Re: Help reading Antenna plots
I decided to test the Balun itself maybe someone can help me read these plots.
I have one plot with the ant lead of balun open, shorted and with 2 100ohm resistors in parallel that read 49.9 ohms on my digital meter.
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Hi Ernest,
No problem abt the name and thanks for the info.
Regards,
Jos
Op 5-11-2020 om 17:40 schreef ERNEST AEC-RADIO:
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Jos:
I apologize for not looking at your name...
I fat fingered my keyboard....again!
On Thu, Nov 5, 2020 at 9:25 AM ERNEST AEC-RADIO via groups.io <aecradio1=
[email protected]> wrote:
Joe:
Because the LCD is adhered to the board, you will need to pry it loose from
its adhesive bond. There is normally a numbering system imprinted on the
display, which denotes manufacturer name, model and possibly more data to
decode display type as well.
Sorry I can not be of more help.
Ernest
KA9UCE
On Thu, Nov 5, 2020 at 9:18 AM Jos Stevens <jrs@...> wrote:
Hi all,
I have to replace the LCD screen of my NanoVNA-H4, please what is the type
number and/or where to buy ?
Thanks in advance,
Jos
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Re: Testing a helix antenna?
I sill have the copy of MININEC that I had to sign for from the Naval OceansResearch Lab 33 years ago.?? Don't do a lot of simulation.? I have an antenna rangethat goes up to 30 GHz.?? Currently have 6 antennas in orbit, and working on3 more at the moment.
The Nano's are very handy tools. ? I own three.? 250 lbs lighter than my 8510!
Have used NEC for 33 years but it cannot simulate the antennas I specialize in.
Printed Circuit Board Antennas| Commercial and Hobby Antennas
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Printed Circuit Board Antennas| Commercial and Hobby Antennas
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Kent
PS ELNEC and EZNEC?? Brings back memories.? Many years ago????? Roy and I both worked at Tek.
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On Thursday, November 5, 2020, 1:04:37 PM CST, David Eckhardt <davearea51a@...> wrote: Yes, quite a number of antennas modeled and built using 4NEC2 by myself!! And,..... I have the professional equipment to do proper testing including an HP 8753C VNA with associated S-Parameter test set and the full line of HP cal standards and several spectrum analyzers.? You are quite mistaken in your statements about 4NEC2.? Dipoles, J-poles, Yagis, Helices,.......? All designed with 4NEC2,? built, and properly tested using the above equipment.? Possibly you believe that 4NEC2 falls in what you state: ? ? ? " Oh, you get nice fancy diagrams and plots, but no where near the test results.? ? There are holes in those programs!!!? Kent ? ? ? ? WA5VJB" Possibly you have not spent the time learnimg how to properly utilize the application? I'll agree, 4NEC2 is not the easiest application to initially use.? I usually recommend potential users first 'cut their teeth' on EZNEC which has far fewer hooks, nooks, and crannies, but it teaches the basics of finally stepping up to 4NEC2.? It is a highly capable application for modeling and analyzing various antenna designs. Dave - W?LEV On Thu, Nov 5, 2020 at 6:46 PM KENT BRITAIN <WA5VJB@...> wrote: ? Pretty models, but have any been tested?
So far we have two families of antennas that HFSS cannot model.
Oh, you get nice fancy diagrams and plots, but no where near thetest
results.? ? There are holes in those programs!!!? Kent WA5VJB
? ? On Thursday, November 5, 2020, 12:42:36 PM CST, David Eckhardt <
davearea51a@...> wrote:
? 4NEC2 can model a helix quite well.? I've designed and constructed several
using that modeling application:
? ?
Dave - W?LEV
On Thu, Nov 5, 2020 at 4:51 PM Martin via groups.io <martin_ehrenfried=
[email protected]> wrote:
On Thu, Nov? 5, 2020 at 12:35 PM, Dr. David Kirkby, Kirkby Microwave Ltd
wrote:
In short, it looks quite a poor design to me.
That could well be the case, when Sandpiper were manufacturing those
antennas back in the day, their test equipment was fairly limited.
I believe they are better equipped now.
--
Regards,
Martin - G8JNJ
--
*Dave - W?LEV*
*Just Let Darwin Work*
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: Testing a helix antenna?
Yes, quite a number of antennas modeled and built using 4NEC2 by myself!!
