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Categories | Microphones | AB5N - HM-36 IC-7200 / -7600 Mic. Modification Help

Show all reviews of the AB5N - HM-36 IC-7200 / -7600 Mic. Modification

You can write your own review of the AB5N - HM-36 IC-7200 / -7600 Mic. Modification.

N2HUC  Rating: 5/5 Feb 17, 2012 17:43  Send this review to a friend!
Top Notch Audio  Time owned: 0 to 3 months
Bob has done it again!

My new Icom IC-9100 came with the stock HM-36 microphone. This is a simple mic with basic functionality. I don’t need anything big and fancy, so getting this to sound “a little better” would be desirable. I did some audio checks with those who know good audio, adjusted the radio’s internal EQ some, and all reports coming back were basically “you sound fine with that stock mic”, and “it sounds clear”. No complaints at all, but no real compliments either. After all the unsolicited “great” audio reports I received with my IC-7000/HM-151 combo equipped with the AB5N mic mod, I decided to try his HM-36 mod on my 9100 to see if I could get the same type of reports. The price couldn’t be beat, and the mod took about a half-hour to do. Afterwards, the audio level came up significantly. I had to lower the mic gain immediately from about 80% to, at most, 40%. With some help dialing it all in, now I get those unsolicited “nearly the best audio I have heard” reports with this 9100 radio/modded MH-36 mic combo. There is something about Bob’s mic elements that come very close to matching those piles of expertly tuned, broadcast processed, studio miced mondo stations out there that spend thousands of dollars to get that type of audio quality. It has those guys mystified how this cheap mod can come so close to that sound. Really, it is just audio spectrum and not hard to balance if you know what you are doing (good ears help). But this is not just a ragchew mic. It also cuts through the DX just fine with the bottom end rolled off a bit. Just like my 7000, people think I’m running more than 100 watts when I’m not. These elements drive the full bandwidth of the TX without distorting. You get every last watt the radio has to offer and no “midrange scooped” holes in the sound. Simple!

After listening to my signal being recorded and sent back to me in a WAV file, I was able to hear what radio EQ adjustments and COMP adjustments were needed to balance the audio out bottom to top end. This is a slightly different animal than the 7000 mod. First, FM and DV levels are louder and have more midrange than SSB. The circuits for each mode sound different. It was hard to find one level setting that worked for both. The only way to do it was to use a little compression on SSB. This ended up having a positive effect by adding punch and ambiance. The mic mod produced a somewhat bass heavy sound, but the internal EQ can fix that and ad the crisp high end that cuts through without sounding harsh. These are the settings that everyone likes the best:

MIC GAIN 33% (ROUGHLY 10:00 TO 10:30)

SSB SETTINGS:
COMP LEVEL 4
TX BASS -2
TX TREB +4
TBW WIDE 100 – 2900 (rag chew)
TBW MED 200 – 2900 (dx)
TBW NAR 200 – 2800 (slightly softer)

FM SETTINGS:
NO COMP (even if it shows on, it isn’t on in FM mode)
TX BASS +2
TX TREB +1

DV SETTINGS:
NO COMP (even if it shows on, it isn’t on in DV mode)
TX BASS +2
TX TREB +1

NOTE: Talk across the mic (not directly into it) and hold it about 6 inches or more away from your mouth for clean full crisp strapping audio. ALC should not ever exceed the limit scale. If it does a little, back off even more. Use the same distance for FM and D-STAR (DV).

Now prepare for some good audio reports!

My thanks to Bob Nagy for supplying an inexpensive solution that really makes these ICOM radios sound great. He could put many others out of business. The best part is you really don’t have to mess with tons of hit or miss combos. Just get it done and rock and roll.

Phil
 
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