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Date
Re: DIY: Repair of HP Step Attenuators

 

Hi Lothar,

I have a 8495A manual step attenuator, and though it has the correct
attenuations on every step(?), but it needs force to switch the
attenuator in different positions, and also the well known "click"
cannot be heard, when turning (with some force) the knob.

Could you help me with some idea and procedure, as you did with the
electronic controlled equivalent ?

Thanks
George Galambos

--- In hp_agilent_equipment@..., "microwaveengineer1968"
<microwaveengineer1968@...> wrote:

Since Agilent continiously ups the spare part prices and discontinues
parts it has become more and more important to go past normal repair
practices.
Step Attenuators for example can be repaired without any special
tools or cleanroom enviroment !
Lets take a look at the failure modes first, there are a few:

1.) Blown pads
Usually common with spectrum analyzers if a level past the damage
level of the attenuator was applied

2.) Cracked pads, pad has developed a hairline crack due to
mechanical stress !

3.) Improper contact, the contact in between the attenuator and
contact fingers is disturbed.

4.) Stuck solenoid
Quite common if attenuator hasnt been used in awhile

After we remove the attenuator from the instrument the first step is
to obtain the pinout and build us a little test bench consisting of a
powermeter and a signal generator, the good old 8481D or 8484A will
do nicely, if you dont have a sig gen use the 50MHz calibrator output
of the 435 or 436 or similar model, connect the cal output to the
30dB pad connect the sensor and zero and calibrate meter, the meter
will read -30dBm.
Disconnect the sensor from the attenuator and insert the Step
Attenuator, set step attenuator to 0dB, note the level on the
powermeter, now switch in the attenuator sections one by one measure
and note the level, 70dB attenuators are comprised of a 10 20 and
40dB Pad while 110dB Attenuators normally comprise of a 10 20 and two
40dB pads !
check every section individually, you should hear a click as you
enable each section, if you find a bad section note the value it
should have if all sections appear to be good repeat the test at a
higher frequency using a sig gen, if everything appears to be ok at
low frequency then most likely you have attenuator that just needs
cleaning.
Now lets take the attenuator apart, looking at the top you will see a
nut on each SMA connector, remove this nut this will allow for you to
remove the nameplate, under the plate you will see a wealth of allen
screws, remove those but note that the screws close to the SMA
connector are shorter than the other ones.
Now look at the small sideplate, not the one with the ribbon cable
but the other side - there are 4 small allen screws, remove those and
then remove the sideplate, careful not to lose the little wire mesh
here ! now slide out the u shaped cover and remove the top side.
You now have two parts, one beein the bottom side containing the
solenoids and the other one beein the top part containing the
attenuator pads.
First lets inspect the pads, you can measure them with a ohm meter,
they should measure in the vicinity of 50ohms , except of the 10dB
pad which can measure up to 70ohms or more.
Inspect the pads visually, are there any burned or cracked pads ? if
all pads look ok and check out at DC take a surgical swab and
isopropilic alcohol and carefully clean the contacts pads on the
attenuators.
Next look at the contacts, enable all solenoids and observe the
position of the contact tongues, they should be slightly above the
surface of the block, carefully clean the contact tongues with
alcohol, be careful not to bend them.
next put the solenoids back into the 0 position and look at the top
of the solenoids, you will see two little white plastic rods where
those meet the solenoid you should see little rubber rings , there
are 4 of those on each segment, usually over the years they go
briddle and then disappear, with those rings gone the attenuator wont
make contact anymore, you can buy the rings from watchmakers supply
stores as they are beein used for sprocket gaskets !
Now if your gaskets are there put the attenuator back together after
you cleaned everything and it should work now.
If you have a broken or burned pad dont stress over it the pads are
used in all HP attenuators so just find a attenuator on ebay and take
the pad you need out of it, you can also buy pads from agilent
however be prepared to pay $100-150 per
piece
Re: HP-8443A Tracking Generator Problems

 

David C. Hallam wrote:

Lothar,

I hate to be stubborn or dense, but where does the marker come from if the
"RF is dead on the tracking generator"?

I do have an operation and maintenance manual. I quote from the manual:

In Marker mode the scan ramp of the spectrum analyzer is stopped momentarily
at a point determined by the Model 844A Marker Position control. At the
point where the scan is stopped, a bright marker appears on the analyzer
display CRT. Simultaneously, the RF Output frequency from the tracking
generator is counted by the Model 8443A counter. If the Function switch is
set to Track Analyzer, the counter frequency indicates marker frequency,
independent of Spectrum Analyzer input signal frequency. If Function switch
is set to Restore Frequency, the counter indicates the Spectrum Analyzer
input signal frequency (as long as the marker is placed on the signal
response).

From the above statement it seems to me the generation of the marker on the
CRT display and the counting of the marker frequency are two independent
operations, i.e., you can generate a marker and still not be able to count
it.

Since I have demonstrated the counter portion of the 8443A is functional as
it will count an external signal from my signal generator and the RF output
the 8443A is functional since there is a marker on the CRT display, the
problem is in the counting of RF output frequency at the point where the
scan is stopped to generate the marker.

