ICOM 7300 and HM-219 Stock Mic: Over-the-air DX test

This is an over-the-air recorded test of the ICOM 7300's stock microphone -- the HM-219, at a distance of 4,800 miles (7727 km), on the 20 meter band.

Although not a fully scientific or comprehensive test -- various Bass, Treble, Bandwidth, and Compression settings are heard. I sought to highlight the excellent job ICOM has done to provide a decent-sounding stock microphone that works well in tough conditions. It is my hope that new ICOM 7300 owners will find this video helpful, as they adjust settings on their rigs.

HL1ZIX (KE0EYJ) was transmitting at 100 watts on a 2-element homebrew Moxon, and VK4YS was receiving on a 4-element Hy-Gain 204BA monobander. Both radios are ICOM 7300s.

My thanks to VK4YS, for his recordings.

 

#IcomEveryWhere

 

Nice sounding audio.

 

Very usefull.

 

Yes, the stock icom mic is quite nice for a handheld mic. It does sound quite good. Thanks for sharing this video.

Now, in fixed station use, a desk or boom mic is preferred by many operators. You can of course use any electret condenser mic with the IC7300.

You can also use some other types of microphones (eg. Dynamic) provided that you use a blocking capacitor in the audio (pin 1 on the icom) line.

What: Consensus after a bit of web sleuthing is to wire in a 1 microfarad, non-polarized 25 volt (can be but does not have to be tantalium) capacitor in series with the audio line (pin 1 on the Icom mic connector) going from the dynamic microphone element to the radio audio input (mic jack).

Why: This cap effectively blocks the 8V phantom DC voltage which is present on the IC-7300 (as with most Icom radios). The 1 microfarad value blocks the DC from the dynamic mic element, but does not change the audio characteristic of the mic audio.

Risk: Not using a blocking capacitor COULD damage the dynamic mic element (or simply freeze it in place) given the phantom voltage on pin 1 / audio input line of the radio. No idea if this would damage the radio, seems a dead short through the mic element coil wouldn't be too good for the radio voltage regulator over time either. Also worth nothing that some dynamic microphones will and some will not have sufficient drive for the Icom radios (as has been the case on most Icom rigs since the early 1980's)....

Result: I've had very good luck with the Marshall MXL-144 studio ribbon microphone ($100 bucks) as well as the Astatic 877 style non-amplified desk mic (around $60) that was common in PA applications. The Shure 444 is hard to beat too. The mic gain has to be run at approx 50 or 60 out of 100, and compression has to come up to 3 or 4, but it sounds nice and you can dial in the audio using the bass and treble adjustments in the 7300 menu and get that Voo Doo audio sound on the 7300 if you so desire without the expense of all those audio companders, expanders, equalizers, mixers, compressors, preamplifiers and such.

I mostly work cw, but it's nice to know the IC-7300 has such smooth audio. Every one that I've heard on air sounds great.

 

I would like to try out my Behringer xm8500, but would need this blocking capacitor, I assume... Do the Heil dongles themselves, have this?

 

What audio chain do you use? I have a pair of Cascade Fatheads that I use for music and they require a preamp. Do you just use the blocking cap and feed it directly into the 7300? Do you do any EQ before the radio or just use the rig? I assume the 144 is a figure-8 pattern. Do you have a problem with room noise?

 

I got my 7300 and basically only adjusted the mic gain, nothing with the tone controls at all. Looking at the meters display, the factory setting of the mic gain seemed very hot, I could whisper at 6-8 inches and get a full output driven well. However, that is not how I use a hand mic, and I turned the gain down to about 35 for normal voice at 2-3 inches like a hand mic is normally used. A desk mic might be better with higher gain settings, until you get too much room noise. Yes, it is a really nice sounding mic that is included with the radio. I need to build an adapter for some dynamic mics I will want to try also. But even though some of them are broadcast quality mics, I would be surprised if they noticeably improved on the hand mic for SSB.

 

That was my thinking,as well. I tend to talk a bit off of the side of the HM-219, as it will pop P's if head-on. In my experience, if the mic gain is somewhere between 35 and 40, I have to go out of my way with some pretty strong bass/treble/compression settings to make this mic sound bad. As long as an operator keeps this between 35 and 40 for mic gain, compression around 2-4, and bass/treble settings not too far off from the middle, they simply cannot go wrong. The only quick/easy way that WILL screw this mic up, is jacking the mic gain higher. I agree, that 50 is too hot.

I find using a hand mic to be the easiest solution, for me, and also wonder how much difference a "better" mic would make. In fact, the Heil ICM is nothing but an elec. condenser -- much like the 219, only it's on the end of an XLR mic. I would like to hear a Heil PR781 on a 7300.

I don't have room for a good boom mic. I operate in a room smaller than some USA closets, and don't have a lot of room on the desk. My daughter's daily art projects cover much of it (whether I like it, or not).

 

My 7300 is used primarily for digital modes. The few times that I worked SSB phone the reports were good so this report is not surprising. My only disappointment with the 7300 is the lack of a second RF out. Overall Icom did a great job and I'm very happy with the 7300.

The primary rig for SSB phone in my shack is a 756 pro III with a Heil microphone. Also good reports but, not a stock mic either.

 

Yes, they left out a few things -- likely for an upgrade path to their more expensive radios.

 

Just as K7JOE said, You need to use a blocking cap on the mic line on all modern Icoms if plugging direct into the radio's mic connector if not using Icom mics needing phantom power. This will block the phantom power output voltage from the radio to the next input source whether a mic, preamp, mixer, etc.

 

Very interesting read, thanks.

As I'm looking to change radios later in the year, IC 7300 vs FT991A

Phillip.

 

FYI, based on my testing, I decided to up my Bass numbers, and Compression, and I managed to get France, Spain, and Argentina, LP today, from Seoul, in pretty crappy conditions. I was receiving 5/5 reports. I worked two on 20m, and one on 40m. I don't think they would have heard me as easily, on the less aggressive settings I normally use. This was at 100w, using a moxon on 20m -- and a combination vertical dipole for transmit, and horizontile doublet for listening, on 40m.

I was running Mic gain 40, Bass+2, Treble+2, and Comp 8. I used both the Wide and Mid bandwidths. That's a huge number for compression, and I know it wouldn't sound good locally, but it did cut through well over distance (as I could also hear from my test video). I actually upped the Bass, as I'm finding that I get more DX punch, at just the right range, when I do that. The HM-219 doesn't have really deep bass, and doing this adds just that much more oomph to the audio. The DX didn't mention any distortion issues. This has totally surprised me, as my Yaesu FT-950 had much stronger bass, and would put out a noticably weaker overall signal, as it spread out over the wider bandwidth, with more bass. The Icom 7300 (probably due to the stock mic) seems a different animal, in this regard, in that increasing the bass to about +2 actuallly helps DX.

Very happy.

 

Yes. I think the Heil "I-series" dongles do have a blocking cap but they are way overpriced versus a 10 minute DIY job.

Tantalum caps are 50 cents or less, and a mic plug and XLR are maybe 2 dollars - all from Ebay.

I disassemble the mic and put the blocking cap right inside the mic. No need to change any cables or dongles. Put the cap in the audio line of the mic element -done.