开云体育

Welcome to the forum, Brent.
There are several guides in the files section, including the Absolute Beginners Guide.?
Go through the forum's Wiki for additional information. There are also many YouTube videos available, just search for nanovna.?


On Thu., 1 Jul. 2021 at 7:38 p.m., Brent Sachnoff<bsachnoff@...> wrote: Hello.? I just received my H4 and I'm finding it difficult to understand the main website and getting this device to function properly.? I'm try to just start with something basic like SWR over 30-40 meters.? Can anyone help me out with calibration and then actually getting readings?

Thanks!
Brent

On Fri, Jul 2, 2021 at 12:35 AM, WB2UAQ wrote:

Many of us have been using a resistance of 49*50 for a test load as we both
have as a starting point but the real antenna is not a simple R.
Pete

I think that is one of the reasons the transformer should ideally be measured as a full 2 port device using a full two port VNA. This can also be done with a TR VNA like the nanovna with a little patience. Once this is done the s2p model can be loaded into a simulator and the load presented to port 2 can be changed to a complex load at will. To make things more realistic, a powerful RF simulator can define port 2 as an s1p model taken from a real antenna for example.

Interesting article, thanks! I think the best way to measure/model the transformer is to take a proper full two port model using the nanovna. This is a bit fiddly to do with a TR VNA but worth the effort I think. I then allows a much more detailed analysis of the transformer on a linear simulator.

I may have missed something but the insertion loss of the dual FT240 transformer looks to be very low below 2MHz. Is this taken with a 50R source and 2450R load? Or is it matched for lowest loss at 2MHz?

I did look at one of these transformers a while back using 2 x FT240 cores but I didn't wind it as an autotransformer. I wound it as a regular 2:14 transformer. I got the best performance up at 28MHz with the turns well squished together into just part of the core. With a matching cap and a 2450R load I think I achieved about 0.5dB loss at 28MHz. This setup isn't ideal for power handling but the insertion loss was impressively low across 2-30MHz. I think it was less than 0.7dB everywhere but the loss at 28MHz was optimised at just 0.5dB.

I just noticed a getting started guide under the files section. Reading thru it now.

Hello. I just received my H4 and I'm finding it difficult to understand the main website and getting this device to function properly. I'm try to just start with something basic like SWR over 30-40 meters. Can anyone help me out with calibration and then actually getting readings?

Thanks!
Brent

Gary
Have you considered what the feed point impedance of an EFHW is against the equivalent source impedance the 1:49 transformer has created? Is there a reasonable conjugate match? I have measured the feed point Z of a 66 or 67 ft wire on 40 meters (all I can use with my small lot) and recently I have worked with 4NEC2 and there is a fair agreement to the measured impedance. I have raised these question to others and get absolutely no responses. Many of us have been using a resistance of 49*50 for a test load as we both have as a starting point but the real antenna is not a simple R.
Pete

Hello,
I regularly use the Zplots.xls Download:
,
I have used it a lot with my antenna analyser SARK100, it is very versatile
and useful, now I want to use it to analyze
the results of the NanoVNA-F .
I ask.. what kind of extension is best for analyzing measurements? sp1 or
sp2?
73
Enrique LU8EFF



--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.

Hi Dave,

Yes, the winding is tapped as an autotransformer and not a bifilar separate primary. I didn't think it would make much difference. But after seeing a couple of comments, I measured things both bifilar and as autotransformer, and indeed, the bifilar winding seems better.

Can you explain why that should be?

Cheers,
Gary

Got it.

??? Mikek

On 7/1/2021 3:22 PM, Jim Lux wrote:

On 7/1/21 12:18 PM, Mikek wrote:

On 7/1/2021 9:18 AM, Jim Lux wrote:

On 7/1/21 7:13 AM, Joe WB9SBD wrote:

I do not understand why a good 75 ohm calibration load would not make
the thing be a 75 ohm test.

Isn't that what the 50 ohm one is doing when you calibrate the dead
short and the 50 ohms load?

exactly.

I'd do the cal at the end of the coax, too.

Ok, but I can't do both, the cal is which ever one I do last. Yes, there
are memories, but then which cal means what?

Mikek

You don't need a cal without the cable.

Essentially, calibrating at the end of your test cable makes the cable
"part of the instrument"

--
This email has been checked for viruses by Avast antivirus software.

Would you please take multiple pictures out of the box so we
can see the winding technique and how things are connected!
It appears the secondary is center tapped. Please - out of the bos!