If I am still off base, HELP.

David
David,
You do seem to have been given a lot of advice on various topics, not all of which seem relevant to your problem. For example, the known 141 problem with bent D-sub connector brackets really only applies to the ones between the RF and IF sections. Usually due to the RF section being put on a flat surface, thus pushing on the connector. If the interconnect between the mainframe and TG is seated well at both ends, and locked in position, you should not have a problem there.

The marker is generated as you know by stopping the scan for a period depending on the resolution selected and simultaneously opening the counter gate. The marker will thus appear on the 141 display regardless of whether the TG is outputting anything. You can therefore have a marker and no output easily enough...

So your statemant:

the RF output (of)
the 8443A is functional since there is a marker on the CRT display
is not the case at all.


The easiest way to test for TG output is to select zero span on the SA and connect the TG output to the external counter input. With the TG output set above -20 dBm then you should now have a frequency reading identical to that you get normally. No output, no reading. You can also receive the TG output signal in a receiver tuned to the output frequency. Hard to avoid in fact with the full scan :^)
Re: HP-8443A Tracking Generator Problems

David C. Hallam
 

Lothar,

I hate to be stubborn or dense, but where does the marker come from if the
"RF is dead on the tracking generator"?

I do have an operation and maintenance manual. I quote from the manual:

In Marker mode the scan ramp of the spectrum analyzer is stopped momentarily
at a point determined by the Model 844A Marker Position control. At the
point where the scan is stopped, a bright marker appears on the analyzer
display CRT. Simultaneously, the RF Output frequency from the tracking
generator is counted by the Model 8443A counter. If the Function switch is
set to Track Analyzer, the counter frequency indicates marker frequency,
independent of Spectrum Analyzer input signal frequency. If Function switch
is set to Restore Frequency, the counter indicates the Spectrum Analyzer
input signal frequency (as long as the marker is placed on the signal
response).

From the above statement it seems to me the generation of the marker on the
CRT display and the counting of the marker frequency are two independent
operations, i.e., you can generate a marker and still not be able to count
it.

Since I have demonstrated the counter portion of the 8443A is functional as
it will count an external signal from my signal generator and the RF output
the 8443A is functional since there is a marker on the CRT display, the
problem is in the counting of RF output frequency at the point where the
scan is stopped to generate the marker.

If I am still off base, HELP.

David

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 11:44 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems


ok for the counter to be able to count the marker frequency it will have
to stop the sweep for a short time count the frequency and then keep on
sweeping
What im trying to get across is that you will always get a marker even if
your RF is dead on the tracking generator or the RF section

"David C. Hallam" <dhallam@...> wrote:
Now I am getting confused.

The spectrum analyzer screen has a line designated CENTER FREQUENCY. As
you
turn the frequency knob on the 8553B RF section to move a signal peak to
coincide with this line, you can read the frequency of the signal from the
linear scale on the 8553B.

When the 8443A tracking generator is connected to the 141T system, it
generates a marker on the CENTER FREQUENCY line of the 141T display. As
above, when you move a signal peak to coincide with this line and place
the
marker at the top of the peak, the 8443A will display the frequency of the
signal.

The marker is on the CENTER FREQUENCY line of the screen all the times,
input signal or no input signal.

What is happening is there is no display of frequency on the 8443A at any
time. Even when the marker is centered on the signal peak.

The 8443A is also capable of being used as a stand alone frequency
counter.
If I connect my signal generator to the 8443A in this mode, the 8443A will
display the frequency of the signal generator output.

David
-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 10:14 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

ok there are two basic ways to create a marker in a swept system, one is
called RF blanking the other one is called intensity modulation, ok
usually
you have a control voltage thats proportional to your RF frequency, if the
analyzer sweeps its basically a ramp, each point of the ramp corresponds
to
a certain frequency, you feed this signal to a comparator and compare it
to
a DC voltage thats adjustable (coming from your marker pot) anytime the
ramp
"hits" this threshold you get a pulse on your comparator output, you route
this pulse back into your display and use it to crank up the intensity
just
a bit at this point and there you have a marker blip on your screen :) you
could also use this pulse to turn the RF of your TG off for just a moment
but then you would end up with a dark spot as a marker for a short time
instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker
along with the statement about you seen the marker even with the calibator
connected to your RF section input makes me certain that your markers are
intensity modulated !

"David C. Hallam" <dhallam@...> wrote:

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would
be
no marker blip on the 141T screen.

one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter
so
you can do the testing

"
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Re: HP-8443A Tracking Generator Problems

John Miles
 

Isn't that what the 86222 sweeper plugin with the marker option does? Those
are pretty common.

