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Author Topic: RF coax testing & verify  (Read 694 times)

Craig Hauber

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RF coax testing & verify
« on: August 05, 2022, 12:38:33 PM »

What would be needed to test and verify antenna coax cables?  I'm using Belden 9913 and LMR-400 and would like to know that there are no issues once lines are installed and terminated. 
Also when I get rental packaged systems for tour I've had some fairly sketchy looking older cables and would love to verify them before trusting.
Most installed lines are either 50, 75 or 100ft and using crimped BNC ends with tools and connectors from the same vendor as the bulk cable.  But would love to be able to verify rack patch BNC's too as well (and if it's capable, use the gear for testing HD-SDI cables.) 
Even factory pre-made cables may have issues after shipping and the unintentional abuses of installation or tour use.

I'm having a suspicion that such dedicated equipment is very expensive, but if there's a way to do it with a multiple pieces of more affordable (or used) gear or equipment that HAMs mights have?  Can overall larger size, longer setup time and overall convenience can be used to compensate for the cost of a new nifty handheld unit that costs $12k?
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Craig Hauber
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Mac Kerr

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Re: RF coax testing & verify
« Reply #1 on: August 05, 2022, 01:48:13 PM »


I'm having a suspicion that such dedicated equipment is very expensive, but if there's a way to do it with a multiple pieces of more affordable (or used) gear or equipment that HAMs mights have?  Can overall larger size, longer setup time and overall convenience can be used to compensate for the cost of a new nifty handheld unit that costs $12k?

Yes. You can get a Chinese SA with a reflection bridge for around $2000. The Siglent SSA3021 is around $1400 and the bridge and additional software to do VSWR measurement is $670. It is a 2.1MHz SA with tracking generator. The downside is it is not battery operated, it requires a 120V supply.

Mac
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Rui Lisboa

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Re: RF coax testing & verify
« Reply #2 on: August 05, 2022, 05:39:33 PM »



Why go scalar when you can introduce time in the equation for further analysis if needed?
Go with a chinese VNA. Cheap and portable.
Also in the Siglent realm: SVA is just a tad more expensive than the SSA. You get 100 hours of several of the costly licenses, you can do TDR and actually measure length and distance to fault if you need it.
Either way go VNA. Little more of a steep learning curve but there is a lot of learning resources on the web.
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Craig Hauber

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Re: RF coax testing & verify
« Reply #3 on: August 09, 2022, 02:04:14 PM »

Yes. You can get a Chinese SA with a reflection bridge for around $2000. The Siglent SSA3021 is around $1400 and the bridge and additional software to do VSWR measurement is $670. It is a 2.1MHz SA with tracking generator. The downside is it is not battery operated, it requires a 120V supply.

Mac
There's a lot of acronyms here to deduce and learn about but thanks for the replies.
-Do I actually need a Spectrum Analyzer?  Could I just send a signal generator tone down the line and measure with some kind of receiver, re-tune and repeat until I cover all the applicable frequencies of the wireless we are installing?
Compare to a known-good line (i.e. one that's been in service for years with no issues)
My TinySA unit generates RF -never done it before and considered such a function fairly "dangerous"

Just trying to avoid $2100 at this moment as unexpected expenses are piling-up this season -budget for this was around $800, but that was totally an uneducated guess.  And uneducated I really seem after following the rabbit-hole of links your acronyms led to.  $2100 seems relatively cheap compared to some of the solutions I've since discovered.
Maybe ignorance is bliss and I should just buy pre-made verified lines and leave the excess coiled above ceiling instead of re-terminating?  Still worried about any "nicks or dings" that may happen during installation.
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Craig Hauber
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Russell Ault

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Re: RF coax testing & verify
« Reply #4 on: August 09, 2022, 03:51:01 PM »

{...} budget for this was around $800 {...}

Something like a PocketVNA would fit that budget, although it's worth reading up on its limitations (there's no such thing as a free lunch, particularly at an almost-two-orders-of-magnitude price reduction).

-Russ
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Rui Lisboa

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Re: RF coax testing & verify
« Reply #5 on: August 09, 2022, 06:19:43 PM »

There's a lot of acronyms here to deduce and learn about but thanks for the replies.
-Do I actually need a Spectrum Analyzer?  Could I just send a signal generator tone down the line and measure with some kind of receiver, re-tune and repeat until I cover all the applicable frequencies of the wireless we are installing?
Compare to a known-good line (i.e. one that's been in service for years with no issues)
My TinySA unit generates RF -never done it before and considered such a function fairly "dangerous"

Just trying to avoid $2100 at this moment as unexpected expenses are piling-up this season -budget for this was around $800, but that was totally an uneducated guess.  And uneducated I really seem after following the rabbit-hole of links your acronyms led to.  $2100 seems relatively cheap compared to some of the solutions I've since discovered.
Maybe ignorance is bliss and I should just buy pre-made verified lines and leave the excess coiled above ceiling instead of re-terminating?  Still worried about any "nicks or dings" that may happen during installation.

