Re: Help reading Antenna plots
Martin:
Re:
If you wish to examine the common mode impedance of chokes like this, connect the VNA across the windings between both wires of the Balun connected together at the input and output of the choke.
Could be a bit more specific about the connections,? Can¡¯t quite figure out your suggested wiring.
Thanks.
Ed McCann
AG6CX
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Excellent work, Martin.
As a first work on this and in a second language to you, you did very well.
Helpful advice: You should expand the section on flashing firmware as this is an area that scares many new users. Feel free to copy sections of the document I edit for this. Also, you should add beside the "Figure 1" that it is an H or H4 with the enclosure since many users might have the open-frame type - or - you could post a small photo of each, so the users knows which model they have. Some forum members don't actually know what their model is supposed to look like according to some posts.
You also posted a photo of the SAA-2 as Figure 2 but didn't reference it anywhere. Again include the model beside the Figure caption along with a short mention that the SAA-2 has different controls AND different firmware.
As for the Firmware, the H and H4 also use different FW that is not compatible with each other even though you can flash either model with either FW version.
Also, please add CHO45's Android app to your PC/External client software list.
Finally, for any and all information you've gathered from other sources, please add a reference section at the end of the document. You could also add links to additional information such as user guides and websites that contain more helpful material for new users as well as links to the 3 or 4 main developer repositories on GitHub.
73 & Regards,
Larry??? VE3LRI
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On Friday, November 6, 2020, 11:41:30 a.m. EST, Martin J.K. <martin.svaco@...> wrote:
I have uploaded file in files section of this group:
Absolute Beginner's Guide to The NanoVNA.
Comments are welcomed here or to my email: 9a2jk _at_ hamradio.hr
As English is not my native language any advice regarding the language would be appreciated too.
Martin 9A2JK
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Martin, odli?an posao, hvala.
(Great job, thank you)
YU7NS
Milan
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On 6 Nov 2020, at 11:41, Martin J.K. <martin.svaco@...> wrote:
I have uploaded file in files section of this group:
Absolute Beginner's Guide to The NanoVNA.
Comments are welcomed here or to my email: 9a2jk _at_ hamradio.hr
As English is not my native language any advice regarding the language would be appreciated too.
Martin 9A2JK
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Hi Andrea,
I have an hp workstation that runs a filter design routine, but ELSIE, is an excellent source for the same tool. Try it.
Alan
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HI Martin, great work! for beginners but also for all the other users. Many thanks 73 de Gabriele. I4JXE Inviato dal mio telefono Huawei -------- Messaggio originale -------- Da: "Martin J.K." <martin.svaco@...> Data: ven 6 nov 2020, 17:41 A: [email protected]Oggetto: [nanovna-users] A guide for absolute beginners #docs #learning #nanovna-h #newbie #tutorials
I have uploaded file in files section of this group:
Absolute Beginner's Guide to The NanoVNA.
Comments are welcomed here or to my email: 9a2jk _at_ hamradio.hr
As English is not my native language any advice regarding the language
would be appreciated too.
Martin 9A2JK
|
Excellent English, Martin... well done for an extremely useful document.
I've only skimmed through it quickly, and the only thing that jumped out at me was misspelling Stimulus? on page 26.
Many thanks for all your work!
Mike - M0MLM
------------------------------------------------------------------------
*From:* Martin J.K. [mailto:martin.svaco@...]
*Sent:* Friday, 6 November 2020, 4:41 pm
*Subject:* [nanovna-users] A guide for absolute beginners #docs #learning #nanovna-h #newbie #tutorials
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I have uploaded file in files section of this group:
Absolute Beginner's Guide to The NanoVNA.
Comments are welcomed here or to my email: 9a2jk _at_ hamradio.hr
As English is not my native language any advice regarding the language would be appreciated too.
Martin 9A2JK
|
Re: Help reading Antenna plots
The #14 wire and the large cores which I use address the requirement of
operating at full power of 1.5 kW. Not that I use that much, but on
occasion on 75 and 160, it is required. There's no doubt your choke will
introduce a bit more loss than my large units, but you should be OK with
100-watts. Key down in CW at 100-watts for a few minutes with the output
of the choke connected to a dummy load and see how much heating occurs. If
minimal, you're fine. If too much heat, yes, larger core and wiremay be
required, but I would venture a guess that you're fine.
