15.6 MHz TCXO Board for Kenwood TS-590S by Mark Goldberg, W7MLG

New (16 Mar 2018) TCXO chips for the next batch of 85 TCXO boards have been ordered. The boards should be available some time this summer. Hopefully, I will finally catch up with the backlog.

New (22 Feb 2018) I have added a page describing my test setup at Test Jig.

New (20 Feb 2018 ) I have built all of the rest of the boards I have parts for. All of the ones that have passed my tests have been shipped. I am working on trying to troubleshoot some of the remaining units. It is possible that the frequency stability test (done at a constant room temperature) is too stringent. I have developed a test that will mimic the real world usage of changing temperature from 20 to 60 C as the radio would warm up. If they pass the spec of +/- .28 ppm, they would be fine to use. If I find more that are OK, I will offer them for sale, otherwise it will be many months till the next batch. Since this is a low volume for the TCXO chip supplier they will not be able to improve the specifications to meet my requirements. Since the yield should be similar on the batch, I will have to compensate by raising the price on the next batch to make up for the percentage of parts that I can't use. The price will now be $59 plus shipping and Paypal fees.

Because this has become a big effort, I have set up Goldberg Labs, LLC to continue this work. For now, www.goldberglabs.com will take you to this page. TCXO questions may be addressed to <Four Letter Acronym Describing This Product><at>goldberglabs<dot>com. Hope you can guess what that email is. Those should not be lost in my personal email.

Keith, G6NHU has done a very nice writeup of my TCXO on his site at http://qso365.co.uk/?p=5157.

Thanks a bunch Keith.

New ( 5 Jan 2018 ) 20 more units have been built.  I will not be doing baking at the elevated temperature suitable for the TCXOs ( 85 Degrees C ) as it may affect the other parts on the board that are in plastic packages. I will test when the parts settle onto frequency after storing at about 45 Degrees C which should be safe for everything. This should provide an aging acceleration factor of about 4 using the Arrhenious equation ( see http://www.itl.nist.gov/div898/handbook/apr/section1/apr151.htm ) and an Ea of 0.578 ( see www.txccorp.com/download/tech_paper/201106_2.pdf  for a similar crystal ).

New ( 16 Dec 2017 ) Clarified status and ordering  a little better below.

New ( 15 Dec 2017 ) Added a link to my buffer board installation for an external SDR panadapter. See Mark's TS590S MODs.
New ( 9 Dec 2017 ) New notes were getting a little long, so moved them to the Archived Notes page. I have dramatically improved my test capability as linked to below. Per a suggestion from TCXO chip manufacturer, I will do a 24 hour bake at elevated temperature to age the crystals after soldering, so I hope to build and test the rest of this batch of boards by the end of the year.


I'm Mark, W7MLG. Take a look at my qrz.com page for more info.

After making measurements of the standard Crystal Oscillator and the cheap TCXOs available for the Kenwood TS-590S, and considering the expensive TCXO available from Kenwood, I decided that there should be another option.

Review my measurements of the various available options here: Mark's TCXO Measurements.

The measurements were made on my TS-590S, but should  be applicable to the TS-590SG and any other variations of the TS-590, as well as the variations of the TS-480 that use the SO-3 TCXO. My board should work in all of them.

The bottom line is the cheap TCXOs are not really TCXOs on the 15.6 MHz frequency at all, but are inexpensive synthesizers with an output at 15.6 MHz, plus lots of spurs and poor phase noise, that degrades the performance of the radio.

I did some limited testing on the real Kenwood SO-3 TCXO, it is very good from what I can measure, at a price of course. They do not provide much information about it. The specifications are not very detailed.

So, I found a TCXO manufacturer that would make custom TCXOs for me that would allow me to order them in a reasonable quantity, and would provide lots of data about their performance. I then designed a custom board with the TCXO, an ultra low noise local 3.3 V regulator to run the TCXO, filtering as needed, and a high quality 10 turn potentiometer to adjust the frequency accurately.

For installation instructions, click here: Installation.

For adjustment instructions, click here: Adjustment.

I test these with the setup described here: Perseus SDR Test Setup.

I use this test jig to hold the board and adjust the temperature during testing: Test Jig.

If you don't want to read all this you can jump directly to How Can I Get One?

If you want to know why I did this, jump directly to Why Did I Do This?

