Re: How do you measure a car antenna?
Can you take a photo of the car antenna connection that's in focus? Zack W9SZ On Sat, Aug 26, 2023 at 8:22?AM Lawrance A. Schneider < llaassllaaass@...> wrote: Enclosed is the photo of a car antenna's mounting. Note it is a single
pin. Also enclosed is a picture of my Baofeng's antenna post. Note that
the car antenna is a single post/pin. The Baofeng's antenna has a pin
inside a mounting. Thus, to measure the Baofeng's antenna you simply
connect it to the nanavna. How to do the car antenna???
The reason I ask is experience with my old Toyota 4Runner's radio and my
new Ford Lightning's radio. The 4Runner radio would work 50 to 80 miles
from a tower. The Lightning will start to fade 20 miles from the same
towers. Is the fault with the antenna or the radio???
Thank you for any cogent answer. larry
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Re: How do you measure a car antenna?
Larry- Perhaps someone here who knows the theory could briefly cover impact of antenna impedance when the antenna is used for receiving.
I am posting because to me it seems the essence of your question is vehicle broadcast radio reception differences between various vehicle models.
That is a big subject probably best suited to an article.
Consider that a vehicle antenna may have a directional pattern, and you need to be driving in the same direction and road when comparing. VHF FM broadcast propagation changes and the effect is more pronounced at distance. You need to make a comparison between vehicles under similar propagation conditions.
I think if you are OK making a physical and visual change to your vehicle, you do what you can to make a better antenna than what was provided "OEM" by the manufacturer. Consider that the OEM radio or entertainment center was built as an integrated system, and changing the antenna might not work well with the OEM radio.
Back in the old days with an analog FM radio in a passenger vehicle, the radio person would mount a 1/4 wave whip at 100 MHz right in the center of the car cabin roof and make a solid connection to the metal roof for the coax shield. These days, nearly all vehicles have a disguised antenna that has compromises this group knows well.
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Re: Not available at Ali Express / Zeenko
I've had good results with Banggood. But you are always taking a risk
ordering from any of these companies. They have zero customers service.
Banggood seems to be the least horrible!
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On Sat, Aug 26, 2023, 9:07 AM G4OJW <g4ojw@...> wrote: Please note: lists Ali Express / Zeenko.
This is no longer available, Zeenko is selling no products currently.
I tried ordering via Ali Express some months ago, a few days after
successfully buying an AT-100M on Ali Express, to be told that they could
no longer accept my Visa card, which has worked and still works for many
years without any problems. I thus cannot recommend Ali Express in general
thus with a 50% success rate only, as their systems are odd.
However, can the above page be updated, and are there any others that are
not listed and reputable? The prices vary substantially, the Ali Express
was the best price via Zeenko before.
Thank you
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How do you measure a car antenna?
Enclosed is the photo of a car antenna's mounting. Note it is a single pin. Also enclosed is a picture of my Baofeng's antenna post. Note that the car antenna is a single post/pin. The Baofeng's antenna has a pin inside a mounting. Thus, to measure the Baofeng's antenna you simply connect it to the nanavna. How to do the car antenna???
The reason I ask is experience with my old Toyota 4Runner's radio and my new Ford Lightning's radio. The 4Runner radio would work 50 to 80 miles from a tower. The Lightning will start to fade 20 miles from the same towers. Is the fault with the antenna or the radio???
Thank you for any cogent answer. larry
|
Re: VNA and antenna matching : calculating reactance needed to match
Thank you for all the replies.
The first six pages of seem to address my question. is very similar content.
"Notes on Antenna Tuners: The L-Network and Impedance Matching" by K6JCA is interesting
Kind regards,
Andrew
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Re: NanoVNA-App SWR graph does not match H4 graph
Thank you, Stan. That makes perfect sense. I was not aware that calibration sources could be different. I will check that option.
Thanks again,
Bob, KN4HH
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On Aug 25, 2023, at 3:50 PM, Stan Dye <standye@...> wrote:
?If the displays are different while doing a measurement, it is very likely
a calibration issue. Nanovna-app allows you to select the vna calibration
or the app calibration. Make sure that is set to vna to compare traces.
Note that the app receives the same exact s11 data that the nano uses for
display, so if the displays are different, there is a difference in the
calibration or display settings between the two.
On Fri, Aug 25, 2023, 10:42 AM W0LEV <davearea51a@...> wrote:
QUOTE: Consider this a benefit of the tiny battery powered Nano VNA. A
measurement can be made with minimal impact on the device under test.