Your plots look just as I would expect. Now you have a 'real' balun / CM
choke. Give yourself a pat on the back, just for me......?? And, you've
learned a whole bunch on the way. Good work!
Dave - W?LEV
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On Fri, Nov 6, 2020 at 5:04 AM <deadman1966@...> wrote: Dave,
I had some 18awg coated solid copper wire i stripped form a piece of
thermostat wire and managed to get 16 loops onto the core. I am 3d printing
a centre insulator for the two wires form the windcamp since their balun
serves that purpose as soon as i get that done i will get this unit on it
and do some readings.
In the interim i have installed a 50ohm resistor to one end and connected
the other end to the nanovna and tooks some readings that are attached If i
read them right it looks like I did something right. It seems to me these
are the sort of readings i should have gotten form the 1:1 balun that came
with the antenna.
One thing I am not sure of is how much power i can transmit through the
unit with 18awg instead of 14. I did order some of the wire you mentioned
could you perhaps let me know what cores you use so i can order the larger
ones.
I want to thank all those the have responded to this thread i have a much
better understanding now on how measure and read results on the nanovna as
a result of all the help.
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Martin J.K. added folder /Absolute Beginner Guide to The NanoVNA
The following files have been uploaded to
the Files area of the [email protected] group.
By: Martin J.K.
Description:
A guide for absolute beginners
|
I have uploaded file in files section of this group:
Absolute Beginner's Guide to The NanoVNA.
Comments are welcomed here or to my email: 9a2jk _at_ hamradio.hr
As English is not my native language any advice regarding the language would be appreciated too.
Martin 9A2JK
|
Re: Help reading Antenna plots
Yes, many use 31 material for this purpose. I've wound many like CM chokes using red cores, 31, and 43 material. Problem is with the higher ?r materials, I end up with a virtual tesla coil at the transition of my open wire feeders and the output of the matching network. Too much inductance. The red cores I use once wound as the CM chokes measure in the vicinity of +j1000 or greater, even at 1.8 MHz. The red cores are the correct cores to use for this purpose. These are also the same core material Amidon offers in their kits. Dave - W?LEV On Fri, Nov 6, 2020 at 1:35 PM Martin via groups.io <martin_ehrenfried= [email protected]> wrote: Part of the problem could be that you seem to be using a Red type 2 low
permeability iron powder core.
This will not provide a high enough value of choking impedance for the
purpose you wish to use it for.
Some suggestions for starting points for choke baluns can be derived from
the chart in this article.
If you wish to examine the common mode impedance of chokes like this,
connect the VNA across the windings between both wires of the Balun
connected together at the input and output of the choke.
You can either measure the S11 impedance or S21 insertion loss in order to
obtain an estimate of the chokes likely effectiveness, but remember that
the common mode impedance that will be found on an antenna system will not
be 50 Ohms, it could be anything between a few Ohms and several thousand,
depending upon the standing wave current at the point the choke is
connected. So if you measure S21 of say 20dB (in a 50 Ohm system) that will
not equate to 20dB of choking impedance in 'real life'.
--
Regards,
Martin - G8JNJ
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: Testing a helix antenna?
"The impedance of a helical antenna is about 140 ohms. To match that to 50
ohms, you can use a quarter wave of transmission line of
sqrt(50 * 140) = 84 Ohms."
Dr. Kirby, I'm trying to get my head around the physicality of this.
Do you mean the 1/4 wave section is inline?
Ie, say I have a 50 ohm device, amplifier, transmitter whatever, with
50 feet of 50 ohm coax connected to it. Now at the end of the coax I
attach a length of 84 ohm coax (if there were such a thing) 1/4 wave
long (adjusted for prop. velocity), which is then attached directly to
an antenna that has 140 ohms impedance (helical or otherwise), I would
have a matched system?
And, if this were true, were I to take measurements with a vna to
determine the characteristics of the antenna, would I calibrate at the
end of the 50 ohm cable, thus considering the length of 84 ohm cable
as a balun (or would it be unum?) and part of the antenna/DUT?
And if this is true, do I have a balanced system, or unbalanced?
Thanks...
