Hojo and the case of the "bouncy" D710

I own a few Kenwood TM-D710 radios (one 710, and one 710G).  Both have been fairly sturdy workhorses, but recently, the D710 in my car started manifesting a BUNCH of problems.

 

 

Last year, I started having intermittent problems where the radio would reboot when I keyed up.  At the time, I tracked it to a weak battery in my battery box (I don't run the radio off the car battery, but rather a separate battery box which I charge from the cigarette lighter socket).  The battery box had a pair of 9AH UPS batteries, and they just wore out.  I replaced them a few times, and then managed to blow the fuse in the cigarette lighter.  

That was just before winter, so I left it for the season, since this is our "backup" vehicle anyway.  Getting back to it this year, I picked up a 100aH LiFEPO4 battery.   I put that in the car and it seemed to work OK, until suddenly, the radio started rebooting on key-up again.  Mainly when I used high power.  Switching to medium or low power seemed to resolve the issue.

I took the radio into my shack and ran extensive tests.  I couldn't make it fail.  I put it back in the car, and it failed within a day or so.

Thinking it might be a dirty wiring connection, I cleaned all of the CAT5 connectors, and cables, and even the GPS connectors.  That seemed to work for a short time, and then it failed AGAIN.

So, I began slowly testing by swapping one wire at a time, still sure it was a wiring issue.  Again, it might work for a day or a week, and then it would fail again.

I was nearing my wit's end when a buddy mentioned that his new radio was causing his LiFEPO4 battery's BMS to crash every time he keyed up.  He resolved it by putting some chokes on the power wires to the battery.

With a forehead-smack, I went out to my car and began by moving my battery farther from the radio.  The problem cleared immediately.  In fact, I used it all day for a public safety event with no difficulties.... until...  a fellow ham drove up behind my car.  He keyed up his radio to check in with net-control, and MY radio crashed!  Yep, it's RF getting into the battery BMS.  Thinking back, I did reposition my antenna at some point along the way.  I think that was probably the root cause all along.

So, I've put a few chokes on the battery wire now.  I moved it closer to the radio and it still seems fine.    

Moral of the story: LiFEPO4 batteries have BMS's.... they are sensitive to RF.  Be advised.

Now, to add insult to injury, during this time I also discovered that my radio had stopped beaconing.  I couldn't even force it manually.  After a bunch of debugging, I found that the radio would actually key up and send a brief silent burst before stopping.   A google search popped out a result that it could be a bad cable between the radio body and panel.  I swapped in a different CAT5 cable and voila, it started beaconing just fine.  So, I took the old cable out and cut off the ends to avoid temptation to use it again.  I'll crimp on some new ones someday and see if it works, but I'm out of patience with fighting with that radio for the moment.

Interestingly, my D710G radio is ALSO failing to beacon right now.  I'm going to grab another CAT5 cable and try the swap on that one, too.  I suspect these (10+ year old radios) are just wearing out those cables.  They live a rough life, under the seat of our cars. 

 

Scrap box APRS iGate / Digipeater

 

So, no shit, there I was. Our Tompkins County Amateur Radio Association is getting ready to support the AIDS Ride for Life event this coming weekend. It occurred to me that it might be handy to have an extra fill-in APRS DigiPeater / iGate running at my house, which could serve some places that have poorer coverage. So, I thought "Self, what would I need?" "Well, self, I'd need a radio, a raspberry Pi running Direwolf, and a magic cable to attach the radio to the Pi." As it happens, I have the perfect radio. Years ago, I picked up an ICOM IC-2000 (VHF Only) radio for $20. It was non-functional. I repaired it fairly easily. If I recall, there was just a blown transistor in the power-on circuit. It's been sitting on the shelf ever since. This is a perfect use for it, so I can get it out of moth balls! 

 

 

 

So next, I considered the magic cable. I figured a decent one would have a CM108 audio card for the Pi, a few audio transformers, and a Optocoupler to isolate the PTT ground (I've run into problems in the past when I tried to do it with a transistor). So, with a rough idea in mind, I started digging through my parts bins. I pulled out my trusty box-o-CM108's, and lo and behold if I didn't find a "KF5INZ Easy Digi" kit board that I had built YEARS ago and completely forgotten. That board has the audio transformers and optocoupler built-in! 99% of my work was done! Though I have no recollection of messing with the Easy-digi, I'm sure my knowledge of what I needed to do was based on playing with it years ago. My brain remembers processes, not details, so that tracks.

 

 

 

So, I desoldered the bodge of wiring that was on it from whatever experiment I must have done (probably an allstar node), and put it all together. I hacked off the end of a CAT5 cable to plug into the Microphone port on the radio. That gives me Mic-IN and PTT controls. To get audio, I just had need to plug into the external audio port on the radio. PTT is driven from the Easy-Digi board. I just have to run a few wires to the Raspberry Pi for it. Direwolf can do the rest with a GPIO port. I did hook up a power supply and a little LED to test the Optocoupler to assure it worked as I expected. It did.

 

So, 2 hours later, I had the magic cable to plug between the Raspberry Pi and the IC-2000. 

 

 

The next day, I configured up a new SD card for a Pi in my parts bin.  I built it on Raspbian Bookwork, which turned out to be a minor hassle.  The version of Direwolf that ships with it (1.6) does not have support for the GPIO changes that were made in Raspbian.  I ended up having to download the Dev branch of 1.8 and build the code from scratch.  

 

Testing went very smoothly.   I had one scare, thinking the radio had failed.  It turned out that it had an Auto Poweroff setting enabled.  Everything else pretty much worked right out of the can.   The audio was pretty sensitive.  I had to turn it WAY down so that direwolf wasn't complaining about it being overdriven.  I also noted that the volume POT on the radio is dirty.  A few times, the volume went from "low" to "off" without touching the knob.  Just wiggling it solved the problem.  I'll spray some cleaner on it.

Since this is really a temporary setup, I just zip-tied the Pi and cabling to the radio to make it somewhat secure.  We ran this over the weekend for the event, and it worked great!