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Hello,
I ordered NanoVNA and it should arrive this week. I'm building wire dipole for my CB and I would like to measure its SWR. The problem is that I will be using the PL-259 connector and the NanoVNA I ordered has only SMA. The PL connector is not attached to the coax (RG-58) yet. Is it possible to measure the SWR just by attaching SMA to the coax provisionally and replacing it with the PL when I'm done? Or do I have to buy SMA to PL adapter?

Thanks for any advice, as a newbie I really appreciate it.

Either of those solutions will work fine.? The only caveat is to be careful not to break loose the connector on the nano.? At 27 MHz you don't need to be very careful about lead length and such.
I got an SMA-to-BNC adapter and do all my connecting from there.? I have various adapters and test leads so I can measure most things.? I measure capacitors, inductors, resistors, coax, antennas, you name it.? Very informative as you watch the changes vs frequency and all.
Bob

On 10/5/20 8:12 AM, vitovsky.petr@... wrote:

Hello,
I ordered NanoVNA and it should arrive this week. I'm building wire dipole for my CB and I would like to measure its SWR. The problem is that I will be using the PL-259 connector and the NanoVNA I ordered has only SMA. The PL connector is not attached to the coax (RG-58) yet. Is it possible to measure the SWR just by attaching SMA to the coax

provisionally and replacing it with the PL when I'm done? Or do I have to buy SMA to PL adapter?

Get yourself some SMA to PL-259 adapters (actually, what you probably want is SMA to SO-239 jacks..

There's two ways to go about it.

a one piece adapter (I got a set of all 4 gender combinations for <$10 from amazon - )

A short cable with SMA on one end and PL-259 (I had one from my mobile rig installation a while ago, about 12" long).

if you go on amazon and search "SO-239 SMA pigtail" you'll get a bunch.. Looks like a pair of 6" ones is $10


I prefer the pigtail - cables with PL-259s tend to be fairly stiff, so having some inches of small diameter cable in between reduces the stress on the VNA.. you really, really do NOT want something like 0.405" coax directly connected to the VNA - you might snap the connector off the board.

Thanks for any advice, as a newbie I really appreciate it.

Adapters make it easy.

But at 27mhz, could use a couple 10cm long test leads
with alligator clips to somehow connect braid to braid
and center conductor to center conductor.
That would work just fine.

Jerry, KE7ER

Having a really hard time imagining how you would "provisionally" attach the nanoVNA to the coax. I highly recommend getting an adapter or pig tail. I have purchased adapters and jumper cables from Amazon and it has been about 50/50 hit or miss on quality and being able to do the job. BNC connectors are particularly bad where I have had them not really mate well because of machining burrs and most don't connect the outer shield properly because the inside bore of the female is too large and/or the fingers on the male have no springiness and fail to contact the inner bore on the female - the shield/ground reins top only connecting through the bayonet pins, maybe OK for video, but not so much for RF.

I have had good luck with R and L Electronics in Ohio, where a UHF female to SMA male adapter is $3.95.

Also, if you test with the PL259 installed, you confirm the integrity of your soldering work and you are equipped to re-check the antenna at any time you have doubts or concerns.

Finally - If you have fun on CB, be sure to look into getting a ham licence, Technician isn't too hard and your options are much wider.

On 10/5/20 10:32 AM, david.hostetler@... wrote:

Having a really hard time imagining how you would "provisionally" attach the nanoVNA to the coax.

clip leads from a SMA connector to the coax (either bare, or with PL-259 attached..


I highly recommend getting an adapter or pig tail. I have purchased adapters and jumper cables from Amazon and it has been about 50/50 hit or miss on quality and being able to do the job.

Or, you can spend $20 at HRO, and they've got several of SO-239 SMA jumpers.

COMET-NCG part # HS-05
ABR Industries, 23316-SM-SO-6 or -3


BNC connectors are particularly bad where I have had them not really mate well because of machining burrs and most don't connect the outer shield properly because the inside bore of the female is too large and/or the fingers on the male have no springiness and fail to contact the inner bore on the female - the shield/ground reins top only connecting through the bayonet pins, maybe OK for video, but not so much for RF.

I have had good luck with R and L Electronics in Ohio, where a UHF female to SMA male adapter is $3.95.
Also, if you test with the PL259 installed, you confirm the integrity of your soldering work and you are equipped to re-check the antenna at any time you have doubts or concerns.
Finally - If you have fun on CB, be sure to look into getting a ham licence, Technician isn't too hard and your options are much wider.
\

I made up a couple cables about 2 feet long with RG-316. One has an SMA on
one end and a BNC on the other end. Another has SMA's on both ends. Greatly
reduced chance of damaging the SMA on the NanoVNA with those cables.

