>From experience with different desktop PC's (386, P2,P3,P4,) I have found
the following fixes things (in time)
The Heil o/p is low but you can with care can get over it. (I checked just
now with a Labtec C-324 headset and its about 30 dB higher on my voice
peaks). Most PC type mics have a built in amplifier.
Glue a 1:1 (High impedance 600 ohm or so) transformer inside the PC plastic
case, and fit a Jack for the LINE OUT to radio with a DC Blocking, capacitor
say 0.1uF, I mounted mine on the FRONT spare plastic plate covering a drive
bay on the PC. (DON'T use a large unshielded transformer they tend to pick
up 60 Hz, Mine is a PICO shielded type. (gets rid of those !@#$%^&*&(*)
ground loops)
For the Heil 1/8" MONO Plug make an adapter (IF needed ) to connect to the
sound card TRS (Tip Ring Sleeve connector at least that's what's on my
SoundBlaster type cards). You may be able to find a adapter but it's a chore
to find one. Make sure the Audio is clean using the line or speaker output
to an external loudspeaker. If it DOES NOT create feedback some
amplification is needed.
If you need an amplifier for the Heil use a BATTERY as the power (gets rid
of those !@#$%^&*&(*) ground loops) AND put a really low pass 10KHz or so
filter on the supply and BOTH the input and output to get rid of RF. A
single stage AUDIO transistor does fine and does not need too much
filtering.
When checking the audio Tx into a dummy load and use a separate receiver
if you can this also let you set the message levels correctly.
Cheers and have fun.
Peter
Ve3pn@igs.net
|