-- john, KE5FX


this is another way but i havent seen anyone using this in
centuries, the last time i saw it was on a old jerrold sweeper,
everything i had ever since was using the approach i described,
problem with the RF method is that its quite expensive to
realize, a directional coupler, sampling mixer and the oscillator
and frequency counter costs money and space and also takes away
from the RF power, another factor is that whenever you use a comb
generator you run the risk of finding your peaks "everywhere"
even in places you dont want them :)
DC or LF stuff is cheap and doesnt take up much space so i
think thats why most companies opted for this approach

J Forster <jfor@...> wrote:
lothar baier wrote:

ok there are two basic ways to create a marker in a swept
system, one is called RF blanking the other one is called
intensity modulation, ok usually you have a control voltage thats
proportional to your RF frequency, if the analyzer sweeps its
basically a ramp, each point of the ramp corresponds to a certain
frequency, you feed this signal to a comparator and compare it to
a DC voltage thats adjustable (coming from your marker pot)
anytime the ramp "hits" this threshold you get a pulse on your
comparator output, you route this pulse back into your display
and use it to crank up the intensity just a bit at this point and
there you have a marker blip on your screen :)

There is another way. You sample the RF, mix it with a (frequency
settable) oscillator, run the output through a LPF, detector, and
comparator and use this output for intensity markers.

This system has the advantage that you can count the oscillator
and have accurate digital markers, and, if you replace the
oscillator w/ a comb generator, you get nice, calibrated pips.
Re: HP-8443A Tracking Generator Problems

lothar baier
 

they actually made several options on the 8444A, one incorporated another fixed frequency oscillator, this option was created for people using the 8444 with the 8558B which only had the first LO routed out while the 141T had two or 3 lo signals coming out (im not really a 141 expert) i also remember them having some L rf or IF sections that deleted one of the LO signal connectors

Alan Melia <Alan.Melia@...> wrote: Hi Thanks Lothar....that is the unit I use most often and have never had to
"take the lid off" (should have looked at the manuals which are out of easy
reach before typing !!)I have certainly had duff connectors inside the RF
head though. I still dont know whether he has a proper output from the
8443....it doesnt sound to me as though he is generating a swept frequency
output but I could be mis-interpreting his narrative. The 30MHz cal signal
test sounds irrelevant to me.

Alan G3NYK

----- Original Message -----
From: "lothar baier" <microwaveengineer1968@...>
To: <hp_agilent_equipment@...>
Sent: Friday, November 16, 2007 4:11 PM
Subject: Re: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems

you are talking about the 8444 not the 8443, the 8443 actually does not
require a 500MHz signal





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Re: HP-8443A Tracking Generator Problems

lothar baier
 

this is another way but i havent seen anyone using this in centuries, the last time i saw it was on a old jerrold sweeper, everything i had ever since was using the approach i described, problem with the RF method is that its quite expensive to realize, a directional coupler, sampling mixer and the oscillator and frequency counter costs money and space and also takes away from the RF power, another factor is that whenever you use a comb generator you run the risk of finding your peaks "everywhere" even in places you dont want them :)
DC or LF stuff is cheap and doesnt take up much space so i think thats why most companies opted for this approach

J Forster <jfor@...> wrote:
lothar baier wrote:

ok there are two basic ways to create a marker in a swept system, one is called RF blanking the other one is called intensity modulation, ok usually you have a control voltage thats proportional to your RF frequency, if the analyzer sweeps its basically a ramp, each point of the ramp corresponds to a certain frequency, you feed this signal to a comparator and compare it to a DC voltage thats adjustable (coming from your marker pot) anytime the ramp "hits" this threshold you get a pulse on your comparator output, you route this pulse back into your display and use it to crank up the intensity just a bit at this point and there you have a marker blip on your screen :)
There is another way. You sample the RF, mix it with a (frequency settable) oscillator, run the output through a LPF, detector, and comparator and use this output for intensity markers.

This system has the advantage that you can count the oscillator and have accurate digital markers, and, if you replace the oscillator w/ a comb generator, you get nice, calibrated pips.

Best,
-John

you could also use this pulse to turn the RF of your TG off for just a moment but then you would end up with a dark spot as a marker for a short time instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker along with the statement about you seen the marker even with the calibator connected to your RF section input makes me certain that your markers are intensity modulated !





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Re: HP-8443A Tracking Generator Problems

lothar baier
 

Lets go back to the basics,
A spectrum analyzer basically is a swept receiver, in the case of the 8553 you have three conversion steps to reduce the input signal to 3MHz IF, the first LO normally is swept by a ramp, the amplitude of the ramp determines the sweep width or span while the DC offset of the Ramp normally determines the start frequency of your sweep.
The tracking generator is basically a "reversal" of your spectrum analyzer, you take the LO signals and mix them with a Fixed lo that represents the IF used, amplify the resulting signal and level it, the signal frequency will track with the frequency of your spectrumanalyzer, now if you insert a filter for example you will be able to measure the filter characteristics !
Now to the markers, the X axis of your analyzer can be scaled in a voltage/div, lets say you sweep the full band of 0-110MHz, your DC offset will be O and your ramp will be 10Vp, now you have 11MHz/Volt, lets assume you desire a marker at 55MHz , 55MHz corresponds to 5Vp on your ramp, you now take a comparator and run the ramp on one input and the 5V reference on the other whenever the two match you get a pulse, all you need to do now is to route the pulse back into your analyzer and use it to either blank the trace for a short period of time or intensify it, so now you got a marker on your screen even without any RF !
now at last you want to know the marker frequency, you have two ways to skin this cat, you can either use a voltmeter to measure your reference voltage scale it and display it on a digital display (this however is not how the 8443 does it) or you can use a frequency counter and connect it to the RF output, now since you only want the marker count you only trigger the counter whenver you get the marker pulse and at the same time stop the sweep for a brief moment to allow the counter to aquire the signal, now you counted your marker !
In this system the only function that will not work if the RF signal is gone is in fact the frequency counter for your marker function ! you will however always get a marker blip on your display whether you have RF or not !
If you look closely at your control cable that connects the 8443 with the 141T you will notice that beside the coax contacts you also have regular Contacts, those contacts carry the control signals, you will also notice that you have more coax contacts than LO signals, this is because one of the coaxes carries your sweep ramp from your 141T mainframe.
I suggest you download the 8443 manual and study the functions, it contains a good overall circuit description as well as block diagrams that will help you understand the functionality

