KX3: Intermittent loss of RX sensitivity

[Scott Manthe-2]

I've noticed that my KX3 occasionally exhibits a loss of RX sensitivity.
It seems to occur most often on 30 meters and possibly 40 meters, and
it's temporarily cured by sending a dit or two. I picked the KX3 up
used, and it needed the VFO B encoder replaced, which I did myself with
the help of some advice from Lyle, Roman and Elecraft support
(Thanks!!!). This obviously required the disassembly of the KX3. I'm not
sure if the sensitivity problem is related to this or not. The encoder
works fine. This seems like a "sticky relay" issue. Has anyone
experienced this issue and have any suggestions on the cause and a cure?

73,
Scott N9AA
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[Dick Dievendorff-4]

I have had this with other radios. It turned out to be a coax connection that cleared up temporarily with application of a bit of power, but then generally got worse.

One was up the tower...

73 de Dick, K6KR

> On Sep 16, 2018, at 07:53, Scott Manthe <[hidden email]> wrote:
>
> I've noticed that my KX3 occasionally exhibits a loss of RX sensitivity. It seems to occur most often on 30 meters and possibly 40 meters, and it's temporarily cured by sending a dit or two. I picked the KX3 up used, and it needed the VFO B encoder replaced, which I did myself with the help of some advice from Lyle, Roman and Elecraft support (Thanks!!!). This obviously required the disassembly of the KX3. I'm not sure if the sensitivity problem is related to this or not. The encoder works fine. This seems like a "sticky relay" issue. Has anyone experienced this issue and have any suggestions on the cause and a cure?
>
> 73,
> Scott N9AA
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[Jim Brown-10]

On 9/16/2018 9:08 AM, Dick Dievendorff wrote:
> I have had this with other radios. It turned out to be a coax connection that cleared up temporarily with application of a bit of power, but then generally got worse.

Yes. This is also a symptom of dirty or failing relay contacts, and of
junk coax connectors and adapters. And of poorly installed connectors,
and of connectors that are not wrench tight.

Definition of junk coax connectors and adapters -- they don't have
Amphenol or a MIL-spec number stamped into them. If you bought new
connectors or adapters at a hamfest or flea market, they're almost
certainly junk.

All connectors are not created equal -- if, for example, the female
center is larger than the male center, they may not make good contact.
This is a common problem with junk connectors of all sorts, not only coax.

F-type are an exception to that branding -- Snap N Seal is one of the
good brands.

73, Jim K9YC

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[Scott Manthe-2]

I appreciate the comments and that good RF connectors are important, but
how would a bad connector cause the KX3 to only lose sensitivity on
30/40 meters?

73,
Scott N9AA


On 9/16/18 2:34 PM, Jim Brown wrote:

> On 9/16/2018 9:08 AM, Dick Dievendorff wrote:
>> I have had this with other radios. It turned out to be a coax
>> connection that cleared up temporarily with application of a bit of
>> power, but then generally got worse.
>
> Yes. This is also a symptom of dirty or failing relay contacts, and of
> junk coax connectors and adapters. And of poorly installed connectors,
> and of connectors that are not wrench tight.
>
> Definition of junk coax connectors and adapters -- they don't have
> Amphenol or a MIL-spec number stamped into them. If you bought new
> connectors or adapters at a hamfest or flea market, they're almost
> certainly junk.
>
> All connectors are not created equal -- if, for example, the female
> center is larger than the male center, they may not make good contact.
> This is a common problem with junk connectors of all sorts, not only
> coax.
>
> F-type are an exception to that branding -- Snap N Seal is one of the
> good brands.
>
> 73, Jim K9YC
>
> ______________________________________________________________
>

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[Don Wilhelm]

Scott,

Do you have an antenna(s) for 30 and 40 meters?
Those antenna systems may have a bad connection somewhere in the the
feedline or the radiator itself.

It is quite common for hams to think their antennas are perfect and the
trouble lies in the radio.

Look at the entire system and pick out the elements that are common to
the affected bands.

73,
Don W3FPR

On 9/16/2018 2:55 PM, Scott Manthe wrote:
> I appreciate the comments and that good RF connectors are important, but
> how would a bad connector cause the KX3 to only lose sensitivity on
> 30/40 meters?
>
> 73,
> Scott N9AA
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