Re: where is the end fed natural resonance
Here¡¯s an idea.. coax (with an RF choke at 1/4 wavelength from end), then continue the center conductor another 1/4 wavelength. That gives you a center fed dipole (so Z is low) AND the feedline coming off the end. Basically a sleeve dipole turned sideways.
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On Feb 27, 2024, at 8:56?AM, Mike <mail@...> wrote:
?On Tue, Feb 27, 2024 at 04:14 PM, Lester Veenstra wrote:
Every ham should have a simple 1/2 wave resonate dipole for A/B testing to
keep a degree of sanity. And yes, I agree this is not lab grade ( direction
and angle of arrival dependent) but it does, after a number of paths and QSOs,
tell some truth. (Like your new is in fact the proverbial wet noodle)
I agree with this completely. Unfortunately my garden isn't long enough for a straight dipole and my wife (the gardener) would not tolerate the dangling feeder.
--
Mike
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Re: where is the end fed natural resonance
On Tue, Feb 27, 2024 at 04:14 PM, Lester Veenstra wrote:
Every ham should have a simple 1/2 wave resonate dipole for A/B testing to
keep a degree of sanity. And yes, I agree this is not lab grade ( direction
and angle of arrival dependent) but it does, after a number of paths and QSOs,
tell some truth. (Like your new is in fact the proverbial wet noodle)
I agree with this completely. Unfortunately my garden isn't long enough for a straight dipole and my wife (the gardener) would not tolerate the dangling feeder. -- Mike
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Re: where is the end fed natural resonance
Every ham should have a simple 1/2 wave resonate dipole for A/B testing to keep a degree of sanity. And yes, I agree this is not lab grade ( direction and angle of arrival dependent) but it does, after a number of paths and QSOs, tell some truth. (Like your new is in fact the proverbial wet noodle)
Lester B Veenstra K1YCM M?YCM W8YCM 6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)
lester@...
452 Stable Ln
Keyser WV 26726 USA
GPS: 39.336826 N 78.982287 W (Google)
GPS: 39.33682 N 78.9823741 W (GPSDO)
Telephones:
Home: +1-304-289-6057
US cell +1-304-790-9192
Jamaica cell: +1-876-456-8898
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Mike Sent: Tuesday, February 27, 2024 3:04 AM To: [email protected]Subject: Re: [nanovna-users] where is the end fed natural resonance On Mon, Feb 26, 2024 at 09:04 PM, Jim Shorney wrote:
That sounds like confirmation bias. When conditions are good you can work the
world on a wet noodle. When they are not good you need a kilowatt and an
aviation hazard stack in the back yard. That's like saying "works great!" Only
if you have not tried something that works greater. :)
73
-Jim
NU0C
Indeed. My main problem with talking to VK land is not the efficiency of my antenna but the pile-ups of European amateurs with kilowatt transmitters and steerable beams. The fun of the hobby is choosing your momment and getting through with the equipment you have. Last year I was working /P with a JPC-12 vertical and heard a VK at 5/9 with no-one calling him. Sadly with only 5 Watts at my disposal he got away. Mike G8GYW
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RF output from nanoVNA-H and H4
Just sharing some data with this group on the RF power employed when making measurements with a nanoVNA. Using a TinySA Ultra spectrum analyzer, recently I made some RF power measurements from my two nanoVNAs, with a CW output set to 14.0956 MHz, in the 20 meter band. These are the RF power output results expressed as dBm and microwatts¡
NanoVNA-H "classic": -12.8 dBm, (53 microwatts) - spectrum image attached
NanoVNA-H4: -8.9 dBm (128 microwatts) - spectrum image attached
The spectra are rich in harmonics of course, as one would expect for a (semi) square wave. As a further check on my measurements I broke out the 200 MHz Siglent oscilloscope, which also functions as a basic spectrum analyzer. (FFT mode) Both RF power measurements from the Siglent were within 0.2 dB of what the TinySA read - that astounded me, given all of the measurement uncertainties lurking between the two setups.
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Re: where is the end fed natural resonance
That implies a 49:1 Balun being used. However in instances of say 2800, the 49:1 leaves a 7:1 needing yet to be tuned.
Much of what was in the prior thread still applies here, and I like the clarification that the higher ratio baluns on EFHWs work well.
So yes measuring the true "as installed" feed point impedance accounts for all of those "X" factors and balun selection.
The larger problem is often measuring it there.
So many good comments here.
Andy
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On Mon, Feb 26, 2024 at 05:22 PM, Ray W8LYJ wrote:
If an antenna is fed at the end it¡¯s an end fed regardless of length. There
are 1/4 wave end fed AM broadcast and 1/2 wave end fed AM broadcast antennas.
The BALUN is not part of the antenna it¡¯s just a fixed antenna tuner with
maybe a common mode choke
If the wire is a half wave then the feed point impedance will be high, 2000
ohms or more. The BALUN turns ratio depends on the antenna feed point
impedance.
Ideally the feed point impedance would be measured and the appropriate BALUN
constructed.
