[Yaesu] D-104. Nice sounding mic.

[Glen Zook]

First of all, the bandpass of the filters does set the bandwidth.  However, you have to remember that the frequency of the BFO crystal is such that the actual audio frequencies are generally between 300 Hz and the upper limit of the filter which will be 300 Hz plus the bandwidth.  For example, if the bandpass of the filter is 2.4 kHz then the audio bandpass is going to be between 300 Hz and 2700 Hz.  

As such, if there is sufficient audio energy in the bandpass at the higher end of the bandwidth then the audio will often "sound better".  If the microphone does not pass these frequencies then the fact that the bandpass of the filter does pass the audio will have no bearing on how the audio "sounds".  Many microphones do not pass audio frequencies that much above 2000 to 2200 Hz and those microphones will not "sound as good" as a microphone that is able to "handle" higher audio frequencies.

Glen, K9STH

Website:  http://k9sth.com


--- On Mon, 11/23/09, Ron Youvan <ka4inm at tampabay.rr.com> wrote:

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.
 
It is my understanding that SSB transceivers transmit through the same 2 to 2.4 kc/s filter that they receive with so I don't understand how one MIC can have "so much better better highs on the air" than another, since all highs are all stripped off.