Dave - W ?LEV

On Thu, Jul 1, 2021 at 8:29 PM Fred, W9KEY <fred.schwierske@...>
wrote:

Gary - very interesting!
I would urge you to also post notice of your work on QRZ.com. There is
active discussion of EFHW 49:1 technology in the "Antennas, Feedlines,
Towers & Rotors" forum, with significant contributions by retired EE
professor Mike Mladejovsky, WA7ARK.
* This should provide a link to the Forum:

* This should provide a summary of posts from WA7ARK:


Have you yet had opportunity to evaluate FT-240-52 mix cores? It's my
understanding a triple stack of 52 cores offers better performance (versus
43 mix) for higher power HF applications - reference this 2019 YouTube
video from Steve Ellington:

It would be very interesting to specifically compare FT-240-43 versus 52
mix cores for HF use with EFHW transformers.

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

Gary - very interesting!
I would urge you to also post notice of your work on QRZ.com. There is active discussion of EFHW 49:1 technology in the "Antennas, Feedlines, Towers & Rotors" forum, with significant contributions by retired EE professor Mike Mladejovsky, WA7ARK.
* This should provide a link to the Forum:
* This should provide a summary of posts from WA7ARK:

Have you yet had opportunity to evaluate FT-240-52 mix cores? It's my understanding a triple stack of 52 cores offers better performance (versus 43 mix) for higher power HF applications - reference this 2019 YouTube video from Steve Ellington:

It would be very interesting to specifically compare FT-240-43 versus 52 mix cores for HF use with EFHW transformers.

On 7/1/21 12:18 PM, Mikek wrote:

On 7/1/2021 9:18 AM, Jim Lux wrote:

On 7/1/21 7:13 AM, Joe WB9SBD wrote:

I do not understand why a good 75 ohm calibration load would not make
the thing be a 75 ohm test.

Isn't that what the 50 ohm one is doing when you calibrate the dead
short and the 50 ohms load?

exactly.

I'd do the cal at the end of the coax, too.

Ok, but I can't do both, the cal is which ever one I do last. Yes, there
are memories, but then which cal means what?

Mikek

You don't need a cal without the cable.

Essentially, calibrating at the end of your test cable makes the cable "part of the instrument"

Ya, I have not looked it over real well, but it does give signal
strength, S/N and IF-AGC %.

?Also the station frequency, and physical channel.

The signal strength indicator is under, Product Support-- Signal
Diagnostics. (Sony)

??????????????????????????????????????? Mikek

On 7/1/2021 11:52 AM, Joe WB9SBD wrote:

Most TV's this "SIGNAL STRENGTH" is not a true signal strength but a
signal to noise measurement.

You could have a very weak signal but if it's channel is free and
clear of any noise, co-channel stations, cell phone, etc.
interference, it could show a better signal strength than a station
that is ten times stronger, but is plagued with all those interference
issues.

Joe WB9SBD

On 7/1/2021 11:41 AM, Fred, W9KEY wrote:

Well I suppose you are looking to have fun with your NanoVNA --- but
there is likely a much easier way to directly accomplish your goal.
Many modern TV's (with digital tuners) have a diagnostic mode that
will display received signal strength (along with other parameters).
So look up your model on the internet, or interrogate the internal
Help File, or even check the User Manual.
Using that mode will allow direct comparison of your various antennas.

For example, many Sony TV's use something like this:



And I recall the (now decades old) Digital TV Converter boxes
included the same feature.

--
This email has been checked for viruses by Avast antivirus software.

Yep, I have had my Sony TV for 10 years and never saw the signal meter,
I finally found it a week ago.

Yesterday, I went to pull it up and had do go through the whole search
again. it's not clearly labeled.

?It does display a lot of information!

???????????????????????????????????? Mikek

On 7/1/2021 11:41 AM, Fred, W9KEY wrote:

Well I suppose you are looking to have fun with your NanoVNA --- but there is likely a much easier way to directly accomplish your goal.
Many modern TV's (with digital tuners) have a diagnostic mode that will display received signal strength (along with other parameters).
So look up your model on the internet, or interrogate the internal Help File, or even check the User Manual.
Using that mode will allow direct comparison of your various antennas.

For example, many Sony TV's use something like this:


And I recall the (now decades old) Digital TV Converter boxes included the same feature.

--
This email has been checked for viruses by Avast antivirus software.

