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WA9CFK asks which side of zero beat?

Jul 27th 2011, 14:01

WA9CFK

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Which side of zero beat?

I am building a QRP rig for 30 meters. The DC receiver is complete and I am working on the transmitter. My question is, which side of zero beat should I transmit on to match the received signal?

My 40 meter transceiver kit says to tune to the lower side of zero beat, so I assume it always shifts the frequency upwards on transmit.

But with separate units, it would seem that if the transmitter is matching the receiver pitch on the same side of zero beat, your signal is on frequency.

Am I correct or am I missing something?

WA9CFK
Jul 27th 2011, 17:26

N0NB

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
It has been a long time since I used a DC rig (HW-8 many years ago) although I'm getting reacquainted with an SDR receiver. As I recall, the documentation for your transceiver has the advice as when the receiver is tuned above zero beat your transmitted carrier will be well off the frequency of the other station and likely out of the passband of his receiver.

With separates you have the freedom to leave your transmitter alone and tune the receiver as needed (much like RIT), That said, your transmitted carrier should be zero beat to the other station's carrier so that you can be heard in his receiver whether he is listening on either sideband or on a DC receiver. If you are calling CQ then he should be sure that his carrier is zero beat to you. If you find that on his next transmission his carrier has changed frequency adjust your receiver or RIT only or else you may find yourselves leap-frogging across the band!

Keep in mind that with a DC receiver that it would be possible to have your transmitter putting a 700 Hz note in your speaker but be 1400 Hz off the other station's frequency. This could happen if you're tuned 700 Hz below the other station and then your transmitter were tuned another 700 Hz below your receiver's zero beat. A bit of practice and you'll do fine.

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