Recently, I was fortunate enough to happen upon an Elecraft K3 on a used equipment site. If you are one of those people that have been looking for a K3/K3S — and you know who you are — this was a big deal! The radio I acquired was well cared for, and technically a K3S, due to the upgrades that were made over the years. I am pretty jazzed about it.
Some of the best features, outside of the K3’s spectacular dynamic range, is the plethora of back-panel access to all sorts of I/O, antenna connections, and the IF.
The purpose of this post is to hopefully save a you a little time and effort in the setup of the HDSDR software and the SDRplay RSP1a as a K3 pan adapter. In some previous posts, including, Ham Radio Deluxe + HDSDR + FT-991 Putting it all Together/, you can see how HDSDR makes a nice centerpiece for a station. Following these posts, plus the following instructions, will hopefully help you to quickly and effectively get your K3/K3S working with HDSDR.
The key differences in the setup from my Yaesu FT-991a and the K3 are the “SDR-Device” configuration and thee “RF Front-End Frequency Options” within HDSDR.
The Setup
The IF of the K3 is available on a BNC jack on the rear of the rig. This can be plugged directly into the RSP1a antenna input. The RSP1a configuration for my setup is:
Note that the Bias-T is disabled and a small amount of frequency correction was applied here. Additionally, it is important to use the Low IF setting of the IF Mode. This setting allows for the IF frequency to sit physically off from the center of your band view. Not using the Low IF setting will place an awkward line down the middle of the spectral display.
The second window of importance is the “RF Front-End Frequency Options” settings screen. This screen is found under the “Options” menu:
The IF frequency of 8.215 Mhz is that of the Elecraft K3. I used the global offset to adjust the HDSDR LO tuning and compensate for the small difference in tuning frequency between the K3 and the RSP1a. The offsets for LSB, USB, and CW_x, were adjusted for best listening match to the K3.
Please note that the “Mirror RF Spectrum for Tune” is checked and set to 49500. This accommodates the direction of the dial of the LO and moves the LO out of the band view.
There is a reason that SDR-based band scopes have become very popular — they are just cool!
Hope you find this helpful,
73 de WR9R