OK, that info helps.
Does the Sub receiver also suffer when sharing the main?
There is a 3db splitter when you share the main antenna, so you should
see that drop in both receives.
When the sub is on AUX antenna, it is using the coax straight out the
back of the sub receiver to either the Aux BNC or to the ATU where it
would use the OTHER antenna (from the main).
So, when the Sub is using MAIN, is it also down?
The 3db splitter is on the little Sub-In board at the back of the sub
receiver, there could be a bad connection there, the relay or solder on
the little wires to the transformer, or cracked solder joint on
something like the little black choke-coil.
If both suffer when using the main, it could also be D25, just shotgun
replace it.
Look for damaged parts on that little daughter board next to D25, BSF
(Band Stop Filter).
It could also be something on the KXV3 transverter interface, you can
pull and put two jumpers per the silkscreen. If it has the old single
3-legged D5, shotgun replace that.
Keith WE6R Elecraft K3/K4 Tech
On 5/10/2021 9:32 AM, Udo DK5YA wrote:
Hello Keith,
thanks for your kind answer. I don't think that KPAIO3 is the suspect
since it also happens at the TVTR RX input. I.e. when I feed exactly
the same amount of HF to the TVTR input and AUX from the signal
generator and hit diversity 6-8 DB are missing intermittent at the
main RX.
73 Udo DK5YA
10.05.2021 17:53:49 Keith Trinity WE6R :
Hi Udo;
In addition to what N6TV suggested, also click above and below
12Watts.
You will hear the relay on the KPAIO3 riser board click.
Do that when the main RX is down, or click it a bunch to see if
you can force the problem.
If so, replace that relay.
Keith WE6R Elecraft K3/K4 Tech
Does rotating the MAIN RF GAIN knob back and forth make any difference? Or
tapping the ANT or RX ANT buttons a lot to exercise the antenna relays?
I assume both receivers are listening to ANT1, and nothing is connected to
AUX RF or RX ANT.
What happens if you move the coax to ANT2?
73,
Bob, N6TV
On Sat, May 8, 2021 at 1:55 AM Udo Langenohl - DK5YA http://mailman.qth.net/mailman/listinfo/elecraft>> wrote:
>/Gentleman, />//>/I have a problem with the main receiver on one of my K3s.
The main />/receiver is between 6 and 8dB worse than the second receiver. The
stupid />/thing about it: it is not always like that, but the poor sensitivity
/>/comes sometimes creeping or sometimes suddenly. It seems to have />/something
to do with the transmit / receive switching. I checked
this />/very carefully with an HP8664A signal generator and a spectrum
analyzer. />/Sometimes both receivers are exactly the same, then the main
receiver />/slowly gets worse and worse (within a minute the amplification
drops by />/6-8dB) sometimes it happens immediately after switching from RX
to TX />/and back. Then it happens that after switching from RX to TX and
back />/again, both receivers are the same again. It can also happen that
the />/main receiver is initially 8dB worse than the second receiver, but
/>/without RX / TX switching the missing 6-8dB are suddenly there
again - />/in the middle of receiving mode, without switching. So it's
intermittent />/and it drives me crazy not to find out what's going on. Is
that
another />/bad pin diode somewhere in the main receiver and if so: which
one? Maybe />/someone has an idea? Help is very much appreciated. />//>/This is a K3
#56xx with all features and all upgrades so its more or />/less a K3S rather than an K3.
/>//>/73 Udo, DK5YA/
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