For those who wish to dwell more in the return loss world instead of the
SWR world, or to gain a link between the two, here is a nice online chart
that converts between the two measurements.
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: Help reading Antenna plots
Re: your open wire fed doublet,
1. do you attach the Twin lead through a banana plug adapter into the VNA
port 0 and measure directly?
No. If you are referring to the data in the Word write-up, the banana
plugs are terminated with the noted loads - good non-inductive carbon comp
resistors. The VNA is connected to the SO-239. The cal is done at the end
of the cable connecting to that SO-239. The measurement plane is the
SO-239.
When measuring the antenna through the choke, yes, the banana plugs are
connected to the open wire feeder in the shack and the SO-239 is connected
to the VNA. Again, the measurement plane is the SO-239.
2. If so. Do you calibrate the input plane at the plug, (OSL).
The cal is done at the end of the cable that connects to the SO-239 so the
measurement plane is at the input of the choke, SO-239. The cal is done
with HP precision OSL cal standards.
What do use as load? 50 ohms? Or 450 ohms? (Assuring feed Zo = 450 ohms)
In the write-up carbon comp resistors are used at the noted resistances.
In that write-up I am evaluating only the performance of the choke over the
noted frequency range with the noted resistive loads. All cals are done
in a 50-ohm system using the HP precision cal standards. The measurements
are all made using the HP 8753C with the associated S-parameter test set
and the HP precision cal standards.
3. If you attached a 9:1 balun between the trim lead and the VNA, wouldn¡¯t
you calibrate OSL with 50 ohms at VNA input?\\
I do not use or believe in good balun performance with an impedance
transformation. I've measured too many. Many of these on the amateur
market are not baluns, but transformers. Transformers are miserable
performers as a balun, especially with reactive loads and resistive loads
much removed from their design impedance. I do not deal with 9:1
'transformers'. I take what the antenna gives me at the shack end of the
open wire feeders, then propagate that through the CM choke(s), through the
L-Network matching network, and into a final CM choke on the 50-ohm port of
the matching network. The network is designed to take whatever the
antenna/feedline/CM choke delivers to its input and transforms that to 50 ¡À
J0. I do not deal with transformers and/or 'baluns' that include an
impedance transformation. Any impedance modulations in the system are the
job of the L-Network.
Consider my notation of S11 as port 0 on the NANOVNA's and are single-port
reflection measurements. All the measurements from the past are made with
the HP gear only.
Dave - W?LEV
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On Fri, Nov 6, 2020 at 9:55 PM AG6CX <edwmccann@...> wrote: David:
Re: your open wire fed doublet,
1. do you attach the Twin lead through a banana plug adapter into the VNA
port 0 and measure directly?
2. If so. Do you calibrate the input plane at the plug, (OSL).
What do use as load? 50 ohms? Or 450 ohms? (Assuring feed Zo = 450 ohms)
3. If you attached a 9:1 balun between the trim lead and the VNA, wouldn¡¯t
you calibrate OSL with 50 ohms at VNA input?
Thanks for the clarification.
Ed McCann
AG6CX
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: Help reading Antenna plots
Baluns
What is a balun really? Something which converts a balanced load, antenna etc to an unbalanced source, a transmitter a VNA etc.
If your antenna is not balanced (a dipole) then you don't need a balun.
A 1:1 balun is really just a choke to reduce common mode currents and prevent RF from traveling on the outside of the coax feed-line which you won't need if you feed it from the 2nd floor straight into your ATU. Feeding the wire from the other end via coax would be better for radiating but then you would have to deal with coax losses and how to ground the braid of the coax at the feed point. Very messy.
These 9:1 "baluns" which are sold with end fed "long-wires" or off center fed dipole antennas are an attempt to bring a random relatively high impedance closer to 50 Ohms or at least within the range of your tuner and allow the antenna to radiate some power. So it's a RF transformer not a balun.
I use a 450Ohm to 50Ohm homebrew balun to feed my balanced & terminated wide-band folded dipole with 50Ohm coaxial cable. The terminating resistor is 450Ohms so I needed to convert from balanced to unbalanced and a RF transformer to go from 450Ohms to 50Ohms.
You don't need a balun, you may need a Impedance transformer IF your tuner can't tune the random wire against whatever ground you can find.
Good luck
73 Bob vk2byf
--
No good deed goes unpunished.
|
Re: Help reading Antenna plots
I can't comment on your VNA measurements as I have no experience with VNAs. Mine hasn't been delivered yet but I do know about antennas. Your predicament is not going to get solved with VNA graphs & smith charts.
Were I in your situation, I would certainly feed the antenna from the high (altitude) end and keep the other end of the wire as far away from any metal as possible. I would somehow find a ground from either a water pipe assuming it's not plastic, or at least use the earth wire from your AC mains connection. Feed this via an ATU. My old TS-440 has a tuner built in and drives a 40m full wave loop antenna at 20 feet or so above ground. It works on 80m, 40m, 17m & 15m. Let's say it loads up and radiates. My 10Watt WSPR beacon has been heard all over the world with this setup.
I have used some pretty weird antennas in the past when portable. Fences, disused telephone aerial telephone cables, Power pole strainer wires coming out of the ground. Metal rainwater drain pipes, a 40m dipole laying on the roof of heritage steam train carriage while under way. All good fun and educational.
