#TOTip

I've been chasing down some antenna issues... let's see if its the coax? I figured out that I had just enough above ground coax that I could pull the cable through the wall and connect both ends to the NanoVNA for an S21 LogMag Thru test. Let's get after it!
The only reliable source for NanoVNAs is R and L Electronics: randl.com
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[@BreakingPintMedia]

Great video!! Concise and straight to the point. I've only ever used my NanoVNA for measuring SWR but really want to start getting better use out of it and this information is exactly what I needed to put me in the path of getting my money's worth. Thank you!

[@temporarilyoffline]

Thanks BP!

[@AlvinMcManus]

great video just what I needed. You're the only guy I see to use the pick and not a stylus.

[@temporarilyoffline]

Thanks! I don't have a stylus, no need to buy one with the pick attached!😇😇

[@SheepdogPreparedness]

Excellent video! Thanks for showing how to do this!

[@temporarilyoffline]

No problem! You know I do this so I don't forget too, right? :-D

[@DougFredericks1]

That tethered pointer is a great idea.

[@temporarilyoffline]

It comes with the kit. I'm a fan!

[@deankq4adj125]

Great instructional video. Thanks for sharing.

[@temporarilyoffline]

Glad it was helpful!

[@jayceew2j202]

Finally a useful radio video :)

[@temporarilyoffline]

Thanks Jay! Glad you liked it!

[@DonzLockz]

those Nano VNA's are really Nano! Very useful in this hobby addiction. :)

[@temporarilyoffline]

It's almost EDC size. Goes in my toolbox for activations!

[@phildurall7466]

TO ... KIng of the calibration! Nice practical use of the VNA to discover coax problems.

[@temporarilyoffline]

Thanks Phil!

[@MyTube4Utoo]

@@temporarilyoffline You are too. Thanks for the great videos. 👍

[@temporarilyoffline]

@@MyTube4Utoo Aww Gee... Thanks!

[@UDX4570PalmSprings-yh1mv]

Great video buy hard to keep up !

[@temporarilyoffline]

Thanks!

[@DonDegidio]

Hi Steve, At least you discovered the problem with the coax to the DX Commander. Stay safe. 73 WJ3U

[@temporarilyoffline]

If you're a ham and you're bored, you're doing it wrong. ;-)

[@barrykery1175]

13 db down ! WOW, yes you do have a serious issue. You went from 100 watts out of the transmitter to QRP at the antenna. But, enjoyed your informative video. Nicely done. I have a table top spectrum analyzer with a tracking generator. But it's so much easier to use my NanoVNA H4 to look for losses on the fly. Barry, KU3X

[@temporarilyoffline]

Feedline is pretty important ;-) The Nano is very handy to have around. Highly recommended.

[@psychodad11]

Probably squirrel or some other rodent chewing on it. This was a constant issue when I worked for the cable company. The coax from the pole to the house, and even the hard line from pole to pole would be damaged from squirrel chew. Not sure why, but they loved coax. Great video btw, 73. N2SCD

[@temporarilyoffline]

squirrels are always a problem

[@paulhastings3109]

Show this again after you fix your coax. Still learning the device. So far I like it. 73 KQ4CD Paul ⚓️

[@temporarilyoffline]

Coming soon to your favorite youtube channel ;-)

[@MyTube4Utoo]

About time someone recognized that I"m awesome. Thank you. 😆

[@temporarilyoffline]

You are!

[@JeffCowan]

This is very cool. Question: is it possible to use the nanovna to do time-domain reflectometry to find the location of issues? If so, I'm wondering if it could have also found this issue.

[@temporarilyoffline]

It is definitely possible and we did this on the live stream... and totally didn't believe the answer that it was giving us... which was right.

[@JeffCowan]

@@temporarilyoffline That's amazing.

[@FEPLabsRadio]

Perfect. would you not want to zero out you adapters during cal also? asking for a friend

[@temporarilyoffline]

You would if you were going that far down the rabbit hole. I was looking for "a difference" vs. "a precise measurement" and I was happy with the results. - Yes, always zero out everything you can for maximum science.

[@markpayne3558]

I watched your video the other day and checked 2 coax cables and found one bad and the other good at 0.22 dB. Today when testing more cables, they looked way off so I tested the one that was great the other day, also tested bad. I must not be following the set up correctly but followed your video. Not sure if it’s when I change the traces. I did recalibrate also. Any thoughts??? I have the Nano H4

[@temporarilyoffline]

Sounds like you're on the right track. Set up the nano precisely and run the tests taking notes and you should get very similar results every time - assuming the test subject hasn't changed.

[@sherrycoady2491]

When I use to have a TDR I had a 50 ohm resistor that I terminated the far end. then I would shoot the coax with a termination then without. I could measure from both ends that way to the trouble spot. No TDR function support ?

[@temporarilyoffline]

Hi Sherry. The NanoVNA has a TDR function and when we tried it on the live stream, we didn't believe it. In hindsight, it was probably right!

[@AlvinMcManus]

There is a good chance your cable got scalped by either a lawn mower or a trimmer with a brush cutting blade. Don't ask me how I know. LOL😂😆😂

[@temporarilyoffline]

Oops!

[@poorman-trending]

You need to cancel out the adapters you used to connect the cal cables as well as the DUT

[@temporarilyoffline]

Yep, "do the best you can"

[@poorman-trending]

@@temporarilyoffline the connectors that come with the nano have known values, and you can use the menus to cancel those out. The other adapters… you can measure directly and then do the same, use the menus to enter in the reactance to cancel it out.

