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Re: NEW TOPIC: Outstanding Rockland Instruments 7000 Plugin; WAS: Slightly OT- Wavetek 7530B?
Hi Dennis,
This job is indeed very busy and complex. The temperature, ice and wind conditions at 3600m altitude forced me to develop a lot of specific equipment for the task. The problem is not only design, construction and repairs. The need for day-long observations depending on a very unpredictable meteo puts chaos on my agenda and consumes most of the time that would be needed for development. Since 2008, I could implement internet remote measurements that were considered impossible by my predecessor. But covid and the impossibility to reach the lab for repairs put it down since november. I would like here to bring to the group attention the probable cause of this failure. We had two IP KVMs to control a vintage critical computer. So, one KVM was a spare. The two died within three months and my diagnostic is that the two forgot their firmware programmed at around the same time. One has to be aware that at 3600m altitude the cosmic rays are more intense and speed-up memory loss. This to say that I see a lot of people careful enough in the HP and Tek lists to remove (sometimes desolder) the eproms in their nice equipment to save their contents (if possible and safer, reprogram them to refresh their contents). Now, the situation got worse with the embedded EEPROMs in microcontrollers. In that case, the contents are not accessible and the instrument is doomed when the contents vanishes with time. I already have IP cameras in the lab that seem to have been attacked by this modern electronic Alzheimer. For sure, this is a very convenient unavoidable obsolescence for the sellers. Your motherboards will also forget their Bios in soldered EEPROMs btw. Socketed EPROMS are long gone. Back to Fourier Transform SA. When you are in the domain, you get quickly the feeling that you can easily buy more resolution by taking more samples, which takes more memory and time. This is the same feeling as an analog SA that needs a slow sweep at small resolution bandwidth. But with FT SA you need a stable source. Otherwise you just would mix-up added noise on top of runing your line profiles. In our case, the target resolution is the one needed to well resolve the thin absorption lines of the atmospheric gases. This means a resolution between 500000 and 1 million. Hence the reason why we usually manipulate 2 million points samples (Nyquist). If the frequency domain of interest is reduced, applying a bandpass digital filter to this set would allow the equivalent of a heterodyne frequency change and the possibility to undersample a lot to speed-up FFT. Otherwise, with a big FFT you can get a 0 to Fmax spectrum at max resolution. The possibility you mention to slow down the clock of the 7530 is indeed to reduce RBW but at the expense of the maximum input frequency at the instrument input. Because the problem is that you can't increase its maximum resolution which is determined by its memory size. Unless an antialiasing low-pass analog filter was put in front of the S/H, Nyquist would hit you hard and mix-up all your frequencies. ;-) I never had the chance to see a J20/7J20 and I would have been very happy to play with. It for sure was very compact. Much more than my 4 meter long interferometer. I remember now that the Rockland synthesizers were operating at 1.6MHz, not 8. I repaired one of them once. A lot of 74xx chips in them and one had failed. So, group members, save all your Eprom contents when possible and be cautious when buying post-2000 equipment containing soldered or embedded EEPROMs. The time bomb is running... |
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Re: Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
Hi Raymond, I meant to look at effective bits as a general view on all DSOs. I don't know what the detailed differences are among the TDS scopes. I actually find it quite confusing with all the various models, since I'm not very familiar with them. One thing I do know, is that I "upgraded" my TDS754 (I think) a while back, to perform as a TDS784, using some mods I found online. As I recall, some BW limiting caps needed to be deleted from the amplifier circuits, and some jumpers needed to be changed to make the brain think it was the higher-end model. It appeared to work.
Ed |
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Re: 7104 readout issue
Said switch is on the front panel of the 7104 - turn the readout pot fully clockwise into the detent at the end (PULSED position). To quote page 2-10 of the manual:
The READOUT control determines the operating mode of the Readout System. With the READOUT control set to free run (out of OFF or PULSED detent positions) the Readout System operates continuously, interrupting the crt display at random (for about 20 microseconds) in order to write each character on the crt. With the READOUT control set to the PULSED position, the Readout System operates in a triggered mode; one complete frame (up to eight words) of readout is displayed. The + GATE or EXT switch determines whether readout is displayed at the end of the + GATE or when an external signal is applied to the rear-panel GRATICULE/READOUT SINGLE SHOT input. The+ GATE switch selects whether A gate or B gate triggers the readout. HtH David |
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Re: Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
I have a couple of TDS3054Bs and have had one TDS3064A, and have done rise time and -3dB measurements on them. Just as others have mentioned, I saw around 700pS rise times and 600MHz -3dB points - on both the '54 and '64! Exactly the same! So, my guess is that Tek somewhere along the line decided to sell a 600MHz labelled version of what was essentially the same electronics because somebody said they could do so (legitimately by some measure), but then had second thoughts or maybe the engineers told the marketing folks to back off!
