IC-9700 fan mod


The frequency stability of the Icom IC-9700 as originally delivered by Icom, has been found to be rather disappointing. Although the radio has a 10MHz frequency reference input, it (as of firmware V1.06) does not discipline the internal reference oscillator to the external 10MHz frequency, and the frequency of the unit varies significantly during both extended transmit and receive periods (With my unit I am seeing variations of the order of 60-70Hz at 432MHz, and up to 200Hz at 1296MHz).

The fan in the unit does not run while the unit is in receive mode, and this appears to be a cause of significant temperature variations within the transceiver.

A minor modification that allows the fan to run at approximately half speed allows the temperature within the transceiver to remain much more constant and (for my unit) has reduced the frequency variations to typically no more than 4-5Hz during testing.

The modification consists of adding a 6.8V Zener diode across the transistor that is used to power the fan.


  • 6.8V 5W Zener diode.


  • Remove the carrying handle if fitted.
  • Remove the 12 small screws securing the bottom cover to the transceiver N.B. Use a JIS screwdriver to avoid damage to the screw heads).
  • Remove the bottom cover.
  • Locate the fan connector (labelled “J2881 FAN”) towards the rear of the transceiver.

Picture: Before.jpg

  • Remove the fan plug to facilitate access.
  • Trim and bend the leads of the Zener diode to fit neatly between the tab connection of the transistor, and the pin of the fan socket that the red wire of the fan is connected to.
  • Tin the end of the cut leads of the Zener diode.
  • Carefully solder the Zener diode into place.

Picture: After.jpg

  • Reconnect the fan connecting plug.
  • Replace the bottom cover of the transceiver.
  • Replace the carrying handle if previously removed.

Gaming on the ham bands!

I was randomly tuning around tonight, testing a new antenna, when I happened upon a lil’ role playing game going down on a local 2 meter repeater. Adults, teens, even kids were playing! So blessed. This is the kind of fun stuff I’d like to see more of on the bands.

MP3 of what I caught below.

Audio of the RPG net on the 146.700 machine

We’re expanding to Twitch!

One of the things I’ve wanted to do for a year or two now is to figure out a way to share my hobby and solder antics with a wider audience. Youtube is one option, but it’s so non-realtime. Over the past year or two, Twitch has expanded a lot of their categories to include more “IRL” (as it was originally called) categories; they’ve now since expanded into various subsections like Science and Technology, Just Chatting, Etc.

Sample shot of the stream – IC-746, MMSSTV, and TrunkPCR (for the PCR1000) in view.

So, without further ado, I’d like to announce that we have started a twice-a-week Twitch stream here, on the mattyzcast. I’ve got a couple cameras and lights set up, we’ve set up Streamlabs to composite our video sources together, and twice a week we’re going to get on live, play radio, solder things up, chitchat and answer audience questions, and just generally run our mouths a bit.

So far (we’ve done one test and one real episode), the response has been great and amazing. I’m so excited and it’s really brought a bunch of energy back to the hobby – anybody that knows me in real life knows that if you bring up just about anything electronic or radio to me, I’ll run my mouth until you tape it shut. So, this is a great outlet for me, and a great source of fun and learning for everybody that tunes in!

(I will advise that it will generally be not-safe-for-kids, just due to the fact that I’ve got some salty language now and then.)

Our schedule for now will be:

3pm Saturdays (mountain time) – 2200 GMT Saturday

7pm Wednesdays (mountain time) – 0200 GMT Thursday