Kenwood TS-590S

Acquired 2026-06-06 at the Rockland Hamfest. Serial number __. I do not yet know if the ALC repair was made.

Adding an panadaptor tap is one of my favorite things to do to HF rigs. I usually prefer IF taps to Rx taps, but on the TS-590S this is a challenge because the radio does both upconversion and downconversion, and there are two IF tap points. On Mark W7MLG's page on adding an SDR panadaptor to the TS-590S here, he mentions the availability of CN101 for an Rx tap before the RF amplifier, or CN201, which also makes use of the band pass filters. That's my preference, so I'll also be using CN201.

Two examples:

1. https://kd2c.com/hi-z-tap-boards
2. https://www.sdr-kits.net/Panoramic-Adaptor-Tap-Boards

Other resources:

1. Mark W7MLG has a good page on an IF tap for the 590: here
2. Good presentation SDR panadapters in general, with some TS-590 specifics: here (note: he does an RF tap)

My unit came with a no-name SO-3 clone installed, with the jumpers in place (meaning the TCXO was running in parallel with the original XO). I have removed the jumpers, and will test the characteristics of the TCXO. I am exploring building an alternative TCXO replacement, as SO-3's are expensive and require the original daughterboard be present.

Mark W7MLG made such a replacement in 2017. He used a made-to-order TCXO with a 3v3 LDO and trimmer potentiometer. Not much information is provided regarding the technical details.

• https://sites.google.com/site/markstcxo/
• https://qso365.co.uk/2018/02/installing-a-good-quality-tcxo-from-mark-goldberg-w7mlg-into-my-kenwood-ts-590sg/

Cheap SO-3 alternatives exist, but may be have suspect phase noise or other issues:

• https://www.egloff.eu/index.php?option=com_content&view=article&id=48:ts590s-so-3-tcxo-replacement&lang=en

Potential DDS/PLL based alternatives?

• SiTime Si3521 - this is not sold as a TCXO, but is a TCXO per its functional description. SiTime only states a stability of 20PPM, but I'm still interested in playing with one. The evaluation board is prohibitively expensive, so I may spin my own board if I wish to proceed further.
• Jason Milldrum NT7S has done a lot of research, development, and testing into the application of a Silicon Labs Si5351A coupled with a 25MHz TCXO. This is a $2 part that could be coupled with a $2 TCXO. With appropriate filtering this could be a strong contender, and there is already a baseline of using this combination in amateur radio projects that demand high stability. Lots of posts on his blog under “Si5351A” - https://nt7s.com/?s=Si5351A
• The MS5351M exists as a Chinese clone of the Si5351A, and has been used favorably by QRP Labs, who also did a great write up on it. Interestingly, in his tests it demonstrated notably better phase noise characteristics than the Si5351A. Their write up can be found here.