And,..... I have the professional equipment to do proper testing including
an HP 8753C VNA with associated S-Parameter test set and the full line of
HP cal standards and several spectrum analyzers. You are quite mistaken in
your statements about 4NEC2. Dipoles, J-poles, Yagis, Helices,....... All
designed with 4NEC2, built, and properly tested using the above
equipment. Possibly you believe that 4NEC2 falls in what you state:
" Oh, you get nice fancy diagrams and plots, but no where near the
test results. There are holes in those programs!!! Kent
WA5VJB"
Possibly you have not spent the time learnimg how to properly utilize the
application?
I'll agree, 4NEC2 is not the easiest application to initially use. I
usually recommend potential users first 'cut their teeth' on EZNEC which
has far fewer hooks, nooks, and crannies, but it teaches the basics of
finally stepping up to 4NEC2. It is a highly capable application for
modeling and analyzing various antenna designs.
Dave - W?LEV
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On Thu, Nov 5, 2020 at 6:46 PM KENT BRITAIN <WA5VJB@...> wrote: Pretty models, but have any been tested?
So far we have two families of antennas that HFSS cannot model.
Oh, you get nice fancy diagrams and plots, but no where near thetest
results. There are holes in those programs!!! Kent WA5VJB
On Thursday, November 5, 2020, 12:42:36 PM CST, David Eckhardt <
davearea51a@...> wrote:
4NEC2 can model a helix quite well. I've designed and constructed several
using that modeling application:
Dave - W?LEV
On Thu, Nov 5, 2020 at 4:51 PM Martin via groups.io <martin_ehrenfried=
[email protected]> wrote:
On Thu, Nov 5, 2020 at 12:35 PM, Dr. David Kirkby, Kirkby Microwave Ltd
wrote:
In short, it looks quite a poor design to me.
That could well be the case, when Sandpiper were manufacturing those
antennas back in the day, their test equipment was fairly limited.
I believe they are better equipped now.
--
Regards,
Martin - G8JNJ
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: Testing a helix antenna?
Pretty models, but have any been tested?
So far we have two families of antennas that HFSS cannot model.
Oh, you get nice fancy diagrams and plots, but no where near thetest results.???? There are holes in those programs!!!?? Kent WA5VJB
toggle quoted message
Show quoted text
On Thursday, November 5, 2020, 12:42:36 PM CST, David Eckhardt <davearea51a@...> wrote: 4NEC2 can model a helix quite well.? I've designed and constructed several using that modeling application: ? ? Dave - W?LEV On Thu, Nov 5, 2020 at 4:51 PM Martin via groups.io <martin_ehrenfried= [email protected]> wrote: On Thu, Nov? 5, 2020 at 12:35 PM, Dr. David Kirkby, Kirkby Microwave Ltd
wrote:
In short, it looks quite a poor design to me.
That could well be the case, when Sandpiper were manufacturing those
antennas back in the day, their test equipment was fairly limited.
I believe they are better equipped now.
--
Regards,
Martin - G8JNJ
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: Testing a helix antenna?
4NEC2 can model a helix quite well. I've designed and constructed several using that modeling application: Dave - W?LEV On Thu, Nov 5, 2020 at 4:51 PM Martin via groups.io <martin_ehrenfried= [email protected]> wrote: On Thu, Nov 5, 2020 at 12:35 PM, Dr. David Kirkby, Kirkby Microwave Ltd
wrote:
In short, it looks quite a poor design to me.
That could well be the case, when Sandpiper were manufacturing those
antennas back in the day, their test equipment was fairly limited.
I believe they are better equipped now.
--
Regards,
Martin - G8JNJ
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: 50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
Thank you Dave,
Got Your point.
I removed the antenna from the roof and brought to the shack and measurements withouth the cable were really close to the real SWR as seen from TX.
Next step would be VNA calibration at the end of the coaxial cable - antenna site.
Not an easy task!
73 de I0MOM Marco
Inviato da iPad
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Hugen had previously posted the part number in the forum. I think if you search his posts and "LCD" from Nov 2019 through to around Feb 2020, you'll find the post.
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On Thursday, November 5, 2020, 11:18:36 a.m. EST, Jos Stevens <jrs@...> wrote:
Hi all,
I have to replace the LCD screen of my NanoVNA-H4, please what is the type number and/or where to buy ?
Thanks in advance,
Jos
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Re: Testing a helix antenna?
On Thu, Nov 5, 2020 at 12:35 PM, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
In short, it looks quite a poor design to me.
