Friday, May 8, 2020

Replacing the VFO encoder (E4) in my mcHF

I've never been a fan of detents used in the tuning encoders of some QRP rigs and this characteristic was one of two annoyances of my mcHF transceiver. The recently installed internal autotuner took care of the main concern - now on to the encoder.

It turns out that all four encoders used in the mcHF are of the same exact part number. But what works well for the first three functions isn't (IMO) necessarily good for VFO functionality.

Looking up the stock encoder on Mouser reveals a list of similar parts of the same brand, size and pinout. The  differences among them are shaft length, detent or no detent, and torque required to turn the shaft.

Each part is only $1.60 so it was an easy decision to order three encoders, each with differing torque characteristics or shaft lengths but with no detents.

The concept of "torque" when applied to such a small part struck me as funny but, in hindsight, I'm
glad to have ordered all three since there is so much tactile difference between them.

It's hard to imagine from the stated torque value (milliNewtons per meter) what it would feel like to actually rotate the control.

It turns out that EC12E24104A6 works best for me. It turns easily but will not spin freely when given a "flick". It seems to very closely resemble the tuning of my old KX2.

The other two encoders were resistant enough to being turned that I didn't even consider them for a second.

Removal of the original and installation of the new encoder was an easy 10 minute job with flush cutters, toothpicks and soldering iron and the end result is a big improvement. The mcHF now seems more like a real radio. While on the bench I also updated the rig to the latest firmware.


  1. Several operating hours later:

    Before, with the original encoder at E4 (TUNE), the frequency of the rig would often jump large amounts if the tuning knob was turned too quickly. With the detentless encoder, this isn't happening. Regardless of how fast I turn the knob, the tuning transition is smooth and predictable.

    I highly recommend this mod. In fact, if I were building a mcHF, I would use detentless encoders for all 4 controls.

  2. Torque is measured in milliNewton-meters, not milliNewtons per meter. To get torque you multiply (not divide) force by distance.

    Glad you've got the thing turning more smoothly.


    David VE7EZM and AF7BZ

  3. Is this still working out for you? I'm about to order a few of the EC12E24104A6.

    1. Yes it is - I use the rig almost daily and still consider this a very beneficial mod.
      73 - John

    2. Thanks for the info! I think I'll make the swap. Not having the VFO jump large distances while tuning would be great, and the VFO is getting a bit wobbly. It looks like our shacks share some similar rigs. I also have an Anan-10E and Hardrock 50.
      Nate - K9BFG

    3. Nate, keep in mind that Dynamic Tuning can be turned off in one of the mcHF's menu's. This will stop the tuning jumps so you may want to try that before ordering the encoders. But, even with Dynamic Tuning still on, tuning with the new encoder is still *much* smoother and more predictable.

      I regret not having ordered more detentless encoders so that I could replace the other controls. I think only the RIT is suitable for the detents - the others would more closely emulate most radios if they were detentless. At $1.60 a pop, I recommend you order 3 or 4 of them rather than just the one since you might feel the same way once you experience how they feel while operating the radio.

      73 - John

  4. my original encoder shaft broke off (plastic). replaced it with a cheap one from amazon. before installing I opened up the replacement encoder and bent back the spring that presses the steel ball against the detent. now it "feels" similar to an optical encoder. too bad that auto tuner is not available anymore.

    73, Nez

  5. would like to crowd fund the ATU and send a percentage of proceeds to Alexey UT0UM . Any one have boards and parts pcb plans to start up again ?