hack@math14.math.umbc.edu (03/20/91)
In a recent Radio Electronics issue (dec 1990) they detail a frequency counter. In their design they use a CD4017 decade counter together with a 7490 bcd counter as a prescaler. The counter is the Harris ICM7216CIJI. The Harris counter is a 10MHz frequency counter. They claim that with their setup the counter is good upto around 1.8GHz ... The problem I have is this. The CD4017 is a cmos device (slow) evan most ttl counters are not usable for much greater than 100MHz. Evan the 7490 is rated for a clock frequency of no more than 35MHZ So how does this circuit do what it says. If I have made some mistake in something somewhere would some kind soul tell me. If not does anyone know of any prescalers usable in this frequency range ( upto 100GHz or evan 1GHZ). Thank you in advance, J. Hack
henry@zoo.toronto.edu (Henry Spencer) (03/21/91)
In article <5463@umbc3.UMBC.EDU> hack@math14.math.umbc.edu () writes: > In a recent Radio Electronics issue (dec 1990) they detail >a frequency counter. In their design they use a CD4017 decade >counter together with a 7490 bcd counter as a prescaler. The >counter is the Harris ICM7216CIJI. The Harris counter is a >10MHz frequency counter. They claim that with their setup the >counter is good upto around 1.8GHz ... The claim was retracted in a later issue. -- "[Some people] positively *wish* to | Henry Spencer @ U of Toronto Zoology believe ill of the modern world."-R.Peto| henry@zoo.toronto.edu utzoo!henry
dmturne@PacBell.COM (Dave Turner) (03/21/91)
In article <5463@umbc3.UMBC.EDU> hack@math14.math.umbc.edu () writes: > > In a recent Radio Electronics issue (dec 1990) they detail >a frequency counter. In their design they use a CD4017 decade >counter together with a 7490 bcd counter as a prescaler. The >counter is the Harris ICM7216CIJI. The Harris counter is a >10MHz frequency counter. They claim that with their setup the >counter is good upto around 1.8GHz ... > > The problem I have is this. The CD4017 is a cmos device >(slow) evan most ttl counters are not usable for much greater >than 100MHz. Evan the 7490 is rated for a clock frequency of >no more than 35MHZ So how does this circuit do what it says. If I >have made some mistake in something somewhere would some kind Check Radio-Electronics, February, 1991, page 21. I quote: "We greatly exaggerated the capabilities of the counter. Because of the components used, the counter cannot perform at frequencies above 25 MHz. We're sorry for any confusion our misstatements caused." They also give the PC patterns which were omitted from the original article, but I can't imagine why anyone would want to build this thing. One prescaler that works to 1.25 GHz is the RCA CA3179E. -- Dave Turner 415/823-2001 {att,bellcore,sun,ames,decwrl}!pacbell!dmturne
mzenier@polari.UUCP (Mark Zenier) (03/21/91)
In article <5463@umbc3.UMBC.EDU> hack@math14.math.umbc.edu () writes: > > In a recent Radio Electronics issue (dec 1990) they detail >a frequency counter. In their design they use a CD4017 decade >counter together with a 7490 bcd counter as a prescaler. The >counter is the Harris ICM7216CIJI. The Harris counter is a >10MHz frequency counter. They claim that with their setup the >counter is good upto around 1.8GHz ... > > The problem I have is this. The CD4017 is a cmos device >(slow) evan most ttl counters are not usable for much greater >than 100MHz. Evan the 7490 is rated for a clock frequency of >no more than 35MHZ So how does this circuit do what it says. They printed a correction a few months later that the counter was only good for thirty some MHz. >If not does anyone know of any prescalers >usable in this frequency range ( upto 100GHz or evan 1GHZ). There have been three or four more counter project in Radio-Electronics over the past several years. They seem fond of the 11c90 prescaler from National. There is also the mc12073, mc12074 and the like from Motorola and some stuff I don't have data on from from Plessy, Telefunken, Siemens, and Fujitsu. Some go up to 2.4 or 2.7 GHz. More go to 1.1 to 1.6 GHz. Mark Zenier markz@ssc.uucp mzenier@polari.uucp
carmijo@hpnmdla.hp.com (Chris Armijo) (03/22/91)
>> The problem I have is this. The CD4017 is a cmos device >> (slow) evan most ttl counters are not usable for much greater >> than 100MHz. Evan the 7490 is rated for a clock frequency of >> no more than 35MHZ So how does this circuit do what it says. If I >> have made some mistake in something somewhere would some kind >> soul tell me. If not does anyone know of any prescalers >> usable in this frequency range ( upto 100GHz or evan 1GHZ). You're exactly right. This was a big error on the maganize's part. If I remember correctly, they printed a small correction in the February (January, March?) issue where they correctly state that the upper frequency limit is more like 10MHz. By the way, there are ECL prescalars on the market nowadays that can work well into the GHZ range. Some samples: NEC UPB585 2.5GHz divide by 4 NEC UPB586 2.5GHZ divide by 512/256 Avantek IFD-50010 5GHz divide by 4 Avantek IFD-50210 3.5GHZ divide by 4 These are all silicon, bipolar technology. (Go Bipolar!) To use parts like these you need to use special layout techniques (of course) -- wire wrap doesn't work too well at 1 GHz!. Microstrip is called for. Chris Armijo