[Yaesu] D-104. Nice sounding mic.

[Jim Hargrave]

I agree with Bob,

I use a D-104 on the FT-920 and have a homebrewed impedance matching circuit
that uses a 3N211 dual gate MOSFET. The input load is 2.7 megohm which
supports the full frequency range of the D-104 element. The output line is
terminated with a 1 k resistor which matches most modern radios with low
impedance mic's. The 3N211 will match a wide range of output impedances. The
1k load seems to suit the FT-920 and my Icom IC-735.

I have not had desirable results using a hi/low impedance transformer
directly to the D-104. They seem to attenuate the HI frequencies too much.
However I do use a 600:600 ohm isolation transformer on the output of my
matching circuit to minimize ground loops.

   * 73's Jim W5IFP *
     w5ifp at gvtc.com


   >-----Original Message-----
   >From: yaesu-bounces at mailman.qth.net
   >[mailto:yaesu-bounces at mailman.qth.net]On Behalf Of KC3VO at aol.com
   >Sent: Monday, November 23, 2009 16:52
   >To: kd7jyk at earthlink.net
   >Cc: yaesu at mailman.qth.net
   >Subject: Re: [Yaesu] D-104. Nice sounding mic.
   >
   >
   >Yes, the D104 can be nice mike, but some users terminate the crystal
   >element in too low of an impedance, which destroys its
   >otherwise good frequency
   >response. If terminated with low impedance, the element loses
   >ability to
   >provide  good low frequency response, and develops an annoying
   >peak in the
   >upper  midrange. This mike was designed to drive the
   >high-impedance grid circuit
   >of a  vacuum tube, typically over 300,000 ohms, so it is
   >greatly mismatched
   >if  connected to a modern, solid-state radio, with its input impedance
   >typically in the 150 to 2,000 ohm range. Usage with such radios
   >requires  a
   >matching transformer or intermediate circuitry for proper
   >performance.---73,
   >KC3VO-Bob Curry
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