FTS-4100 Cesium Standard tests

It wasn’t too hard for the guys to convince me to take a Cesium frequency standard to my portable location in Michigan to drive the HPSDR receiver that will do band recordings for the HamSci 2017 Total Solar Eclipse HF Wideband Recording Experiment. I had been planning to use a GPSDO, but that would be too simple. My “sort of” portable Cesium is an old FTS-4100 that came out of military service. It was designed for shipboard use (I think […]

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Hermes SDR as spectrum analyzer

I was fussing about signal generator output accuracy because I wanted to calibrate my HPSDR Hermes software defined radio (“SDR”) so that I could calculate the absolute power input in dBm, assuming a 50 ohm load impedance) based on the dBFS (db full scale of the ADC chip) output from the radio. This is in preparation for the upcoming solar eclipse, where as part of the HamSci 2017 Total Solar Eclipse HF Wideband Recording Experiment I’m planning to use the […]

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Update on Boring Signal Generator Stuff

Just when you thought it couldn’t get more boring (reference my last post about signal generator calibration… I did all these careful calibrations of my signal generator to check its accuracy and linearity. Everything looked good, except that the signal reading was about 1 dB low. HP power meters have a calibrator providing a 50 MHz signal at 0 dBm that is (supposedly) very precise. I have a total of four meters with those calibrators, and I decided to cross […]

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Boring Signal Generator Accuracy/Linearity Data

I want to calibrate my software defined radio receiver prior to doing a bunch of recordings of the ham bands for the upcoming solar eclipse (check out the HamSci web page for details). I have an HP 8642A signal generator which has high-precision attenuators and should be a very good reference to measure recorded amplitude vs. actual. Unfortunately, this generator is a decade or two out of calibration, so I thought I’d try to check its performance (amplitude accuracy, and […]

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$20 P25 Trunking Scanner (Part 4)

SDR

With op25 successfully decoding the control channel, now you just need to set up the trunking configuration. To do this, you’ll probably need to set up three files: 1. trunk.tsv defines the sites to be monitored. 2. site_name.tsv provides a table of talkgroup numbers and names for that site. 3. Because you probably only want to listen to a subset of the talkgroups, you can optionally create a file called site_name_wl.tsv with a list, one talkgroup per line, of the […]

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$20 P25 Trunking Scanner (Part 3)

SDR

The info in this and in part 4 was aided tremendously by several folks on the “op25-dev” mailing list. Without their help, I would not have even known where to start in getting my system running. I hope that what I’m documenting here will be helpful for others going down this path. If you’ve successfully installed Linux, Gnuradio, and op25 on your computer, you are ready to test the system, and then configure it for trunking. The scanner application is […]

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$20 P25 Trunking Scanner (Part 2)

SDR

Here’s how to install the OP25 scanning software. If you don’t already have Gnuradio installed on a Linux system, do those two things first. Any current Linux distribution works. I use Linux Mint which is very similar to Ubuntu. The easiest way to install Gnuradio is to use a script from the SBRAC radio astronomy group called build-gnuradio. Click on the link, then save the contents of the browser screen (easiest way is to select everything on the web page, […]

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$20 P25 Trunking Scanner (Part 1)

SDR

A couple of weeks ago at the Dayton Hamvention I bought a fancy Whistler TRX2 scanner that can receive the new P25 digital trunking system that’s been rolled-out statewide here in Ohio. Unfortunately, after a lot of attempts, I still can’t get it to reliably receive the talkgroups I’m most interested in. Out of frustration (and boredom) I decided to research the couple of projects I’d heard about to implement P25 decoding, and after a few hours work (and some […]

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Pulse Per Second Dividers, Overdone

Several years ago I designed a little circuit board called the T2-Mini that provides life support for one of Tom Van Baak’s very wonderful picDIV PIC-based frequency dividers. The idea is to convert the 1, 2.5, 5, or 10 MHz output from a frequency standard to a one pulse-per-second (PPS) signal for use in frequency stability measurements. I don’t do things in a small way, so I built a rack enclosure (using the Front Panel Express service to hold 8 […]

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TICC Timestamping Counter

My latest project has turned out to be my most complex (so far…), involving both new-fangled hardware and quite a bit of software, but it’s now finished and working well. Meet the TICC, an Arduino Mega 2560 shield that implements a two channel timestamping counter that has resolution of better than 60 picoseconds (that’s 60 trillionths of a second). TAPR did a production run (we still have them available; go to http://tapr.org/kits_ticc.html) and the units have been in peoples’ hands […]

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