El Radio: The EF Johnson 51SL

Bam! It’s big, it’s bad, it’s heavier than sin, and it redefines awesome. What is it, you ask?


It is the EF Johnson 51SL. A huge radio designed and marketed to US Government and Part 90 customers. It is larger than your average business radio, with a little extra fatness in its design. It’s bristling with knobs, buttons, and a dot matrix LCD display. Most importantly, it’s backlit by a 100% “1993 cell phone green.” The one aspect that may confuse: the speaker is on the bottom and the microphone mid way up. We humans need the other way around…

You may ask, Why The Fudge?

You really need to understand radios to understand awesome radios. On the scale of radios, we have the simplest: the humble Radio Shack FRS walkie talkie. This is what you buy your kids for christmas when you know they’ve outgrown those lame squelch-less heathens that we all used to play with. They have 14 (or 22) channels and they let you play around in your backyard (although they’ll claim up to 387 miles of range). Unfortunately, these aren’t tremendously useful. They only transmit on a select set of frequencies, and they have very limited power and characteristics.

So now I’m not 12 anymore, which radio do I want?

The answer is clear: the HAM radio. For those unaware, ham radio is a radio service authorized by the FCC and the ITU which is basically designed around radio experimentation and two way communication between licensed operators. It is within this field that people will pay thousands of dollars for the Kenwood TS-2000 and the like. Quality is the name of the game, and features are so expansive as to confuse you to no end if you don’t have an engineering degree (oh goodie!).

This unit is a part 90 certified business radio, but they were also made for US Government users. In practical terms, this radio can provide the “you turn it on and it works but I can’t change the channel because I’m inept and the mystical man who programmed this knows best” experience or the “I can reprogram the frequencies from the front panel” experience.

So obviously you wrote this at 1 am, what am I supposed to get out of this article?

The 51SL (and the entire EFJ 5100 series) is an extremely solid radio. It’s available in VHF, UHF, 700/800, and 900 MHz frequency bands. My unit is a UHF rig, which allows transmission on the ham band from 430-450, as well as out of band transmission (oops, I mean, receive only) for others.

Most importantly, this radio is capable of P25 digital encode/decode. This means that when your local police department goes all P25 on you, this is probably your cheapest option to listen in. Furthermore, P25 is pretty fun to play with and allows static-less voice transmission for nearly as far as FM is intelligible. On the fringes of coverage, FM deteriorates in quality and gains static. P25 maintains constant quality until it drops out. At the point where P25 drops out, FM may be intelligible if you open up the squelch. Overall, P25 uses excellent forward error correction to achieve very robust data transfer on a single 12.5 KHz channel. Future systems will allow two voice paths on a single 12.5 KHz channel by using TDMA. This radio doesn’t support that, unfortunately.

But how do I get it to talk to other radios?

You’re a wise man, a very wise man. As shipped these radios do not allow you to select very much of anything at all from the keypad. Why? Because the FCC would really rather you NOT be able to select much of anything from the front. The last thing they need is NYPD complaining that some hot shot keeps making inappropriate sexual comments over their repeater.

To program these part 90 radios, you’ll generally need very expensive software and a weird programming cable. (To illustrate wierdness, my Motorola P1225 requires that you slide the programming cable over where the battery would normally be. I mean, really? This one simply attached to the accessory connector) For the EF Johnson this means an elusive “PC Configure” program (mine requires PC Configure 2.10.2 and is running Firmware 4.14.5.

But dear jesus, did you say this will work on Windows 7 64bit???

Yes my friends, PC Configure is a 32 bit compatible windows application. It will run on any version of Windows from 98 to present (you’ll need a usb-serial adapter, unfortunately).

The converse of this software is how it allows one to program these radios so that any neanderthal could switch it on and use it on one channel. Only 1 button works. You can even disable the volume knob (lest it confuse the poor neanderthal. they’re not that intelligent, come on). You can even attach a screw which locks the speaker microphone onto the radio. It is, dare I say, nearly idiot proof.

Conversely, with a little hex editing, you can open up the mythical “Front Panel Programming” or FPP for short, which allows the humble ham radio operator to enter in repeaters without needing to go through this computer cable wishy washyness. Furthermore, there is a great degree of customization of the parameters available.

Lessons for the future

I have decided that when my kids ask for a cell phone, they’ll receive one of these. I’ll even set it up with Telephone interconnect. It will teach them self discipline and make their arms stronger.

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