ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2]  All   Go Down

Author Topic: RF coax testing & verify  (Read 1429 times)

Rui Lisboa

  • Newbie
  • *
  • Offline Offline
  • Posts: 23
Re: RF coax testing & verify
« Reply #10 on: September 29, 2022, 10:29:10 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.
... or buy a cheap VNA or cheap SA with a TG and get it done in seconds once a calibration of the device is accomplished.
https://www.youtube.com/watch?v=91ZRTFZ40rw
Here is a recent video which is probably one of the clearest on you tube about VNA.
« Last Edit: September 29, 2022, 10:32:22 AM by Rui Lisboa »
Logged

Paul Johnson

  • Full Member
  • ***
  • Offline Offline
  • Posts: 157
  • Currently - Lowestoft - UK
Re: RF coax testing & verify
« Reply #11 on: September 30, 2022, 04:21:56 PM »

Of course, but many people cannot make sense of the results VNAs produce. Even my analyser and the VSWR bridge need interpreting and knowing you are losing 3Watts at 430MHz but only 1.5W at 145MHz can make more sense than dB and the simplified displays.
Logged

Andrew Broughton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2059
    • Check Check One Two
Re: RF coax testing & verify
« Reply #12 on: September 30, 2022, 06:36:17 PM »

Looks like there's dozens of products calling themselves the "NanoVNA". Any idea which ones are "legit" or which is the best one (for the price)?
Logged
-Andy

"Well, my days of not taking you seriously are certainly coming to a middle..."

http://www.checkcheckonetwo.com
Saving lives through Digital Audio, Programming and Electronics.

Rui Lisboa

  • Newbie
  • *
  • Offline Offline
  • Posts: 23
Re: RF coax testing & verify
« Reply #13 on: October 01, 2022, 04:15:03 AM »

Of course, but many people cannot make sense of the results VNAs produce. Even my analyser and the VSWR bridge need interpreting and knowing you are losing 3Watts at 430MHz but only 1.5W at 145MHz can make more sense than dB and the simplified displays.

People link budget in dB. Brands are converging their receivers RSSI in dBm instead of dBuV. As long as one gets the loss of cable in dB per frequencies of interest I see no swifter, precise and less expensive method for what is requested on the post. Just scroll thru the freqs and see what the insertion loss is. Compare to what the manufacture's specs claim (but do take into account the connectors loss). Take notes (I usually stick them on the cables themselves). Compare notes with future measurements done in the same conditions.
Using S21 insertion loss measurement is straightforward and in a relatable scale to the entire system. If one desires to measure cable loss the entire process probably started from link budgeting.
Of course you do have to calibrate the device each time you change the stimulus (freqs of interest). But the calibration kit comes in the box and it is a relatively straightforward process.
I do use the Smith Chart to make sure SOL is good after calibration.
If you have a SMA unit I do use small jumpers or SMA to BNC/N adapters and this requires e-delay to compensate. Either way for measuring insertion loss from cables this is not crucial. Less precise but not crucial.
But for having a clear idea if the cables are compromised again: using these affordable bugs that fit inside your bag is a game changer.

@Paul: Your point is spot on when we dive into the VNA's capabilities. However insertion loss (S21) is pretty simple and the data is ready to use. One just aims at the frequencies of interest.

@Andrew: In Europe radio equipment shops provide trustworthy purchases for these Chinese units: WIMO (Germany); Passion Radio (France); Astro Radio (Spain).
« Last Edit: October 01, 2022, 04:31:32 AM by Rui Lisboa »
Logged

Diogo Nunes Pereira

  • Full Member
  • ***
  • Offline Offline
  • Posts: 194
  • Barcelona, sometimes...
Re: RF coax testing & verify
« Reply #14 on: October 21, 2022, 06:37:24 AM »

Looks like there's dozens of products calling themselves the "NanoVNA". Any idea which ones are "legit" or which is the best one (for the price)?

Hi Andy. There's definitely a NanoVNA rabbit hole and lots of resellers of bad clones.

The NanoVNA site is helpful in identifying the good from the bad: https://nanovna.com/?page_id=21 There are link to the US shop there.
The user group is very active: https://groups.io/g/nanovna-users/

I own a original (sandwich type) NanoVNA-H with DiSlord firmware and use it mostly to test/measure cables kinks and loss (TDR and insertion loss-S21) and antennas (return loss-S11).

