Questions for Users: Power dissipation in a hand-held tester

[Wowbagger]

OK guys, here's a question for you all to think about.

Suppose a test equipment vendor (who shall remain nameless but curiously enough appears on my paycheck...) were considering requirements for future design of a handheld type service monitor. Now, being that a handheld unit doesn't have a large mass and big fans to shed heat, there will be limits on how much power it can dissipate from the unit under test.

So, how do you, the users, use such devices: do you mostly test larger devices, like mobiles or base rigs, with such a portable (e.g. "If the mountain will not come to Mohammad, then Mohammad must go to the mountain"), with portable radios being tested on a bench rig (since in those cases the mountain (UUT) can come to Mohammad (the tester)), or do you do lots of mobile testing with portable tester? Do you have a problem with using external attenuators to bring the power down, and at what power level do you find an external attenuator acceptable?

As usual with what I do, I'm limited in what I can discuss - but it's pretty obvious that a company like Aeroflex is always looking at the next design, and since I am one of the principal engineers here it isn't surprising that I would be involved in such research. I cannot say where in the design cycle we are, and I cannot answer specifics until products get announced, but I would like to get good information.

And if you REALLY want to give your discussions weight, give me input as to how many service monitors you have, how many UUTs you test (basically, how much money do you really mean to us?)

[Bill_G]

Hi Wow - Still using my 120B for it's sweep gen and spectrum analyser along with my two 1200S monitors for day to day work. Mostly base stations. I also have an 40Ghz Anritsu (with spec anal and sweep gen) to sweep lines and waveguide with an external pwr head good to +30, and an Agilent power meter good to +40. And I have a Marconi spectrum analyzer good to 25Ghz (looks very similar to the 120B). An Aeroflex is available to me if I ever have to work on a P25 system. While most of the systems I'm responsible for are still analog, I suspect I will be seeing more digital systems before I retire.

If I were to use a handheld service monitor that required an external atten, I would probably need at least a +50dbm / 100w unit with an appropriate cable, or even a convenient method for attaching it to the device - preferably screws or clips - with a jumper to the input with a standard connector - not the planar crown.

I would also want the screen sweep rate to be reasonably fast - down into the uS - and somewhat independent of the BW. My Anritsu, while conveniently small and battery powered, is incredibly slow, and misses intermittent emissions that the 120B and Marconi captures. It is also too slow to easily tune duplexers and combiners. You have to be very patient if you spread it out more than a couple meg. OTOH, it lets you capture and store a lot of images that you can dl, print, and interpret. Very handy for finding and proving interferers.

[mike m]

I have recently been doing avionics wideband antenna testing for harmonic and DO-160 certification and my anritsu is either just too slow or always complaing about wanting me to lower the RF level.

I need something in a handheld with >100 dB dynamic range on the spec anal, I can't stand having to constantly change the reference level or add in some attenuation when a near by strong transmitter comes on.

The Anritsu is always overloaded when i'm looking down -110 dBm and I absolutely need to look at fast changing signals from about 0 dBm down to -110 dBm for harmonic testing.

Also the Anritsu battery always dies just when I start getting into some serious measurements.

I can't carry a bunch of external pads either, the capability to handle 50 watts or more would be nice. How about a coffee maker too ?

BTW I love the Aeroflex 2940 that you guys sent me to eval, if I could get that in a handheld I'd never leave home without it.

My mistake, That should be Aeroflex 2948B service monitor not 2940


Mike

[Wowbagger]

I need something in a handheld with >100 dB dynamic range on the spec anal, I can't stand having to constantly change the reference level or add in some attenuation when a near by strong transmitter comes on.

100dB range gets to be pretty damn tricky - for a digitized spec-an, you have to have at least a 14 bit ADC, and preferably 16 bits. For any given span, you have to digitize at least as many Msamples/sec as you have span MHz - so if you want a 100MHz span, that's 100Msamples/sec at 16 bits or so I and Q.

I can't carry a bunch of external pads either, the capability to handle 50 watts or more would be nice. How about a coffee maker too ?

50W dissipation requires forced air cooling - hold onto a 50W lightbulb sometime for a few minutes if you want to see what happens without forced air. Forced air means holes in the case and there goes water proofing.