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 the 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:
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