The old spectrum analyzers in the AR SIG

Interest Groups Amateur Radio
#1

It has been close to a year and no one has chosen to work on these currently non-functional spectrum analyzers. I propose that we offer these things on craigslist or perhaps simply put them out for disposal (contain CRT’s so we can’t just throw them out).

I don’t think a spectrum analyzer is a good fit for the space given how incredibly easy the front end could be fried by an inexperienced user. I suggest that a network analyzer such as this http://miniradiosolutions.com/minivna-pro/ be something we work toward acquiring.

What do you’ll think?

@krgrantham
@zmetzing

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#2

I keep intending to drag my Tek 7104 and some modules up there to try and figure out if it is the chassis or the module that is having problems. But I’ve been too busy.

I’ll offer $50 for it, and deal with the disposal headache if I can’t make it work for me.

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#3

Why can’t we have nice equipment? If it is easy to break then it should require a lot of training and maybe a sign in sheet?

#4

I believe both of these were donated broken, in hopes they would be easy fixes.

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#5

Best I can recall we had the Tek when we moved here. The other unit was from an anonymous donor. Had video of donor when he brought it in. Nobody recognized him.

#6

A VNA would be very cool!

As a side note, we would (most of the time) keep a capacitor on all of the fancy high speed equipment front-ends like the VNAs, PNAs, and spectrum analyzers. For our work we never needed 0 Hz info and would joke that the manufactures didn’t include the caps in hopes that we would soon be calling them to repair the front-ends after some new engineer connected a DC-biased signal outside the input range of the equipment.

#8

@richmeyer
:blankspace:

#9

I didn’t realize they were non-functional. Any idea what’s wrong with them?

73,

Kevin Grantham
N5KRG
214-763-1279

#10

I take a shot at repairing the unit. I’ll be in tomorrow (Friday) and pick the portable Spectrum Analyzer and take a look at it.

If some one needs a real nice Spectrum Analyzer to use, I have one that I can bring in. It’s an HP 8594 that is good from 9kHz up to multi-GHz. Due to it’s very sensitive front end I’d prefer to be present and teach someone how to properly use it. I know from experience as I just got done replacing the front end do to an oops on my part.

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#12

I went by and messed with them today. The small one did not power up properly. I had to put in a 1A fuse and move the fuse holder cap from the DC fuse holder. Anyway, the standby Indicator lit but when I switched the power to Line nothing came on other than the reticle/grid. The LCD frequency indicator didn’t light.

I did not try running it on 12Vdc to determine whether or not the internal ac supply was good.

It needs a fuse cap anyway.

I then turned my attention to the Tek. It powered up just fine and went through the paces. It appears that many of the push button and rotary switches are very dirty. It may be that a thorough spraying with tuner cleaner might make it much happier. And I’m sure a basic cal would be indicated. But other than that it seemed to work.

Neither one - as well as I can determine - has a tracking generator. Which is not the end of life as we know it but makes it somewhat less useful from a duplexer and filter tuning/test perspective. Good enough to prove that your recent Baofeng purchase is/is not compliant with FCC part 90 :wink:

So, if we want to save our pennies for a new bit of kit, do we want a VNA or a service monitor or what?

Another thing - Andy and I installed a new 3U wall rack and remounted the access panel. However, the wall anchors on the left didn’t hold. Probably need to be replaced with a toggle bolt or something. So it droops on the left. But the Alinco power supply is on a shelf above the panel. I still need to dress the wires and so forth underneath but I think it looks better overall.

Anyone with some spare minutes and a wall anchor is welcome to fix the left mount and dress in the wires!

What became of the 900MHz repeater project? Did anyone file for a repeater frequency pair? And what is this 60’ tower of which you speak?

73,

Kevin Grantham
N5KRG
214-763-1279

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#13

My vote will be for a VNA, with the radio classes I will be teaching, the VNA will be extremely helpful in tuning the filters. The existing spectrum analyzer(tek) had serious issues when Zach and I looked at it, not to mention that it takes up an enormous amount of our very limited space.

I have not used a service monitor, so correct me if I am wrong, but are those used to align fm tranceivers?

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#14

ill be coming to all of those! what about FM and AM radio?

#15

A service monitor can be used for many purposes depending on features. It can generate signals - SSB, FM, AM, PSK, CDMA, and more, with modulation, single frequency or swept (tracking generator) and used to align receivers, test filters, test receivers, align duplexer, etc. it can test transmitters including demodulation, spectral purity and spurs, filtration, frequency stability, deviation, etc. Using an external RLB they can be used as antenna analyzer (most SWR analyzer are really measuring RL and just presenting it as imputed SWR.)

As far as I know VNA’s are for testing passive elements and are not used for transmitters or receivers for that matter. VNA’s are smaller, typically, although I’ve seen some four-wheel-drive HP VNA S-parameter units. And are often “laboratory” precision.

VNA’s - and many antenna analyzers - are easily swamped in a high RF environment and can be damaged if more than nominal input levels are applied. This is why antenna analyzers are challenging to use in a multiple transmitter environment like the top of the hospital where the MARS club has VHF FM, UHF FM, UHF DMR and 900MHz FM repeaters coexisting with three commercial UHF DMR machines, a VHF FM commercial machine, 900 MHz patient telemetry and a 220 MHz law enforcement system. Lots of transmitters that can swamp the front end of an analyzer or VNA.

Obviously, we need both (!) for different reasons and purposes.

73,

Kevin

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