"David C. Hallam" <dhallam@...> wrote:
Now I am getting confused.

The spectrum analyzer screen has a line designated CENTER FREQUENCY. As you
turn the frequency knob on the 8553B RF section to move a signal peak to
coincide with this line, you can read the frequency of the signal from the
linear scale on the 8553B.

When the 8443A tracking generator is connected to the 141T system, it
generates a marker on the CENTER FREQUENCY line of the 141T display. As
above, when you move a signal peak to coincide with this line and place the
marker at the top of the peak, the 8443A will display the frequency of the
signal.

The marker is on the CENTER FREQUENCY line of the screen all the times,
input signal or no input signal.

What is happening is there is no display of frequency on the 8443A at any
time. Even when the marker is centered on the signal peak.

The 8443A is also capable of being used as a stand alone frequency counter.
If I connect my signal generator to the 8443A in this mode, the 8443A will
display the frequency of the signal generator output.

David

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 10:14 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

ok there are two basic ways to create a marker in a swept system, one is
called RF blanking the other one is called intensity modulation, ok usually
you have a control voltage thats proportional to your RF frequency, if the
analyzer sweeps its basically a ramp, each point of the ramp corresponds to
a certain frequency, you feed this signal to a comparator and compare it to
a DC voltage thats adjustable (coming from your marker pot) anytime the ramp
"hits" this threshold you get a pulse on your comparator output, you route
this pulse back into your display and use it to crank up the intensity just
a bit at this point and there you have a marker blip on your screen :) you
could also use this pulse to turn the RF of your TG off for just a moment
but then you would end up with a dark spot as a marker for a short time
instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker
along with the statement about you seen the marker even with the calibator
connected to your RF section input makes me certain that your markers are
intensity modulated !

"David C. Hallam" <dhallam@...> wrote:

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would
be
no marker blip on the 141T screen.

one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter
so
you can do the testing

"
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Re: HP-8443A Tracking Generator Problems

J Forster
 

lothar baier wrote:

ok there are two basic ways to create a marker in a swept system, one is called RF blanking the other one is called intensity modulation, ok usually you have a control voltage thats proportional to your RF frequency, if the analyzer sweeps its basically a ramp, each point of the ramp corresponds to a certain frequency, you feed this signal to a comparator and compare it to a DC voltage thats adjustable (coming from your marker pot) anytime the ramp "hits" this threshold you get a pulse on your comparator output, you route this pulse back into your display and use it to crank up the intensity just a bit at this point and there you have a marker blip on your screen :)
There is another way. You sample the RF, mix it with a (frequency settable) oscillator, run the output through a LPF, detector, and comparator and use this output for intensity markers.

This system has the advantage that you can count the oscillator and have accurate digital markers, and, if you replace the oscillator w/ a comb generator, you get nice, calibrated pips.

Best,
-John


you could also use this pulse to turn the RF of your TG off for just a moment but then you would end up with a dark spot as a marker for a short time instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker along with the statement about you seen the marker even with the calibator connected to your RF section input makes me certain that your markers are intensity modulated !
Re: HP-8443A Tracking Generator Problems

 

Hi Thanks Lothar....that is the unit I use most often and have never had to
"take the lid off" (should have looked at the manuals which are out of easy
reach before typing !!)I have certainly had duff connectors inside the RF
head though. I still dont know whether he has a proper output from the
8443....it doesnt sound to me as though he is generating a swept frequency
output but I could be mis-interpreting his narrative. The 30MHz cal signal
test sounds irrelevant to me.

Alan G3NYK

----- Original Message -----
From: "lothar baier" <microwaveengineer1968@...>
To: <hp_agilent_equipment@...>
Sent: Friday, November 16, 2007 4:11 PM
Subject: Re: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems


you are talking about the 8444 not the 8443, the 8443 actually does not
require a 500MHz signal
Re: HP-8443A Tracking Generator Problems

lothar baier
 

ok for the counter to be able to count the marker frequency it will have to stop the sweep for a short time count the frequency and then keep on sweeping
What im trying to get across is that you will always get a marker even if your RF is dead on the tracking generator or the RF section

"David C. Hallam" <dhallam@...> wrote:
Now I am getting confused.