As we say in VK land , suck it and see. Experiment.
73 Bob
--
No good deed ever goes unpunished.
|
Re: Help reading Antenna plots
David:
Re: your open wire fed doublet,
1. do you attach the Twin lead through a banana plug adapter into the VNA port 0 and measure directly?
2. If so. Do you calibrate the input plane at the plug, (OSL).
What do use as load? 50 ohms? Or 450 ohms? (Assuring feed Zo = 450 ohms)
3. If you attached a 9:1 balun between the trim lead and the VNA, wouldn¡¯t you calibrate OSL with 50 ohms at VNA input?
Thanks for the clarification.
Ed McCann
AG6CX
|
Re: Help reading Antenna plots
At the very end of your plot, you might squeeze in 50 MHz, 6-meters, as
well where you should not need a tuner.
Dave
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On Fri, Nov 6, 2020 at 9:25 PM David Eckhardt <davearea51a@...> wrote: You're certainly looking good at 40 and 15 meters. Also at 36 MHz where
we don't have an allocation. Looks very good!
Now, you might zero in on both 40 and 15 meters and do a measurement of
those bands to assure you are less than 3:1 over the whole band. Set up to
scan 7.000 to 7.300 MHz (40-meters) and 21.000 to 21.350 MHz (15-metes).
That will tell you whether the internal tuner in the Kenwood will correct
for SWR. I have the TS-2000X and its internal tuner will properly match up
to and including 3"1 SWR, but not much more. Most of the internal tuners
stop at 3:1.
On your return loss plot, only these two amateur bands show less than 6 dB
which is an SWR of 3:1. So, you are limited to those bands.
Dave - W?LEV
On Fri, Nov 6, 2020 at 8:48 PM <deadman1966@...> wrote:
I have the antenna spooled out to exactly the 7Mhz silver markers on the
wire here is the readings on the antenna with my homemade choke on it. Not
sure what other improvements i can make yet. Based on the readings are
there frequencies i should not transmit on I really don't know how the AT
unit works in the kenwood and how much range it has to correct SWR.
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: Help reading Antenna plots
You're certainly looking good at 40 and 15 meters. Also at 36 MHz where we
don't have an allocation. Looks very good!
Now, you might zero in on both 40 and 15 meters and do a measurement of
those bands to assure you are less than 3:1 over the whole band. Set up to
scan 7.000 to 7.300 MHz (40-meters) and 21.000 to 21.350 MHz (15-metes).
That will tell you whether the internal tuner in the Kenwood will correct
for SWR. I have the TS-2000X and its internal tuner will properly match up
to and including 3"1 SWR, but not much more. Most of the internal tuners
stop at 3:1.
On your return loss plot, only these two amateur bands show less than 6 dB
which is an SWR of 3:1. So, you are limited to those bands.
Dave - W?LEV
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On Fri, Nov 6, 2020 at 8:48 PM <deadman1966@...> wrote: I have the antenna spooled out to exactly the 7Mhz silver markers on the
wire here is the readings on the antenna with my homemade choke on it. Not
sure what other improvements i can make yet. Based on the readings are
there frequencies i should not transmit on I really don't know how the AT
unit works in the kenwood and how much range it has to correct SWR.
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: Help reading Antenna plots
I have the antenna spooled out to exactly the 7Mhz silver markers on the wire here is the readings on the antenna with my homemade choke on it. Not sure what other improvements i can make yet. Based on the readings are there frequencies i should not transmit on I really don't know how the AT unit works in the kenwood and how much range it has to correct SWR.
|
That sounds like an excellent idea!
Roy
WA0YMH
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On Fri, Nov 6, 2020, 1:36 PM n5kzw <n5kzw@...> wrote: Dental floss is a good way to cut through the adhesive, and it doesn't
stress the LCD.
Ed - n5kzw
|
Re: Help reading Antenna plots
To measure the total inductance, or more importantly, the +jX of the
windings: Short both conductors together at both ends so the choke forming
a single conductor consisting of two paralleled conductors on the core.
This is for test purposes, only. Then connect one end to the S11 center
pin and the other to the S11 backshell. Then, on the Smith Chart using the
cursors, you can measure the total inductance and +jX of the windings on
the core. To provide adequate choking, the total +jX should be at least 5
times the system impedance (some state 10X). For a 50-ohm system
impedance, this, of course would be +j250, ideally at the lowest frequency
of interest. If you don't want 160-meters, that requirement becomes much
easier to reach.
With my doublet fed with open wire transmission line, I measure (from 1.8
through 29.5 MHz) : real: 25 to 5 ohms ¡ÀjX: -200 to +80
So I have read data to address with my choke designs. You might make the
same measurements of your antenna to properly design your CM choke as I
have. No single solution fits all applications. Fortunately, with the
advent of the NANOVNA's, we now have the tools to measure and to design to
what we have installed as an antenna.
Dave - W?LEV
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On Fri, Nov 6, 2020 at 6:03 PM AG6CX <edwmccann@...> wrote: 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
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Dental floss is a good way to cut through the adhesive, and it doesn't stress the LCD.
Ed - n5kzw
|
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
|
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
|
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
|
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
|
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*
|
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
|
Bob