That could well be the case, when Sandpiper were manufacturing those antennas back in the day, their test equipment was fairly limited. I believe they are better equipped now. -- Regards, Martin - G8JNJ
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Jos: I apologize for not looking at your name... I fat fingered my keyboard....again! On Thu, Nov 5, 2020 at 9:25 AM ERNEST AEC-RADIO via groups.io <aecradio1= [email protected]> wrote: Joe:
Because the LCD is adhered to the board, you will need to pry it loose from
its adhesive bond. There is normally a numbering system imprinted on the
display, which denotes manufacturer name, model and possibly more data to
decode display type as well.
Sorry I can not be of more help.
Ernest
KA9UCE
On Thu, Nov 5, 2020 at 9:18 AM Jos Stevens <jrs@...> wrote:
Hi all,
I have to replace the LCD screen of my NanoVNA-H4, please what is the type
number and/or where to buy ?
Thanks in advance,
Jos
|
Joe:
Because the LCD is adhered to the board, you will need to pry it loose from
its adhesive bond. There is normally a numbering system imprinted on the
display, which denotes manufacturer name, model and possibly more data to
decode display type as well.
Sorry I can not be of more help.
Ernest
KA9UCE
toggle quoted message
Show quoted text
On Thu, Nov 5, 2020 at 9:18 AM Jos Stevens <jrs@...> wrote: Hi all,
I have to replace the LCD screen of my NanoVNA-H4, please what is the type
number and/or where to buy ?
Thanks in advance,
Jos
|
Hi all,
I have to replace the LCD screen of my NanoVNA-H4, please what is the type number and/or where to buy ?
Thanks in advance,
Jos
|
Re: Testing a helix antenna?
On Wed, 4 Nov 2020 at 18:03, <aleatorii.yg@...> wrote: Thanks for the reply, attached are some photos. Note this was sold in the
UK as a 13cm antenna (I think by Sandpiper, but I may be wrong), many years
ago.
I've never actually built a helix design myself, so am not that clued up
on any theory of them.
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. The bending of the conductor near the bottom is some attempt to achieve that, but it is probably not working well. Soldering a bit of copper on should help. That groundplane looks very small, with the helix not in the centre. You have a large support structure, which is sure to mess up the normal equations, making it impossible to predict the performance without some sort of EM simulation package. In short, it looks quite a poor design to me. Dave
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Re: 50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
On Thu, 5 Nov 2020 at 08:20, I0MOM via groups.io <morelli= [email protected]> wrote: Hi Gunter,
I made the measurements in the shack, the antenna was connected to the VNA
via 28 meters of RG-213 Coaxial cable.
As you suggested I¡¯ll try to make direct measurement directly at the
antenna without the coax and see what does change.
Thanks for You interest,
73 de I0MOM Marco
Inviato da iPad
The usual technique would be to calibrate to have the nanoVNA in the shack, but perform the calibration on the end of the coax. Then when you connect the antenna to the coax, you will make an accurate measurement. Of course, if the coax is faulty, all bets are off. Dave
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Re: Testing a helix antenna?
Dear Aleatrii,
Regarding the group, I was not making a whinge at you, just a general frustration that there are three different groups here covering nanovnas and I try to follow all three.
I certainly agree that most tasks the nano devices are put to could be undertaken on most of the various types and therefore it should not matter. The two groups of SAA2, which has a different architecture, were formed by a split because of disagreements between a few people regarding certain matters which you can find out about with a little research.
And I think you are right; the SAA2 groups are going on a lot about hardware, firmware etc, rather than practical use. I am guilty of this myself to a degree, but you can learn a lot about vnas etc from it because there are some very clued-up professionals and semi-professionals on those two groups.
And by the way, I am learning sonething about helical aerials.
Steve L. G7PSZ
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Re: Help reading Antenna plots
WONRP, The current charts are on a new factory ended 100ft length of RG8X now.
I also think they must be something wrong with the balun as well since there is not much
that could be wrong with the wires on it, although i wonder if it could also be the fact that
there is extra wire on the spools which according to windcamp does not effect it.
I just received 2 - T130-2 cores today just need to find a schematic to wire up an new balun
with them at 1:1 to test it again before i see if i can open the factory balun on it. I think i need
150 watts for the kenwood.
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Re: 50Mhz 3 element Yagi SWR results quite different from NanoVna predictions!
Hi Gunter,
I made the measurements in the shack, the antenna was connected to the VNA via 28 meters of RG-213 Coaxial cable.
As you suggested I¡¯ll try to make direct measurement directly at the antenna without the coax and see what does change.
