K3 at SE0X gets major upgrade

The Elecraft K3 transceiver at SE0X is an early first batch model. It was ordered within days from the K3 announcement at the Visalia DX convention 10 years ago. Many improvements has been introduced over the years and most of them have been implemented in our K3.

One upgrade that wasn’t done until now is the KSYN3A synthesizer upgrade released a few years ago. Finally I got the replacement synths ordered, delivered and installed in time for CQ-160. The benefit of the upgrade is a dramatic improvement in local oscillator phase noise, resulting in improved receiver dynamic range and reduced transmit spurious output near the operating frequency.

After completing the replacement of the synthesizers I noticed that the birdies where much stronger than they used to be. After spending some time re-routing the coax cables to and from the synths the signal leakage into the K3 receiver was reduced down to almost nothing and the cables secured with cable ties in a few locations.

Another modification waiting to be done was the Hardware AGC mod. This mod raise the threshold for the hardware AGC which improves AGC performance when tuning the band using a wide filter in CW contests. A quite an easy mod to do, but for some reason I didn’t get to it until now.

The area of the main board when the mod is done is easily accessible by removing the bottom front cover. Three SMD resistors are removed, then three resistors, two shorts and a LED used for voltage regulation added. In this photo you can also see 47 Ohm resistor and 1N4148 diod part of the “VFO tuning noise reduction” mod applied much earlier.

More information on the synthesizer upgrade can be found in this QST article.

A full list of mods for the K3 from Elecraft is found here.

So thats whats going on this week at SE0X. CU in CQ-160 CW this weekend!