Posted by
Ron D'Eau Claire-2 on
Dec 04, 2006; 5:45pm
URL: http://elecraft.85.s1.nabble.com/Heil-Handi-Mic-tp441511p441522.html
I don't have personal experience with the Heil mic, but you are describing a
K2 making full power output if I understand your comments correctly.
When the first (right hand) ALC bar just flickers, that means the mic is
providing *more* audio than the K2 needs for full RF output and the ALC is
turning down the overall transmit gain. So, if you have the POWER set for a
K2 to produce 10 watts or a K2/100 to produce 100 watts, and one ALC bar
flickers, more audio from the mic will do no good at all.
It's important to check that at full RF power. As you turn down the power
you'll see more and more ALC bars light as the level control reduces the
output to match the POWER control setting. (The K2 should not be run above
10 watts on SSB to avoid unnecessary distortion, although running the power
"wide open" on CW is FB).
You also need to have whatever maximum level of compression you want to use
switched On and do the test on the band where the K2 has the *least*
transmit gain. That's always been 10 meters on all the K2's I've heard about
and seen.
If you get an ALC bar flickering under those conditions, more mic gain does
nothing for you. If not, then perhaps a preamp will help.
Watching your RF output, the bar associated with the maximum power should
just lightly flicker unless you are using a lot of compression. Human voice
has a huge average-to-peak amplitude ratio, and the peaks are very brief
and infrequent compared to the rest of the spectrum. The RF bargraph display
is a "peak reading" display so it fairly accurately indicates the very brief
and infrequent voice peaks.
One very simple change in the K2 that makes a large difference for mics with
marginal output is to change resistor R14 on the SSB module board from the
original value of 1k ohms to something between 5.6k and 10k. That resistor
is across the mic input. Increasing its value raises the audio level
presented to the speech compressor.
Ron AC7AC
-----Original Message-----
Greetings, all
I recently acquired a Heil Handi-Mic with the HC-5 element, intending to use
it with a new K2 radio (#5510). I used straight-across wiring for the
configuration connector in the front panel since the Handi-Mic is equipped
with a cable wired for Kenwood mikes. No resistor from pin 1 to pin 6 since
the element is dynamic. The mike does work, but the output seems low -- the
ALC indication barely lights the top bar, and the RF output barely shows on
the louder peaks. A MH-2 mike shows a little more output, though not that
much more. The over-all feeling is that the Handi-Mic has a relatively low
output level and may need a preamp to work properly with the K2. The mike
works about the same with either K2 here. I've noted the diagram for a mike
preamp for the K2, but before I build up something like that, I'm just
wondering if anybody else has tried the Handi-Mic, and what any experience
has been with respect to driving the K2 with that mike. Comments, anyone? ?
?
TIA,
Van W1WCG
K2 #2634, 5510
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