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HP-8443A Tracking Generator Problems
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David C. Hallam
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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Hi,
The counter 'MODE' switch simply switches it between the output of the tracking generator and the external socket, so if it works only on 'EXTERNAL' you probably have a fault with the generator and not the counter. Try looping the RF output (at about 0dBm) from the 8443A into the counter input, switch to external and see what you get. You should see a varying display as the analyzer sweeps. If you don't get anything, there is a problem with the tracking generator or the outputs from the 141 itself. My money would be on the crappy cable, plugs and sockets on the back of the unit. If it isn't them, remember that the 8443A just mixes together several signals from the 141T, filters them and outputs the leveled result from the front panel so it is not difficult to track down problems. All of the boards come out quite easily so that you can work on them on the bench one by one. I don't know what test gear you have but a scope and a signal generator would help. Just follow the block diagram (Fig 8-19) in the manual. Cheers - Joe G3LLV |
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microwaveengineer1968
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: issues. The nixie tube display shows all 0. I believe the tracking generatoris still working because the marker is on the screen of the 141T. I canconnect the RF output of the 8443A to my HP-5245L counter which will displaythe marker frequency. I can move the maker with 8533B frequency control andthe display on the 5245L will change with the movement of the marker.external mode and use it as a frequency counter.reach the end point where it says to repair A5. However in the service sectionfor A5, I get oscilloscope displays from each of the 6 test points on A5 thatmatch the photo in the manual which leaves me wondering. I don't have thevoltages, etc. at the points indicated on the repair table.conclusion that the tracking generator portion functioning properly logical?My skill level as an electronics technician is not that great withinstruments like this. |
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I have for sale most of the parts from a 8443A. Email me off list if I can help although postage from France may be expensive. I'm looking for a second-hand 08443-60009 inter-connect cable.
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Steve ----- Original Message ----
From: microwaveengineer1968 <microwaveengineer1968@...> To: hp_agilent_equipment@... Sent: Friday, November 16, 2007 3:30:52 AM Subject: [hp_agilent_equipment] Re: HP-8443A Tracking Generator Problems . edebris.com/ manuals/hp/ 8443a/ 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_equipmen t@yahoogroups. com, "David C. Hallam" <dhallam@... > wrote: issues. The nixie tube display shows all 0. I believe the tracking generatoris still working because the marker is on the screen of the 141T. I canconnect the RF output of the 8443A to my HP-5245L counter which will displaythe marker frequency. I can move the maker with 8533B frequency control andthe display on the 5245L will change with the movement of the marker.external mode and use it as a frequency counter.reach the end point where it says to repair A5. However in the service sectionfor A5, I get oscilloscope displays from each of the 6 test points on A5 thatmatch the photo in the manual which leaves me wondering. I don't have thevoltages, etc. at the points indicated on the repair table.conclusion that the tracking generator portion functioning properly logical?My skill level as an electronics technician is not that great withinstruments like this. ____________________________________________________________________________________ Get easy, one-click access to your favorites. Make Yahoo! your homepage. |
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David C. Hallam
I don't have the test equipment you outlined. My counter is a HP-5245L and
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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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lothar baier
have you ever considered a 5345A ? they are cheap, and they go to 500MHz
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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: issues. The nixie tube display shows all 0. I believe the tracking generatoris still working because the marker is on the screen of the 141T. I canconnect the RF output of the 8443A to my HP-5245L counter which will displaythe marker frequency. I can move the maker with 8533B frequency control andthe display on the 5245L will change with the movement of the marker.external mode and use it as a frequency counter.reach the end point where it says to repair A5. However in the service sectionfor A5, I get oscilloscope displays from each of the 6 test points on A5 thatmatch the photo in the manual which leaves me wondering. I don't have thevoltages, etc. at the points indicated on the repair table.conclusion that the tracking generator portion functioning properly logical?My skill level as an electronics technician is not that great withinstruments like this. --------------------------------- Be a better pen pal. Text or chat with friends inside Yahoo! Mail. See how. |
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One very big problem with the 141T frame and its plug-ins, that can cause
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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 |
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David C. Hallam
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-----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. . |
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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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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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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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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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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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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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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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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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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
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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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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