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 _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
