K2 volume

[G4JQT]

Hi,

 

I’m still trying to pin down the cause of
the low-ish volume of my K2 (s/n 6905), which seems to be something occasionally reported with
this transceiver.



Dave White, VE6DRW, recently sent me the
documentation of the AGC mod to try. (Thanks Dave for digging it out for me – I
tried to thank you via email, but they kept bouncing.) According to Dave the
mod usually fixes the problem, but this doesn't explain why sometimes it's necessary and not others.


 

I know the K2 does not have a huge amount
of audio gain (for reduced battery consumption during portable operation), nevertheless, most
users say it is more than adequate in a normal environment.

 

I always have the RF gain set to max and need
AF set to max, or near max. I am listening in a very quiet shack. (And last time
my hearing was tested about two years ago it was normal.) I have a separate active
receive antenna, but this only confirms the situation is not due to a poor
antenna. (The main antenna is 120 ft random wire at 40 ft high via an ATU.)

 

The audio amp in my K2 is working properly
as far as I can tell by tests carried out using the side tone set to max and
measuring the peak-to-peak voltage across the speaker (1.7 V p-p) which is
about right by all accounts. The speaker in not faulty and I have used various makes/types
of headphones all with similar results.

 

The AGC voltage is set to 3.75 volts and
with no antenna connected there is no difference in noise between AGC ‘on’ and ‘off’.

 

L34 is peaked and the alignment procedures
were followed.

 

Reading through the threads again it seems
there is a real ‘issue’ here, not a variation in expectation from owner to
owner, but ‘something’ that is going on.

 

What seems odd to me is that most owners
say volume is fine, so there genuinely appears to be a variation in audio
volume - though not necessarily sensitivity as far as I can tell. But what is causing it?


 

I am considering building the Elecraft SP2
speaker, but I don’t feel this should be necessary given the complexity and
design of the K2; and it's not really getting to the cause.

 

So… is this a consequence of component tolerances
or just incorrect/sub-optimal alignment?

 Thanks and regards,
Ian, G4JQT


 

 







     
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[Guy, K2AV]

On Thu, Aug 18, 2011 at 11:38 AM, Ian Liston-Smith <[hidden email]>wrote:

>
> I’m still trying to pin down the cause of
> the low-ish volume of my K2 (s/n 6905), which seems to be something
> occasionally reported with
> this transceiver.
>

There are some number of things you do not mention.

1) is the S-meter showing AGC in action when you are having the low volume?

2) are you using the internal speaker in the top cover or are you using an
external speaker?

2a) if external, what speaker is it, brand and model number, what is its
impedance, and is it amplified?

2b) if internal in the top cover, does its sound seem "constricted" or
"narrow banded", or does it seem "full ranged"?

Would need the answers to the above to make any intelligent comment.

73, Guy.
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[Mike K8CN]

Hi Ian,

Do you have access to a RF signal generator, or can you build the crystal oscillator source shown in the troubleshooting section of the K2 manual?  I've found the receiver signal tracing protocol described there to be helpful.  The RF probe supplied with the K2 is useful if you have a good high input resistance DMM.  There are several possible sources of unintended signal attenuation along the path from antenna connector to audio output, so more experiments will be required to deduce the section(s) in which problems may exist.

You mentioned using an ATU with your longwire antenna -- if it's the KAT2 inside the K2, did you check to be sure that your antenna port selection in the menu is for the connector to which the antenna is actually connected?

Do you notice a difference in audio signal levels on different bands or is the audio output uniformly low on all bands?

73,
Mike, K8CN