[ICOM] D-104 on old Icom (IC-745)?

[Art]

At 04:28 PM 8/13/04, you wrote:
>Art: The D-104 microphone was designed for audio amplifiers with a high 
>impedance input in the hundreds of thousands to megohm input region. The 
>IC745 is typical of todays tranceiver which requires a 600 to 900 Ohms 
>output impedance microphone. You can use the D-104 if a suitable interface 
>circuit is employed between the microphone and the transceiver. This can 
>usually be put inside the microphone stand. A good description of this can 
>be found on N4JK's web page at http://members.cox.net/n4jk/d104.htm.
>Good luck. Larry K4LXV

Thanks Larry, that's just what I needed. I want a hand mic and a desk mic 
(both have advantages) for my ICOM IC-745. But they are very expensive, 
even when purchased on ebay. I just watched a stock hand mic close for 
$33.00 there (auction 5713983098).

So, it occurred to me that perhaps I should just use a D-104 from 
my  junkbox, which would serve nicely as a desk mic.

The last time I used the D-104 was quite a few years ago on my Drake C 
line, which had an input impedance of 50 k ohms, and even there, it was 
noticeably lacking in the lows, but usable. I can't even imagine what it 
would do when hooked up for a rig with 1k input impedance:>:

The reference you gave shows a fet, but I had thought of a basic low power 
bjt with 1 to 2 megohm stick bias resistors, which would draw well under a 
ma of quiescent current and would probably work just as well.

When I first asked on the list, I was hoping for a simple LC or RC circuit 
that would roll off the highs. Since the D-104 has a big output voltage, I 
was thinking the highs could be rolled off and there would still be plenty 
of drive left.

Thanks again!

Art