Thanks for You interest,
73 de I0MOM Marco
Inviato da iPad
Inviato da Posta per Windows 10
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Re: Testing a helix antenna?
On Thu, Nov 5, 2020 at 12:26 AM, Roy Appleton wrote: Interesting that a book written in 1950 is the authority on the helical
antenna. From the stand point of theory or practical application? Nearly everything we know and use is based on science from the past few centuries. It's easy to think that everything we create and use today has been discovered//designed in the past 20 or so years, but that's just not the case. All we've really done recently is made things smaller and quieter and sometimes easier to use (or harder), but todays tech hasn't really changed much over the past 50 years if you think about it, some say we're stagnating as far as tech goes (which is not good at this point considering how much waste and damage we create). Your mobile phone uses tech from the 1950's and older (the transistor, plastic, glass etc), the internal combustion engine in just about every vehicle is still the same as it ever was in the 1860's (a little smaller and little more efficient but still the same dirty explosive tech). Your car runs on round things that were discovered who knows when! Battery tech stalled virtually a few decades after it was first discovered (the lithium battery is not as advanced from the original lead acid battery as you might think), it's hardly advanced at all as far as tech goes (much like the engine). A younger (20 odd years old) member of my distant family laughed at me recently about using a walkie talkie and pressing a button to talk, he told me it's a very old fashioned box (a modern yaesu it was), I said to him his mobile phone is just a radio that presses the PTT for him a few 10's of times a second whilst he's talking, he doesn't believe me and doesn't believe it's a radio at all (but can't explain how peoples voices are transferred with it) .. this is unfortunately the level of knowledge the average human being has these days, easy to think otherwise but that's how things are.
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Re: 75 ohm cable to match 50 ohm to 300 ohm folded dipole
I don't know who you are as you have not identified yourself.
But yes but the author did not explain himself.
1.??? Take ONE end of the _electrically half wave-length of 75 ohm coax_ (RG-79 type) and connect the center conductor to the center conductor on one side of the antenna.
2.??? Disconnect the soldered shield of the feeder coax from the other side of the antenna.
3.??? Solder the shield of the electrically half wave length of 75 ohm coax to the shield of the feeder coax.
4.??? Solder the shield from the OTHER side of the electrically half wave length of 75 ohm coax to the other two shields. Isolate the coax ends from the other connections.
5.??? Solder the enter conductor of the OTHER end of the electrically half wave length of 75 ohm coax to the other side of the antenna.
There you have a 4:1 coaxial balun matching the 75 ohm feeder coax to the 300 ohm impedance of the antenna (for that band only).
How it works...
If you look at the point where the two center conductors are connected together, that is where the feeder RF current is *split*.
If you look at the point where the OTHER side center conductor of the electrically half wave length of 75 ohm coax is connected to the other side of the antenna, it is where RF voltage is equal to the feeder voltage but OPPOSITE in phase. This contributes to TWICE voltage in respect to the other side of the antenna.
So, the NET feed point to the antenna is twice the voltage but half the current gives us a 4:1 (2 / 0.5) Impedance transfer.
Read below for more info...
Good luck, who ever you are...
Larry, K4MLA
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On 11/2/2020 8:32 AM, AllassoPraise wrote: I saw in this video the other day at 1:40:
The presenter talks about using a length of 75 ohm cable inline to
match a (theoretically) 300 ohm folded dipole to (presumably) 50
ohms. Has anyone else ever heard of doing that?
It sounds like it might be easier than using the 1/2 wave phasing coax
balun method, especially at 1 to 2 GHz frequencies, where tweaking the
antenna can require a lot of adjustments to the 3" to 6" coax loop.
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Re: Help reading Antenna plots
Don't overlook the simple stuff. Disconnect the coax from the antenna and use an ohmmeter to check for shorted coax, especially if you are not really confident in your quality of connector assembly. Verify infinite resistance between the shell and center pin. Verify very low resistance (~1 ohm) between the center pins at both ends, and between the shells at both ends.
More than likely the antenna itself is OK. The info I saw shows it has a 1:1 balun, so if you can identify the ends of the windings, verify continuity of each winding and make sure there is isolation (infinite resistance) between them. Check the endpoints of the elements at the connector for shorts or opens.
The NanoVNA is a fantastic piece of gear, but it's easy to get caught up in trying to interpret the readings and overlooking fundamental tests.
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I0MOM
Dr. David Kirkby, Kirkby Microwave Ltd