Reinhard |
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Re: bandwidth
Don Bitters
Jim,
I was one of those HP/Agilent field cal guys doing the MTE, never did it for Raytheon, but did it for 100¡¯s of other customers. We verified that every instrument made published specs - no matter what manufacturer HP, TEK, Fluke, etc. we never adjusted any MTE without notifying the customer - he/she had to authorize it and quite often had to provide the adjustment procedure if it was a manual procedure. I did the manual verification procedures on about 100ea. 11032¡¯s, CSA803¡¯s and plugins. One time I was pressured by a high level manager to ¡°pencil whip¡± the test procedure to speed it up. I pointed out to him that I would not/could not do that because of the damage to our reputation, let alone the legal liability if I passed something that actually failed. You know how many pages the manual test performance for the 11032/CSA803 is - about 75, and the SD-24, SD-26 plugins - about 30 pages. Doing the performance procedure on an 11032 with 2ea. SD-26 plugins was most of a day calibration without the additional paperwork. I did not know of any HP/Agilent/Keysight techs, engineers that would ¡°cheat¡± on a calibration, and I knew well over 100 of them personally to talk to. I also doubt that any of the Tektronix, or Fluke, or Dayton calibration people that I knew, and even a large number of the independent cal labs that I dealt with would also ¡°cheat¡± on a cal. On the other hand I did know of a few labs that were notorious for selling the customer the cal stickers and the certificates for a fee. One of our NA customers went looking for a cal lab in Mexico (Agilent-Mexico declined, they had neither the ETE nor the trained people to do the required tasks). They found a guy that had a small shop above a pharmacy in Guadelejara that said he could do the job calibrating production line optical test systems. He had a 100MHz o-scope and a 4-1/2 digit DMM. The NA customer hired Agilent-Midwest to go down to Reynosa, Mexico for 3 weeks to calibrate his calibrating production line optical test systems, for a princely sum, but got it done to NIST traceable, with data. Don Bitters |
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Re: P6131, T-coils and other probe stuff
Hi Mark,
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Very nice to see you here! Your review article on sampling scopes is a true classic. I blame and thank you for the happy hours I've spent trying to chase down and then read, all the references you cite. :) I can't imagine the hours you spent amassing all of that information. Simply amazing. Gabor is a dear friend, one of the last remaining links to that earlier generation, a rarity who knows that "Bartlett bisection" isn't a medical procedure. Cheers Tom Sent from an iThing, so please forgive the typos and brevity On Jan 31, 2021, at 16:29, "Mark Kahrs" <mark.kahrs@...> wrote:
I can't resist commenting about: |
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Re: Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
On Mon, Feb 1, 2021 at 01:02 AM, Ed Breya wrote:
Sure, important and interesting. Is there a special relevance to the point I was trying to make? AFAIK, the architecture and hardware are the same across the whole family, incl. the TDS3064 600 MHz version. Any suggestion re. how to find out? Basic resolution for these 'scopes is 9 bits. Max. RT sample rate is 5 GSa/s. Raymond |
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Re: P6131, T-coils and other probe stuff
I can't resist commenting about:
"If there is a network theorist left on your faculty (very rare these days)," In fact, it appears that circuit theory classes have nearly vanished. One of the few I know of is taught by none other than Gabor Temes: I find that some of the old classiques, such as Van Valkenburg or Kuo are truly edifying, for example, conversion from one 2-port form to another. Great stuff, highly recommended, , etc. Once you've seen transfer matrices (ABCD), you'll never look at circuit analysis the same way again. I'll stop before I wax even more ecstatically. On Tue, Jan 19, 2021 at 5:19 PM Dennis Tillman W7pF <dennis@...> wrote: When it is safe come and stay with us as our guest. We have a large house |
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Re: 7104 readout issue
Chuck Harris
Hi Sean,
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I remember now. My 7104 spends most of its time, all dressed up, with no place to go... So, it is not one of the scopes that I am most familiar with. If you look on the front panel, you will see an outlined area that has two intensity pots (A and B), a READOUT intensity pot, and two push buttons for the readout. The one button is marked +GATE or OFF, and sets the readout to be on at the end of the GATE signal, or off. The other push button is marked "MAN", which causes the readout to be on always. Something there is probably in the wrong position, or misbehaving. Also, I keep my plugins off of AUTO on my 7104. Because of the MCP's limited life, you do not want to be wasting it with continuous readout display, or baseline display. I keep my readout in "GATE" mode, so it is off if the sweep isn't being triggered. Typically, I also keep the A and B intensity turned off when the scope is off, to avoid intensity flair during turn on. -Chuck Harris [email protected] wrote: Chuck, |
