05 June 2021

The IC-705 Reassessed

Two months ago I wrote an initial review of the IC-705, giving it all-around high praise.

Today I have to pull back on that somewhat slobbering fanboy of a review, and remove the IC-705 from my 'recommended' list. The radio has a major, and crippling, RFI issue if you want to run it on digital modes over USB under field conditions.

Simply put, the induced or coupled RF noise picked up by the USB cable floods the rig with RFI. We are talking noise and hash from one end of the band to the other, and the noise gets worse if the software you are running, like Winlink, initiates a command dialog with the radio (in Winlink, that's referred to as 'starting a session'). And it's a complex issue. It's not simply USB line coupling, or laptop interference, or antenna location. It seems to be a sensitive interplay of all three. You can never really be sure what the real root of the problem is. The one key factor, however (based on my testing) seems to be antenna location. The further away your antenna, the less of a problem you will have.

I didn't notice this issue when I did my first post back in March because I hadn't run the IC-705 in a portable (field) environment. All my testing was done in my shack, where my antenna is 75 feet away on the other side of my house. Operating this way, the radio is a champ on digital modes, and that's how I wrote it up in my March review. But a week later I set the radio up at a local park using my Chameleon vertical antenna and the same laptop I use in my shack, and that's when I discovered to noise. I've since had the rig in the field twice more, testing with various antenna setups - a mag loop and an EFLW - and the problem is always present.

Here's a video I made while using the IC-705 and my Chameleon mag loop antenna a few weeks ago during a POTA activation:

Now, this RFI problem is not unique to me, or to my radio. I have three friends in my local Amateur Radio club who own IC-705's and they report the same issue. If you go to the IC-705 Facebook page or the IC-705 Groups.io email reflector you'll find plenty of discussions on this issue. Of course the fanboys will crawl out of the woodwork and tell you you're not keeping enough cable separation, or you are using the wrong type of USB cable, or you've got a 'noisy' laptop, or you are not using enough chokes, or the solar flux-to-ground coupling ratio is too low, or some such bullshit. I have tried every reasonable fix for this issue. I've tested against multiple laptops and Windows 10 tablets, I've tried a wide variety of heavily choked USB cables. I have enough common mode chokes attached to the feedlines to soak up a nuclear-level EMP. Nothing fixes the problem entirely - the 'hash' is always there at some level.

As I mentioned above, the one big delta - the variable that seems to provide the best mitigation - is antenna location. All things being equal - the same radio, laptop, USB cable, feedline chokes and antenna design (EFLW) - at home I get virtually no noise or hash when running digital modes, in the field the radio is overwhelmed by RFI.

The IC-705 was specifically designed for portable field use, and that's how Icom markets it. The owner has a right to expect that the radio will work in the field, on all modes, with a less-than-ideal antenna and cabling setup. The expectation shouldn't be that the owner has to schlepp around 75' of coax and enough iron ferrite (in the form of chokes) to sink sink a small boat, just to send a Winlink message. 

So let me recap where I'm at with the IC-705:

  • On voice modes, whether in your shack or portable, this is a superb little rig. It is every bit as good as its fanboys claim it is
  • On digital modes, in the right environments, the IC-705 is a digital mode beast. I have run my rig, in my shack, on JS8CALL for eight hours continuously and it never broke a sweat
  • Portable on digital modes, however, it's a mess, particularly with Winlink and JS8CALL. The RFI issue makes it all but unusable and it's virtually impossible to fully mitigate the interference

Because of this last bullet point, I no longer recommend the IC-705.

This RFI issue is Icom's to address and fix. Frankly, I'm surprised this issue wasn't caught by Icom in testing, and I'm disappointed that the ARRL test lab didn't catch is in its otherwise outstanding review of the radio.

There's more to come on this RFI problem. Right now I'm focusing on the radio's wi-fi connectivity feature as a solution, but I'm still testing and evaluating. So stay tuned for an update on the 705 saga!

W8BYH out


  1. My IC-705 also picked up noise issues when connected to my Windows 10 tablet using a generic (cheap Chinese) cellphone USB cable. However, I installed two small clamp on ferrites, one at each end of the USB cable. Each one has 4 turns on it. This has COMPLETELY removed all signs of any noise in the receiver and noise displayed on the waterfall. This is the part that I strongly disagree with you - this very small issue (which in my situation I have proved is 100% curable), will not and will never put me off purchasing or owning this radio. I was using a cheap generic USB cable designed for simple charging and data transfer for cellphones. My cable was NOT designed for what I wanted to use it for. Therefore, my fix with two torroids was necessary, and TOTALLY fixed the issue. Would this minor inconvenience of having two clip on torroids on a non-icom generic cheap USB cable, stop me from loving/using/owning my IC-705 ??? Hell no !!!!!

    1. Oh, my callsign is currently 5Z4J, and also ZS5J, C91J and A25J

    2. Seems as if this guy has a SETUP PROBLEM. not a RADIO problem! Were he to substitute ANY other quality radio, it is VERY likely the noise from his (apparently) noisy computer accessories would STILL be a problem! Using quality SHIELDED and grounded interconnect cables, keeping antenna gar away, etc are very important. No matter what radio is used, but if a radio with poor sensitivity is used, the noticability of the noise may decrease,ALONG WITH the weak signals!- go TRY another radio in the same situation, see if the situation changes!-73, KC3VO.

    3. Bob, go check my latest post on this blog, "Told Ya' So". Seems even Icom recognizes there's a problem.

  2. I used a 90cm USB cable and wound 6 turns on an Amidon FT114-43 toroid core at the radio micro USB connector and a clip on random macaroni type ferrite at the computer side solved the problem for me. I tested a Winbook TW-700 tablet and a GPD Micro PC and all noise went away! The antenna is a 57cm diameter Magnetic Loop hanging on the window, only 1 meter above my IC-705 while the tablet and laptop was only 1.2 meters away from the antenna and 50 cm away from my radio! Even if i bring my tablet or laptop next to the radio, there is no noise! I've had a few JS8 QSOS and quite a few WINLINK/VARA sessions with this setup and I am extremely happy with my IC-705 doing Digital modes! 73 and good luck de Demetre M0SUY/SV1UY

  3. Oh and I nearly forgot, have you tried connecting your laptop to the IC-705 via WLAN instead via the USB port? This is an option too, but I have not bothered doing Digital Modes via WLAN yet, simply because I have no noise via the USB Cable. If I did have noise problems I would definately try the WLAN way.
    Has anyone had experience with this option? It would be interesting to know!
    73 de Demetre M0SUY/SV1UY