73, Zack W9SZ

On Mon, Oct 5, 2020 at 12:33 PM <david.hostetler@...> wrote:

Having a really hard time imagining how you would "provisionally" attach
the nanoVNA to the coax. I highly recommend getting an adapter or pig tail.
I have purchased adapters and jumper cables from Amazon and it has been
about 50/50 hit or miss on quality and being able to do the job. BNC
connectors are particularly bad where I have had them not really mate well
because of machining burrs and most don't connect the outer shield properly
because the inside bore of the female is too large and/or the fingers on
the male have no springiness and fail to contact the inner bore on the
female - the shield/ground reins top only connecting through the bayonet
pins, maybe OK for video, but not so much for RF.

I have had good luck with R and L Electronics in Ohio, where a UHF female
to SMA male adapter is $3.95.

Also, if you test with the PL259 installed, you confirm the integrity of
your soldering work and you are equipped to re-check the antenna at any
time you have doubts or concerns.

Finally - If you have fun on CB, be sure to look into getting a ham
licence, Technician isn't too hard and your options are much wider.

<>
Virus-free.
www.avast.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

Thanks for advice, just like Jerry suggested, I could for instance use alligator clips. I should have been more precise and say that the NanoVNA came with a short cable with SMA on both ends and I wanted to attach the coax to that, so snapping the connector of the board won't be an issue.

BTW I got my license few days ago, OK9PVV here :) I just don't have HF TRX yet, so I just wanted to experiment with my CB a bit.

W5SWL is a good person to buy adapters from. Prices are reasonable and he has just about everything. eBay store or .

73

-Jim
NU0C

On Mon, 5 Oct 2020 09:59:02 -0700
"Jim Lux" <jimlux@...> wrote:

On 10/5/20 8:12 AM, vitovsky.petr@... wrote:

Hello,
I ordered NanoVNA and it should arrive this week. I'm building wire dipole for my CB and I would like to measure its SWR. The problem is that I will be using the PL-259 connector and the NanoVNA I ordered has only SMA. The PL connector is not attached to the coax (RG-58) yet. Is it possible to measure the SWR just by attaching SMA to the coax

provisionally and replacing it with the PL when I'm done? Or do I have
to buy SMA to PL adapter?

Get yourself some SMA to PL-259 adapters (actually, what you probably
want is SMA to SO-239 jacks..

There's two ways to go about it.

a one piece adapter (I got a set of all 4 gender combinations for <$10
from amazon - )

A short cable with SMA on one end and PL-259 (I had one from my mobile
rig installation a while ago, about 12" long).

if you go on amazon and search "SO-239 SMA pigtail" you'll get a bunch..
Looks like a pair of 6" ones is $10


I prefer the pigtail - cables with PL-259s tend to be fairly stiff, so
having some inches of small diameter cable in between reduces the stress
on the VNA.. you really, really do NOT want something like 0.405" coax
directly connected to the VNA - you might snap the connector off the board.

Thanks for any advice, as a newbie I really appreciate it.

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

BTW I got my license few days ago, OK9PVV here :) I just don't have HF TRX
yet, so I just wanted to experiment with my CB a bit.

In that case, you will eventually want to use the NanoVNA on other antennas as well. It will be REALLY worthwhile to get a few connector adapters. I have gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in pairs or sets of 4, with combinations of the 4 possible gender setups. Male to male, male to female, and so on. You may get one you don't need, but it's cheaper to get the sets. And later on, you will wish you had another one! Even if it is to help a friend with his project instead of your own. Amazon has many sellers of various sets and assortments, and of course there are usually reviews to help decide if their quality is good enough. And of course there are many more sources on ebay and aliexpress - which might be easier or better for some people outside of the USA or where Amazon might not ship to.

I was surprised to find that I needed (well, wanted) an adapter with female SMA to female UHF (SO-239) - it was for testing a mobile 5/8 wave 2-meter whip antenna. Of course, a "double SO-239" 'barrel' connector adapter would help instead, but add weight and bulk and a little inconvenience. After you become well accustomed to your VNA, you may find that you want to test other CB antennas, and they may have permanently attached PL-259's. You might be helping friends with their problems, as well as using it for your own station.
You might even want adapters for type F connectors for television antenna checking.
I have a clear plastic box with about a dozen compartments, for organizing and storing my many adapters. It is very useful, almost a necessity.

Congratulations on getting your license! There is so much you can do with amateur radio. And so much that you can enjoy learning!

