PMEL Forum

Quick Poll. . . What would you rather use for Tuned RF Level Measurements

A.  MMR
B.  8902MS
C.  1295
D.  Other

Reason I ask is I wonder who else hates using the MMR.  For our MMR it takes 10 Minutes minimum for each frequency due to our firmware revision.  (Ya sadly we read our manual).  And dont get me started on the specifications at the lower end.

8902, hands down. It's not even close. The MMR is VASTLY overrated. The Air Force really took it in the shorts on that acquisition.

Quote from: Duckbutta on 04-15-2009 -- 20:52:22
8902, hands down. It's not even close. The MMR is VASTLY overrated. The Air Force really took it in the shorts on that acquisition.

I agree. However, a 1295 is nice to have for 26.5 Ghz or higher.

Set up an actual poll for ya BigPMELDude...

8902, no doubt... Thee MMR has some good qualities such as not needing the downconverter but it is sorely lacking in the speed of measurement department.

I noticed you mentioned revision, in the latest AFMETCAL Newsletter there was a section about this very thing. The Newsletter states that any MMR with a rev less than A.11.04 needs to be upgraded at either Offutt or Elemndorf. Now this won't help any with the this specific subject but thought I would add it in as they say it can cause problems with NextGen Software because the way the program is written for the MMR relies on the revisions being the same across the board.

Smokey,

You hit the nail on the head. The MMR is extremely Sloooooooow. Especially the modulation measurements. The one nice feature that it has regarding modulation (displaying the modulation and distortion measurements simultaneously) is completely negated by the length of time it takes to make a measurement after the HP/LP filters are activated or deactivated. It is very frustrating to use and I avoid using it unless absolutely necessary.

Also, regarding TRFL, as you use it more and more, you will discover that the MMR has residual responses that are created by the various clocks inside as well as ones that are the result of internal mixing products. These will be readily apparent when the noise level of your signal approaches the level of the response. If you suspect one, switch to the Spectrum Analyzer mode (don't change any other settings), and it will automatically display the signal you were measuring in the Modulation Analyzer mode. Then disconnect the signal and terminate the input and look for a residual response. Agilent makes reference to these spurious responses in the commercial data but minimizes  their actual impact. They say that you can especially expect to see them at 50 MHz and at the harmonics thereof but that they can occur almost anywhere (and trust me, they do). I found that they are much more common than they lead you to believe.

Don't even get me started on NextGen. We had our MMR upgraded and I haven't seen any improvement when it is used with the software. The problem is the program itself. It's garbage. By any objective standard, NextGen has been a disaster. The problems that have shown up on the MMR calibration portion should have been identified in the validation process. The amount of problems that are readily visible makes one wonder what is going on behind the scenes as the program is running. What are the problems that I can't see? The shoddy nature of the software makes all readings suspect.

Duck,
Thanks for the info on TRFL. I have noticed certain problems like that but have not been able to do enough research to figure out what was actually causing the problem due to the fact I can simply go back to the 8902A for now.

As for NextGen I couldn't agree more, with any program there is supposed to be a validation process before implementation. I think they are using the field to do this for them by reporting problems found. Just the other day I was trying out the new program for the 68369NV, and in two different sections the hookups were were wrong. Example: when doing the pulse modulation they have the hookup w/ the scope and crystal detector for both sections when the first section you need a Spec An. Since I had done these before I caught it right away so no real loss but I would imagine some new kid coming out tech school or someone just learning this area something as simple as this could cause a lot of wasted time.

I mean how hard is it to simply validate the procedure, go back and edit the image to reflect what it is suppose too?

Another big problem I have with NextGen is it's lack of versatility with substituting standards within a program. Most of the programs they have written are useless to those who don't have every standard available that program was written for. I understand you can't write a program that is compatible with everything but maybe have some additional options available for suitable standard substitutes.

Thanks Hoopty. . .



Really pretty concerned about the lower levels accuracy after looking at the spreadsheet that AFMETCAL made.

Funny enough..why I like the 8902 MMS..

They have a great approved program for doing many things with it, not just attenuators..

While I've just given side inputs and insights, our guru of the 8902 MMS has written many procedures to automate signal generators to the point where an 8340/41 can be done in hours..and an 8663A in less than a day, including phase noise..

Now, we are integrating the MMR into these procedures, but not liking the TRFL..the 50 GHz spec an is great, but I still don't trust the modulation measurements..

Big problem..how do you do AM or FM distortion without the audio output?

But then, I'm over in fiber optics, what do I know

Mike

mdbuike,

We don't use the Audio Input on the MMR to do Modulation Distortion. The demodulated signal is routed internally.

