SDR radiation
 

A local ham friend bought a SDR transceiver one of the KX series I
think. He noticed while he had another transceiver on another antenna
and compairing the two , the other transceiver seemed to be picking some
inerference when the KX was on or very near the frequency.


Does the SDR receiver have an oscillaotor in it that can cause this like
an old regernrative or direct conversion receiver will do to a station
on or very near the two ?

SDR radiation
 

In article t,
Ralph Mowery wrote:

A local ham friend bought a SDR transceiver one of the KX series I
think. He noticed while he had another transceiver on another antenna
and compairing the two , the other transceiver seemed to be picking some
inerference when the KX was on or very near the frequency.

Does the SDR receiver have an oscillaotor in it that can cause this like
an old regernrative or direct conversion receiver will do to a station
on or very near the two ?

That's entirely possible for SDRs, although I don't know the specifics
of the one you're referring to.

Most SDRs I've looked at _are_ direct-conversion repeaters of a sort.
They use a local oscillator running at a frequency near (or in) the
band being received (or at a multiple of it) and do a quadrature
down-sampling of the incoming signal. The resulting I and Q signals
are then demodulated by software (sometimes hardware-assisted).

So, yeah, they can leak LO just as a traditional direct-conversion
receiver does. The leak might be through the case and power lines and
other cables, or might be traveling back up the coax to the antenna
and being radiated.

If it's a pure receiver (not a transceiver) then adding an RF
buffer/amplifier with high reverse isolation can help limit
antenna-radiated LO interference. A JFET stage running common-gate or
a bipolar stage running common-base might be a good choice for this.