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Re: where is the end fed natural resonance
Don?t compete with those, call cq yourself.
73
Peter, DJ7WW
-----Original-Nachricht-----
Betreff: Re: [nanovna-users] where is the end fed natural resonance
Datum: 2024-02-27T09:04:48+0100
Von: "Mike" <mail@...>
My main problem with talking to VK land is not the efficiency of my antenna but the pile-ups of European amateurs with kilowatt transmitters and steerable beams.
?
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Re: where is the end fed natural resonance
On Mon, Feb 26, 2024 at 10:22 PM, Ray W8LYJ wrote: Ideally the feed point impedance would be measured and the appropriate BALUN
constructed.
This is the EZNEC simulation of the feed point resistance of my EFHW varying with source position. -- Mike
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Re: where is the end fed natural resonance
On Mon, Feb 26, 2024 at 09:04 PM, Jim Shorney wrote:
That sounds like confirmation bias. When conditions are good you can work the
world on a wet noodle. When they are not good you need a kilowatt and an
aviation hazard stack in the back yard. That's like saying "works great!" Only
if you have not tried something that works greater. :)
73
-Jim
NU0C
Indeed. My main problem with talking to VK land is not the efficiency of my antenna but the pile-ups of European amateurs with kilowatt transmitters and steerable beams. The fun of the hobby is choosing your momment and getting through with the equipment you have. Last year I was working /P with a JPC-12 vertical and heard a VK at 5/9 with no-one calling him. Sadly with only 5 Watts at my disposal he got away. Mike G8GYW
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Re: where is the end fed natural resonance
?Ok so I meant to say UNUN or a transformer could be used.
I recommend reading ARRL antenna book 25 edition, 3.2.6.
Counterpoise systems.
If not available look at the definition of counterpoise in Laport. His book ¡°Radio Antenna Engineering¡± is available on the internet or Cebik¡¯s ¡° Counterpoise? The Use and Abuse of a Word.¡±
Ray
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Re: where is the end fed natural resonance
A Balun can be a transformer, but not all transformers are baluns.
A balun can also be a suitable "RF choke" that prevents RF from travelling down the outside of the coax, or unbalanced currents in a transmission line.
A well designed 2:1 turns ratio transformer could also be a choke for the unbalanced (coax) side.
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-----Original Message----- From: < [email protected]> Sent: Feb 26, 2024 5:13 PM To: [email protected] < [email protected]> Subject: Re: [nanovna-users] where is the end fed natural resonance A balun is a device used to connect to a symmetrical fed antenna, what you mean is a transformer. 73 Peter, DJ7WW -----Original-Nachricht----- Betreff: Re: [nanovna-users] where is the end fed natural resonance Datum: 2024-02-26T23:23:08+0100 Von: "Ray W8LYJ via groups.io" An: " [email protected]" If an antenna is fed at the end it’s an end fed regardless of length. There are 1/4 wave end fed AM broadcast and 1/2 wave end fed AM broadcast antennas. The BALUN is not part of the antenna it’s just a fixed antenna tuner with maybe a common mode choke If the wire is a half wave then the feed point impedance will be high, 2000 ohms or more. The BALUN turns ratio depends on the antenna feed point impedance. Ideally the feed point impedance would be measured and the appropriate BALUN constructed.
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Re: where is the end fed natural resonance
I recommend Cebik¡¯s,
¡°Verticals without Vertigo¡±
I find his comments about the counterpoise enlightening.
QRP Quarterly Cebik Publications ( )
on5au.be ( )
( )
( )
Ray
W8LYJ
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Re: where is the end fed natural resonance
A balun is a device used to connect to a symmetrical fed antenna, what you mean is a transformer. 73 Peter, DJ7WW -----Original-Nachricht----- Betreff: Re: [nanovna-users] where is the end fed natural resonance Datum: 2024-02-26T23:23:08+0100 Von: "Ray W8LYJ via groups.io" <rcbenedict1545@...> An: " [email protected]" < [email protected]> ?If an antenna is fed at the end it¡¯s an end fed regardless of length. There are 1/4 wave end fed AM broadcast and 1/2 wave end fed AM broadcast antennas. The BALUN is not part of the antenna it¡¯s just a fixed antenna tuner with maybe a common mode choke If the wire is a half wave then the feed point impedance will be high, 2000 ohms or more. The BALUN turns ratio depends on the antenna feed point impedance. Ideally the feed point impedance would be measured and the appropriate BALUN constructed. ?
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Re: where is the end fed natural resonance
Same. I've built a lot of antennas- My wife would say a garage full. Barring a beam, the endfed gives me great results from little work. One of the better ones I've built/used.