I will provide more information as time permits, but some manufacturer's specifications are as follows:

Frequency 15.6 MHz
Temperature Stability +/- 0.28 PPM over 0 to 50 degrees C guaranteed, typically meets this over 0 to 70 degrees C.
Aging First Year 1.00 ppm
Total Frequency Tolerance (20 Years)
4.60 ppm
Integrated Phase Jitter (BW=12kHz to 20MHz)
0.3 ps rms Typical, 1.0 ps rms Maximum
SSB Phase Noise at 10Hz offset
-90 dBc/Hz Typical,  -70 dBc/Hz Maximum
SSB Phase Noise at 100Hz offset
-115 dBc/Hz Typical, -100 dBc/Hz Maximum
SSB Phase Noise at 1KHz offset
-135 dBc/Hz Typical, -130 dBc/Hz Maximum
SSB Phase Noise at >10KHz offset -152 dBc/Hz Typical, -145 dBc/Hz Maximum
SSB Phase Noise at >100KHz offset
-154 dBc/Hz Typical, -150 dBc/Hz Maximum
Frequency Tuning Range at 25 degrees C
+/- 10 ppm

My test results show that I have achieved the same specs on the finished board. The jitter and phase noise contribution from the 3.3 V regulator and the noise contribution from the resistors is way below that of the TCXO itself, so they do not affect the results. The potentiometer could change in time, but since I am using it as a true potentiometer with no other resistors that have varying temperature or time varying characteristics, it should not result in any changes either.

This TCXO board is known to fit correctly in the TS-590S and TS-590SG. If someone has fit it into a TS-480, please let me know.

Typical Performance

I have built several prototypes and the typical performance is shown below.

Phase Noise

The phase noise pretty much matches the typical specifications. All tested so far are within a few dB of each other.

Frequency Drift Over Temperature

If you set the frequency when the radio is warm, for example at 30 degrees C, the frequency drift over temperature of the samples measured all meet the specified +/- 0.28 ppm, although they tend to drift slightly more in the positive direction. Because there is a 10 turn pot, you can reset the frequency accurately. It may need to be done every so often, as it would be with any TCXO.

Typical Waveform

The TCXO output is about the same voltage but is more square than the standard crystal oscillator output. This performs well in the radio. Performance is indistinguishable from the standard oscillator. See my Mark's TCXO Measurements site for more details. This TCXO is called the Reference TCXO on that site.

What Does It Look Like?

The top side has only the connector and the 10 turn pot. The mounting holes and overall size match other TCXOs. Note that there are lots of stiched vias between the top and bottom, which provides a true RF ground to the circuit. The mounting holes are not plated, to avoid damage if screwed on too tight, but there is a ring of ground vias between the top and bottom pads.

The bottom side is where the action is. The TXCO is U1. It is in a castellated surface mount package where the leads are on the bottom and come up the sides. It is very hard to solder by hand. The other parts are also surface mount, with 0603 sized caps, also hard to solder by hand. As you might guess, it was not soldered by hand.

How Was It Made?

The board was built using smt reflow soldering. I have a homemade reflow oven. See Mark's Controleo2 Build for details on how it was made.

The first step is to get a PWB from my design. I chose OSH Park, a high quality board maker that is very reasonably priced.

Solder paste must be applied. I got a stainless steel stencil from OSH Stencils. They just started making stainless steel stencils, and I highly recommend them. They work very well and are still reasonably priced.

The board is held by a jig, and the stencil is taped to the same jig. These are unframed stencils, but it was easy to line them up this way.

Then I flipped the stencil down and lined it up. I included three fiducials to help with that. They are the small round features at the outer perimeter of the board.

Then, I applied solder paste. I used lead free solder paste.

Then I held the stencil down and smeared the solder paste over the holes in the stencil using a card that came with the stencil.

Lift the stencil up, and the solder paste is perfectly applied on the pads.

Then, I placed all the components by hand, using a foot switch controlled vacuum pickup and some tweezers to nudge them around if they were not perfectly placed. I used a binocular microscope to be able to see the small parts.

Then, off the reflow oven, which logs the reflow profile to the computer at the right of the picture.

The reflow is done and it is cooling.

The board is on the tray in the oven.

