May 15, 2022

New project: a replacement head unit for the Yaesu FT-857(D)

So, for a long while now I’ve been a user of a Yaesu FT-857D. I bought it back in 2011 as shop-soiled stock (someone bought it before me thinking they could make it work on 27MHz!) and have used it on the bicycle pretty much ever since.

The FT-857D is a great rig. Capable of all common amateur bands from 160m through to 70cm, 100W on MF/HF/6m, 50W on 2m, 20W on 70cm, and able to work AM/FM/SSB/CW, in a nice small package. It’s ideal for the bike in that regard. The only thing I could wish for is an actually waterproof head unit, but the stock one has been good, until now.

Last time I rode the bike I had no issues with the head unit display, things were stable and working just fine. That was some months back. Today fired it up to check the battery voltage: it seems I’ve got the dreadded zebra stripe issue. The bike has been in the garage for the past few months, so under cover, not in the sun… anecdotal evidence is that this problem is caused by vibration/heat in vehicle installations, but some reports suggest this can happen for indoor fixed installations too.

The problem

Either way, the zebra has made its home in my radio’s head unit and the display is now pretty much unreadable. Reports suggest I can send it back to Yaesu, pay them $200 (I presume that’s USD, and does not include shipping), and they will replace the defective LCD. However… given they discontinued making these things a few years back, I think I’ve missed the boat on that one!

Time for replacement?

Buying a new replacement isn’t viable right now — Yaesu don’t make anything equivalent: the FT-991A is too big (same size as the FT-897D), the FT-891 doesn’t do 2m/70cm, the FT-818ND is only QRP. Icom’s IC-7100 is the nearest competitor, not out of the question, except it’s a pricey unit for something that will be out in the weather.

Also, a lot of these options are out-of-stock with a big lead time.

Most of the Chinese units only do FM, and are at best quad-banders. Not that I’m interested in buying one: I hear they’re not the longest-lived of transceivers and right now I wish to avoid buying from China anyway.

Kenwood are basically out of the market here in Australia, and they never had an offering like the Icom or Yaesu units; their TS-480SAT was the closest, but does not cover 2m/70cm. The TS-2000 is a monster.

Alinco don’t have anything in a mobile format that competes either. The DX-SR9T does not cover 2m/70cm and is rather big; none of their 2m/70cm sets do HF or SSB.

Keeping the old faithful going

The radio itself works fine. It looks like the wreck of the Hesperus… with paintwork rubbed off the body, screws missing, a DIY fix on the antenna ports, and miscellaneous fixes to other bits. It still works though.

DIY Repair

This could be tricky as I’m not entirely sure what the issue is. It could be just a need for re-flowing everything, or there’s talk of parts needing replacement. The information I have is pretty murky and I could wind up making my partially-working head unit completely non-working.

Replacement used head unit

If someone had a working head unit that they were willing to part with, that might be an option. That said, the used unit could have the same problems my existing unit has, so no guarantee it’ll fix the problem.

CAT port auxiliary display

There are projects that link to the CAT port and present a UI on a separate screen. I was planning on putting a Raspberry Pi 4 there for SDR work, so that’s an option.

Homebrew head unit

Another option is to make a new front head unit. It turns out this has been partially reverse-engineered, so might be a worthy avenue to consider. That would give me a head unit that I can purpose-build for the bike: an attractive option. The hardware interface is 5V TTL UART with a 62kbps baud rate and 8-bits, no parity, two stop bits.

I have a big LCD (128×64) that has been kicking around for a while as well as some TFT resistive touchscreen displays with STM32F103VEs.

The Raspberry Pi 4 scraping the data and presenting it via a remote UI is also an option, in fact may be the direction I wind up going simply because Python on an ARM CPU is much easier to use prototyping something than doing C on a MCU whilst I bed down the finer details of the protocol.

The attraction of this is that I can use what I have on-hand now. Possibly use my tablet as the front-end in the short term. Not good in the rain, but can’t argue with the price!

I’ll go ponder this some more… one thing I am short of though is time to work on this stuff. This week-end is through, and the next one I’ll already be tied up on the Saturday, so I guess I’ll have to squeeze something in.