Programming Legacy Series 1 EF Johnson 5100 Radios on Windows 10 with USB-Serial Adapter

Series 1 EF Johnson 5100 radios are getting a little old by this point but are available relatively economically on eBay et al.

The main drawbacks of these radios over a newer Series 4 or 6/ES series 5100:

  • Older hardware revision and older components will have higher failure rate.
  • Programming software has issues on Win10, but works with compatibility settings (see below)
  • Poorer encryption support. A lot of the encryption is apparently implemented in software instead of a dedicated processor or DSP like newer radios. This isn’t a huge deal for Hams and casual users.
  • If the batteries are original, they’re likely dead. To keep compatibility with chargers you can find used NiMH on eBay (choose ones with verified capacity on the listing) or search for “ntn8923” for after-market Motorola compatible. Chinese Lithium knockoffs are available but require separate janky wall-wart chargers which break sometimes — if you were super adventurous you could modify an existing charger to support Lithium (this post has a picture of the board). If you want lithium, you’ll probably want to stick with OEM or other quality equipment to avoid fire and get a new legit charger.

Other than that, these radios seem pretty amenable to Ham use (would never ever consider trying to run one of these Part 90 certified radios on GMRS or MURS ;).

Also I have validated that FPP, once enabled, seems to reject entries above 450 MHz on Version 4 series. However, both the Version 1 and Version 6 radios I’ve tried allow FPP from 450-470 as well. The feature was targeted at federal users in the 380-450 area which I believe is the origin of the restriction on V4.


The latest version of firmware for the 1.X radios is 1.18.15, with the updater available online pretty easily.

The PC Configure software for file version 5.8 is, also available online. It’s possible to modify the band limits using hex editing to support other frequencies. In testing, I was able to make a Version 4 5100 RX and TX into a service monitor around 485 MHz with perfect performance. Haven’t tried this on my Version 1 yet.

Two points regarding software compatibility:

  1. There are issues with PC Configure version and modern computers. I had success with selecting the binary to Windows 98/ME compatibility mode (Right Click exe => Compatibility Mode). There were several scary access violation errors but the radio programmed just fine. Assuming you recently sold your Windows XP toughbook with dedicated RS-232 port, this is probably the best option.
  2. USB-Serial adapter compatibility may be less-than-desirable. According to online, the USB-Serial adapter needs to support RS-485, not just RS-232. I was able to use my Pluggable USB-Serial adapter with the above compatibility settings.

I was able to program as well as use the 1.18.15 software update utility and PCConfigure with these settings, despite horrifying access violations periodically. The update process worked fine as well.

Other Updates

My rubber keys are feeling a little squishy. I have no doubt that a 2002-era radio may need additional TLC moving forward, perhaps capacitors. I’ll update if I have any problems.

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