I've tested a version 2 NanoVNA V2Plus4 last month and was really impressed by it. I was on a gig with (somewhat old) 1.6GHz radio links and decided to borrow one from Amazon. Again, lots of bad clones, the real stuff is here: https://nanorfe.com/nanovna-v2.html

Truly agree with Rui Lisboa (where are you from mate?) that they are very handy tools to have in your toolcase. All my coax is labeled with loss now, and slowly doing the same with my clients cable also. Confirmed my suspicions about a couple of broken/bad antennas already with it. Still have no understanding of the Smith Chart...
« Last Edit: October 21, 2022, 06:42:25 AM by Diogo Nunes Pereira »
Logged
Diogo Nunes Pereira
[email protected]
--------------------------
"I envy not those who own charriots, horses or land. I envy only those who drink water from every fountain." - Popular Song from Portugal

Rui Lisboa

  • Newbie
  • *
  • Offline Offline
  • Posts: 23
Re: RF coax testing & verify
« Reply #15 on: October 21, 2022, 02:36:47 PM »



Truly agree with Rui Lisboa (where are you from mate?)
[/quote]
Im from your home town Nuno. Cheers!
Logged

Diogo Nunes Pereira

  • Full Member
  • ***
  • Offline Offline
  • Posts: 194
  • Barcelona, sometimes...
Re: RF coax testing & verify
« Reply #16 on: October 26, 2022, 04:15:10 AM »

Im from your home town Nuno. Cheers!

Great. Is good to see another Portuguese here. Bom dia.
Logged
Diogo Nunes Pereira
[email protected]
--------------------------
"I envy not those who own charriots, horses or land. I envy only those who drink water from every fountain." - Popular Song from Portugal

Tim Hite

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1081
    • Bad Quail
Re: RF coax testing & verify
« Reply #17 on: October 26, 2022, 04:31:46 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'm inclined to think that renting the tool you need or hiring a subcontractor may be desirable.
Logged
Bad Quail
Sound + Light
Joshua Tree, California
Authorized Dealer for all this stuff

Craig Hauber

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 836
  • Mondak Sound Design - Plentywood MT/Grenora ND
Re: RF coax testing & verify
« Reply #18 on: October 28, 2022, 12:22:32 AM »

I'm inclined to think that renting the tool you need or hiring a subcontractor may be desirable.
I have back-burnered this project for the last few busy months and about to get back into it.

A subcontractor capable of this in my area is nonexistent and flying anyone in and the lodging costs would make just buying the gear much cheaper.

Yes on large jobs in cities we do exactly that, -subcontract, but I'm usually not onsite when this happens which is probably a good thing or I would be pestering them with a thousand questions!

Got my NanoVNA and TinySA sitting on the bench and just waiting for some adaptors for BNC and the time to sit down and watch endless videos.  Learn the concepts with these low cost devices and see if it's then worth the investment in more serious gear.
Logged
Craig Hauber
Mondak Sound Design
-Live PA
-Installs
-Theatre

Tim Hite

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1081
    • Bad Quail
Re: RF coax testing & verify
« Reply #19 on: October 28, 2022, 12:17:03 PM »

I have back-burnered this project for the last few busy months and about to get back into it.

A subcontractor capable of this in my area is nonexistent and flying anyone in and the lodging costs would make just buying the gear much cheaper.

Yes on large jobs in cities we do exactly that, -subcontract, but I'm usually not onsite when this happens which is probably a good thing or I would be pestering them with a thousand questions!

Got my NanoVNA and TinySA sitting on the bench and just waiting for some adaptors for BNC and the time to sit down and watch endless videos.  Learn the concepts with these low cost devices and see if it's then worth the investment in more serious gear.

I always try to stay engaged with my subs on any job I'm running. Working with specialists is a fantastic learning opportunity. I've picked up tons of knowledge that way. I'm getting to the point where I can estimate pricing within 10% with some of my vendors. Makes everyone's life easier.

Mini-caircuits adn Pasternack are both good for RF accessories. Both have excellent RF engineers on hand for tech support, as well.
Logged
Bad Quail
Sound + Light
Joshua Tree, California
Authorized Dealer for all this stuff

ProSoundWeb Community

Re: RF coax testing & verify
« Reply #19 on: October 28, 2022, 12:17:03 PM »


Pages: 1 [2]  All   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.086 seconds with 21 queries.