn't be shifted - the actual TX frequency should be equal to the frequency as shown on the display.
During RX, the frequency needs to be shifted to the same amount as the side tone frequency setting.

73 Allard PE1NWL

Daniel Conklin
 

In the CEC firmware manager there is a field to change the CWL, CWU displayed frequency, and there is also a field to change the side tone frequency.  You can also adjust the CW BFO separately from the SSB BFO.  I suspect all of those settings are interactive.  I haven't played with them much yet, but as I was reading your posts I wondered if you could set the side tone to -800 HZ.  I might try playing with all of the CW settings later this evening.
Dan, W2DLC

Daniel Conklin
 

When I matched the CW BFO calibration with the USB BFO calibration, then the displayed CW received frequency was the same as the transmit frequency. It was not possible to use a negative number for the side tone, however I did match the side tone to the offset when I moved the CW BFO back. 

Tom, wb6b
 

Thanks Daniel,

I'll explore what you tried. 

I've had a little time to start looking at the CEC firmware code. He has a number of additional "switches" in the code regarding CW that are not in the original factory code. I've finally got the CEC uBITX Manager program working well enough on my Mac that I can experiment with the settings it provides.  I'm curious what the "Enable Adjust CW Frequency" checkbox in the Manager program does. I'll have to try it to see. 

Tom, wb6b

Daniel Conklin
 

Tom,  I checked the box and left the setting at 0.  Now, when I switch to CWL the readout shows the correct transmit frequency.
Dan, W2DLC