Indeed. You hit the nail on squarely on the head. Consider the HP 8753C
with the S-Parameter test set. It weight in around 100+ lbs. I can not
use it with anything that requires a counterpoise or isolation from the
instrument as its too large, sits on a metal shelf, and is connected to the
power grid: a MAJOR increase in any counterpoise. The NANOVNAs allow me
to make measurments that the 8753C really can not make.
However, when one needs to measure at or above our 70-cm band, the size of
the NANOs become significant.
Dave - W?LEV
On Fri, Aug 25, 2023 at 3:50?PM Greg Strickland <greg@...>
wrote:
Last night I was measuring a high Q resonant circuit on the bench with
Nano VNA on battery. The battery was getting low and without physically
moving anything I connected a USB cable from Nano VNA to laptop a few feet
away. The measurement moved just a bit. Not a cause for concern because
it makes sense. Consider this a benefit of the tiny battery powered Nano
VNA. A measurement can be made with minimal impact on the device under
test.
--
*Dave - W?LEV*
--
Dave - W?LEV
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Re: NanoVNA-App SWR graph does not match H4 graph
If the displays are different while doing a measurement, it is very likely
a calibration issue. Nanovna-app allows you to select the vna calibration
or the app calibration. Make sure that is set to vna to compare traces.
Note that the app receives the same exact s11 data that the nano uses for
display, so if the displays are different, there is a difference in the
calibration or display settings between the two.
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Show quoted text
On Fri, Aug 25, 2023, 10:42 AM W0LEV <davearea51a@...> wrote: QUOTE: Consider this a benefit of the tiny battery powered Nano VNA. A
measurement can be made with minimal impact on the device under test.
Indeed. You hit the nail on squarely on the head. Consider the HP 8753C
with the S-Parameter test set. It weight in around 100+ lbs. I can not
use it with anything that requires a counterpoise or isolation from the
instrument as its too large, sits on a metal shelf, and is connected to the
power grid: a MAJOR increase in any counterpoise. The NANOVNAs allow me
to make measurments that the 8753C really can not make.
However, when one needs to measure at or above our 70-cm band, the size of
the NANOs become significant.
Dave - W?LEV
On Fri, Aug 25, 2023 at 3:50?PM Greg Strickland <greg@...>
wrote:
Last night I was measuring a high Q resonant circuit on the bench with
Nano VNA on battery. The battery was getting low and without physically
moving anything I connected a USB cable from Nano VNA to laptop a few feet
away. The measurement moved just a bit. Not a cause for concern because
it makes sense. Consider this a benefit of the tiny battery powered Nano
VNA. A measurement can be made with minimal impact on the device under
test.
--
*Dave - W?LEV*
--
Dave - W?LEV
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Re: Trouble calibrating NanoVna Classic after upgrade to 1.2.20
Flash old firmware and see if you get the same problem.
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On Fri, 25 Aug 2023 at 19:58, kumuzu1 <bulchandani@...> wrote:
I'm hoping someone can help me with my inability to calibrate my NanoVna
classic after upgrading
sucessfully to 1.2.20h.dfu.
While attempting to debug this problem, I did the following:
1) Ran a 'clearconfig 1234' via putty
2) Did a Touch Cal
3) Reduced the si535I frequency to 290 Mhz
4) Reset the calibration before starting the calibration process
But the nanoVna just wouldn't confirm a successful calibration when I
tested the Smith Chart with a 50 ohm or short load. I've attached an image
of what i see.
The odd part is that every so often the nanoVna does calibrate successfully
but when
I try and repeat the process it fails to calibrate.
Any clues? I love this little device and it is now a matter of personal
pride to get it to work!
Sanjay
AI6PM
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Trouble calibrating NanoVna Classic after upgrade to 1.2.20
I'm hoping someone can help me with my inability to calibrate my NanoVna
classic after upgrading
sucessfully to 1.2.20h.dfu.
While attempting to debug this problem, I did the following:
1) Ran a 'clearconfig 1234' via putty
2) Did a Touch Cal
3) Reduced the si535I frequency to 290 Mhz
4) Reset the calibration before starting the calibration process
But the nanoVna just wouldn't confirm a successful calibration when I
tested the Smith Chart with a 50 ohm or short load. I've attached an image
of what i see.
The odd part is that every so often the nanoVna does calibrate successfully
but when
I try and repeat the process it fails to calibrate.
Any clues? I love this little device and it is now a matter of personal
pride to get it to work!
