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Hello,
Is it possible to measure PCB trace antenna Gain with the NanoVNA?
Thanks
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Yes, but you need a source antenna and an antenna for the same frequency with known gain.? ?Kent WA5VJB
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On Tuesday, August 23, 2022 at 08:56:38 AM CDT, Diane BONKOUNGOU <dianebonk2@...> wrote:
Hello,
Is it possible to measure PCB trace antenna Gain with the NanoVNA?
Thanks
|
A dipole works fine for the reference antenna. Nominally 2.2_ dB gain over
isotropic.
Dave - W?LEV
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On Tue, Aug 23, 2022 at 2:00 PM KENT BRITAIN <WA5VJB@...> wrote: Yes, but you need a source antenna and an antenna for the same frequency
with known gain. Kent WA5VJB
On Tuesday, August 23, 2022 at 08:56:38 AM CDT, Diane BONKOUNGOU <
dianebonk2@...> wrote:
Hello,
Is it possible to measure PCB trace antenna Gain with the NanoVNA?
Thanks
-- *Dave - W?LEV* *Just Let Darwin Work*
--
Dave - W?LEV
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On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB gain over
isotropic.
That is the gain of a dipole antenna in free space at resonance. Over ground the gain is higher. How much higher depends on height and ground characteristics. Roger
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A dipole, by definition, is resonant: +jX = -jX = 0. A doublet is a dipole, but not resonant where you require. My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly 950 kHz, but does not show resonance in any of the HF ham bands. Yes, measurements need to be made to reduce / minimize unwanted reflections. That's the devil in the details. Dave - W?LEV On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB gain
over
isotropic.
That is the gain of a dipole antenna in free space at resonance. Over
ground the gain is higher. How much higher depends on height and ground
characteristics.
Roger
-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV
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Good afternoon Dave.
Just out of curiosity, why would you want a 450 ft doublet resonant at 950
kHz?
Fred - N4CLA
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On Tue, Aug 23, 2022 at 2:01 PM W0LEV <davearea51a@...> wrote: A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
Dave - W?LEV
On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB gain
over
isotropic.
That is the gain of a dipole antenna in free space at resonance. Over
ground the gain is higher. How much higher depends on height and ground
characteristics.
Roger
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
|
he does not want it ... but it is ;-)
fed with a balanced tuner it should work any band from 160 to 10
maybe the ladderline length needs some tuning if you are at a very high or low impedance spot on a higher band but in principle a doublet (or biiiiig loop) is the best multibander you can have ... just needs a good tuner
dg9bfc sigi
ps i am using a 168m loop ... also fed via ladderline
Am 23.08.2022 um 20:15 schrieb Fred Moore:
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Good afternoon Dave.
Just out of curiosity, why would you want a 450 ft doublet resonant at 950
kHz?
Fred - N4CLA
On Tue, Aug 23, 2022 at 2:01 PM W0LEV <davearea51a@...> wrote:
A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
Dave - W?LEV
On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB gain over
isotropic.
That is the gain of a dipole antenna in free space at resonance. Over
ground the gain is higher. How much higher depends on height and ground
characteristics.
Roger
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
|
On 8/23/22 11:00 AM, W0LEV wrote: A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
You're not going to be measuring the gain of a 450 foot antenna with a NanoVNA. The OP was for a printed circuit antenna, presumably well above 100 MHz. The fundamental problem will be the free space loss. Let's assume isotropes for the moment. Let's further assume that the probe/reference antenna is 5 wavelengths away. At 300 MHz, that's 5 meters. Loss = 32 + 20*log10(0.005) + 20 *log10(300) = 32-46+50 dB = 36 dB loss. So that's plausibly ok - your S21 readings will still be big enough that the uncertainty due to SNR won't be too bad. And you can measure that in a backyard range. You need to move the probe up and down so that you can quantify the "ground bounce" contribution. By the way, the usual guideline for antenna test distance of 2*D^2/lambda isn't really valid for low gain antennas. But if you take D as 1/2lambda, you wind up with 2*0.5^2 * lambda^2/lambda which is 1.4 lambda.
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QUOTE: " Just out of curiosity, why would you want a 450 ft doublet
resonant at 950 kHz?"
Just to install as much wire in the air as is reasonable. I could string
well over a couple thousand feet, but ....... We live on 40-acres in
Northern Colorado in the foothills of the Rockies. So, why not? It is fed
with parallel conductor XMSN line, a robust (home brew and meticulously
characterized) common mode choke (actually several, depending on frequency)
and an over designed (again, pretty robust) L-Network matching network
(a.k.a., "antenna tuner").
An antenna or set of wires doesn't have to be resonant where one desires to
be a good radiator/receiver of RF energy. I use these wires from
630-Meters (with additional inductance) through 6-Meters. I also have an
NVIS 40-meter dipole and a 6-Meter inverted Vee on the hillside, but seldom
used. Most of the antennas are for radio astronomy and/or ionospheric
profiling (mainly E-Layer).
