Highland Ham wrote:
cliff wright wrote:

Well I've got all my TX problems sorted out fine now.
However I am beginning to think that the receiver is somewhat noisy.
When set up as per manual I am getting about a S3 internal noise level
on sideband.
My unit has had the RF stage modified as per the International Radio
mods and also the balanced mixer. In the next few days I hope to have
a look at this problem too, it is possible that the mixer balance is
not very perfect for example.
It was also fitted with back to back 1N4148 diodes across the RX input
and these might just have been damaged with the tx problem.
Has anyone else had a similar experience with this rig?
Regards Cliff Wright ZL1BDA ex G3NIA.

============================
Is it really the receiver ? Suggest you check by connecting a dummy
load inside a metal can . Are you sure that your house electrical power
wiring with attached equipment is NOT causing the noise?

Frank GM0CSZ / KN6WH
Well Frank I've done just that. In the past I've had a lot of QRN from
"dirty" mains around here even if it is underground in this area.
So my first step was to ring the local power company.
However bad as it was when they had a faulty pole transformer about 600
metres or so away, it was variable according to loading etc.
This noise seems pretty constant under any conditions, just like the
noise from the mythical "Big Bang".
The mods I carried out are supposed to improve the noise floor of the
820S but although sensitivity is very good and any AGC action quietens
the noise considerably, I am still not entirely happy about the front
end of the RX. This is especially so as I have always been interested in
weak signal CW contacts on 20 metres especially to the Antipodes of New
Zealand in Spain and the western Med.
When it was done I had a few problems caused by a tiny solder bridge
on the IF board. This caused me to do a lot of messing around with the
front end before I found the problem as it had appeared to be RF stage
instabilty.
So I think that I will check out all the FET's and try and match even
more closely the pair in the balnced mixer.
Apparently Kenwood were not entirely happy with this circuit as
different units have at least 3 different source circuits for the
balanced mixer stage.
73"s Cliff Wright.