TADD-3 Enclosure

Just finished the second piece of my multiplexed measuring system. This one isn’t too sexy, but is a necessary part — a pulse-per-second (“PPS”) distribution system. This enclosure contains 4 TADD-3 PPS distribution boards. Each board has 2 sets of 3 outputs, plus 2 RS-232 level outputs. So, there are 8 input connectors on the rear, as well as 4 DE9 connectors (the PPS signal is on the DCD line, and I’m only bringing out the RS-232 signal from the […]

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TASS System Multi-board RF Performance

The TASS switch system made a design compromise that means its RF performance has some variation depending on which combination of ports is selected. When using a port that’s not at the far end of the board from the common, there is a transmission line stub of varying length that affects VHF performance. A single TASS board works well through 150 MHz. The question has been what happens when you build a multi-board system? Now that I have the TASS […]

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TASS System enclosure

Several of the design projects I’ve done for TAPR were part of a larger concept I’ve been working on for several years: a measurement system that will allow me to compare the pulse-per-second (PPS) outputs from a bunch of test devices against one of several reference clocks over long time periods (sometimes a year or more). A key part of that system is a “multiplexer” or switch matrix that allows selecting one of several devices under test (DUT) and reference […]

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Pinouts for FTS 1200 9110 1000A-100 1000B OXCO

I rediscovered a post from Corby Dawson with pinouts for the DB9 connector on the above OCXO and wanted to preserve the info here.  Thanks, Corby! 1000B 1000A-100 1200 and 9110 1 EFC ground EFC ground EFC ground 2 EFC +- 10V EFC +- 10V EFC 0 to +10V 3 coarse wiper NC NC 4 +12 pot ref. (10K) NC NC 5 Ground Ground Ground 6 oven mon. oven mon. oven mon. 7 +28V oven +18V oven NC 8 +28V […]

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An interface from Hermes/ANAN to the TASS relay board

I didn’t even think of it when I was designing the TASS-R relay switch system, but the relay board can be used with an HPSDR Hermes, ANAN-10, or ANAN-100/200 radio without requiring use of an Arduino or other controller.  These radios provide 7 open collector outputs that can be programmed from within the PowerSDR software.  A simple interface board allows the TASS-R to be controlled by these outputs. The idea is that two of the outputs can be used as […]

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3 Vintage Sulzers Compared

I did two hour measurement runs of three ’60s vintage Sulzer frequency standards against perhaps the best modern quartz standard available.  These are pretty amazing results.

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TASS Switching System announced, and fun with enclosures

Today TAPR announced availability of a project I’ve been working on for a while, a computer-controlled switch system called the TASS.  It consists of an 8-port relay bank that handles from DC to 150 MHz, a shield for an Arduino, and open source software for the Arduino. You can order the boards from http://tapr.org/kits_tass.html. I also designed an enclosure for a TASS board plus touchscreen controller, and had that built by Front Panel Express.  Here are some pictures of the […]

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Testing a ’60s vintage Sulzer OCXO — with a twist

Over the years I’ve acquired a whole bunch of Sulzer OCXOs.  One is dead, several have oven temperature control problems, but I have three powered up in the rack that still work amazingly well. This one, Sulzer #3, is particularly interesting.  It’s not on the standard 2.5 or 5 MHz frequency.  Instead it runs at 5.006 880 MHz.  That happens to be a submultiple of the Cesium transition frequency.  And I’ve been told, but unfortunately can’t prove, that this unit […]

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More OCXO Adjustments

More twiddling of the OCXOs this afternoon. Austron 1250A:  was tune 375, +3.9e9; now tune 340, +4.5e12 FTS 1050A: was tune 55000, +2.1e9; now tune 54614, -1.7e12 Sulzer #1 (2.5 MHz): was tune +0.39, +7.2e9; now tune -0.56 (CCW past zero), -3.2e12 Sulzer #2 (5 MHz): was tune 9.23, -1.4e9; now tune 9.31, -1.2e11 All these comparisons are against an HP 5061A Cesium standard that tracks GPS at about -2e13.  The Sulzers have mechanical tuning (flexible shaft to a piston […]

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Some Frequency Trimming

I normally don’t adjust the frequency of the half dozen high quality quartz oscillators I have running in the lab.  I don’t rely on them for absolute frequency precision as I have better sources for that.  But I thought it was time to get them all tweaked reasonably closely so the offset isn’t too bad for a new set of experiments I’m getting ready to start. First was my OSA 8607-008 BVA, which was powered on in 2012 and hasn’t […]

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