[Elecraft] Microphone for K2

[G3VVT at aol.com]

Another option may be to use a PC microphone/headset that are available in  
the market at very low prices. I use an Altec Lansing AHS-201 headset electret  
boom microphone with a single earpiece with my K2. As the headset is  
terminated in the standard 2 x 3.5mm stereo jacks I made up the  necessary connectors 
and a PTT in a small plastic box with two leads out for the  K2,  8 pin mic 
connector and a 3.5mm stereo plug for the headphone  connector. A foot switch 
could be added if desired for PTT. The +5V bias voltage  is already available 
at P1 on the K2 Front Panel board. All it takes  is a suitable resistor to 
provide the bias voltage needed from the +5V  on P1 pin 6 to the designated AF pin 
or pin 1 on the K2/KSB2 side. There is  already a 2.2uF isolating capacitor, 
C34 on the KSB2 I/P, so no other  isolation is required with the standard 
K2/KSB2. The bias voltage needed for the  Altec Lansing AHS-201 does not seem 
critical. I used a single AA 1.5V dry cell  in tests and with that was able to 
overdrive the K2 in the microphone high  setting.
 
An added advantage with this particular headset is the microphone is noise  
cancelling for use in noisy situations and the earpiece seems to work well with 
 the K2 giving a good RX audio level. I had built the setup originally  to 
use with a Yaesu VHF/UHF mobile and it was pleasing to find that it  worked very 
well with the K2. Trying it out was easy as I already used the Yaesu  
standard for the K2 8 pin microphone connector. The Altec Lansing  AHS-201 should be 
retailed from about $10 in the USA. The  obsolete AHS-15 should also work well 
at an even cheaper price if still  available.
 
Bob, G3VVT
K2 #4168