[Elecraft] KX3: No RX - SWR 25 to 1

[Fred Carvalho]

Geofrey and Matt

I have done what Matt suggested and used an oscilloscope probe at the ouput
of the receiver to check for the LO carrier with the RX ISO off. Nothing.
So this seems to be the problem

However during my tests, the reception went back on for a while. It does
this !!! I will try to check for the LO when it returns to make sure I have
both situtions checked.

BTW I have tried to find a bad connection on the main board by applying
some pressure with my fingers, but nothing happens.

In case the Rx returns I will check for the carrier with the osciloscope.
Thanks Fred

2012/8/27 Geoffrey Mackenzie-Kennedy <lx2ao at pt.lu>

> Hi Fred,
>
> The problem as you have described it does suggest that either 1) The KX3's
> LO (the synthesiser) is not working, or 2) The LO is working, but its
> output is not getting to the receiver and transmitter mixers because of a
> broken connection or a bad solder joint.  I do not have any details of the
> pcb layout to see how the LO is connected to the mixers.
>
> It would be a good idea, I believe, to try the experiment which Matt W6NIA
> suggested.  But because the LO might be working and its output is not
> getting to the mixers, I would do one more thing if you do not hear the LO
> on your main receiver (Matt's test 4).  I would use a "Sniffer" connected
> to the input of your main receiver to see if the LO is working or not.
>
> In case you are not familiar with "Sniffers", a useful "Sniffer" can be
> made from a loop of insulated wire (not enamel) about 3 cms long, one end
> connected to the centre conductor of small coax, the other end to the
> coax's braid.  It is wise to insulate the connections.  In this case the
> other end of the coax is connected to your main receiver.
>
> By placing the "Sniffer" close to the LO chip, if the LO is working you
> should hear it at good strength on your main receiver.  By placing the
> "Sniffer" close to each of the mixers, you should also be able to tell if
> the LO signal is reaching the mixers or not.
>
> Good luck!
>
> 73,
> Geoff
> LX2AO
>
>
> On August 27, 2012 at 12:50 AM, Fred Carvalho wrote:
>
> < snip>
>
>
>  If it was an analog equipment one could say that the local oscillator stop
>> oscillating.
>>
>
> <snip>
>
>
> On August 27, 2012 at 2:43 AM, Matt Zilmer wrote :
>
>
>  Hi Fred,
>>
>> To pin this down a bit further, maybe you could try an experiment.
>>
>> 1.  Set the KX3's RX ISO to OFF.  This is a MENU function.
>> 2.  Put the KX3 on a freq on 40m.  Leave it on RX.
>> 3.  Put the "main station" on the same 40m freq.
>> 4.  Note if your main receiver can hear the KX3's LO (should be able
>> to hear carrier if RX ISO is OFF).  You may need to offset the
>> receiver's carrier frequency a little to hear the carrier from the
>> KX3's LO.
>> 5.  If #4 is no, you may be correct.  The synth isn't producing any
>> injection frequency.  It's a good idea to have some type of antenna,
>> even a short piece of wire, so that the KX3 radiates just a little
>> energy that the other receiver can copy.
>>
>


-- 
Fred C Carvalho - PY2XB
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