Service monitor

[w3jn]

I finally got sick of sig gens with iffy attenuators, and my ancient HP 3571A/HP3330B specan/tracking generator that needed 20 minutes of setup, moving cables around, and setting up the scope every time I wanted to measure a filter or something.  So I did a bit of research and found that HP/Agilent made a FB line of CDMA and TDMA service monitors, intended for cell site service, that have hit the surplus market at bargain prices.

The secret of these monitors is that they also include a spec an, tracking generator, and all the analog tools you'd ever need in addition to the digital cellular capabilties.  I mustered the money in the wallet left over from selling stuff at NearFest and bought a Agielent 8935/E6380 CDMA analyzer from Ridge Equipment in Eldersburg MD.




This late model (circa 2000) instrument is of course made to traditional HP quality and includes the following features:

100 KHz-1000 MHz and 1700-2000 MHz coverage
Spectrum analyzer with 300 Hz RBW (wish it went narrower, but the Tek 495 does that), offset markers, averaging, etc.
RF generator with AM/FM mod (int or ext)
Receiver with squelch (AM/FM/SSB) and internal speaker (or audio out to a BNC)
Tracking generator with a cool RF toolset
Cable fault locator to find that break in the coax
Cable loss meter
RF wattmeter/dummy load with 60W capability (1 watt below 100 MHZ)
50 KHz digital oscilloscope
Various audio HP and LP filters
Tunable audio notch filter
Audio gozintas and gozoutas
A video monitor output, if the internal monitor ever craps out
AM mod % (average, set to ref, peak, etc)
FM deviation meter
Freq counters for AF and RF
SINAD, S/N, and distortion meters
Digital voltmeter (AF and DC)
Automated test capability - and HPIB/RS232 I/O
And probably a ton of stuff I havent' discovered yet.

This particular unit has a bit of screen burn and so it was a steal for what it does.  There are some on eBay now for about $1700 but they often go cheaper.  Also similar is the HP8924C CDMA analyzer, which has almost the same features but is bigger and less expensive (often selling for <$1K)

The only gotchya I've found is that this thing's narrowest IF filter is 30 KC for the receiver, as opposed to 15KC for the HP8920 2-way service monitor.  I can live with it!

Warning, though, Wavetek and others made CDMA analyzers that do NOT have the analog capability.  THose things are pretty much useless.

I highly recommend Ridge Equipment.  Great bunch of guys and a warehouse full of gear to drool over!  If you wanna get rid of that pile of test equipment and invest in one instrument that does it all, this is the best deal I've found.  IFRs and Motorolas don't even come close in feature/price ratio. 

I'm not easily impressed by test equipment, having had access to some of the best stuff ever made thru work, but despite a few shortcomings (wish it had better specan RBW, the connectors are on the side, and a better receiver IF filter) I gotta give it a strong recommendation.

[WA1QHQ]

I have always admired the Agilent service monitors above all others. Most of my lab gear is Agilent/HP and their quality and performance is second to none. One of the things that a service monitor does well is to be able to generate an audio test tone that can be used to modulate a transmitter and then to be able to tune the TX in on the service monitor receiver and then to make off the air distortion measurements, doing this with individual pieces of test gear is a real PITA.

[flintstone mop]

I'm pretty happy with my IFR. The cal is not that critical for what we do in Hamdom and the atten. seems to be close enough for Gov't work when I need to check sens of the R390A.
I never went down that path of drifty tempermental sig gens. I too was spoiled by the goodies from work.

Fred

[W3SLK]

Nice rig Jon. That's about 1/3 the size of my 141 and tracking generator. I would like to see if there is something on the web about setting up my stuff and using it more often. I thought I would beable to do 'front-end alignment' on receivers easier using a spect. analyzer. Like I said, I guess I have to play with it a little more.

[W2JBL]

it's amazing how much they pack in to the newer service monitors. we are looking at a few new Aeroflex (formerly IFR) units at work, and for a cool 30 grand they do everything but make a grilled cheese sandwich for you to munch down after you get Joe's Taxi back on the air...

[W2PHL]

Thanks for the info W3JN. Have you tried using an external video monitor with it? Does it output baseband NTSC video or something more exotic?
-Phil

[w3jn]

I haven't tried the external video output yet, but the manual proclaims it's NTSC.

[W2PHL]

If the FEDEX guy ever gets here I'll get to find out first hand. I have an E6380a on order and the external monitor feature is something I think I can make use of. Hopefully it arrives in one piece.

[John K5PRO]

Nice device, good catch W3JN. I wonder why the dummy load is only for 1 Watt below 100 MHz and 60 watts above?

[Jim, W5JO]

Nice device, good catch W3JN. I wonder why the dummy load is only for 1 Watt below 100 MHz and 60 watts above?

This is a strange spec John.  It has been the case for Agilent since they started making service monitors.  But the thing really was designed for cell phone work and the max power of a cell site base is 60 watts.  They really didn't sell these for land mobile work where the normal power is 100 watts. 

[WU2D]

These cellular test sets are rented and paid for by the rental and then as technology marches on, they get dumped. The old idea of an IFR having a 25 year life on the bench at a company is simply gone (like the 200 or so we had at Motorola in Plantation) it is history. The technical cycles and life of the programs (and companies for that matter) are simply too short. Keep your eyes open for old analog AMPS test sets.

Mike WU2D

[WA1GFZ]

Rentals are a tax write off so many times it saves money to rent.
They are not like a reantal car because you get nailed if you damage the device or lose any books or probes.

[w4bfs]

hey Mike ... i'm an old 'bat winger' from Plantation ...was there 82 & 83 in paging prod dev ... worked for Rob Lockhart ...how about you?

[W9RAN]

Tnx for the good suggestion.  Some in the Chicago area know about Valuetronics, who let a couple of guys haul a vanload of the older test gear to hamfests for sale at bargain prices.  A lot of it came out of old cellphone factories when the technology changed.

Speaking of the 141 and tracking generator - anyone have a spare (or know of sources for) a HP 11652A kit, or a 50 ohm 8721A directional bridge?  Or plans to make a clone?

73, Bob W9RAN

[WA1GFZ]

I was a bat winger for two years. Worst job I ever had. Crappy install means many a service call. Boss was a sleeze. Nothing written down.  I was telling our Police Chief walking out of the election. Our town was the only one they didn't mess up because the comm guy on the force was up their 6 every step of the way. When I saw a guy use coax with a brown shield on a $300K system. I knew it was time to go. It wasn't on the air a week and  there were RX noise gripes. This was in the middle '90s when Chris-ie in the process of destroying the family business with his bean counter pals. Outsourced radios were trash.
The only good thing was those blue tee- shirts. I still wear them all the time.
Thank God got back into Mil Electronics

[WU2D]

hey Mike ... i'm an old 'bat winger' from Plantation ...was there 82 & 83 in paging prod dev ... worked for Rob Lockhart ...how about you?

I was hired out of college into the special applications group under Bill Pagones and was an active member of the ham club. Worked on all kinds of stuff using bits and pieces from all over. I left in 1983. John Stahl, Burt Fischel, Bruce Burke and Mike Macaluso were in my group. We had a ball.

Mike WU2D