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ps.: select: ST7796 touch
--
*** If you are not part of the solution, then you are the problem. ( ) ***
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Re: 50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
I have excellent results operating NanoVNASaver remotely via VNC from my iPad (and iPhone for that matter). I have not tried it with my Android pad, but since I use VNC clients from the same developers on both, it should work fine.
This is very convenient for calibrating out the cable length at the point of antenna attachment. Saving that calibration also allows later damage testing from the shack.
I do the calibration first and then reconnect the cable and proceed. I get good agreement between readings taken this way and results immediately afterwards at the antenna connection point (Using the more normal calibration).
M
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Re: Help reading Antenna plots
Part of the problem could be that you seem to be using a Red type 2 low permeability iron powder core.
This will not provide a high enough value of choking impedance for the purpose you wish to use it for.
Some suggestions for starting points for choke baluns can be derived from the chart in this article.
If you wish to examine the common mode impedance of chokes like this, connect the VNA across the windings between both wires of the Balun connected together at the input and output of the choke.
You can either measure the S11 impedance or S21 insertion loss in order to obtain an estimate of the chokes likely effectiveness, but remember that the common mode impedance that will be found on an antenna system will not be 50 Ohms, it could be anything between a few Ohms and several thousand, depending upon the standing wave current at the point the choke is connected. So if you measure S21 of say 20dB (in a 50 Ohm system) that will not equate to 20dB of choking impedance in 'real life'.
--
Regards,
Martin - G8JNJ
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Re: Help reading Antenna plots
Dave,
Thank you for those clear photo's and measurements.
From the Smith charts I think we me conclude that the windings (forming a 2 wire transmissionline) have a Z0 of about 100 ohms. The enameled wires on the red core seem close to a 50 ohm transmission line.
New inspiration because of your contribution. Off to the shack this weekend to measure some of my own chokes. :-)
73 all,
Arie PA3A
Op 6-11-2020 om 00:49 schreef David Eckhardt:
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Attached are the measured data sets for the CM chokes I illustrated in the
previous email plus a couple of others
Dave - W?LEV
On Thu, Nov 5, 2020 at 11:40 PM David Eckhardt <davearea51a@...>
wrote:
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Re: Help reading Antenna plots
Dave,
I had some 18awg coated solid copper wire i stripped form a piece of thermostat wire and managed to get 16 loops onto the core. I am 3d printing a centre insulator for the two wires form the windcamp since their balun serves that purpose as soon as i get that done i will get this unit on it and do some readings.
In the interim i have installed a 50ohm resistor to one end and connected the other end to the nanovna and tooks some readings that are attached If i read them right it looks like I did something right. It seems to me these are the sort of readings i should have gotten form the 1:1 balun that came with the antenna.
One thing I am not sure of is how much power i can transmit through the unit with 18awg instead of 14. I did order some of the wire you mentioned could you perhaps let me know what cores you use so i can order the larger ones.
I want to thank all those the have responded to this thread i have a much better understanding now on how measure and read results on the nanovna as a result of all the help.
|
Re: Help reading Antenna plots
Bob, I do understand the antenna is low to the ground to go any higher i only have one option and that is to slope the wire from the 2nd floor of house so around 25 to 30 feet down to the back fence line which is 6.5 to 7 feet at the post but i would have to but i would have to feed it from the high end.
With that in mind are you saying the actual readings i posted for the balun itself connected to calibrated cables on the vna with a 50 ohm termination reflect no issues with the balun itself?
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Re: Help reading Antenna plots
Is this the antenna which is 6 feet (1.8m) above the ground we are complaining about?
What can one expect with such a large capacitor to ground. Let's get back to basics. Pre VNAs.
The most important component of an airial is the air. They need to be up there as high as possible which is a good start.
If it's not a balanced antenna then it also needs a good ground.
This idea has served me well since I built my first twin triode Regen Receiver in 1959.
73 Bob
--
No good deed goes unpunished.
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Re: Testing a helix antenna?
helix antennas
I have built a few for L band and they work. Decoding Inmarsat and AERO around 151East.
Can't wait to get my NanoVNA H4 so I can test it to see if building it agrees with the theory.
What are the names of the other VNA groups?
For working the satellites I built some QFH antenna's for RX & TX
Check them out on satNOGS.org if you like ground station 568 & 724
73 Bob vk2byf
--
No good deed ever goes unpunished.
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Gyula Molnar
Arie Kleingeld PA3A
Bob