Ham Radio In The Airplane

In rec.aviation.owning Jim Weir wrote:
"Paul"
shared these priceless pearls of wisdom:

-
-"Jim Weir" wrote in message
.. .
- I don't know. I've never used a handheld. I've got a Kenwood 231 mounted
-like
- an airplane radio in the stack and plumbed through the audio panel to the
- headsets.
-
-
-Are the mike inputs and audio outputs compatible with the aviation headset
-impedance?

Not really. The standard aircraft mic simulates an old carbon element. You get
roughly half a volt to a volt p-p across something like 300 ohms. A standard
dynamic input to a ham rig is a few millivolts across a couple of dozen ohms. A
standard electret input is a couple of tenths of a volt across 2K or so.

The standard aircraft earphone wants a volt or two p-p across 150 ohms. The
normal ham rig output is speaker level (a couple of volts into 8 ohms).

The point is, there IS no ham radio standard, while the aircraft headset
standard is quite well defined. You can't just hook the aircraft headset into
the ham rig on a PNP basis. You always wind up dicking around with voltage and
impedance shifters to make it play well.

Jim

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

FWIW, the July QST Hints & Kinks column had this discussion with a simple
circuit to use an aviation headset with a ham rig.

--
Jim Pennino