[@temporarilyoffline]

@@poorman-trending #ProTip, thanks!

[@Kevin_KC0SHO]

Looks like some squirrel with a weed eater got it twice.

[@temporarilyoffline]

Yeah. All fixed up and running good now.

[@aa3konthego]

Been there, had that. I had to bury mine in a plastic electrical conduit to protect the coax.

[@temporarilyoffline]

I think I might have fixed it, same solution here.

[@gilrand6224]

Just wondering if you set the limits before the thru cal, or if that was what happened by default. My nano vna does not go to 5G. More like 1.5 as I recall. I probably wouldn't need a 5G test as I won't be stuffing more than UHF down the coax. 73 de ve7bul

[@temporarilyoffline]

I set the limits based on what I use the COAX for, I rarely go above HF

[@neilgould9018]

Any way to test the coax if you don't have access to both ends to do a 'through'?

[@temporarilyoffline]

There is a TDR (Time Division Reflectometry?) test that you can do and if you know the specs of your coax from the manufacturer the NanoVNA will say "Your coax is no longer coax at NN feet" - and if your coax is 25 ft and it says 25 ft long, then its good coax... but if it says 8ft on a known 25ft run... then there is your break!

[@danielwallace8434]

Do the start and stop frequency range settings matter?

[@temporarilyoffline]

Not really, but should be within the spec of your coax in question

[@tonan5440]

did you use tdr to locate the discontinuity?

[@temporarilyoffline]

We did on a live stream, but thought it wasn't possible... turns out it was

[@mesapysch]

Hello. Have newbie question. If Uhf and Vhf transmit on FM w a repeater, does that mean a tech class can't use a repeater for Vhf and Uhf? Thanx!

[@temporarilyoffline]

Hey MP! A tech license allows you to transmit on 10,6,2,70cm. You'll want to search for "ARRL Band Plan" to get a graphic showing where a (T)ech class license can operate and on what modes. 10m and 6m would let you make contacts world wide while 2 and 70 will let you talk locally, through a repeater, or over the internet.

[@mesapysch]

@@temporarilyoffline I'm no where near there yet but I did program the repeaters into my Baofeng successfully and I wanted to familiarize myself with the freq I'll be eventually transmitting on. Thanx!

[@2EOGIY]

WOW! Do you realize what did you discover? That coax was consuming power. Much more than just for heating. I would try to connect a dummy load and check SWR. If it would be in safe range then just for a fun experiment I would call CQ.

[@temporarilyoffline]

I used the antenna on a snowy day while this was chewed up - and I used it for a long time before it got this bad. One day it wouldn't tune anymore and I had to fix it. Radio is fun... since its not my "job", I don't have to do the same level of routine maintenance, but there is still some. Thanks for watching!

[@TyeMorrisVlog]

I know you’re doing it on screen for the commentators, but in a real world scenario how often does the nanovna actually require calibration?

[@temporarilyoffline]

You can save your calibration and as long as you recall that calibration and use that same "test harness" you should be fine. The real key to calibration is that you can calibrate at the base of your antenna and test at your desk to eliminate feedline losses from the equation. There is a lot of "scientific method" stuff to wrap your head around when you're doing these tests. Even a cheap bathroom scale that you know is wrong can be used to track your weight loss/gain - use the tool for what it can provide and you'll be golden!

[@Snakebyte70]

Ive used my Nanovna H4 about 3 times since ive had it and i tried doing this 6 times and every time after i do the thru calibration and save it...the log isnt sitting on zero but bouncing around with all kinds of different numbers. I know im calibrating it right with the adapters and im hitting reset before i calibrate. The frequency at the bottom doesnt make a difference does it??

[@temporarilyoffline]

You have to calibrate the device for the frequency range you're interested in testing. So 7.000‐7.350 for 40m for example. Maybe pad a bit on each end.

[@Snakebyte70]

@@temporarilyoffline I tried the freqs u were using and it still acted funny, only thing that made it close to being 0.0 was doing the isolation calibration with the 50 ohm cap on the jumper on channel 1. That gave me a steady flat line but it wasnt 0.0. I tried different jumpers other than the ones that came with the vna and i tested 3 different coax's that I know were good and it was a lot more steady.

[@temporarilyoffline]

@@Snakebyte70 ok, join us over on TOADs discord (link in description) for a better discussion.

[@user-kw9ec1dr5q]

you didnt tell what the starting and stopping frequencies are, looks like star 50mhz but too blurry to read

[@temporarilyoffline]

This test was done at the defaults of 50KHz to 5Mhz, but "not zero to zero" is what you're looking for. If you did pick 0-0 or 5-5 you'd likely see a single dot on the screen. What you want is a straight line over your personal frequencies of interest.

[@johnwest7993]

Have you calibrated? :)

[@temporarilyoffline]

Not even once. 😇

[@kk2ak14]

I tough it was Mitch Conner

[@temporarilyoffline]

Very close!

[@rilosvideos877]

Seems you have mice or rats in your garden. Could also be a weasel or similar...

[@temporarilyoffline]

Yeah, that was my thought too

[@alanseidner3713]

You GO too FAST sorry no up for you!

[@temporarilyoffline]

Thanks for watching