How Joe keeps his Icom IC-705 cool during long FT8 sessions

Many thanks to Joe (KD2QBK) who writes:

Hi Thomas:

I’ve recently discovered QRP FT8, which I’ve been working with my Icom IC-705. I run with an end-fed sloper that runs out of my 2nd floor shack window using a 49:1 unun and a length of RG-58. I’m also using an Emtech ZM-2 tuner between the antenna and the radio when needed.

The set up works really nicely, except for the way FT8 heats up and overtaxes the radio after a while. Searching around a bit, I’ve found just the right solution for that issue. The AC Infinity MULTIFAN S1 USB-powered table fan.

https://amzn.to/3DvqemJ (affiliate link)

It’s basically just a 3-inch square fan like you’d find in a computer or some other electronic devices, with rubber “feet” attached. It can stand upright or lay flat depending on your need. it’s stated purpose is to cool or ventilate routers, game consoles, audio equipment, etc.

The AC Infinity MULTIFAN S1 includes a speed control switch and an inline USB socket to daisy-chain other devices. One caveat with the inline socket: because it’s placed in the line between the fan and the speed control switch, the switch must be set to high speed else the socket won’t have adequate power for the attached device.

All I do is plug the fan into a USB socket and place it at the rear of the radio, sans battery, to keep it cool. I have it set up to blow onto the radio. Obviously I need to power the radio with an external source when the battery isn’t attached. I’ve not tried to use the fan with the battery attached, but I don’t think it would help much. The ventilation slots next to the battery compartment don’t seem wide enough to let much air in.

A big positive, the fan is extremely quiet. Even on high you can hardly tell it’s on.

I’ve been able to run FT8 for at least four hours with only a small rise in radio temp. I’ve not found a location in the IC-705 that gives a numerical value for temperature, but I can say that after 3 or 4 hours, the temp meter display only rises perhaps 2 ticks or so past the word “cool.”

I’m quite happy with the AC Infinity MULTIFAN S1 for this purpose.

Prior, I had to keep the radio at the edge of my desk with a normal room fan blowing on it from the floor. Cooled off the radio, but I needed a sweater.

By the way, I case anyone is interested, that’s a Magnus ZH-3 Z-Head camera mount I’m using as a stand. It’s very adjustable while being heavy enough to hold the radio securely and not tip over, but still light enough to carry here and there.

https://amzn.to/3fwCITk (affiliate link)

I hope this info might be helpful for someone else having overheating issues with the IC-705 or any other comparable radio running digital modes.

Joe Patti (KD2QBK)

Thank you so much for the tip, Joe! I love how practical this is for cooling the IC-705. I’m sure it could help other small radios that lack heat fins/sinks during high duty cycle applications.

In addition, it might make for a nice, quiet shack fan! I’ve used little 12V fans for a number of projects, but the air volume they push isn’t necessarily enough that it would keep me cool on a hot day.

6 thoughts on “How Joe keeps his Icom IC-705 cool during long FT8 sessions”

I preferred reducing the transmit power instead of wasting energy for external cooling, especially when operating from batteries. 50% P/max of the trx is generally recommended for FT8 and similar modes and barely recognised on the other end.

And as much as I for myself like the comfort of these multiband-antennas including wide-band transformators, it’s better to invest in resonant antennas without transformation losses. Helps the rx, too…

73, Tom, dm4ea

Thank for sharing. We need more suggestions like this.

That’s a really expensive radio to push to it’s limit heat-wise at the home station regularly. For day-to-day home digi modes, I would prefer to stay around 1/3 power, upping to 1/2 power, at absolute most, only when necessary.

In the long run, it may be much, much cheaper to upgrade that antenna system to something more efficient (so you can reduce tx power and have the same actual signal in the air), or finding an amplifier so that you can simply keep the 705 at low power all the time.

How long is the rg58? Switching to better coax or open wire can reduce losses. Is it possible to set up a wire antenna that won’t require such an extreme transformer? EFHWs are nice and convenient, but if you want absolutely minimal losses, maybe a dipole or a loop? That manual tuner can be pretty efficient as long as it isn’t tuning high SWR into a long length of poor coax.

Of course, the cheapest option might just be to run at low power into your current setup and see what you can do with that. I’m not sure I have the discipline to do that though 😉

Lön says:

November 8, 2022 at 11:30 am

I totally agree with everything you’ve said,Jason.
Heat really is such a problem. ( I’ve just lost one of my venerable 32 year old desktop rigs ( Kenwood TS-850sat) because the cooling fan quit – unbeknownst to me.i noticed it when it was too late. So I’m running my backup 850. But these new rigs have it’s computer to cool and its finals. . Good coax, or twinlead, and amp would be advantageous running this rig in a high duty cycle. especially running digital modes they are really a high duty cycle, Well said Jason,and good luck to the OP. Lön de N3TGY

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