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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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27th Dec 2003, 12:51 am | #1 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,643
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Frequency Counters
I'm currently converting my garage in preparation for more serious things (ie radio restoration). I have most of the test equipment I need, but am on the lookout for a frequency counter as my elderly valve sig genny is probably not of sufficient accuracy for realignment. Has anyone any experience of the modern DVMs with a frequency measuring function. They seem to be sufficiently accurate for IF/MF realignment, but do they work?
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28th Dec 2003, 6:37 pm | #2 |
Retired Dormant Member
Join Date: Mar 2003
Location: Bishop's Waltham, Hants, UK.
Posts: 939
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Re: Frequency Counters
Bill,
several things come to mind...... 1. the range of the frequency counters in DVMs is limited, many only go to 1MHz or 10MHz - neither of which is any good if you want to do FM IFs or FM front ends. 2. Many (all?) DVMs use the normal leads for a frequency input, and not a proper screened connection, you will pick up noise on the input, leading to erroneous readings, and, more importantly, any high level signals will leak out, causing problems with the alignment process. 3. Does your signal generator have a counter output? If not, you will either have to connect the meter each time you want to check the frequency (tedious), or connect the generator permantly to the counter, with a high level output, and use an external attenuator (see point 2), or fit a counter ouput socket (again, see point 2). 4. Many older generators use harmonics to give the highest frequency bands (Taylor / Windsor model 65, some Advance units). In this case, no matter what counter you have, you won't get a valid reading - you can cure this by building a low pass filter to go in front of the counter, but you will, again, have to have a high ouput level to drive it. On the whole, I would reccomend buying a seperate counter with a good screened input, there are many good units available on the surplus market at present, with the Racal 9000 series units having quite a good spec at a fairly low price (upwards of £35 plus the chancellors cut). They come as both frequency counters and counter/timers, though the latter will only usually read to 50MHz. Hope this is of some help. Jim. |
28th Dec 2003, 9:34 pm | #3 |
Retired Dormant Member
Join Date: Sep 2003
Location: Wrexham, North Wales, UK.
Posts: 799
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Re: Frequency Counters
I bought a Thandar frequency meter at the swapmeet at haydock park holiday Inn in November, it was £25.00 and goes up to 200Mhz it seems to work pretty well I bought a screened lead for it with two mini probes on, the only drawback is that it's battery powered and doesn't have an auto off facility. Hope this is of some help.
Mike |
29th Dec 2003, 2:41 pm | #4 |
Hexode
Join Date: Mar 2003
Location: World Heritage Village of Saltaire, Shipley, West Riding of Yorkshire.
Posts: 324
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Re: Frequency Counters
I use a Racal 9520 bought from J. Birkett for £30 including postage. I like this type because they have the Nixi tubes fitted!. I would agree that you must use the correct leads and plugs to connect up with. I was just using bits of wire until someone on this forum pointed out my error.
Paul E |
29th Dec 2003, 8:12 pm | #5 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,643
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Re: Frequency Counters
Thanks Jim/Mike/Paul.
I think that is about what I expected to hear, but it was probably worth airing. I don't need yet another DVM, so it'll have to be a pukka counter! My SG (an old Tripplett) hasn't a counter out, but it shouldn't be rocket science to add one taking the precautions above. |
29th Dec 2003, 9:20 pm | #6 |
Retired Dormant Member
Join Date: Mar 2003
Location: Bishop's Waltham, Hants, UK.
Posts: 939
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Re: Frequency Counters
Bill,
the easiest way is to turn the generator ouput up and use a T-piece to feed the counter, then an external attenuator. If you add a counter output to the generator, you can take it from the point which feeds the output attenuator, and adjust the level to get a reliable count - put in a simple potential divider, and couple it with a capacitor. For the socket, use a good qaulity BNC with a metal dustcap - it is amazing how much RF can leak from the centre pin of an unconnected socket! Jim. |
4th Jan 2004, 1:31 am | #7 |
Guest
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Re: Frequency Counters
If your counter has a trigger level control, it will be easier to use on those service-grade signal generators that don't have a good sinusoidal output. For the most part, as you adjust the level control, you'll either being reading the actual frequency or some other frequency that isn't anywhere near the dial setting of the generator, so it's obvious where the correct setting is.
Dean |