It’s been just shy of 2 years since my KX-3, one of the first kits to roll off the line, arrived in my shack. In that 2 years we’ve seen many firmware enhancements, a few accessories, and some bug fixes to the KX3. If serial numbers are to be believed there are now well over 5000 of these little guys in the field.

There have been a few production changes so far in the KX-3’s lifecycle, and I figured with so many in the field the hardware platform was fairly mature and now was as good time as any to do some routine maintenance on mine. As my friend says, it was time for me to pay my Early Adopter tax.

4 items from the Elecraft Appnotes and Mod kits jumped out at me as issues I have experienced.

Tuning Noise Suppression Modification

This is one of those little things, it doesn’t actually affect anything. It just annoys you a lot if you have the type of personality who cares about such things. In a nutshell, the radio generates noise in the audio output every time you move the VFO knob. Stop moving the knob and the noise goes away. There were some firmware settings to reduce the noise, but they didn’t work that well for me and they had other sometimes undesirable effects. The hardware mod has made a significant improvement with no ill effects.

 

Replacement KX3 VFO A Encoder

Early KX-3’s shipped with a magnetic encoder for the VFO-A knob. It was stiffer and ‘grittier’ than most of us were used to and despite what Elecraft said no level of adjustment changed it significantly. The design choice actually made some sense to me. The radio was intended to be used when portable, hiking, mobile, in generally bouncy environments where you don’t really want subtle jostling to impact your frequency. That doesn’t mean I liked it. Where there are some HAMs who appreciated that, I’m not one of them. I’m not that active, and neither is my KX-3. It turns out, most of the KX-3 customers agreed with me, and now a nice smooth ball-bearing optical encoder is standard equipment on KX-3s. Incidentally, this one can easily be adjusted using the felt pad for those who do prefer a stiffer knob.

 

BNC VHF/UHF Filter

I don’t know if I was the first person to report this problem, but they certainly hadn’t heard the complaint enough to know what the issue was when I reported it.

I assembled my KX-3 about 2 weeks before my friends and I took our annual trip to Dayton. Of course, the KX-3 was the mobile star of the show. We like our toys, right? It turns out, quite often the KX-3 would throw an error and enter into self-protection mode, and occasionally shut down. We couldn’t figure out why until we experienced an unrelated problem with our APRS station. There’s only so much antenna separation you can have on a minivan, and every time our APRS transmitter sent out a beacon, it was overloading the KX-3.

I’m really glad to now have this mod in my KX-3.

 

Per-Band RXSBNUL Modification

Straight up performance modification. I’ll just quote Elecraft:

“Nulling of (rejecting or suppressing) the opposite sideband or 16-kHz image is achieved by slightly adjusting the gain and phase of one of the DSP’s two I.F channels in relation to the other. When the gain and phase are closely balanced, the DSP-based demodulator can suppress the unwanted sideband by 60-70dB or more. Since the gain and phase change slightly with different filter settings and on different bands, the adjustments must be repeated on each band for each filter.”

Yep, what they said.

I’m blessed with a older, but nice, HP service monitor. I could do the procedure they describe. I think I’d rather saw off my leg with rough twine than spend 8+ hours performing that procedure over 30 times. Elecraft has a solution that performs the entire alignment automatically in 21 minutes. It just requires that you purchase or borrow a XG-3 Signal Generator and request the software from their support department. In short, I now own a XG-3.

Since this process makes a multitude of changes to the KX-3 in an automated manner, I decided I’d do a backup of the radio first. I’d recommend everyone else do the same as the KX-3 isn’t like other brands of radios. There is no such thing as a factory default reset,  each one is individually aligned and tested as part of the build process and those values are stored in EEPROM. That’s actually how this process is able to work, it updates several of those values. When you backup your radio using the KX-3 Utility, you also get those ‘permanent’ values. When you restore your rig, you restore them.  Saving those values is a really good idea, but after you’re done and happy with the process you need to be aware to not restore an old copy over top of them.

 

KX3 VFO Temperature Compensation

I haven’t done this one yet. It’s fairly straightforward but it hasn’t been a big issue for me. I will likely get around to it in the next couple of months.

Here is a gallery of pictures from the upgrade process.