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Re: 7104 readout issue
Chuck,
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Looks like mine has a more modern readout board, that contains no switch. It has a large socketed ROM where the switch would be in an older style readout system...the plot thickens... Sean On Sun, Jan 31, 2021 at 01:30 PM, Chuck Harris wrote:
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Re: Tek 4041 GPIB Controller
After the 4041 console has changed to the COMM0: serial port on the back of the 4041, you then use a terminal emulator program on your PC and a USB to RS-232 serial adapter to send programs to your 4041, and view the console on your terminal emulator. I also found a free terminal emulator for windows called Tera Term that is simple to use and it includes both VT and Tektronix terminal emulation. I have been using that program today with my 4041, and it works with EZ-TEST Generator with a couple of quirks. You need to modify the Tera Term properties following these instructions to be able to resize the Tera Term Tek window to match the size of the text so the EZ-Test menus look right: I have Tera Term screenshots running EZ-TEST in my vcfed thread: |
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Re: Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
On Mon, Feb 1, 2021 at 12:05 AM, Bob Albert wrote:
I realize "step response" is the term commonly used. During adjustment/calibration, step response is made to follow the applied electrical voltage step as accurately as possible. Some overshoot is commonly accepted. Raymond |
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Re: 7104 readout issue
Chuck,
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Good call; I should open it up and take a look. I'm not sure where the readout board even is on a 7104...the internal layout is *vastly* different compared to the 7904(a)! Sean On Sun, Jan 31, 2021 at 01:30 PM, Chuck Harris wrote:
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Re: Tek 4041 GPIB Controller
I think I have a solution to the 4041 tape issues - I call it my 4041 Console Commander :) My Console Commander is a tiny Arduino module connected to and powered by the 4041 keyboard connector with inexpensive Dupont jumper cables. You simply turn on your 4041 and after it finishes self test - press the button on the Arduino and the Arduino sends to commands to the 4041 at 4800 N82: Here is a link to a photo of my Console Commander prototype: More details in my 4041 thread at vcfed.org: |
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Re: User Experience of Sampling Scopes
Another gotcha (that is really really expensive) are the 50 ohm female loads that came in 3.5mm cal kits made by HP. They contain super tiny "fingers" inside that help with the match. One flinch while mating that results in accidentally spinning the female connector will ruin these instantly.
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btw, I *highly* recommend investing in a set of connector gauges for SMA and up. I have a set of 3.5mm gauges in my VNA cal kit, and I also have a set of SMA gauges (these are 4 gauges since you also have two gauges for the dialectric). Sean On Sun, Jan 31, 2021 at 02:07 PM, Tom Lee wrote:
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Re: Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
Bob Albert
What do you mean, adjusting the step behavior?
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On Sunday, January 31, 2021, 02:51:21 PM PST, Raymond Domp Frank <hewpatek@...> wrote:
Inspired by recent postings in this group, I've decided to describe my experience with a TDS3054 and a TDS3054B. These 'scopes have a published bandwidth of 500 MHz on all channels. The TDS3000-series Service Manual (071-0382-01) on page 1-3 mentions a *calculated* rise time of 700 ps. This complies with BW = 350/tr (BW in MHz, tr in ns). 350 is the accepted number for analog 'scopes (Gaussian fall-off). Apparently, Tek didn't want to use the larger (400 - 450) value that makes sense for digital 'scopes with their much steeper fall-off. I measured both TDS 'scopes to indeed have about 700 ps rise time on all four channels, with only a few percent overshoot, in line with the rise time as per the specifications (although mentioned there as calculated). Two interesting things: - Both TDS 'scopes have their -3 dB points clearly above 600 MHz on all four channels! If this applies to "all" samples of this model, it indicates that 400 - 420 would be more applicable than 350 but Tek decided in their sales documentation to do as if the number 350 that everybody knows from the analog age would apply, calculating BW from tr. The assumption "Nobody is interested in BW, rise time is what counts" wouldn't be surprising in these digital times. - Tek sold a TDS3064 having a BW spec. of *600 MHz* with V/div. settings that nicely match my checking results for the two TDS3054's! AFAIK, checking and (automatically) calibrating frequency behavior in these 'scopes is done by adjusting the step behavior. Any comments? Raymond |
David C. Partridge
Raymond Domp Frank
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