Dave - W?LEV
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On Tue, Aug 23, 2022 at 6:15 PM Fred Moore <n40cla@...> wrote: Good afternoon Dave.
Just out of curiosity, why would you want a 450 ft doublet resonant at 950
kHz?
Fred - N4CLA
On Tue, Aug 23, 2022 at 2:01 PM W0LEV <davearea51a@...> wrote:
A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
Dave - W?LEV
On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB
gain
over
isotropic.
That is the gain of a dipole antenna in free space at resonance. Over
ground the gain is higher. How much higher depends on height and
ground
characteristics.
Roger
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
-- *Dave - W?LEV* *Just Let Darwin Work*
--
Dave - W?LEV
|
No, Jim, absolutely no attempt to ever consider measuring the "gain" of my
450-foot doublet!!! At best, I model it using 4NEC2 and even that with a
large crystal of salt.
Measuring the gain (directivity?) of an antenna applies to VHF and above!
HF? Do the modeling. But, then, the NEC code does a miserable job of
handling "ground" (earth).
Dave - W?LEV
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On Tue, Aug 23, 2022 at 7:08 PM Jim Lux <jimlux@...> wrote: On 8/23/22 11:00 AM, W0LEV wrote:
A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
You're not going to be measuring the gain of a 450 foot antenna with a
NanoVNA.
The OP was for a printed circuit antenna, presumably well above 100 MHz.
The fundamental problem will be the free space loss. Let's assume
isotropes for the moment. Let's further assume that the probe/reference
antenna is 5 wavelengths away.
At 300 MHz, that's 5 meters.
Loss = 32 + 20*log10(0.005) + 20 *log10(300) = 32-46+50 dB = 36 dB loss.
So that's plausibly ok - your S21 readings will still be big enough that
the uncertainty due to SNR won't be too bad.
And you can measure that in a backyard range. You need to move the
probe up and down so that you can quantify the "ground bounce"
contribution.
By the way, the usual guideline for antenna test distance of
2*D^2/lambda isn't really valid for low gain antennas. But if you take D
as 1/2lambda, you wind up with 2*0.5^2 * lambda^2/lambda which is 1.4
lambda.
-- *Dave - W?LEV* *Just Let Darwin Work*
--
Dave - W?LEV
|
Thank you for your reply. Very interesting.
Fred - N4CLA
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On Tue, Aug 23, 2022 at 3:23 PM W0LEV <davearea51a@...> wrote: QUOTE: " Just out of curiosity, why would you want a 450 ft doublet
resonant at 950 kHz?"
Just to install as much wire in the air as is reasonable. I could string
well over a couple thousand feet, but ....... We live on 40-acres in
Northern Colorado in the foothills of the Rockies. So, why not? It is fed
with parallel conductor XMSN line, a robust (home brew and meticulously
characterized) common mode choke (actually several, depending on frequency)
and an over designed (again, pretty robust) L-Network matching network
(a.k.a., "antenna tuner").
An antenna or set of wires doesn't have to be resonant where one desires to
be a good radiator/receiver of RF energy. I use these wires from
630-Meters (with additional inductance) through 6-Meters. I also have an
NVIS 40-meter dipole and a 6-Meter inverted Vee on the hillside, but seldom
used. Most of the antennas are for radio astronomy and/or ionospheric
profiling (mainly E-Layer).
Dave - W?LEV
On Tue, Aug 23, 2022 at 6:15 PM Fred Moore <n40cla@...> wrote:
Good afternoon Dave.
Just out of curiosity, why would you want a 450 ft doublet resonant at 950
kHz?
Fred - N4CLA
On Tue, Aug 23, 2022 at 2:01 PM W0LEV <davearea51a@...> wrote:
A dipole, by definition, is resonant: +jX = -jX = 0.
A doublet is a dipole, but not resonant where you require.
My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly
950 kHz, but does not show resonance in any of the HF ham bands.
Yes, measurements need to be made to reduce / minimize unwanted
reflections. That's the devil in the details.
Dave - W?LEV
On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna. Nominally 2.2_ dB
gain
over
isotropic.
That is the gain of a dipole antenna in free space at resonance.
Over
ground the gain is higher. How much higher depends on height and
ground
characteristics.
Roger
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
|
NBS (now NIST) published the dimensions of a reference dipole for such uses: 2 1¦Ë dipoles above a 1.6¦Ë x 2¦Ë ground plane. Built properly it should have gain accurate to a few tenths dB or less at the design frequency.
The EIA published a similar standard gain antenna, shown in 5.2.5 of this document: The paper also has good information on antenna gain testing.
