Re: CW OPERATION

Lawrence Galea
 

Perfectly correct.
On receive it is the BFO which must be offset and NOT the transmit frequency.

When we had separate Tx and RX and the RX had a variable BFO (CR100/B28, CR300, Atalanta and their siblings, AR88 etc and all the old  ex-service Boat Anchors). the BFO was set at the centre of the IF, zero beat the incoming signal and then shift the BFO up or down the IF passband for your favourite (or xtal filter) tone. You could also peak the signal if you had an S meter and shift the BFO accordingly.

Same used to be done when listening to SSB where you had to choose the correct injection frequency for USB or LSB.

Some of the old boat anchors had the local oscillator on the high side of the received signal on lower frequencies and on the lower side on higher frequencies than the signal so that when you adjusted the BFO to receive LSB on lower frequencies you would receive the USB on higher frequencies and vice versa as this caused sideband inversion.

This was done for better tracking on lower frequencies and better (how much) stability on the higher frequencies as the local oscillator was lower in frequency than if it was on the high side of the received signal. 

On the TX side, usually the TX was switched on "net" which powered the VFO buffers etc but not the pa so that you will hear the TX signal in your receiver, zero beat with the incoming signal you wanted to answer and you will be tuned to his / her frequency.

Memories and regards from an old timer



On Mon, Sep 3, 2018 at 4:28 AM Jim Sheldon <w0eb@...> wrote:
The explanation is absolutely correct.  

To all programmers of CW for the uBITX.  You do NOT offset the transmitter by the sidetone frequency!  When you press the key, the uBITX must transmit exactly on the display frequency and the RECEIVER must be offset from that frequency by the value of the sidetone.  Watch the video that W2CTX posted the link to and it explains how it should work.

Jim Sheldon, W0EB
CW operator for over 50 years.

On Sep 2, 2018, at 9:01 PM, W2CTX <w2ctx@...> wrote:

Found this video explaining CW Zero-beating.  So based on this explanation the following is illustrated

for 7.040.000:    Dial displays 07.040.000, you transmit on 07.040.000, and the receive is offset by the

sidetone value.


Of course this is based on the video being correct.


https://www.youtube.com/watch?v=CrC7JmNw1eY


rOb

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