[time-nuts] Broadband synthesizer

Will Matney xformer at citynet.net
Wed Jul 13 13:30:30 UTC 2011


Bill,

Well, if the frequency you want is below 10 MHz, then the counter/readout
on a HP 3335, as Paul mentioned, will reach the 100 millihertz range, as
it's readout is 8 digits, I think. That is anything from say 9.99 MHz and
below, the resolution will go up from there, but to be honest, I can't
remember using mine this way. The problem is, even though the 3335 is a
level sine generator, it's signal is not quite as clean as the 8640B,
though it may be clean enough, as I've never used mine for this. Here, the
8640B falls out over the range of its counter, as I think it may be only 7
digits, without looking, and I think it might not count that low, or no
lower than 1 Hz, as I can't remember.

Really, about the only way you can get that much resolution, over 10 MHz,
is use an external counter with a high resolution display, and there's not
that many out there, unless using one like an EIP 538B microwave counter,
and that's for counting up to 26.5 GHz. They have them that will go up to
around 12 digits in resolution, like this one, but some of them are limited
in the lowest frequency they'll count, and if I recall, the 538B models
lower limit is around 10 Hz, so no hertz or millihertz.

There's limits on other counters too, in their low count, but with all the
different manufacturers and models, I couldn't begin to tell you which ones
they are. I've never used anything over eight digits of resolution, here,
so others on here may know more about which to use, if you end up having to
use one. The problem is, these high res counters cost out the ying yang.

What you need is a clean signal for this, since you're thinking about
mixing signals, and you might ought to look for something fixed, that will
produce it in say an OCXO, and use an easily fixed frequency that you don't
need to see the millihertz range to use, say a simple 5 to 10 MHz, that's
just been calibrated to be on the money. The problem is, the smaller, low
cost, RF generators that will cover this, aren't clean at all, and the
resolution of their internal counter is only around 6 digits at most. Also,
if you don't want to lay out a pile of cash, you can rent these for a
month, off a dealer, having plenty of time to do the test. However, some
may want as much for reat as you could buy a working used one for.

On the generator or synthesizer you get, say one of the models I listed
earlier, or the HP 3335, a decent one will still run you around $300.00
plus, now that a lot of the government surplus has dried up. A few years
back, these could be bought at around $75 to $100 each, and even some of
the EIP counters.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/13/2011 at 7:38 AM Bill Dailey wrote:

>Thanks for the input.  I think i am asking for too much in one package
(looking toward future projects).  How about 1.8Mhz to 15Mhz.... To meet
the needs of the primary project (fmt).  I would prefer to not have to also
use a counter.  
>
>Thanks,
>
>Doc
>KX0O
>
>Sent from my iPad
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