I then soldered the connector and potentiometer on by hand, using lead free solder and a Metcal iron. Lead free solder is much harder to use than standard solder, and lots of flux is necessary.

Why Would I Want One?

If you want a well designed TCXO, for less than half the cost of the Kenwood one, you might want one of these.

If you only care about frequency, you can buy the cheaper ones. There is no way that these can compete with those low prices.

How Can I get One?

Since this is very difficult to make, I am providing them as group buys. I built 10 prototypes and am finishing a second build of 60. Parts are being ordered for a third batch. I have determined that I need to have at least 35 orders to make another batch at a reasonable cost. You cannot buy the TCXOs in single quantities and the supplier has a minimum buy going forward.

I am offering these on a first come basis for $59 plus shipping and PayPal fees.

I had a couple early prototypes that are electrically identical, but have a spacer so one part does not hit the sheet metal under the mounting screw. Those were sold for $43 plus shipping and work just as well, but are gone. There is plenty of room in the radio for them to fit with the spacer and it is what I am using in my radio. You can see the spacers in the picture below, keeping the regulator marked LLVB from hitting the sheet metal under the mounting screw. In later prototypes seen above, the components were moved farther away from the mounting hole.

Early Prototype

I need to have requests for 35 more to buy parts for the next batch.

To request one or more TCXO boards, fill in this form. Your email and comment will not show up publicly in the spreadsheet below, but I will see them. You should get a confirmation email also. The list below the form should update in a few minutes to show your request.

TCXO Purchase Requests

You can also email me at <Four Letter Acronym Describing This Product><at>goldberglabs<dot>com with any questions.

Current Order Status (See notes below):

Order Status Notes:
1. First 10 were prototypes
2. Second batch is 60 boards. 40 have been built with 5 not passing final test. 
3. 20 more to be built 12/2017.
4. If the ones not passing final test can be fixed then the ones labeled "Undetermined" may get a board out of this batch. Otherwise, they will be pushed to the next batch.
5. Parts need to be ordered for the next batch. I need to finish the second batch of 60 and see how many have issues before ordering the next batch.

Why Did I Do This?

I started out annoyed with the state of available TCXOs, but I realized that this would be an exercise that would allow me to develop and enhance my skills. I did not realize when I started about a year ago how many diversions would result. Look up "Yak Shaving".

Some of the skills I have been able to develop or enhance due to this project are:

TCXO selection and understanding of specifications
TCXO board RF design, schematic capture, simulation and layout (Using Elsie, LTSpice, Kicad, Gerbv)
Low noise regulator selection and circuit design
3D printing to make foot for board vise (Using FreeCAD and Wings3D)
SMT soldering (Purchased METCAL equipment)
SMT Reflow soldering (Built reflow oven, studied IPC industry specs and supplier datasheets for best temperature profile)
Arduino coding and driver library development (to run reflow oven and modify operation from original design)
Sheet metal work, brake, shear, corner notcher, digital height guage (for reflow oven sheet metal and jigs to hold boards for solder stencils)
SDR concepts, especially using Perseus SDR (to do phase noise measurements without $100k equipment)
HP 8642A signal generator repair (bought one that was supposed to be working, did not work)
Google Sites website development, forms development, Google Analytics

I would like to thank the following people who assisted me with guidance and a sounding board for my rants.

Adam Farson VA7OJ
Rob Sherwood NC0B
Andy Durbin K3WYC
Israel Vicente AD7ND
Bob Doyle WA3TGF
Mike Allred AE4G

Here are some of my other sites:

Modifications to my RV, including solar power and extra storage:                   https://sites.google.com/site/marksrvmods/
My Controleo2 based SMT Reflow Oven:                                                          https://sites.google.com/site/markscontroleo2build/
My TS-590S MODs including a buffer board install for a panadapter:              https://sites.google.com/site/marksts590smods/
An explanation of various TCXO Characteristics in Kenwood TS-590 Radios:  https://sites.google.com/site/markstcxomeasurements/
Modifications to allow use of an external clock in a Perseus SDR:                    https://sites.google.com/site/perseusmods/
How I use Spectrum Lab Software to do frequency measurements:                  https://sites.google.com/site/spectrumlabtesting/
Pictures I took of the 2017 Total Solar Eclipse from Menan Butte, Idaho:         https://sites.google.com/site/marks2017eclipsephotos/

Revised March 16, 2018