Sanjay
AI6PM
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Re: NanoVNA-App SWR graph does not match H4 graph
QUOTE: Consider this a benefit of the tiny battery powered Nano VNA. A measurement can be made with minimal impact on the device under test. Indeed. You hit the nail on squarely on the head. Consider the HP 8753C with the S-Parameter test set. It weight in around 100+ lbs. I can not use it with anything that requires a counterpoise or isolation from the instrument as its too large, sits on a metal shelf, and is connected to the power grid: a MAJOR increase in any counterpoise. The NANOVNAs allow me to make measurments that the 8753C really can not make. However, when one needs to measure at or above our 70-cm band, the size of the NANOs become significant. Dave - W?LEV On Fri, Aug 25, 2023 at 3:50?PM Greg Strickland <greg@...> wrote: Last night I was measuring a high Q resonant circuit on the bench with
Nano VNA on battery. The battery was getting low and without physically
moving anything I connected a USB cable from Nano VNA to laptop a few feet
away. The measurement moved just a bit. Not a cause for concern because
it makes sense. Consider this a benefit of the tiny battery powered Nano
VNA. A measurement can be made with minimal impact on the device under
test.
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: NanoVNA-App SWR graph does not match H4 graph
Dave, I understand your point about the counterpoise extension. However, I would think that the SWR readings would shift the same for both displays. What am I missing.
Bob, KN4HH
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On Aug 25, 2023, at 11:18 AM, W0LEV <davearea51a@...> wrote:
?When connected to the PC or laptop, the effective counterpoise is much
longer than when not connected. The counterpoise consists of anything
connected to the measuring unit, including the laptop/PC through the USB
cable. There is nothing wrong with either measurement. You must
electrically remove the "extension" of the counterpoise when connected to
the PC/laptop.
Dave - W?LEV
On Fri, Aug 25, 2023 at 3:05?PM Bob Watson via groups.io <kn4hhptc=
[email protected]> wrote:
I am using a NanoVNA H4 and NanoVNA-App for SWR display. I connected my
end fed half wave antenna to the CNA and compared the two graphical
displays. Both the NanoVNA and H4 displays were set for identical SWR and
frequency ranges (1:1 to 3:1 and 1-30Mhz).
The difference in displays is dramatic (ie 3Mhz. 2.1:1 vs over 3:1 SWR).
Has anyone observed a difference between the H4 and external display
software.
I would appreciate any comments.
Bob, KN4HH
--
*Dave - W?LEV*
--
Dave - W?LEV
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Re: NanoVNA-App SWR graph does not match H4 graph
On Fri, Aug 25, 2023 at 08:50 AM, Greg Strickland wrote:
Last night I was measuring a high Q resonant circuit on the bench with Nano
VNA on battery. The battery was getting low and without physically moving
anything I connected a USB cable from Nano VNA to laptop a few feet away. The
measurement moved just a bit. Not a cause for concern because it makes sense.
Consider this a benefit of the tiny battery powered Nano VNA. A measurement
can be made with minimal impact on the device under test.
Performance/measurements of the NanoVNA might change slightly with battery level. Try making the same standalone measurement with a full battery. Roger
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Re: NanoVNA-App SWR graph does not match H4 graph
Last night I was measuring a high Q resonant circuit on the bench with Nano VNA on battery. The battery was getting low and without physically moving anything I connected a USB cable from Nano VNA to laptop a few feet away. The measurement moved just a bit. Not a cause for concern because it makes sense. Consider this a benefit of the tiny battery powered Nano VNA. A measurement can be made with minimal impact on the device under test.
|
Re: VNA and antenna matching : calculating reactance needed to match
If you calibrate with the measurement plane at the antenna end of the choke
balun, you can measure the antenna impedance correctly. You need to
calibrate out the choke balun.
Dave - W?LEV
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On Fri, Aug 25, 2023 at 3:32?PM Fran?ois <18471@...> wrote: I have traps doublets (3 or 4 bands) connected by about 10 m of coax to
the station. I have always measured the impedance of my antennas at the
level of the center by calibrating (open short load) at the end of the
caoxial removed from the antenna, from my PC and nanovna-saver. I then
calculated and made my 'L' adapters to place them in the center of the
doublet. It worked without a problem, without a chock balun. The ROS
becomes correct and it is correct at the station, at the calculation
frequency only, obviously
When I go to the nanoVNA of the chock balun, I doubt that we can measure
anything correct beyond the chock balun. But hey, hope gives life, as well
as those who sell chock-balun.