The spectrum analyzer screen has a line designated CENTER FREQUENCY. As you
turn the frequency knob on the 8553B RF section to move a signal peak to
coincide with this line, you can read the frequency of the signal from the
linear scale on the 8553B.

When the 8443A tracking generator is connected to the 141T system, it
generates a marker on the CENTER FREQUENCY line of the 141T display. As
above, when you move a signal peak to coincide with this line and place the
marker at the top of the peak, the 8443A will display the frequency of the
signal.

The marker is on the CENTER FREQUENCY line of the screen all the times,
input signal or no input signal.

What is happening is there is no display of frequency on the 8443A at any
time. Even when the marker is centered on the signal peak.

The 8443A is also capable of being used as a stand alone frequency counter.
If I connect my signal generator to the 8443A in this mode, the 8443A will
display the frequency of the signal generator output.

David

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 10:14 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

ok there are two basic ways to create a marker in a swept system, one is
called RF blanking the other one is called intensity modulation, ok usually
you have a control voltage thats proportional to your RF frequency, if the
analyzer sweeps its basically a ramp, each point of the ramp corresponds to
a certain frequency, you feed this signal to a comparator and compare it to
a DC voltage thats adjustable (coming from your marker pot) anytime the ramp
"hits" this threshold you get a pulse on your comparator output, you route
this pulse back into your display and use it to crank up the intensity just
a bit at this point and there you have a marker blip on your screen :) you
could also use this pulse to turn the RF of your TG off for just a moment
but then you would end up with a dark spot as a marker for a short time
instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker
along with the statement about you seen the marker even with the calibator
connected to your RF section input makes me certain that your markers are
intensity modulated !

"David C. Hallam" <dhallam@...> wrote:

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would
be
no marker blip on the 141T screen.

one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter
so
you can do the testing

"
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Re: HP-8443A Tracking Generator Problems

 

Hi,

The marker blip, when using an 8443A with the 141T, is simply the
trace stopping for the blinking of an eye. The marker intensity
control just varies how long it stops for - there is no 'Z' mod
involved.


Cheers - Joe G3LLV
Re: HP-8443A Tracking Generator Problems

lothar baier
 

you are talking about the 8444 not the 8443, the 8443 actually does not require a 500MHz signal

Alan Melia <Alan.Melia@...> wrote: Hi, just a though triggered by Chuck's posting. Some of the connectors for
the tracking gen were fitted as an "update" I think (without looking at my
frame) there is another cable inside from the back of the frame and the
plug-in bay. So there are a lot of connectors in series. It would only take
one of the 2 or 3 cables/conns from the LOs to the TG to be open for the Tg
to produce no output. I hesitate on this because without checking the manual
I am not sure whether you would get a marker in that state. Another though
but I dont remember whether it refers to this unit is that some RF heads
dont output the third LO with is 500MHz and this must be generated locally
in the TG . failure of this unit there would mean no output too. You dont
say whether you have measurable output from the TG (scope??) and whether it
is actually on the right frequency (I would imaginne the output goes via a
100MHz LPF so one osc off and no signal). Separate test equipment is better
than trying to define the problem all in the same two units.

Alan G3NYK

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: <hp_agilent_equipment@...>
Sent: Friday, November 16, 2007 2:41 PM
Subject: Re: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems

One very big problem with the 141T frame and its plug-ins, that can cause
many a vexing symptom, is the D style connector on the back of each
plug-in.
The aluminum framework that holds these D style connectors is too thin and
poorly braced to handle the insertion force necessary to properly mate the
connectors... particularly when the connectors get older, and dry of all
lubricant film... so, it just bends out of the way. Generally this
results in
a partially working SA.

Perhaps this has happened to yours?

-Chuck Harris





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Re: HP-8443A Tracking Generator Problems

David C. Hallam
 

Now I am getting confused.

The spectrum analyzer screen has a line designated CENTER FREQUENCY. As you
turn the frequency knob on the 8553B RF section to move a signal peak to
coincide with this line, you can read the frequency of the signal from the
linear scale on the 8553B.

When the 8443A tracking generator is connected to the 141T system, it
generates a marker on the CENTER FREQUENCY line of the 141T display. As
above, when you move a signal peak to coincide with this line and place the
marker at the top of the peak, the 8443A will display the frequency of the
signal.

The marker is on the CENTER FREQUENCY line of the screen all the times,
input signal or no input signal.

What is happening is there is no display of frequency on the 8443A at any
time. Even when the marker is centered on the signal peak.

The 8443A is also capable of being used as a stand alone frequency counter.
If I connect my signal generator to the 8443A in this mode, the 8443A will
display the frequency of the signal generator output.