73, Don N2VGU
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Using the substitution method in measuring emissions from equipment for regulatory purposes, a dipole and a signal generator is used. There many reference dipoles out there to be had on the used market. I have several. They are also easy to make, but be sure to decouple the feedline with a number of ferrites of appropriate mix. Page 25 of the First Edition of J. D. Krauss *ANTENNAS* may also be useful. While it won't get you the closest 0.1 dB, it offers a simple method without using a reference antenna. [image: image.png] I'll also attach the page in case this group does not support in-text images. Dave - W ?LEV On Tue, Aug 23, 2022 at 8:59 PM Donald S Brant Jr <dsbrantjr@...> wrote: NBS (now NIST) published the dimensions of a reference dipole for such
uses: 2 1¦Ë dipoles above a 1.6¦Ë x 2¦Ë ground plane. Built properly it
should have gain accurate to a few tenths dB or less at the design
frequency.
The EIA published a similar standard gain antenna, shown in 5.2.5 of this
document: The paper also
has good information on antenna gain testing.
73, Don N2VGU
-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV
|
On 8/23/22 1:59 PM, Donald S Brant Jr wrote: NBS (now NIST) published the dimensions of a reference dipole for such uses: 2 1¦Ë dipoles above a 1.6¦Ë x 2¦Ë ground plane. Built properly it should have gain accurate to a few tenths dB or less at the design frequency.
The EIA published a similar standard gain antenna, shown in 5.2.5 of this document: The paper also has good information on antenna gain testing.
73, Don N2VGU
It's also in the ARRL Antenna book. But in reality, you can build two identical reference dipoles in almost any configuration (they don't even have to be resonant or matched to 50 0 ohms) and do a three cornered hat to remove the common term. Let Gunk be the gain of the unknown. Let Gref1 and Gref2 be the gain of the reference antenna Make three measurements at the same distance, with each possible pair. M1 = Gunk * Gref1 M2 = Gref1 * Gref2 M3 = Gunk * Gref2 M1*M3/M2 = (Gunk^2 * Gref1 * Gref2)/(Gref1 * Gref2) = Gunk^2 So Gunk = sqrt (Gunk^2) Doing it in dB is easier, of course. This doesn't account for ground bounce, reflections, etc. - That's another technique.
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So Gunk = sqrt (Gunk^2) So Gunk = M1 * M3 / M2
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M1 = Gunk * Gref1
M2 = Gref1 * Gref2
M3 = Gunk * Gref2
This assumes that Gunk Gref1 and Gref2 are constant during the three measurements. I do not see at all how one can fulfill this condition already because of the directionality of the antennas.
Or do you suppose that it is, for example, 3 yaggi that we reorient in the axis of each measure?
--
F1AMM (Fran?ois)
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-----Message d'origine----- De la part de Jim Lux 24 ao?t 2022 03:24
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On 8/24/22 1:36 AM, F1AMM wrote: So Gunk = sqrt (Gunk^2) So Gunk = M1 * M3 / M2
No, Gunk = sqrt(M1*M3/M2)
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On 8/24/22 1:46 AM, F1AMM wrote: M1 = Gunk * Gref1
M2 = Gref1 * Gref2
M3 = Gunk * Gref2
This assumes that Gunk Gref1 and Gref2 are constant during the three measurements. I do not see at all how one can fulfill this condition already because of the directionality of the antennas.
Or do you suppose that it is, for example, 3 yaggi that we reorient in the axis of each measure?
Yes, the antennas are mounted in the same positions, relative to each other, for all measurements. The reference antennas can be dipoles. There's no need for all 3 antennas to have the same (approximate) gain. This was for a "nose to nose" gain measurement. If you need to do a radiation pattern, it gets trickier. Essentially you calibrate the "probe" antenna with a duplicate at known range. if you want to measure radiation patterns, then reflections and such becomes a bigger issue.
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Are you measuring at the antenna?
You can't measure SWR accurately at the rig unless your antenna is zero reactance at 50Ohms.
Mike W9MDB
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On Tuesday, August 23, 2022 at 01:01:10 PM CDT, W0LEV <davearea51a@...> wrote: A dipole, by definition, is resonant:? +jX = -jX = 0. A doublet is a dipole, but not resonant where you require. My 450-foot doublet exhibits its first 1/2-wavelength resonance at roughly 950 kHz, but does not show resonance in any of the HF ham bands. Yes, measurements need to be made to reduce / minimize unwanted reflections.? That's the devil in the details. Dave - W?LEV On Tue, Aug 23, 2022 at 5:54 PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Tue, Aug 23, 2022 at 10:13 AM, W0LEV wrote:
A dipole works fine for the reference antenna.? Nominally 2.2_ dB gain
over
isotropic.
That is the gain of a dipole antenna in free space at resonance.? Over
ground the gain is higher.? How much higher depends on height and ground
characteristics.
Roger
-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV
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Roger Need
Donald S Brant Jr
