HM-36 Microphone Upgrade

I had been getting reports that the HM-36 shipped with the IC-7200 ( IC-718, IC-7600, IC-7700, IC-7800) is low and muffled. I checked on on the bench- and indeed - that's the case. It's better than the stock HM-151, but still isn't delivering the quality of audio that can show what the radios are capable of.

There are a few mods out there that give slight improvement, but they still use the stock element. None of them get you where you need to be. I use my custom type #2 element - (the one I use in the HM-151 for the IC-7000) - and it brings the HM-36 to life. The improvement is significant. The frequency response opens up top and bottom. Audio drive level is also increased by about +60%. It goes from muffled - to clean and robust. You can then easily adjust the TX sound to whatever you like with you rig's TX tone controls (those that have it). For FM and AM, you will have the top and bottom frequencies for great audio. On SSB, you can dial it down for a narrower passband. Without plenty of clean audio drive to begin with, you can't get there from here. (get great TX audio)

 

The upgrade is actually more complex than the one for the HM-151. This is because the DC biasing resistor and audio coupler cap are incorrect as well. This means that the resistor, the coupling cap and the element have to be replaced. There is no room for an additional weight ballast inside the HM-36 shell - because it already has one.

 

NOTE: There are cheap ($20) Chinese HM-36 clones in circulation. I have developed an upgrade for these. They either say Japan in the back or are very light (noticably light). You can send them in for upgrade. They aren't the same physical quality as the real Icom mics.

 

I know you have other options (on-line mods), but I can guarantee that
if you use my Type #2 element and full upgrade, you will have much better audio.
(check my reviews : http://www.eham.net/reviews/detail/6580)

 

Note: Please tell me what radio you have so I can customize the response curve for it.

 

Even though it's a more complex mod than the HM-151, I'm keeping the price at only $42.00 plus shipping. Insured Priority 2-3 day return shipping right at $10 with full insurance, so the total is: $52.00 Ship it to:

 

Bob Nagy
103 Georgian St.
Hot Springs, AR. 71901

 

 

 

 

 

 

 

 

 

 

 

 

 

Recording Conditions:

I used a FT-897D as the receiver (7600 for TX). I set the stock microphone for a S-5 signal coming in. When the element was changed, it had enough increased drive to give a S-9+ RX signal at the same mic level. The RX AGC then kicked in, lowering the background noise. Rather than lower the record volume, I just left it as it was- to show you the difference in drive. My observation is that the Type #2 element does these things:

It increases audio drive by about 40%- More power output on SSB.
It has more clarity over the entire range - opening up the sound.
It provides a considerably more present and articulated audio.

It isn't quite as dramatic a difference as on the IC-7000's mic - because the HM-151 on the IC-7000 is a much worse stock performer. On the HM-36 Chinese edition, this will give you the audio drive that can reveal what the radio's TX section is capable of...and that is a much better signal.

Created by Bob Nagy - AB5N