Frequency counters: Racal-Dana Vs Thurlby Thandar - Page 1
Forum section: electronics / general

author: Mike99
author_rank: Frequent Contributor
timestamp: March 20, 2025, 10:23:41 am
content: I have a Racal-Dana 1991 to which I have fitted an OCXO reference. I have the opportunity to buy. a Thurlby Thandar TF830. Apart from the extended frequency range does it have any other advantages, e.g. better precision?Mike

author: 807
author_rank: Frequent Contributor
timestamp: March 20, 2025, 11:57:41 am
content: Quote from: Mike99 on March 20, 2025, 10:23:41 amThey are both 1.3GHz counters. Unless you mean the lower limit (TTI = 5Hz, Racal = 10Hz).

author: Mike99
author_rank: Frequent Contributor
timestamp: March 20, 2025, 02:01:39 pm
content: Not true, the 1991 is 160MHz. I was wondering if the TT had better resolution. I might buy it anyway, can't have too many 😃.Mike

author: EC8010
author_rank: Frequent Contributor
timestamp: March 20, 2025, 02:05:49 pm
content: The TTi has an external 10MHz reference input. Useful if you have one of Mr Bodnar's 10MHz GPS-locked boxes.

author: andrewtaylor
author_rank: Contributor
timestamp: March 20, 2025, 05:32:44 pm
content: Depending on your usage ideas:TTI has battery powered opearion included,which racal 1991/1992 do not have.Maybe of yuse for you, or unneeded feature.seehttps://www.testequipmenthq.com/datasheets/THANDAR-TF830-Datasheet.pdf

author: 807
author_rank: Frequent Contributor
timestamp: March 20, 2025, 06:09:33 pm
content: Quote from: Mike99 on March 20, 2025, 02:01:39 pmOops! Sorry. I was thinking of the 1992.

author: Mike99
author_rank: Frequent Contributor
timestamp: March 20, 2025, 07:31:45 pm
content: Quote from: EC8010 on March 20, 2025, 02:05:49 pmI've built a 10MHz GPSDO so that's good to know, thanks.Mike

author: Mike99
author_rank: Frequent Contributor
timestamp: March 20, 2025, 07:40:07 pm
content: Quote from: andrewtaylor on March 20, 2025, 05:32:44 pmThanks for the data sheet. If I'm reading it correctly the TT has 100Hz resolution at 25MHz. My 1991 reads to 0.01Hz at 10MHz so it's considerably better.Mike

author: lowimpedance
author_rank: Super Contributor
timestamp: March 20, 2025, 10:37:04 pm
content: Quote from: EC8010 on March 20, 2025, 02:05:49 pmThe Racal 1991 also has an external ref input BNC,compare your GPSDO to the OCXO !

author: edpalmer42
author_rank: Super Contributor
timestamp: March 21, 2025, 04:54:51 am
content: Quote from: Mike99 on March 20, 2025, 07:40:07 pmYou might want to check that. Press the up arrow until you get to 0.01 Hz, then press & hold the up arrow for a couple of seconds. The most significant digit falls off the left side of the display, the gate time goes to 10 sec. and the resolution goes to 0.001 Hz.This applies to both the 1991 and 1992. It is documented in the manual, but it's easy to miss.

author: Gertjan
author_rank: Frequent Contributor
timestamp: March 21, 2025, 11:11:46 am
content: Quote from: edpalmer42 on March 21, 2025, 04:54:51 amThis is one of the reasons I like the 199x range of racal-Dana counters!The 1998 and 1999 are using a 20s gate time for 1mHz resolution @ 10MHz, and are showing a digit more in the display (instead of the exponent of the 1991 and 1992)That display is another reason for liking these Racal-Dana's: I can read the big red LED displays from the other side of the room. Try that with the (non-backlit?) LCD display of the TF830....In favour for the TF830 is it's very low power consumption.regards, Gertjan.

author: Datman
author_rank: Regular Contributor
timestamp: March 21, 2025, 12:24:34 pm
content: Some time ago I bought my Racal Dana 1991 with an added prescaler, a switch and a BNC. It was dividing by 1000, but it was done by a divider by 64, then losing 2 times a pulse every 5 and a divider by 10. I kept only the divider by 64 and I made a sequencer with an ATmega328P (but you can use a pair of CD4017 if it is only for that) to compose on the keyboard a division by 0.015625 (= x64):https://youtu.be/Vci8i0bSz7Y

author: Mike99
author_rank: Frequent Contributor
timestamp: March 21, 2025, 12:58:39 pm
content: Quote from: Gertjan on March 21, 2025, 11:11:46 amThank you, I didn't know that and I've had the counter for several years!Mike

author: Datman
author_rank: Regular Contributor
timestamp: March 26, 2025, 09:19:33 am
content: 1991 for a 100Hz frequency measures microHz in a fraction of a second!