[Elecraft] K2 Microphone

[Arjen Raateland]

Don Brown wrote:

>I have the TenTec desk mike and it works well with the K2. You will need to change the plug as it comes a 4 pin to fit TenTec radios. You can use the internal 9 volt battery in the base or wire the connector for power from the K2. The mike works better with 8-9 volts of power but will work with 5 volts from the K2 mike connector. You could pick off 8 volts from the RF board for the mike connector. The 8 volt supply is not on the front panel board so you would need to kludge a wire from the connector to the RF board. The TenTec hand mike will work also and it is a little smaller than the Elecraft mike but again you will need to change the plug. The desk mike comes as a kit also. After trying all of the above I still like the Elecraft mike the best even though all of the TenTec mikes work fine
>  
>
I have also used the Ten-Tec desk mike with my K2, but I made quite a 
few modifications.
Firstly I had problems with sensitivity of the mike amp circuit to the 
signal from a mobile phone nearby and I used a lot of ferrite to get rid 
of this.
Further like Don writes, the amp works better on a higher voltage than 
what is readily available on the K2. I changed some bias resistors and 
also the OPAMP IC to one designed for low voltage operation. (Removing 
the battery holder created space for the ferrite on the leads going in 
and out of the base.)
I also changed some audio response shaping RC-circuits after doing 
calculations on the circuit myself.
(The mike kit came with a circuit schematic, which helped a great deal 
in making the changes.)
I know the result of my changes were very positive, but as I haven't 
used the rig very much lately and have also adapted a hand-held mike to 
my K2, I unfortunately don't recall the whole story.
I also added a tiny push button to the base. I see the mike every work 
day on my desk at the office, but I can't remember what the button is 
for. Old age (I'm 54) ...

Now, if I could only find the documentation of these changes I could be 
more specific or even send the write-up that I made about it. I think 
I've posted about this subject some years ago and maybe my notes can be 
found in some net archive. I've got a new computer now and have 
apparently removed my 'Elecraft files'. They must be on a CD-ROM 
somewhere, though.
When and if I find my notes, I'll post them to the reflector.
I do think the Ten-Tec mike needs some work to make it perform best with 
the K2.

73 es gl,
-- 
Arjen Raateland
OH2ZAZ

be�digd vertaler Fins-Nederlands
virallinen k��nt�j� suomi-hollanti
Helsinki, Finland
Email: Arjen.Raateland@welho.com