Looking for help with an HP 8554B spectrum analyzer plugin

[Fred Abse]

On Tue, 12 Aug 2003 14:27:21 +0100, Leigh W3NLB wrote:

My 8554B says "Maximum 10 dBm" on the front in big red letters.

There's probably a reason why they put that on the panel.

That's the absolute maximum safe input.

10dBm is about normal for that age of analyzer, but they're not usually
usable up to that, the figure to look for is the input level for 1dB
compression. Above that, the analyzer wil start generating significant
spurii of its own. As a rule of thumb, put another 10dB attenuation in,
if everything drops by 10dB, what you see is what you've got. Anything
that drops by more than 10dB is probably an artifact of the instrument.


--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Pete KE9OA]

I think it must go back to what devices were available at that time; my
8558B specifies no more than +30dBm.

Pete

Leigh W3NLB <w3nlbREMOVETHIS@amsat.org> wrote in message
news:5lqhjvsanhrfo5bm2or2esr4ei7125u3j2@4ax.com...

On Mon, 11 Aug 2003 21:40:39 +0100, Fred Abse
excretatauris@cerebrumconfus.it> wrote:

On Sat, 09 Aug 2003 17:52:22 +0100, Pete KE9OA wrote:

It looks like somebody
must have accidently transmitted into this unit.

You don't need to transmit into most older analyzers. Much more than
10dBm
will croak some of them. You could do that with some signal generators.

BTDT

My 8554B says "Maximum 10 dBm" on the front in big red letters.

There's probably a reason why they put that on the panel.


73 de Leigh W3NLB

 

[PhilW]

you might be better of using a modern SMD dual schottky diode, better
match, lower capacitance etc. You will have to devise some neat way of
fitting them in. Circuit is in series config so try HSMS-2814, or 2 in
one package HSMS-2815. Try Farnell or Newark? for these parts.Yes the
service manual says you need a matched pair of
1902-0385. I suspect a pair of 5082-2835 would do OK also.

Eric F. Richards wrote:

Greetings...

I don't know where to ask this, so I'm shooting for multiple groups.

I purchased an HP 140T mainframe plus spectrum analyzer plugins,
including the 8554B mentioned in the subject, at a hamfest. It turns
out that it is working but is quite "deaf." From asking around I have
been told that this is a common problem for this plugin and the
culprit is the first mixer.

Well... the first mixer is an upconverter to 3 GHz, and one of those
magical microwave "cans" that make no sense to those of us used to
thinking in lower frequencies. The only semiconductors in the can are
a pair of diodes, back to back, with the designation "385" on them.
HP weenies have suggested that it could be short for 1901-0385, but
that part number turns up very few references, and none with the
nature of the diodes and their operating characteristics.

So I'm wondering if anyone out there knows what type of diodes these
are likely to be and what kind of characteristics I should be looking
for in replacement parts.

Does anyone know anything about this dinosaur? Any help would be
appreciated.

Oh, BTW, the rest of the analyzer and frame work fine. I'm using a
borrowed 8553B plugin with it now and getting the results I'd hoped
for. While I don't plan on doing any critical work with it, the 8554B
is a more capable plugin and I do have to return the borrowed one...

Thanks much!