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Re: where is the end fed natural resonance
A BALUN is not a transformer. If impedance matching is required, from the feedpoint toward the coax feed: 1) Attached at the feedpoint of the wire: The transformer to match impedances, then 2) In series between the transformed impedance side of the transformer and the BALUN. The sole purpose of a BALUN is to bilaterally modify the circuit (not a part of the antenna) from differential mode to common mode (the coax cable). Note that even with a good counterpoise (other than the coax outer surface of the shield) the EFW is NOT a balanced source/load. It's unbalance varies as a function of frequency. Enough Dave - W?LEV On Mon, Feb 26, 2024 at 10:22?PM Ray W8LYJ via groups.io <rcbenedict1545= [email protected]> wrote: If an antenna is fed at the end it¡¯s an end fed regardless of length.
There are 1/4 wave end fed AM broadcast and 1/2 wave end fed AM broadcast
antennas.
The BALUN is not part of the antenna it¡¯s just a fixed antenna tuner with
maybe a common mode choke
If the wire is a half wave then the feed point impedance will be high,
2000 ohms or more. The BALUN turns ratio depends on the antenna feed
point impedance.
Ideally the feed point impedance would be measured and the appropriate
BALUN constructed.
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: where is the end fed natural resonance
?If an antenna is fed at the end it¡¯s an end fed regardless of length. There are 1/4 wave end fed AM broadcast and 1/2 wave end fed AM broadcast antennas.
The BALUN is not part of the antenna it¡¯s just a fixed antenna tuner with maybe a common mode choke
If the wire is a half wave then the feed point impedance will be high, 2000 ohms or more. The BALUN turns ratio depends on the antenna feed point impedance.
Ideally the feed point impedance would be measured and the appropriate BALUN constructed.
|
Re: where is the end fed natural resonance
That sounds like confirmation bias. When conditions are good you can work the world on a wet noodle. When they are not good you need a kilowatt and an aviation hazard stack in the back yard. That's like saying "works great!" Only if you have not tried something that works greater. :) 73 -Jim NU0C On Mon, 26 Feb 2024 18:45:34 +0100 (CET) "Peter Voelpel" <dj7ww@...> wrote: I always need to laugh when I hear such argument for an "antenna".
I several times worked a VK station on the long path who was using a whip on his bicycle and 20W in SSB.
Is that antenna better or worse considering the much greter distance ?
73
Peter
-----Original-Nachricht-----
Betreff: Re: [nanovna-users] where is the end fed natural resonance
Datum: 2024-02-26T18:18:45+0100
Von: "Mike" <mail@...>
An: "[email protected]" <[email protected]>
Sorry for straying off the OP's topic but ...
I've never known an antenna polarise amateurs like the EFHW (pun intended).
Those who've built one properly love it. Those who haven't say it doesn't work. I've had QSOs from Texas in the west to Jakarta in the east on 100W SSB with my antenna at my QTH west of London.
-- 73 -Jim NU0C
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Re: where is the end fed natural resonance
And remember an EFHW is a 1/2-wavelength at only one frequency. Other than
that it's just an EFW: End Fed Wire.
Dave - W?LEV
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On Mon, Feb 26, 2024 at 8:52?AM Jim <jim.kx0u@...> wrote: It should be noted that an antenna can be an "end fed" without being an
"end fed half wave." Antennas that are not half wave but are, in fact, end
fed, are often used with a 9:1 balun.
73,
Jim KX0U
On Mon, Feb 26, 2024 at 2:09?AM Mike <mail@...> wrote:
If you are using a 9:1 unun then it's not an end fed. My EFW4010 gets me
around the world on 100W SSB. My measured SWR is the same as simulated by
EZNEC. If you're interested I can send you details when I get home.
--
Mike G8GYW
-- *Dave - W?LEV*
--
Dave - W?LEV
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Re: PCB for hands-on to experiment with RF (tips welcome)
Yes, one can very well use SMD parts in 3D, dead-bug construction style.
I have attached a photo of a buffer amplifier for digimodes that I added to the underside of a board in my Kenwood TS-450SAT. It's a simple op amp buffer, small enough to fit in the space between the PCB and the chassis. The SMD IC lies with its pins pointing up, and the passives grow over it. The whole thing is self-supported.
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Re: where is the end fed natural resonance
I always need to laugh when I hear such argument for an "antenna". I several times worked a VK station on the long path who was using a whip on his bicycle and 20W in SSB. Is that antenna better or worse considering the much greter distance ? 73 Peter -----Original-Nachricht----- Betreff: Re: [nanovna-users] where is the end fed natural resonance Datum: 2024-02-26T18:18:45+0100 Von: "Mike" <mail@...> An: " [email protected]" < [email protected]> Sorry for straying off the OP's topic but ... I've never known an antenna polarise amateurs like the EFHW (pun intended). Those who've built one properly love it. Those who haven't say it doesn't work. I've had QSOs from Texas in the west to Jakarta in the east on 100W SSB with my antenna at my QTH west of London. -- Mike G8GYW ?
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Re: where is the end fed natural resonance
Sorry for straying off the OP's topic but ...
I've never known an antenna polarise amateurs like the EFHW (pun intended).
Those who've built one properly love it. Those who haven't say it doesn't work. I've had QSOs from Texas in the west to Jakarta in the east on 100W SSB with my antenna at my QTH west of London.
--
Mike G8GYW
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Jim Shorney
