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Author Topic: SPECTRUM ANALYZER  (Read 412 times)
WB9JOX
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Posts: 103




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« on: January 27, 2006, 05:40:46 PM »

I want to purchase a spectrum analyzer for trouble shooting and repairs on my own ham radio gear.Any advise on range and etc. I dont plan on buying new one they are very expensive.Im retired and have time to learn something new.So I would really appreciate any help. Again as always Tnx..  Ted
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KZ1X
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Posts: 3228




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« Reply #1 on: January 27, 2006, 07:17:58 PM »

Opinions...

1.  Get the best resolution bandwidth you can afford
2.  Get the matching tracking generator
3.  Get a set of fixed input pads
4.  You'll also want at least one good signal generator
5.  Get a nice step attenuator
6.  Get a power attenuator or thruline meter with tap
7.  Get a good directional coupler
8.  Get some good precision loads
9.  Try and get one that would cover up to 2 GHz

I could go on.  

The message is:  once you start doing this kind of thing, you'll find that the spectrum analyzer is just the *center* of a *whole sphere* of stuff you need to do the work you'll want to do.

Now, as to the gear itself ... some of what's available for low prices is great, but also is likely to be quite aged.  If it dies, it's dead.  

The analogy to a car is remarkably similar ... the stuff costs about the same as a car and at typically the same vintage.  If you spent $1000 on a 20 year old car, and it died six months later ... well, that's about the same as buying a 20 year old analyzer.  A 5 year old nicer car will set you back, say, $10k ... same as a similar-age nicer analyzer, with the same hope of longevity and service.

I'd offer to sell you my early-80s spectrum analyzer and tracking generator, but I could not afford the $$ to replace it with the modern unit I'd like to have.
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KB4EMF
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Posts: 387




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« Reply #2 on: January 27, 2006, 09:12:40 PM »

Among all the test equipment that one would want/need to repair radio gears, spectrum analyzers would probablly be the most expensive piece of equipment.  Although it would be very nice to have one, it would not be the most useful or absolutely necessary most of the time, especially for repairs.

My recommendation would be to purchase such things as decent signal generators and multi-trace o-scopes before even considering spectrum analyzers.  

If you already have everything else, unless you have unlimited budget, you'll probablly have to make do with what's available.  What type of equipment are you thinking of working on?  

If I am to purchase one, I'd pick one that covers at least 5 times the frequency of the radio, so I can watch the harmonics.  Lowest end would be probablly be around 1Mhz or so.  Resolutions and dynamic ranges would probablly be sufficiently good on almost all units.  I've seen many units on surplus that has the input impedance of 75 ohms for CATV uses.  I'd make sure it's for 50 ohm service.

Matching tracking generators are nice to have.  
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K6AER
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Posts: 3524




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« Reply #3 on: January 27, 2006, 09:52:26 PM »

A 5-10 year old HP8900 series spectrum analyzer can be had for $2000-5000 dollar range.

Unless the analyzer comes with a 90 day warranty and money back guarantee, these are things you should check for:

•   Is the analyzer still supported by the manufacture?

•   Check the front end attenuator very carefully on all settings. These frequently have settings burned out.

•   Check that the IMD specification from the calibrator. If the levels do not meet spec. the mixer is probably burned out and they typically cost $1500 to replace.

•   Make sure you have a service manual with the purchase.

•   Analyzers used in field work have a much higher incidence of failure.

•   You can call the manufacture with the serial number for the service history.

•   Good analyzers cost more than $15,000 when new with 26 GHz units costing $40,000 or more.


Should you have any questions send me an E-Mail. My address is on QRZ.com
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W4DL
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Posts: 182




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« Reply #4 on: January 28, 2006, 02:57:57 AM »

Rather than the SA, I would suggest you look for a used service monitor such as the types used by the commercial two way radio shops.  For general troubleshooting they will serve you better at less cost.  I see used IFR's and Motorola units at hamfests and on e bay for 1 to 4 K bucks.

Mike W4DL
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K0BG
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« Reply #5 on: January 28, 2006, 05:37:33 AM »

Personally, I'm leery about buying used service monitors are hamfests. While you might find a bargain, it has been my experience that most are on their last legs, and too old to find parts for.

You can find fully reconditioned IFR units, from $7K to about $12K depending on the model. 1200S monitors, 1600s, even 2944s are all over the internet if you really want to spend this kind of money. Used Cushman CE50s are a good investment too, it they are in good condition. Parts are getting scarce for the old stuff (older than 1990), so due caution should be exercised.

Alan, KØBG
www.k0bg.com
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K6AER
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Posts: 3524




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« Reply #6 on: January 28, 2006, 07:37:06 PM »

I bought my HP 8920B service monitor at Dayton for $4800. Bargains are everywhere if you do some research. Know your product and you will be able to recognize a bargain when you encounter one.
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KL0S
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Posts: 132




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« Reply #7 on: January 29, 2006, 06:04:13 AM »

The service monitor route is a good way to go as long as you want to work below 1 GHZ.  Built signal and tracking generators make it a snap to tune receivers, filters and duplexers.  Same caveat emptor notes for service monitors....one of the big things that seem to go south are the signal generator attentuators, most especially the analog type.  The attenuator in my IFR 1500 went bad a couple of years after I got it -- they are EXPENSIVE to replace (ended up putting a digital attenuator in its place).
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