Doug, K8RFT

On Tue, Oct 6, 2020 at 02:32 PM, DougVL wrote:

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

In that case, you will eventually want to use the NanoVNA on other antennas as
well. It will be REALLY worthwhile to get a few connector adapters. I have
gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in
pairs or sets of 4, with combinations of the 4 possible gender setups. Male
to male, male to female, and so on. You may get one you don't need, but it's
cheaper to get the sets. And later on, you will wish you had another one!
Even if it is to help a friend with his project instead of your own. Amazon
has many sellers of various sets and assortments, and of course there are
usually reviews to help decide if their quality is good enough. And of course
there are many more sources on ebay and aliexpress - which might be easier or
better for some people outside of the USA or where Amazon might not ship to.

I was surprised to find that I needed (well, wanted) an adapter with female
SMA to female UHF (SO-239) - it was for testing a mobile 5/8 wave 2-meter
whip antenna. Of course, a "double SO-239" 'barrel' connector adapter would
help instead, but add weight and bulk and a little inconvenience. After you
become well accustomed to your VNA, you may find that you want to test other
CB antennas, and they may have permanently attached PL-259's. You might be
helping friends with their problems, as well as using it for your own station.
You might even want adapters for type F connectors for television antenna
checking.
I have a clear plastic box with about a dozen compartments, for organizing and
storing my many adapters. It is very useful, almost a necessity.

Congratulations on getting your license! There is so much you can do with
amateur radio. And so much that you can enjoy learning!

Doug, K8RFT

Thank you! I will definitely get them sooner or later, the question was more about possibility to do it once or twice, because my local store does not sell them and there is a CB event this friday, so I wanted to have the dipole ready by then.

On Tuesday 06 October 2020 08:32:50 am DougVL wrote:

On Mon, Oct 5, 2020 at 01:42 PM, <vitovsky.petr@...> wrote:

BTW I got my license few days ago, OK9PVV here :) I just don't have HF TRX
yet, so I just wanted to experiment with my CB a bit.

In that case, you will eventually want to use the NanoVNA on other antennas as well. It will be REALLY worthwhile to get a few connector adapters. I have gotten sets of UHF/PL259 and of BNC adapters to SMA. They often are sold in pairs or sets of 4, with combinations of the 4 possible gender setups. Male to male, male to female, and so on. You may get one you don't need, but it's cheaper to get the sets. And later on, you will wish you had another one! Even if it is to help a friend with his project instead of your own. Amazon has many sellers of various sets and assortments, and of course there are usually reviews to help decide if their quality is good enough. And of course there are many more sources on ebay and aliexpress - which might be easier or better for some people outside of the USA or where Amazon might not ship to.

Amazon has enough money, they don't need any more.

I got a pair of SO239 and BNC adapters from R&L when I ordered my H4, and figure that should cover my needs nicely. I've seen others post links to these particular parts recently in here. $3.95 each.


--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

On 10/06/2020 11:06 AM, Roy J. Tellason, Sr. wrote:

Amazon has enough money, they don't need any more.

I got a pair of SO239 and BNC adapters from R&L when I ordered my H4, and figure that should cover my needs nicely. I've seen others post links to these particular parts recently in here. $3.95 each.

Also MPJA.com out of Florida has the adapters. No connection to the company other than being a satisfied customer.

Vince.
--
K8ZW

On Mon, Oct 5, 2020 at 07:05 PM, Jerry Gaffke wrote:

Adapters make it easy.

But at 27mhz, could use a couple 10cm long test leads
with alligator clips to somehow connect braid to braid
and center conductor to center conductor.
That would work just fine.

Jerry, KE7ER

Probably a stupid question, but does the length or type of the wire used to connect the SMA to the coax matter? Will it change the measured values?

It depends on the frequency.? For low frequencies, lead length is unimportant.? As long as the lead is much shorter than about one tenth of a wavelength, it won't matter much.
Therein lies one of the strengths of the nano or any other VNA.? Make a measurement and change the lead length to see how much difference it makes.? You will learn a lot about this stuff.
Bob

Be careful with large plugs. I already broke. I had to temporarily rewire from another port.

What about a balun. If I connect two wires directly to any measuring device without a balun, I don't get any results. Readings don't change no matter what I do.

Your question has insufficient information.? Explain what you are doing and what your observations are.? Not getting any results makes no sense.? What readings don't change?? What are the parameters and what is the device?

Below 30 MHz, so long as you keep it short and sweep, you can get away with
(short) clip leads. When lengths approach 1/20 of a wavelength in free
space, you should consider and use more rigorous connections.

BTW: 1-wavelength / 20 = [c / f] / 20
where: c = 2.997925 E+10 cm/s
f = frequency in Hz

Dave - W?LEV

--
*Dave - W?LEV*
*Just Let Darwin Work*

The main problem as said , is the mechanical weakness of SMA connectors.

First I've fastened vna with SMA-N adapter to an aluminium frame for mechanical stability (good for field operations).

Next, due to impractical tiny display, I've boxed it into a metal case , and used exclusively with PC software.

All kind of adapters are your friends.....

Federico
ik3umt