David

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 10:14 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems


ok there are two basic ways to create a marker in a swept system, one is
called RF blanking the other one is called intensity modulation, ok usually
you have a control voltage thats proportional to your RF frequency, if the
analyzer sweeps its basically a ramp, each point of the ramp corresponds to
a certain frequency, you feed this signal to a comparator and compare it to
a DC voltage thats adjustable (coming from your marker pot) anytime the ramp
"hits" this threshold you get a pulse on your comparator output, you route
this pulse back into your display and use it to crank up the intensity just
a bit at this point and there you have a marker blip on your screen :) you
could also use this pulse to turn the RF of your TG off for just a moment
but then you would end up with a dark spot as a marker for a short time
instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker
along with the statement about you seen the marker even with the calibator
connected to your RF section input makes me certain that your markers are
intensity modulated !

"David C. Hallam" <dhallam@...> wrote:

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would
be
no marker blip on the 141T screen.

one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter
so
you can do the testing

"
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Re: HP-8443A Tracking Generator Problems

 

Hi, just a though triggered by Chuck's posting. Some of the connectors for
the tracking gen were fitted as an "update" I think (without looking at my
frame) there is another cable inside from the back of the frame and the
plug-in bay. So there are a lot of connectors in series. It would only take
one of the 2 or 3 cables/conns from the LOs to the TG to be open for the Tg
to produce no output. I hesitate on this because without checking the manual
I am not sure whether you would get a marker in that state. Another though
but I dont remember whether it refers to this unit is that some RF heads
dont output the third LO with is 500MHz and this must be generated locally
in the TG . failure of this unit there would mean no output too. You dont
say whether you have measurable output from the TG (scope??) and whether it
is actually on the right frequency (I would imaginne the output goes via a
100MHz LPF so one osc off and no signal). Separate test equipment is better
than trying to define the problem all in the same two units.

Alan G3NYK

----- Original Message -----
From: "Chuck Harris" <cfharris@...>
To: <hp_agilent_equipment@...>
Sent: Friday, November 16, 2007 2:41 PM
Subject: Re: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems


One very big problem with the 141T frame and its plug-ins, that can cause
many a vexing symptom, is the D style connector on the back of each
plug-in.
The aluminum framework that holds these D style connectors is too thin and
poorly braced to handle the insertion force necessary to properly mate the
connectors... particularly when the connectors get older, and dry of all
lubricant film... so, it just bends out of the way. Generally this
results in
a partially working SA.

Perhaps this has happened to yours?

-Chuck Harris
Re: HP-8443A Tracking Generator Problems

lothar baier
 

ok there are two basic ways to create a marker in a swept system, one is called RF blanking the other one is called intensity modulation, ok usually you have a control voltage thats proportional to your RF frequency, if the analyzer sweeps its basically a ramp, each point of the ramp corresponds to a certain frequency, you feed this signal to a comparator and compare it to a DC voltage thats adjustable (coming from your marker pot) anytime the ramp "hits" this threshold you get a pulse on your comparator output, you route this pulse back into your display and use it to crank up the intensity just a bit at this point and there you have a marker blip on your screen :) you could also use this pulse to turn the RF of your TG off for just a moment but then you would end up with a dark spot as a marker for a short time instead of beein brighter.
Your statement about you seein a bright blip on your screen as a marker along with the statement about you seen the marker even with the calibator connected to your RF section input makes me certain that your markers are intensity modulated !

"David C. Hallam" <dhallam@...> wrote:

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would be
no marker blip on the 141T screen.

one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter so
you can do the testing

"
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Re: HP-8443A Tracking Generator Problems

David C. Hallam
 

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of lothar baier
Sent: Friday, November 16, 2007 9:21 AM
To: hp_agilent_equipment@...
Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator
Problems


have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are
blanked in on the sweep trace not on the RF level, i havent looked in the
manual but thats how most generators and sweepers are doing it, the fact
that you see a marker blip without the RF output of the generator beein
connected to the SA input supports this.

I don't understand this statement. I have the 8443A connected to
the 141T SA system with the interconnect cable. Without this there would be
no marker blip on the 141T screen.


one possibility is to build a pre-scaler for your counter to extend the
frequency range, the other one is that i could loan you a 500MHz counter so
you can do the testing

"
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Get your business

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Going Green

Share your passion

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.
Re: HP-8443A Tracking Generator Problems

 

One very big problem with the 141T frame and its plug-ins, that can cause
many a vexing symptom, is the D style connector on the back of each plug-in.
The aluminum framework that holds these D style connectors is too thin and
poorly braced to handle the insertion force necessary to properly mate the
connectors... particularly when the connectors get older, and dry of all
lubricant film... so, it just bends out of the way. Generally this results in
a partially working SA.

Perhaps this has happened to yours?

