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HP-8443A Tracking Generator Problems
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I said that two sentences later:
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"At narrow RBW settings, you have to fine-tune the TG to be exactly on frequency, that's the screwdriver adjustment on the front panel. Since you don't know that it's spot-on, start with a wide RBW then narrow it down." Said screwdriver adjustment trims the 3MHz LO which mimics the final I.F. of the 8552. Late versions of the 8443A have a "Restore Signal" mode which uses the actual IF signal from the 8552. In that mode, as long as it's within the SA's RBW, the TG puts out exactly the frequency presented to the SA's RF input. Note: This doesn't work with early 8552's, they don't bring their final IF out to the bulkhead. While the mod is conceptually simple, it's physically difficult due to the location of the contacts, so I haven't done it to my 8552A. And another note: When the 8553B is in FULL scan mode, it puts out its own marker in addition to the one from the 8443A. Fortunately they are recognisably different: the former is a dip in trace height while the latter is a change in trace intensity. And a note about that. How much brighter it gets depends on the Marker Intensity control, which adjusts the time the scan is paused at the marker position. Regards, Dave Wise -----Original Message----- |
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J Forster
ONLY, if the TG is actually putting out the same frequency as the SA is
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tuned to. I have an AIL 757 and TG. If the tracking control is not tuned right, the YIG in the SA's front end will be tuned to a different frequency than the TG and you see little to nothing on the SA. -John David Wise wrote: You don't even have to select zero span. The function and |
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J Forster
Take a look at the Wiltrons. The advantage is that the marker accuracy is independent of the GHz/Volt calibrations. In fact, I have a little home brew unit in a Tek TM-500 PI that does just that... mixer, LPF, detector, comparator.
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-John lothar baier wrote: 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 :) |
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You don't even have to select zero span. The function and
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purpose of a TG is to output, at all times, whatever frequency the SA is listening to. As the SA scans, so does the TG. In all scan modes, the SA should show a horizontal line at a height determined by the TG's output amplitude. So just route the TG RF out to the SA RF in. If the trace rises, you have RF, if it doesn't, you don't, and either the TG is not outputting or it's off frequency. At narrow RBW settings, you have to fine-tune the TG to be exactly on frequency, that's the screwdriver adjustment on the front panel. Since you don't know that it's spot-on, start with a wide RBW then narrow it down. You could also view the TG output on your scope, at low frequencies. If the SA is on low band, the TG will be between 100kHz and 11MHz. However, the counter is tapped off at a different point so it's possible for the TG to output RF without counting, even if the counter works in EXT mode. Check the condition of A6W1 (Service Sheet 3) and scope it for RF. You've received good advice when it comes to checking the connections; with their inadequate brackets, those bulkhead-mounted hybrid-D's are notorious for "signalus interruptus". A couple of minor corrections to earlier postings: 1. The 8552 47MHz LO is not fixed; it's tuned by the Fine Tuning control, and swept on spans narrower than 50kHz. The 8443A's predecessor, the 8601A Option <mumble>, used with the 8553L, did not input the 47MHz LO. The 8601A generates its marker with RF blanking. 2. The marker is not necessarily at the SA center frequency, it can be moved side-to-side with the Marker Position control. Regards, Dave Wise -----Original Message----- |
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I cant be bothered to look at the manual as it it out of reach, but has it
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occured that you are assuming that the marker and RF output are connected......they may not be. Check you actually have a RF output on a scope or an RF voltmeter. The marker could be generated from the scan and the RF signal could get lost before the counter take-off and the output terminal. Like all fault finding you need to go round the loop checking for signals with an independent piece of gear. Dont just make assumptions about how it works. Things that "must" be working usually arn't from my experience, until proved otherwise !! Alan ----- Original Message -----
From: "David C. Hallam" <dhallam@...> To: <hp_agilent_equipment@...> Sent: Friday, November 16, 2007 6:09 PM Subject: RE: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems Since I have demonstrated the counter portion of the 8443A is functionalas it will count an external signal from my signal generator and the RFoutput the 8443A is functionalNO not necessarily....measure it ! since there is a marker on the CRT display, the problem is in the counting of RF output frequency at the point where the |
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lothar baier
yes i think so
John Miles <jmiles@...> wrote: Isn't that what the 86222 sweeper plugin with the marker option does? Those are pretty common. -- john, KE5FX
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David C. Hallam wrote:
Lothar,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)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 :^) |
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David C. Hallam
Lothar,
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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 " Recent Activity a.. 7New Members b.. 6New Files Visit Your Group New web site? Drive traffic now. Get your business on Yahoo! search. Y! Messenger Send pics quick Share photos while you IM friends. Yahoo! Groups Going Green Share your passion for the planet. ... --------------------------------- Never miss a thing. Make Yahoo your homepage. --------------------------------- Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how. |
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John Miles
Isn't that what the 86222 sweeper plugin with the marker option does? Those
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are pretty common. -- john, KE5FX
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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
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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 notrequire a 500MHz signal --------------------------------- Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how. |
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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. --------------------------------- Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try it now. |
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lothar baier
Lets go back to the basics,
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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 " Recent Activity a.. 7New Members b.. 6New Files Visit Your Group New web site? Drive traffic now. Get your business on Yahoo! search. Y! Messenger Send pics quick Share photos while you IM friends. Yahoo! Groups Going Green Share your passion for the planet. ... --------------------------------- Never miss a thing. Make Yahoo your homepage. --------------------------------- Never miss a thing. Make Yahoo your homepage. |
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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. |
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Hi Thanks Lothar....that is the unit I use most often and have never had to
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"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 notrequire a 500MHz signal |
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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
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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 " Recent Activity a.. 7New Members b.. 6New Files Visit Your Group New web site? Drive traffic now. Get your business on Yahoo! search. Y! Messenger Send pics quick Share photos while you IM friends. Yahoo! Groups Going Green Share your passion for the planet. ... --------------------------------- Never miss a thing. Make Yahoo your homepage. --------------------------------- Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how. |
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lothar baier
you are talking about the 8444 not the 8443, the 8443 actually does not require a 500MHz signal
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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 causeplug-in. The aluminum framework that holds these D style connectors is too thin andresults in a partially working SA. --------------------------------- Get easy, one-click access to your favorites. Make Yahoo! your homepage. |
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David C. Hallam
Now I am getting confused.
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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 " Recent Activity a.. 7New Members b.. 6New Files Visit Your Group New web site? Drive traffic now. Get your business on Yahoo! search. Y! Messenger Send pics quick Share photos while you IM friends. Yahoo! Groups Going Green Share your passion for the planet. .. --------------------------------- Never miss a thing. Make Yahoo your homepage. |
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Hi, just a though triggered by Chuck's posting. Some of the connectors for
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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 causeplug-in. The aluminum framework that holds these D style connectors is too thin andresults in a partially working SA. |
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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.
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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 " Recent Activity a.. 7New Members b.. 6New Files Visit Your Group New web site? Drive traffic now. Get your business on Yahoo! search. Y! Messenger Send pics quick Share photos while you IM friends. Yahoo! Groups Going Green Share your passion for the planet. .. --------------------------------- Never miss a thing. Make Yahoo your homepage. |
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