Hi Gerard,I'm not fully set up at the moment but if you've had no better offers I may be able to help.I'm located in Cambridge. My equipment includes a Thunderbolt GPSDO, two Efratom FRK-L Rubidiums, Oncore VP GPS, Phillips PM6654 time interval counter, Odetics satsync 325 GPSDO, Datum FTS-1000B OCXO and the usual 'scope, RF generator, spectrum analyser etc. Robert G8RPI. --- On Sat, 27/2/10, Gerard PG5G <p...@b737.co.uk> wrote:
From: Gerard PG5G <p...@b737.co.uk> Subject: [time-nuts] My DIY frequency counter and a request for help To: time-nuts@febo.com Date: Saturday, 27 February, 2010, 9:36 Hello all, First post here, so I'll start with a quick introduction. I trained as an electronic engineer but don't work in that field any more, which has given me the appetite back to do some electronic engineering as a hobby. I have been a licensed ham for over 25 years (more than 60% of my life I realised the other day) and used to be rather active on HF as PA3DQW. At the moment I live in the UK where I am licensed as M0AIU. I recently designed and build a frequency counter and I need some help with verifying its performance. I believe it gives me 11 digits in 1 second. I say believe because I have not got the hardware to verify this. At the moment my assumption is based on calculations and limited testing with the equipment available to me. My counter is a "continuous time stamping reciprocal counter". I implemented this as a USB powered device, with the hardware taking the time stamps and sending it over USB to a windows PC. Some software written in C++ takes care of analysing the data. The hardware takes 5000 time stamps per second using a high speed TDC. The hardware is a single PCB measuring about 50 by 80 mm. it requires an external 10MHz reference and apart from using this as the time base it also uses this for self-calibration of the TDC. The unit requires no further calibration. The PC software takes these time stamps and the associated counts and uses regression to calculate the slope. This slope represents the frequency of the input signal. I am sure people on here are familiar with the counters made by Pendulum, and I have to confess that their marketing material was helpful in putting this thing together. Since the hardware is true zero dead time, the final capabilities of this counter are determined by software. At the moment I can simultaneously display the input at multiple gate times (see the attached screen shot). For gate times over 1 second I have the option to use overlapping gates, so that the display gets updated every second. Because there is no dead time I can also calculate Allan Deviation. The two displays at the bottom of the page show both normal and overlapping Allan deviation at tau=10s. I am still working on the software to do this at multiple tau in real time and display it as a graph and a table. So, after this lengthy introduction here is my request for some assistance. Is there somebody on the list who can assist me in verifying the performance of this frequency counter? Ideally somebody with access to two highly stable and known frequency sources. I can send the hardware by mail, but if there happens to be somebody with this kind of gear not too far from where I am (50 north of London) I will travel. In exchange you get to keep the hardware and will be supplied with whatever software I come up with. Thanks in advance and regards, Gerard, PG5G -----Inline Attachment Follows----- _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.