PTS Synthesizer Programming Info

There are lots of PTS (Programmed Test Sources) synthesizers available on eBay. They go for reasonable prices because they are usually set up for remote control and don't have any front panel at all.

These are nice units because they have low phase noise and the spurious outputs are way down in the mud. The best place to find details is on the PTS website) where they have a fair bit of technical info and a PDF catalog. However, the web site doesn't provide info on how to program the units via their rear panel connectors. This page fills that gap for two units that I've worked with: the PTS160 and PTS250 units (I also have a 40MHz PTS040, but it has the direct digital synthesis option and some other quirks that I haven't fully figured out yet).


The PTS synthesizers are very modular in design. They offer various frequency step sizes from a minimum of 100kHz down to 0.1Hz. If you happen to find yourself with more than one unit, you can mix and match the divider modules to get the resolution you want. Looking down at the unit with the front facing you, the right-hand seven slots may or may not be populated with boxed modules. These are the "digit modules" that provide the resolution settings. If all the slots are full, the unit has 0.1Hz resolution; each missing box (from the right end) drops one digit.

You can add additional digit modules from another unit. However, you need to tell the unit that they're there. To do that, open the bottom of the box and look at the long PC motherboard that's nearest the front of the unit. There will be a wire running from pin 3 (from the front of the box) on the right-most slot over to pin 3 of the last slot that has a module installed. Simply plug in the extra modules and move that lead to so that it now connects to pin 3 of the last slot that you've filled (still leaving the right-most end anchored), and you're all set. I modified a PTS160 unit to go from 1kHz to 1Hz resolution this way.


The PTS synthesizers have very clean output spectra and low phase noise. Here is a screenshot of the phase noise of my PTS160 taken from an Agilent E4440A PSA Series spectrum analyzer:

PTS Programming

The 50 pin connector on the back of the unit is a standard Centronics male plug. The connector carries BCD programming lines for each digit as well as a few other signals. All the logic signals are TTL level and are tied high internally; to activate, ground the appropriate pin on the connector. Looking at the back of the unit, pin 1 is at the lower left, pin 25 at the lower right, pin 26 at the upper left, and pin 50 at the upper right of the connector.

Pin 42 is the "remote enable" pin and it must be tied low before you can program the unit.

NOTE: The PTS250 pinouts below are in error. I believe the PTS160 pinouts apply to both units.

The PTS160 and PTS250 have some differences in pinouts, so make sure you use the proper column from this table:

Pin PTS160 PTS250 Pin PTS160 PTS250
1100kHz200kHz 26400kHz800kHz
2200kHz400kHz 27800kHz1MHz
310kHz10kHz 2840kHz40kHz
420kHz20kHz 2980kHz80kHz
51kHz1kHz 304kHz4kHz
62kHz2kHz 318kHz8kHz
7100Hz100Hz 32400Hz400Hz
8200Hz200Hz 33800Hz800Hz
910Hz10Hz 3440Hz40Hz
1020Hz20Hz 3580Hz80Hz
111Hz1Hz 364Hz4Hz
122Hz2Hz 378Hz8Hz
130.1Hz0.1Hz 380.4Hz0.4Hz
140.2Hz0.2Hz 390.8Hz0.8Hz
1510MHz20MHz 4040MHz80MHz
1620MHz40MHz 4180MHz100MHz
182MHz4MHz 43  
194MHz8MHz 44  
208MHz10MHz 45