[AMRadio] Ranger Audio

[Larry Taft]

I have three D104 mics wired up for different rigs.  On the SDR-1000 
into a Delta 44 sound card I use the built in preamp in the mic base to 
get enough audio to drive the line-in input.  This minimizes the RF 
pickup through the audio wiring.

For the Drake 4 series I run straight into the mic input.  Same for the 
TR-7.  My guess is the TR-7 doesn't sound as good as the 4 stuff because 
of the lower input Z.  But then again I don't listen to myself either.  
And I usually run a 7077 mic on the TR-7 which is a dynamic.

On the O'scope a good "Hooie-yah" gives 200 mv P-P from each of the 
elements.  Thats 0.2 volts using a 10X probe on the scope input.  You 
can do the same test with a digital voltmeter too.  Then you should see 
70 mv RMS if my math is good today.  Needs to be a 10 meg input meter, 
an old Simpson will give a lower reading.

Google the D104 or Astatic and you can find a bunch of good info on the 
care and feeding of the crystal elements.  One site had a comment 
attributed to an Astatic engineer who said that the preamp was necessary 
to get the mic sounding good because of impedance matching.  Just turn 
the preamp gain down a bit

73, Larry  K2LT
drakerepair.com


>> I know this is a dumb question, but are you sure the D-104 is of the 
>> High Z variety?
>
> Not dumb at all.  How can I tell?  It puts out about 10mv ptp into a 
> scope.  Did not measure the DC resistance because I am not sure I can 
> apply voltage to it safely.
>
> js
>