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Re: HP-8443A Tracking Generator Problems

David C. Hallam #9105 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 toggle quoted message Show quoted text -----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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