I donít know exactly how much your time costs but measuring frequency by frequency of interest it is both time consuming as it is perhaps frustrating hence costly.
I carry that pocket VNA Russel refers and I am quite pleased with the results for the tasks you are requiring. It surely doesnít hurt to buy one and it opens the door to quite a satisfying universe (of which you might get pleasantly hooked to).
I also have other units including the afford mentioned Siglent SVA which are certainly more precise. However I donít find that level of precision critical for most day to day tasks. These costly VNAs might be required for other measurements and tuning some apparatus but I would start with that pocket VNA (vector network analyzer) and dive further if required.
Again, search for pocket VNA amongst the ham radio community on the web. Youíll even find curious comparisons to much more expensive VNAs.
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Pete Erskine

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Re: RF coax testing & verify
« Reply #6 on: August 10, 2022, 02:13:51 PM »


I'm having a suspicion that such dedicated equipment is very expensive, but if there's a way to do it with a multiple pieces of more affordable (or used) gear or equipment that HAMs mights have?  Can overall larger size, longer setup time and overall convenience can be used to compensate for the cost of a new nifty handheld unit that costs $12k?

https://www.tinysa.org/wiki/

Unit has rf gen out and in... sufficient to measure rf cable loss.   Cost is around $100
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Scott Holtzman

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Re: RF coax testing & verify
« Reply #7 on: August 11, 2022, 01:05:50 AM »

https://www.tinysa.org/wiki/

Unit has rf gen out and in... sufficient to measure rf cable loss.   Cost is around $100
I picked up an Agilent Spectrum/Network analyzer on eBay for $600 that had a calibration cert.  It may be heavy, the TDR works great as does Z axis functions (that used to be a separate box that was bolted underneath the analyzer) it gives you return loss over a given frequency range. 

It also has the tracking
generator so you can tune filters duplexors, combiners and cavities.  I thought it was an 8920 but that's a service monitor and spectrum analyzer.  If anyone wants I can get model from shop.

They are heavy but the functionality is really worth it.  It rides in a pelican with wheels anyway.  Ready for fly dates!



Sent from my LM-V405 using Tapatalk

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Brad Harris

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Re: RF coax testing & verify
« Reply #8 on: September 28, 2022, 09:41:13 PM »

I've been using an inexpensive hand held VNA for this and other things over the past few months. So far, it has worked great and follows what I should be seeing based upon spec sheets regarding cable lengths, loss, SWR, etc.

Running S11 and more accurate S21 measurements when possible on cable runs to verify and better choices regarding gain staging and signal level at the distribution units and end receivers has been great (I end up running several hundreds of feet of coax on multiple antennas on most larger scale events)

Checking helical antennas that the free element is still in the proper tuning, let alone verifying which SMA antennas are still radiating in the correct pass band.

S11 length to fault measurements has been spot on with the correct VF% from cable spec sheets.


It may be the bottom of the barrel $$ wise, it might not preform as accurate as a more expensive unit, but shows the ballpark close enough for me. I'd love to check it out against something that costs much more (and is as portable) from an established measurement brand, but I don't have that access, or funds to do so..


A decent spectrum analyzer with a tracking generator can pull double duty and handle most cable and filter devices as well, and be more useful for frequency coordination overall. The VNA is a handy tool to supplement my Spectrum Analyzers, right next to a decent and inexpensive frequency counter.

Brad


What would be needed to test and verify antenna coax cables?  I'm using Belden 9913 and LMR-400 and would like to know that there are no issues once lines are installed and terminated. 
Also when I get rental packaged systems for tour I've had some fairly sketchy looking older cables and would love to verify them before trusting.
Most installed lines are either 50, 75 or 100ft and using crimped BNC ends with tools and connectors from the same vendor as the bulk cable.  But would love to be able to verify rack patch BNC's too as well (and if it's capable, use the gear for testing HD-SDI cables.) 
Even factory pre-made cables may have issues after shipping and the unintentional abuses of installation or tour use.

I'm having a suspicion that such dedicated equipment is very expensive, but if there's a way to do it with a multiple pieces of more affordable (or used) gear or equipment that HAMs mights have?  Can overall larger size, longer setup time and overall convenience can be used to compensate for the cost of a new nifty handheld unit that costs $12k?
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Paul Johnson

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Re: RF coax testing & verify
« Reply #9 on: September 29, 2022, 10:14:26 AM »

There is little point in buying verified and tested cables unless you stick them on the shelf and don't use them. As the higher frequencies suffer first, a power meter and dummy load on the far end with a short jumper at the transmit end will ket you squirt your highest frequency in, and get a reading. Then connect without the long feeder, using just the jumper and do the same test. The cable is the difference between the two. If you used one of the easily available multi band radios you could do the measurement starting at low VHF, then ending at 520MHz or so where the radios stop and excel spreadsheet the results. A signal generator shows you exactly what is happening, in a flash, but with a decent plan, Wattmeter, dummy load and transmitter can do the same thing, just less elegantly and in less gentle chunks.
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ProSoundWeb Community

Re: RF coax testing & verify
¬ę Reply #9 on: September 29, 2022, 10:14:26 AM ¬Ľ


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