[Icom] D-104 Silver Eagle microphone

Mon, 10 Feb 2003 00:00:36 -0600

There are some good articles on the D-104 on www.arrl.org and if you do a
search with google you might come up with some really good results to do
some of these modifications to it.

73's
Dale Miller, KC2CBD

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Bill Gode, Sr.
Sent: Sunday, February 09, 2003 4:34 PM
To: [email protected]
Subject: Re: [Icom] D-104 Silver Eagle microphone

The Silver Eagle has a high impedance crystal cartridge, but it also has
a transistor preamp in the base for driving a wide range of radios and
load impedances.  The stock mic will work with your Icom (use that DC
blocking capacitor), but you can improve things with a little time and a
soldering iron.

If you rewire the microphone so the preamp is powered by the DC present
on the mic jack, you can dispense with the 9 volt battery.  You can
further rewire it to keep the preamp "on" all the time to permit VOX
operation with PTT override.

If you add a 500k or 1 megohm resistor in series with the crystal
element at the preamp's input, you can realize better low end
performance, if desired.  Finally, a small resistive pad to further
attenuate the preamplifier's output is advisable, along with a 1 uF DC
blocking capacitor.  Play with the rig's transmit bandwidth and tone
controls to fine tune the mic to your voice and personal preferences.

The stock preamp is quite resistant to RFI and a modified D-104 can
sound considerably more extended in both highs and lows than a Heil HC-5
cartridge.  It will also have enough output to preclude cranking up the
mic gain and compression controls.  If you want Heil sound, get a Heil
mic and don't destroy that Silver Eagle - the current new price is $200
from most dealers!

73,

Bill, W9NHQ

Adam Farson wrote:
> Hi Dave,
>
> If the D-104 is fitted with a high-impedance crystal or ceramic element,
it
> will not match the low-impedance Icom mic input correctly. I would
recommend
> that you install a Heil HC-5 element in the D-104 head (Heil may even
offer
> a mounting kit). This will ensure the correct impedance match and drive
> level. You will need to connect an 0.47 ?F capacitor in series with the
> element and the mic input lead, to block the radio's electret polarising
> voltage from the element.
>
> If the D-104 already has a low-impedance (500 or 600 ohm) dynamic element,
> it should work. You will need the same series capacitor as described
above.
> It may be necessary to turn up the MIC GAIN and COMP controls for adequate
> drive.
>
> The mic connector pinout is shown in the user manual for each radio.
>
> Best 73,
> Adam, VA7OJ/AB4OJ

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