Audio Amplification from FT1000MP to SoundCard Input
I don't know about you folks, but I can never seem to get enough audio from the
FT1000MP to drive my soundcard properly, even when I boost the input control all
the way up. I believe there are probably other solutions equally good, but Phil,
IC8POF has found a very good solution (a preamp) that he built and is using is
his station. His instructions and pictures are attached.
Solution: You have had luck in that I have
solved it already some years ago for my old radio a Drake TR7 and then my first
FT1000 and now on the new FT1000mkVF. I used the first version of the AFpreamp
some 20 years ago between my first computer a Sinclair ZX Spectrum and an
This MicPreamp (see schematic) is a part
of a complete 2 radio-switcher unit for my nowadays setup : FT1000 and
FT1000mkVF. It is fine to switch between the 2 radios but the buttons are
doubled, but this is another story HI HA HO :--))
(see picture of this circuit)
Now on the circuit: I have taken it from an old microphone preamp-compressor
kit. print one or both pages so you do not need to have the pc on during the
reading. (see picture of circuit).
The signal at AF-OUTof the RTX is about 50 millivolt PeP very low for the
Soundblaster input. This circuit drives it up to 6 volts, but already 500
millivolt are quite enough for the SBL input before overdriving it.
You need very few parts and I use the same numbering as on the circuit. I have
used the half of an mc1458 (double 741),but you can use an 741 or equiv. too.
Refer just on the first half opamp ic1a:
R1 input potentiometer , not trimmer because I can setup it from the outside
whenever is it needed. I used a 1megaohm but 100kohm or even 47kohm are ok too.
C1-C4 input and output capacitors: I used 2 x 1microfarad-polyesther(mylar too,
not elkos) but 100nF are ok too.R2 any value from 4700 to 10000 ohm, I had an
8200 at hand.C2 R3 R4 R5 are same values, I have omitted the C3 because no
improvement on the output signal was noted. As you see in the photos all is
mounted almost flying.
It is needed:
1 piece of AF cable from AF out to preamp
1 piece of AF cable to SBL on rear of the PC
2 mini stereo jacks with left-right pins soldered togheter
1 small alu-box
If someone needs stereo then should build 2 preamps and run 2 wires cable from
AFout to the SBL. But never needed till now at my side for such stereo setup.
This preamp is very useful every time one needs to look\work at audio signals on
the PC even with the volume tied to zero on the front.
Of course this circuit is of use during digital modes. Therefore my circuit
comprehends also all the switching needed to and from the SBL. All possible
switching for the rig microphones: handmic and or headset mic\hear. Mixing mic
with SBL output and mic to SBL input. Also connecting a table recorder to rig
AFout and SBL so do not need to have the PC on for recording.
All these are doubled by the radio switcher an 2 position\11 ways switch (RF
I would now only need a good HAM fellow how could write a little program to get
synchronized both FT1000 via CAT. It should not be too complicated for a
programmer. Of course If you need more info I am ready to pass them.
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