[time-nuts] EIP545A 18GHz counter query

paul swed paulswedb at gmail.com
Sun Dec 9 16:29:37 UTC 2012


Didier is 100% correct though I use a 10 db pad for exactly the same
purpose. You have to be careful. In your case there is a +28 db power amp
that feeds the yig mixer in the 545. That would destroy the spectrum
analyzer frontend. In fact if measuring that component you would want 30 db
of loss using a 2 watt pad. Most spectrum analyzers run in the 0 to +5 or
so db range.

All of that said I actually have to look at your other comments to make
some sense of what you are seeing.
Regards
Paul
WB8TSL

On Sun, Dec 9, 2012 at 7:22 AM, <shalimr9 at gmail.com> wrote:

> Good practice with a spectrum analyzer is to put a 20 dB pad at the input
> all the time unless you are sure you don't need it for a particular
> measurement.
>
> It has saved my bacon many times.
>
> It also protects the input connector from excessive wear.
>
> Didier KO4BB
>
>
> Sent from my Droid Razr 4G LTE wireless tracker.
>
>
>
> -----Original Message-----
> From: Chris Wilson <chris at chriswilson.tv>
> To: Chris Wilson <chris at chriswilson.tv>, Discussion of precise time and
>  frequency measurement <time-nuts at febo.com>
> Sent: Sun, 09 Dec 2012 5:54 AM
> Subject: Re: [time-nuts] EIP545A 18GHz counter query
>
>
>
> > Did do some more reading and I think what I suggest is the right
> approach.
> > Band 2 and 3 use the same VCO. So if band 2 is generally working
> > then its possibly the rf multiplier yig filter mixer diodes etc. But
> > if the RF detectors show RF then its going to be a much more interesting
> issue.
> > I do not know what sort of test equipment you might have. I have
> > spectrum analyzers and such. And do agree without extenders that I don't
> have its a royal pain.
> > Regards
> > Paul.
>
>
> 09/12/2012 11:45
>
> Thanks very much for your input with this, much appreciated. I do have
> a spectrum analyser, but it's a bit like having a set of surgeons
> implements. Interesting to have, but needing the requisite skill to
> use safely :) I can do only the most basic stuff, to be frank I am
> very wary of blowing the input stage up by doing something daft!
>
> I think I follow your train of thought here Paul. But, before seeing
> your post I did some tests at TP4, to see if the unit was constantly
> scanning for a signal when on Band 2. here is what I found and saw:
>
> I have now refitted the new Q12, and removed the test 1k resistor.
>
> OK, the trace from TP4 does different things depending what band it is
> on. Bands 1 and 3 it just sits there, #1. On Band 2 it gives what appears
> to be two traces, #2. Changing the timebase gives the other trace I show
> linked, #3. On bands 1 and 3 only a single trace appears. So Band 2 is
> doing something different at TP4, with no input signal. Warm Q12 with
> an input signal to Band 2 and the two traces change to a single trace,
> #4.
>
> Once it cools again the two traces return.
>
> Traces:
>
> #1  http://www.gatesgarth.com/scope/TP4-band1.jpg
>
> #2  http://www.gatesgarth.com/scope/TP4-band2.jpg
>
> #3  http://www.gatesgarth.com/scope/TP4-...t-timebase.jpg
>
> #4  http://www.gatesgarth.com/scope/TP4-...put-signal.jpg
>
> I would need explicit instruction to poke about using the SA. It's an
> HP 8568B. Thanks again Paul :)
>
>
>
> --
>        Best Regards,
>                    Chris Wilson.
>
>
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