On Thu, 2008-06-26 at 13:08 -0600, DW Holtman wrote:
> Steve,
>
> What type of amp do you use with your D-104? Is it a really small amp built
> into the base? Is it home brew? Do you still have the schematic drawing?
>
> Thanks,
> DW Holtman
> WB7SSN
>
Amplified D-104 were made for the CB trade. The makers of CBs have
decided to prevent over modulation by limiting the audio gain, to the
point of killing communications range. Base stations talked better with
the amplified D-104. It used probably 1 or two transistors on a PC board
mounted in the G stand base. Ham gear doesn't need the gain.
Many sources indicate the rising response with higher frequency is good
for SSB. Some have found that the audio stages can be over driven by
audio spectrum components outside the SSB transmit filter. That HF
characteristic is dependent on the crystal element being loaded by a
megohm or more. A low impedance like 50K can reverse that characteristic
and make the D-104 sound muffled.
Many years ago, I mounted a Shure communications cartridge in my D-104
case. It has a flat response limited to something like 300 to 2500 Hz
and gives very good punch. I'm sure some Heil element that is available
today will do about the same.
The rising response of the D-104 was designed for AM in a day when the
receiver selectivity had a gradual roll off above 1.5 or 2 KHz and so
the D-104 compensated for that receiver roll off. That's not what SSB
needs with modern equipment.
73, Jerry, K0CQ
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