73
--
F1AMM
Fran?ois
-- *Dave - W?LEV*
--
Dave - W?LEV
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Re: VNA and antenna matching : calculating reactance needed to match
I have traps doublets (3 or 4 bands) connected by about 10 m of coax to the station. I have always measured the impedance of my antennas at the level of the center by calibrating (open short load) at the end of the caoxial removed from the antenna, from my PC and nanovna-saver. I then calculated and made my 'L' adapters to place them in the center of the doublet. It worked without a problem, without a chock balun. The ROS becomes correct and it is correct at the station, at the calculation frequency only, obviously
When I go to the nanoVNA of the chock balun, I doubt that we can measure anything correct beyond the chock balun. But hey, hope gives life, as well as those who sell chock-balun.
73
--
F1AMM
Fran?ois
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Re: NanoVNA-App SWR graph does not match H4 graph
When connected to the PC or laptop, the effective counterpoise is much longer than when not connected. The counterpoise consists of anything connected to the measuring unit, including the laptop/PC through the USB cable. There is nothing wrong with either measurement. You must electrically remove the "extension" of the counterpoise when connected to the PC/laptop. Dave - W?LEV On Fri, Aug 25, 2023 at 3:05?PM Bob Watson via groups.io <kn4hhptc= [email protected]> wrote: I am using a NanoVNA H4 and NanoVNA-App for SWR display. I connected my
end fed half wave antenna to the CNA and compared the two graphical
displays. Both the NanoVNA and H4 displays were set for identical SWR and
frequency ranges (1:1 to 3:1 and 1-30Mhz).
The difference in displays is dramatic (ie 3Mhz. 2.1:1 vs over 3:1 SWR).
Has anyone observed a difference between the H4 and external display
software.
I would appreciate any comments.
Bob, KN4HH
-- *Dave - W?LEV* -- Dave - W?LEV
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NanoVNA-App SWR graph does not match H4 graph
I am using a NanoVNA H4 and NanoVNA-App for SWR display. I connected my end fed half wave antenna to the CNA and compared the two graphical displays. Both the NanoVNA and H4 displays were set for identical SWR and frequency ranges (1:1 to 3:1 and 1-30Mhz).
The difference in displays is dramatic (ie 3Mhz. 2.1:1 vs over 3:1 SWR).
Has anyone observed a difference between the H4 and external display software.
I would appreciate any comments.
Bob, KN4HH
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Re: VNA and antenna matching : calculating reactance needed to match
Based on my limited knowledge I think with regard to L networks there are choices in topology, depending on antenna impedance and desired phase shift in the L network. Also practical concerns such as desire to isolate DC from the transmitter, or to put an otherwise floating antenna at DC ground potential without having to use (and analyze) a separate "static choke".
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Re: VNA and antenna matching : calculating reactance needed to match
B. Whitfield Griffith, Jr., "Radio-Electronic Transmission Fundamentals," McGraw-Hill, 1962 discusses the design of L-networks and provides graphical methods for such designs. ARRL used to sell this book, but I don't see it at the ARRL website now. Some used book dealers on the Web have it for under $10, although some of them want fantastic prices for it.
And there are many other text and reference books that provide design information for various networks.
"Octave for L-Networks," QEX, Mar/Apr, 2011 provides GNU Octave code for implementing Griffith's methods and points out that networks can often be oriented either way if the impedances to be matched are complex.
"More Octave for L-Networks," which I referenced earlier, provides Octave code that determines whether a network is reversible and, if so, provides element values for both orientations.
73,
Maynard
W6PAP
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On 8/25/23 00:14, Andrew (G1RVD G0Z) wrote: Thank you for all the superb replies.
I'm looking for a source that either has the relevant formulas or, where I can figure out the formulas. Ultimately to implement them in some form of auto tuner. (An intelligent version of an autotuner matching algorithm - if that makes any sense).
I'm investigating: GNU Octave code and TLW (i have a version of the ARRL Antenna Book).
I've used SimSmith, it's a great programme. (Effectively, I'm looking for the underlying math to automate the match.)
Kind regards,
Andrew
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Thank you everyone for responding.
Last time I measured an AM broadcast antenna I used a Delta Electronics OIB-3 operating impedance bridge. Using the Delta OIB the measurement would have been completed in less than an hour with no complications. This time I am trying a VNA because I thought it would be more interesting. I will continue the parallel LC "trap" in-series approach. It is possible the trap could be designed into the ATU matching network and remain in the circuit.
If all goes well, eventually I will be using Nano VNA to measure the load "seen" by the transmitter output devices.
Goal is conveying the RF spectrum of the transmitter into radiated EM wave without significantly changing the RF spectrum in the intervening networks.
I am enjoying the VNA, but would eventually like to get accurate results in the field. Obviously, there is a difference between the lab or backyard antenna in a low ambient RF environment, and a broadcast antenna that has voltage from strong nearby RF sources.
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Bob Watson
Roger Need