-Chuck Harris

David C. Hallam wrote:

I don't have the test equipment you outlined. My counter is a HP-5245L and
limited to 50 MHz. I have been looking for additional plug-ins to extend
its range but at the moment I don't have any. My scope is a TEK 465 which
has a bandwidth of 100 MHz. Since my interest is in the HF (3-30 MHz)
portion of the ham radio spectrum, I just never saw the need to have
extended range test equipment.
I did what I will call a quick and dirty test. I connected the 30 MHz
calibration signal from the 8552B IF section to the RF input of the 8553B RF
section. At a 30 MHz setting on the 8553B frequency dial, I get the signal
peak on the 141T screen along with the marker from the 8443A. I can turn
the 8443A on and off and the marker pip also goes on and off. The 8433A
display reads all 0's.
If I set the 8443A to the external (counter) mode, it will correctly display
the frequency of a signal from my signal generator.
Rightly or wrongly, what do I conclude from all of this?
1 The counter portion of the 8443A is working correctly
2 The tracking generator working correctly
3 The no display problem in the tracking mode is related to counting of
the signal output of the tracking generator rather than a signal generation
problem in the tracking generator.
David
-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of
microwaveengineer1968
Sent: Thursday, November 15, 2007 9:31 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems

This is the link for a manual for the 8443A
Now down to the bone my friend, i have looked at the manual and
compiled some preliminary checks for you to do, this assumes that you
have acess to a counter to 500MHz and maybe a powermeter or scope
with appropriate bandwidth.
First off you need to verify the operation of the tracking generator
portion of your unit, dont worry about the counter for now, basically
the 8443 receives three signals from the 8553 and 8552 units, those
signals are mixed together sequentially to form a 0-110MHz signal
which is then amplified and leveled, the manual has a nice block
diagram in it btw !
The first signal is a 200-310MHz which is basically the 1st LO of the
8553, the amplitude is supposed to be -6dBm, the next signal is a
150MHz fixed LO @ -2dBm and the third Signal is a 47MHz fixed lo @ -
7dBm
First connect your counter to the RF output of your 8443A, set the
attenuator to 0dB and then set the analyzer to zero span and tune the
frequency and see if the counter indicates a frequency reading in
accordance to your analyzer scale, if you dont get any indication you
will have to verify the presence of your LO signals, you may just
have a bad interconnect cable to your analyzer, measure the 150MHz
signal on A11 J1 (you have to remove the cable and then measure the
signal coming out of the cable) , measure the 47MHz signal on A13 J1
(once again measure whats coming out of the cable) and the 3MHz fixed
LO on J3 (cable) then move on to A9 J1 on this cable you should be
able to measure a signal from 200-310MHz the frequency should be
tuning when you turn the tuning knob on your RF Section.
Do those tests and let me know the outcome.
--- In hp_agilent_equipment@..., "David C. Hallam"
<dhallam@...> wrote:
>
> I have some problems with my 8443A and need help locating the
issues. The
> nixie tube display shows all 0. I believe the tracking generator
is still
> working because the marker is on the screen of the 141T. I can
connect the
> RF output of the 8443A to my HP-5245L counter which will display
the marker
> frequency. I can move the maker with 8533B frequency control and
the
> display on the 5245L will change with the movement of the marker.
>
> The 8443A will function as a counter because I can set it in the
external
> mode and use it as a frequency counter.
>
> I followed the counter trouble shooting tree in the manual and
reach the end
> point where it says to repair A5. However in the service section
for A5, I
> get oscilloscope displays from each of the 6 test points on A5 that
match
> the photo in the manual which leaves me wondering. I don't have the
> extender to remove the module from the 8443A and measure the
voltages, etc.
> at the points indicated on the repair table.
>
> Does anyone have any suggestions about what to do next? Is my
conclusion
> that the tracking generator portion functioning properly logical?
My skill
> level as an electronics technician is not that great with
instruments like
> this.
>
> David
> KC2JD/4
>
Yahoo! Groups Links
Re: 3575A - useful ?

John Day
 

At 06:06 AM 11/16/2007, you wrote:


----- Original Message -----
From: "John Day" <<mailto:johnday%40wordsnimages.com>johnday@...>
To:
<<mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@...>
Sent: Friday, November 16, 2007 3:24 PM
Subject: Re: [hp_agilent_equipment] 3575A - useful ?

At 03:25 PM 11/15/2007, Dave Brown wrote:
Be aware there is a 3571 out there which is a later 'version' of the
3570 and looks to a first glance to be identical, but it does NOT
allow phase measurements, only relative amplitude.
The 3571A is in fact a tracking spectrum analyzer - a different
beast
altogether.

John
Hi John-
They are not really all that different. Main difference is one is dual
channel while the other is single channel.
In essence, both are dual conversion superhet receivers with
dedicated digital processing to control their measurement functions
and generate the log amplitude (dB) and (3570 only) phase angle
outputs.

<snipped>

(I had to cheat and go look at them both to read off the bandwidth
settings-no way I could remember that detail!)
You got the advantage on me, because I haven't physically seen either
of them for at least 10 years. It is all so long ago that I don't
remember details, but I know that we even had them together in a
single rack with the synthesizer, some other interface boxes and a HP
2100 series computer. Later the 2100's were replaced with what might
have been 21MX series, and eventually 9000 series 200's. Maybe they
were 226's in the mid-80's.

We used to use the same computers in automated RF spec-ans based on
the 141T/8555A and 8510 network analysers. The RF gear started out
with 9836's and moved to the 226's, the LF gear bypassed the 9836's.

All of this reminiscing makes me glad that today the equipment is
much smaller and lighter and more importantly doesn't produce
anything like the heat or noise!

