Ramsey Electronics 500mhz prescaler question, - Page 1
Forum section: electronics / projects

author: CaptDon
author_rank: Super Contributor
timestamp: June 11, 2023, 03:11:19 pm
content: Anyone here know what prescaler chip Ramsey used in their stand-alone divide by 100 prescaler? It is a 16 pin chip with pins 1,6 and 9-13 grounded. Just curious. They sanded the part number off the package. Mine still works but it may be nice to have a spare I.C. around. The mystery chip drives a 74LS196 which provides the final output. End to end it is divide by 100 so guessing the prescaler is divide by 10?Thanks!!

author: Stray Electron
author_rank: Super Contributor
timestamp: June 11, 2023, 07:00:11 pm
content: I have a very early Optoelectronics FC-50C FC and it probably uses the same IC. But I can't remember the part number. Mine has the optional prescaler card in it and it is complete but it's missing the socketed IC. I have looked and looked and looked for the IC but I can't find anything but counterfeit ones from China.I looked around at other prescaler ICs but that was the only one that I could find that was a divide by ten and that came in a DIP package.I will do some digging around and see if I can find the part number again. I think it was a 9310 or something like that and was made by Intersil (??). I'm pretty certain that it was an ECL part.

author: Stray Electron
author_rank: Super Contributor
timestamp: June 11, 2023, 07:08:40 pm
content: LOL. I couldn't find my old data sheet for the part, but I did post about it on this forum! See <https://www.eevblog.com/forum/rf-microwave/old-1970s-divide-by-10-prescaler-ic/>Look up the data sheet and then reply back and let us know if you think that this is the same part.

author: Benta
author_rank: Super Contributor
timestamp: June 11, 2023, 08:17:12 pm
content: National 11C90 could also be a possibility.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 11, 2023, 09:02:15 pm
content: Motorola MC12013 ?

author: factory
author_rank: Super Contributor
timestamp: June 11, 2023, 09:10:41 pm
content: The Plessey SP630 is another divide by 10 prescaler IC (ECL).Edit: can't be this one, as it only has 14 pins.David

author: Benta
author_rank: Super Contributor
timestamp: June 11, 2023, 09:19:29 pm
content: Quote from: Andy Watson on June 11, 2023, 09:02:15 pmGood call. I think you nailed it.

author: CaptDon
author_rank: Super Contributor
timestamp: June 12, 2023, 12:11:40 pm
content: Thank-you indeed. The MC12013 does seem to be the correct part based on all 16 pin connections. I also have a Ramsey 650Mhz battery operated frequency counter and it uses an 11C90D, but that has a totally different pinout. Strange story here, I was testing two ArcShell AR-6 handy-talkies that didn't seem to work with each other. They were bought about two years apart. Turns out only about half of the 16 channels had common programming. My 500Mhz prescaler showed 462.124300Mhz and the 650Mhz portable counter showed 577.656Mhz for a difference of 115.532Mhz which when multiplied by 4 gives the 462.124Mhz number. My spectrum analyzer doesn't go high enough in frequency to do the test but I ponder if the power output at 462.124 and 577.656 are nearly equal? These radios are notoriously illegal for almost any application. They can be programmed for FRS/GMRS frequencies but are not type accepted for that use. These are what the company bought for the deck hands and amazingly even with the lanyards these goof-ups seem to drop one overboard about once a month. We seem to have about 20 charging stands for about 5 radios!!! Cheers mates!!! Thanks for the info on the I.C.!!