Hi Bryon,
If you look further down to the "core size" experiments you will see that I did indeed test 2 FT240-43 cores with 2:14 turns. It is a reasonable choice, and with the large volume and surface area of ferrite, you should be able to handle 100W without any trouble. As long as the transformer doesn't get too hot on 10m, the compensation cap is probably a good idea because otherwise you may not be able to get a good SWR and not be able to drive the band very well.

Good luck!
Gary AF7NX

I have made a 50 to 75 ohm adapter for the connectors I need. I used the
insulation and center conductor inside the F connector

and butted the SMA? panel mount connector center pin and RG6 center pin
together and soldered. It's the best I know to do now.

?????????????????????????? Mikek

On 7/1/2021 10:33 AM, n2msqrp wrote:

This is what I do to measure 75 ohm loads

- build or buy a 50 to 75 ohm minimum losspad. Install on S11 port. My 75 ohm end has a F connector.

- fabricate a 75 ohm O S L kit. Calibrate using this kit. Your measurement plane is at the F connector

- measure your 75 ohm load.

Mike N2MS

On 07/01/2021 8:38 AM Zack Widup < w9sz.zack@... > wrote:


The best way would be to use a quarter-wave section of 62 ohm cable.
Lacking that, you may have to build some sort of antenna tuner.

73, Zack W9SZ

On Thu, Jul 1, 2021 at 7:13 AM Mikek < amdx@... > wrote:

Testing a couple of TV antennas for Signal strength and just curious about

what they might look at on the NanoVna.
I'll be looking at them through about 70 ft of RG-6 and a SMA to F
adapter.
Measuring from 180MHz to 610MHz.
Pretty much a novice here.
Mikek

--
This email has been checked for viruses by Avast antivirus software.

I probably wasn't clear, my TV has a good signal strength meter in it, I
just wanted more fun trying to measure the impedance.

??????????????????????????????????????? Mikek

On 7/1/2021 9:54 AM, Donald S Brant Jr wrote:

Mikek: Unless I am misunderstanding your test intentions, a network analyzer will not give you any signal strength indication. You would need a measuring receiver or a spectrum analyzer to check out signal levels.
The antenna impedance and its gain/pattern/signal strength are not really related.
73, Don N2VGU.

--
This email has been checked for viruses by Avast antivirus software.

On 7/1/2021 9:18 AM, Jim Lux wrote:

On 7/1/21 7:13 AM, Joe WB9SBD wrote:

I do not understand why a good 75 ohm calibration load would not make
the thing be a 75 ohm test.

Isn't that what the 50 ohm one is doing when you calibrate the dead
short and the 50 ohms load?

exactly.

I'd do the cal at the end of the coax, too.

Ok, but I can't do both, the cal is which ever one I do last. Yes, there
are memories, but then which cal means what?

Mikek

--
This email has been checked for viruses by Avast antivirus software.

OK, this looks easy, I already put a 75 ohm termination on the coax, but
I''l go back and calibrate with the 75ohm at the NanoVna output.

????????????????????????????????????? Thanks, Mikek

On 7/1/2021 9:17 AM, Jim Lux wrote:

On 7/1/21 6:41 AM, Zack Widup wrote:


I wouldn't sweat all these matching transformers, etc.? 75 isn't far
from 50, so you're not going to have a "math and measurement"
precision issue.


What I would do is get your 75 ohm cable, Calibrate using 50 ohm load,
short, and open at the *end* of the cable and the fact that it's a 75
ohm cable is absorbed into the calibration.

Then, if you want to know VSWR or S11 for a 75 ohm system, convert
your 50 ohm data to a 75 ohm reference impedance using math.

OR - get a 75 ohm termination, do the cal using 75, short and open,
and your data will all be with reference to a 75 ohm system.? S11 and
VSWR will be correct. What might not be correct is the resistance in
the .s1p file and the reference impedance at the center of the Smith
chart.

--
This email has been checked for viruses by Avast antivirus software.

Precision not necessary, just trying to get my feet wet again. I'm
comparing a couple of DIY TV antennas and thought while

I was comparing signal strength, I'd look at impedance.

On 7/1/2021 9:14 AM, Larry Dodd via groups.io wrote:

Yes building or buying a 75 to 50 ohm matching transformer if that’s what you need (MiniCircuts sells them) is possible but it will cause a small insertion loss that needs to be accounted for if a precision measurement is needed. You didn’t say if precision is necessary or just a comparison is the goal.
Larry

--
This email has been checked for viruses by Avast antivirus software.