I'm a little confused by your post. I was under the impression that the MMRs procured by the Air Force all contained the same package of options. Are you sure you don't have the Audio Input (Opt.107) on the front of yours? It would be located in the upper left hand corner of the instrument. Even if you don't, it's not needed for the Modulation Distortion as long as you have the Measurement Receiver Personality (Opt.233), which you obviously do.

I think what Mike is referring to is not having the Audio output on the MMR's like the 8902's  did and you would connect that with say the 8903B and do your distortion measurements. You can still do the modulation distortion measurements on the MMR b/c as you said it is done internally  but many have questioned the accuracy of of the modulation distortion measurements on the MMR. I think mostly b/c they are used to doing it the other way.

I think thats it anyway.

8902, all day, every day.

I use my MMR with a handy excel file for attenuators, filters, couplers, reflection stds, vswr bridges and that's about it. I even have it on it's own controller so my workhorse (8902) can be used at the same time to turn some equipment.

Granted, IF I am turning a LOT of attenuators that are all same freq range, I can fire and forget with the MMR and a little automation, interrupting it to do disconnects and swapping out TIs. But that has more to do with the advantages of having a decent program to run it for me.

By chance, has anyone else out there used Agilent's TME and accompanying "rack of death" to cal these things? I was (and still am) a guinea pig for the Army running these, and even after running around 10 of these in the past few weeks (E4440 and E4448s), it is all voodoo if you ask me.

Also, heh, can't wait til you have to replace the battery....... gotta love "new" equipment, dang battery was DEAD when I took it out of the box last fall, OUT of warranty already. YAY ME   :roll:  Thing has more screws than that little "house" in the "ville".

Quote from: Duckbutta link=topic=1266. msg12926#msg12926 date=1239891008
Don't even get me started on NextGen.  We had our MMR upgraded and I haven't seen any improvement when it is used with the software.  The problem is the program itself.  It's garbage.  By any objective standard, NextGen has been a disaster.  The problems that have shown up on the MMR calibration portion should have been identified in the validation process.  The amount of problems that are readily visible makes one wonder what is going on behind the scenes as the program is running.  What are the problems that I can't see? The shoddy nature of the software makes all readings suspect. 

We recently had some of the Engineers from AFMETCAL at out lab testing some NextGen Software and I think the biggest problems arise due to the fact the Software guys have no clue how the test equiment is used.  They just throw code into and hopes it works.  That being saidit does seem they were willing to comments/suggestions we were making to them.  The new PMCS software seems like it wll be pretty nice

You mean they actually test the software? This would be a shocking development that could rock the PMEL community.

We need to also mention that the MMR takes longer to measure AM/FM Mod. at least that is my experience. 8902 takes a much faster reading.

Quote from: flew-da-coup on 05-16-2009 -- 13:40:37
We need to also mention that the MMR takes longer to measure AM/FM Mod. at least that is my experience. 8902 takes a much faster reading.

Have you looked at the cal procedure for the MMR?  How do they ceritify the AM/FM calibration?  Implied?

Maybe an old argument..but I'll use the 8902A

Mike

Agilent claims that if the Tuned RF Level and Spectrum Analyzer portions of the instrument pass, all other parameters are "guaranteed by design". This makes sense to a certain degree being as though you can measure modulation depths (AM) and rates (FM) on a spectrum analyzer. I'm assuming that the instrument uses the spectrum analyzer circuitry (amplitude and frequency markers, span, etc.) to compute the modulation and convert it to a easy-to-read numerical display via the Measuring Receiver Personality option.

Quote from: mdbuike link=topic=1266. msg13216#msg13216 date=1242530724
Have you looked at the cal procedure for the MMR?  How do they ceritify the AM/FM calibration?  Implied?

Maybe an old argument. . but I'll use the 8902A

Mike

I have been trying to get AFMETCAL to tell me how AM/FM and even TRFL measurements are made.  No such luck.  They can't tell me what specifications guide is the correct one.  Been told June 2008, even the lovely spreadsheet they made.  So VERY frustrating.

Whats a MMR?  Who makes it.
I've got a Rhode & Schwarz FSMR with sensor head-it's very fast in tuned RF compared to the 8902A.  The part that impresses me during verification vs. the 8902A is that an arbitrary waveform generator is used to make actual AM & FM signals of a known level, the 8902A seems like it's all relative measurements.
It's furfigtestin!

Quote from: Bryan on 05-28-2009 -- 16:24:39
Whats a MMR?  Who makes it.
I've got a Rhode & Schwarz FSMR with sensor head-it's very fast in tuned RF compared to the 8902A.  The part that impresses me during verification vs. the 8902A is that an arbitrary waveform generator is used to make actual AM & FM signals of a known level, the 8902A seems like it's all relative measurements.
It's furfigtestin!

Its a fancy spec an that replaces the 8902A ( or supposed to ).