Adding a brake pad to Elecraft’s K1
Last summer, I had the pleasure of building an Elecraft K1 — quite a relaxing change from the KX1, with its tighter spaces and height restrictions for some of the components.
Not so much with the K1. It has lots of space to work with. And once finished, what a quiet receiver! The AGC mod I made during construction (thanks for the info, Bruce, N1RX), substantially reduced the initial blast from strong stations. It’s a wonderful QRP radio.
But the 10-turn pot used as the main tuning control is too smooth by half. When trying to zero-beat on a station — tuning to match its signal’s pitch to that of the radio’s sidetone — it was too easy to overshoot or undershoot the correct setting.
A quick consultation with Dr. Google led me to some posts from the early ’00s on http://www.qsl.net. They provided a solution. Essentially, you add a brake pad between the knob and the front panel.
In my case, the brake pad happened to be a foam washer that came off of something I unpacked. It was easy to trim the excess from around the tuning knob. The washer’s central hole fit snugly over the mounting nut on the potentiometer. And it was thick enough to do the job by itself. I could adjust the resistance by changing the position of the knob along the tuning shaft.
In some ways, the foam washer is a test of the concept using what was on hand at the time. Others on the qsl.net list suggested building up the brake pad using several layers of thin felt. This allows you to vary the thickness of the collective brake pad to achieve a comfortable level of resistance to turning the knob. That’s worth a try.
On the other hand, Don Brown, KD5NDB, suggested using circular felt pads made for Dremel tools. They are thick and so might need some scraping to thin them, and you’d have to add the center hole. Or one could keep them thick and, as with the foam washer, merely change the knob’s location along the shaft. Ultimately, Don wrote at the time, he replaced the pot with one he liked better.
At least at the time (2002):
Mouser has them for about $14 P/N 652-3540S-1-104.
These day’s it looks like it’s the 652-3540S-1-104L, for, wait for it, $28!
Whatever the approach, adding a break pad is simple; and it works!
This entry was posted on 2014/05/24 at 19:25 and is filed under Projects, QRP with tags amateur radio, CW, Elecraft K1, Ham radio, portable operating, QRP. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.