John


Regards
DaveB, NZ
Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

 

Yeah, I know. That's what I tried to remind everyone of: that you merely
asked for a set of gears to look at, then return.
No, you still misunderstand, I had no intention of returning the 8640B,
I intended to pay for it by providing gear sets, and by making the specs,
and gear sets available to anyone that wanted them.

I was willing to do the work, but wanted an 8640B /1/2/3 in return for the
effort. I don't know what you get paid, but $175 for a days work seems
like a give-away to me.
Ah ha, OK I get it, I guess no reading comprehension score for me that day :)

I gues it's still a fair enough deal. I wish I could get a good deal on two
8640Bs, then I could keep one, send you another one, and get the first one
fixed mechanically!

Cheers, Kuba
Re: HP-8443A Tracking Generator Problems

lothar baier
 

have you ever considered a 5345A ? they are cheap, and they go to 500MHz

The marker does not really say anything, most of the time markers are blanked in on the sweep trace not on the RF level, i havent looked in the manual but thats how most generators and sweepers are doing it, the fact that you see a marker blip without the RF output of the generator beein connected to the SA input supports this.
one possibility is to build a pre-scaler for your counter to extend the frequency range, the other one is that i could loan you a 500MHz counter so you can do the testing

"David C. Hallam" <dhallam@...> wrote:
I don't have the test equipment you outlined. My counter is a HP-5245L and
limited to 50 MHz. I have been looking for additional plug-ins to extend
its range but at the moment I don't have any. My scope is a TEK 465 which
has a bandwidth of 100 MHz. Since my interest is in the HF (3-30 MHz)
portion of the ham radio spectrum, I just never saw the need to have
extended range test equipment.

I did what I will call a quick and dirty test. I connected the 30 MHz
calibration signal from the 8552B IF section to the RF input of the 8553B RF
section. At a 30 MHz setting on the 8553B frequency dial, I get the signal
peak on the 141T screen along with the marker from the 8443A. I can turn
the 8443A on and off and the marker pip also goes on and off. The 8433A
display reads all 0's.

If I set the 8443A to the external (counter) mode, it will correctly display
the frequency of a signal from my signal generator.

Rightly or wrongly, what do I conclude from all of this?

1 The counter portion of the 8443A is working correctly
2 The tracking generator working correctly
3 The no display problem in the tracking mode is related to counting of
the signal output of the tracking generator rather than a signal generation
problem in the tracking generator.

David

-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of
microwaveengineer1968
Sent: Thursday, November 15, 2007 9:31 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems


This is the link for a manual for the 8443A

Now down to the bone my friend, i have looked at the manual and
compiled some preliminary checks for you to do, this assumes that you
have acess to a counter to 500MHz and maybe a powermeter or scope
with appropriate bandwidth.
First off you need to verify the operation of the tracking generator
portion of your unit, dont worry about the counter for now, basically
the 8443 receives three signals from the 8553 and 8552 units, those
signals are mixed together sequentially to form a 0-110MHz signal
which is then amplified and leveled, the manual has a nice block
diagram in it btw !
The first signal is a 200-310MHz which is basically the 1st LO of the
8553, the amplitude is supposed to be -6dBm, the next signal is a
150MHz fixed LO @ -2dBm and the third Signal is a 47MHz fixed lo @ -
7dBm
First connect your counter to the RF output of your 8443A, set the
attenuator to 0dB and then set the analyzer to zero span and tune the
frequency and see if the counter indicates a frequency reading in
accordance to your analyzer scale, if you dont get any indication you
will have to verify the presence of your LO signals, you may just
have a bad interconnect cable to your analyzer, measure the 150MHz
signal on A11 J1 (you have to remove the cable and then measure the
signal coming out of the cable) , measure the 47MHz signal on A13 J1
(once again measure whats coming out of the cable) and the 3MHz fixed
LO on J3 (cable) then move on to A9 J1 on this cable you should be
able to measure a signal from 200-310MHz the frequency should be
tuning when you turn the tuning knob on your RF Section.
Do those tests and let me know the outcome.

--- In hp_agilent_equipment@..., "David C. Hallam"
<dhallam@...> wrote:

I have some problems with my 8443A and need help locating the
issues. The
nixie tube display shows all 0. I believe the tracking generator
is still
working because the marker is on the screen of the 141T. I can
connect the
RF output of the 8443A to my HP-5245L counter which will display
the marker
frequency. I can move the maker with 8533B frequency control and
the
display on the 5245L will change with the movement of the marker.

The 8443A will function as a counter because I can set it in the
external
mode and use it as a frequency counter.

I followed the counter trouble shooting tree in the manual and
reach the end
point where it says to repair A5. However in the service section
for A5, I
get oscilloscope displays from each of the 6 test points on A5 that
match
the photo in the manual which leaves me wondering. I don't have the
extender to remove the module from the 8443A and measure the
voltages, etc.
at the points indicated on the repair table.

Does anyone have any suggestions about what to do next? Is my
conclusion
that the tracking generator portion functioning properly logical?
My skill
level as an electronics technician is not that great with
instruments like
this.

David
KC2JD/4







---------------------------------
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