Building a VHF Contest Rover, Insides

Posted on July 9, 2020 by Chris Lumens in radio, rover.

Years ago, I promised some writeups on how I was going about building a VHF contest rover. I never got around to doing that, partially because I am not any good at keeping my website up to date. In this post, I’m going to try to start taking care of that by talking about what’s on the inside of the rover. In particular, I’m going to cover the radios and radio related boxes.

The rover box

In the two years since I wrote the intro post, my goals have changed a bit. Instead of sticking to the lower four bands, I’ve decided that more bands is more fun. I now rove with everything through 9cm, and I am working on bands above that but in a more limited fashion. I think that above 9cm, there aren’t enough people and contacts take long enough that it’s not worth a full setup for those higher bands. I’m instead building small radios that can be used to work other rovers or work people from their driveway without too much setup.

The heart of the operation is the rover box. This is just four pieces of plywood I glued and screwed together. The key is that the box is 19” wide, which is the standard size of a rack shelf. I picked up two 8U rails and a couple shelves from amazon. I initially thought the rack setup would be the way to go, but nothing has holes that line up with the holes on the shelves. I just end up zip tying everything down.

Inside the rover box, I’ve got a ton of gear:

Raspberry Pi with a touch screen interface. This runs my own switching UI. With this interface, I can switch to the calling frequency on any transverter with one touch, as well as switch modes. It also displays the actual frequency instead of me having to think about input frequencies and offsets when I am trying to log. I’ll talk more about this in a future post.
The Yaesu FT-818. This radio can be set to low output power levels that transverters expect, which helps prevent me from breaking anything by putting too much power into it. It’s also nice to have a second radio to monitor one thing while I’m operating on the other. The front coax port is for the 1.25m transverter on the bottom shelf, and the rear coax port is for a single piece of coax that goes to the microwave box.
The Icom IC-7000. This radio handles 6m, 2m, and 70cm. I use one coax port for 6m and another for 2m and 70cm, which are split apart at the antennas with a diplexer.
Custom K1EL Keyer box. This is hooked up to both radios. The knob on the left is CW speed. The buttons in the middle are hooked up to the K1EL’s control functions but don’t currently do anything. There’s another knob hiding behind the mic cord that lets me select the radio. I got a good deal on a cheap knob and pile of connectors, so this box supports up to ten radios.
American Morse Equipment paddle on its base.
K9JEB Power Connector. This supplies power to a bunch of miscellaneous little things. It can also supply enough voltage over USB for the Rasbperry Pi, which is the real reason I went with me.
W1GHZ Simple Yet Still Fool-Resistant Sequencer. This runs the 1.25m gear. I had to convert my amp from RF sensing to hard keying because it was turning on when I was transmitting on other bands. This sequencer controls when the various 1.25m pieces turn on. It’s connected to a PTT cable on the back of the FT-818. It’s in a box I 3d printed. It’s ugly because I ran out of filament part way through.
Transverters Store 222 MHz transverter. This gets 28 MHz input from the FT-818 and turns it into 222 MHz output that it feeds to the amp.
TE Systems 2110G amp. This takes the seven-ish watts of output from the 1.25m transverter and turns it into 130-ish watts. I modified it to be controlled by a sequencer instead of turn on when it senses RF.

Advantages

This setup is the product of several years of trial and error. Roving is all about making things as easy on yourself as you can so you can focus on making contacts. It also takes a lot of complicated and expensive gear, so anything you can do to keep from making costly mistakes is useful. I think this setup has a lot of advantages:

Everything is in just one box. I pick this up, put it in the back seat, hook up power once and coax at each site, and I’m done. I don’t have to run around the house looking for parts before I go.
Having two radios means I can work microwave contacts while monitoring 6m or 2m. This lets me either be listening for new contacts or have a way of talking to the station I am trying to make microwave contacts with.
The touch screen UI controls switching everything so I can’t make a mistake when I am in a hurry trying to make microwave contacts. It switches to the right transverter, sets the radio to the calling frequency, and lets me quickly switch modes. If for some reason a transverter goes down, I can disable it in a config file and then am prevented from transmitting into something that’s broken (or unattached). In the future, I may also have it check that the power level is set correctly.

Problems

Of course, there are still some things I am working on:

I could really use handles on the box to make it easier to carry. It’s pretty heavy.
The rack shelves were not as useful as I thought they might have been.
The raspberry pi should also handle logging, and the switch UI should talk to the logger so I don’t have to type in the frequency manually. My logging program is written in a whole lot of Haskell, and compiling it puts too much of a strain on the Pi.
The 1.25m gear is hard keyed, but there’s only one PTT port on the FT-818. This means that when I transmit on a microwave band, the FT-818’s PTT line gets triggered so the 1.25m amp will come on. I added a power switch to the sequencer but that didn’t fix the problem. I am working on a computer-controlled PTT switch that the touch screen interface will also control.