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Thankyou Kent, from someone who can still use a Leacher Line :-) 73 de GK8NXD

OK, for the youngsters in the group a bit of history.
It's over 100 years ago.Coax has not been invented yet.There are no SWR metersThere are no VNA's.? ?(Well, an RF Bridge and a lot of math will get much the same answer)
So you would walk along the parallel transmission lines between the transmitter and the antenna with a voltmeter.
At one point along the line you measured 50 volts, at another point you measured 25 volts.
Voltage Standing Wave Ratio is 50/25? or 2
These peak and nulls were waves of voltage that pretty much stayed in the same place, thus were called? "Standing Waves"
If at some point you got a ZERO voltage, this usually happened when there was an open or a short in the system, then.
VSWR was 50/0 and was just called "Infinite"
Now if you walked along the line and got 50 - 50 - 50 - 50 - 50
Then VSWR was 50/50 or 1And they liked to say the SWR was "FLAT"
Hope this helps, Kent
For the other old farts in the group, yep, still have a slotted line in the back garage.? Think I still know how to use it, but the HP-8510C does such a better job. hihi? ? Oh yea, the Nano's do a pretty good job and weight 200 lbs less!

On Wed, Aug 3, 2022 at 09:10 AM, Kenneth Hendrickson wrote:

If the load is not perfectly matched to the source, there will be a voltage
standing wave ratio (VSWR) because of the mismatch.

On Wednesday, August 10, 2022, 12:30:34 PM EDT, Russ <u.rusty@...> wrote:

So, you are saying that VSWR is based on voltage, but caused by an impedance mismatch.

VSWR is a *MEASURED* voltage difference along the transmission line. Yes.

On Tue, Aug 9, 2022 at 09:58 PM, F1AMM wrote:

H4_REV4_3.pdf

Would you have the same for my nanovna-F I don't understand anything in github
to treat this myself.
--

The NanoVNA-F is not an open source design. The manufacturer does not publish schematics or source code for this product.

Roger

VSWR
Voltage Standing Wave Ratio

The cause is the impedance mismatch.
The measurement is in volts.???

Kent

On Wed, Aug 3, 2022 at 09:10 AM, Kenneth Hendrickson wrote:

If the load is not perfectly matched to the source, there will be a voltage
standing wave ratio (VSWR) because of the mismatch.

So, you are saying that VSWR is based on voltage, but caused by an impedance mismatch.

Resonance has no effect on antenna performance so it’s not
a concern if an antenna is resonant or not. I don’t think I ever saw an US AM broadcast
antenna that was resonant.

It's not just US broadcasting stations that are like that, in France too. I did part of my out-of-school internship at a station that was broadcasting

300 kW on 600 kHz
150kW on 890kHz

All in AM, modulated screen plate so x4 for PEP.

The antenna was a 40 m high radiating tower, guyed, supported by a large insulator. Each of the two transmitters came via a 135 Ω pseudo coaxial (in wires) to a small cabin where there was a plug at each frequency which served as a duplexer and a series choke to compensate for the residual capacitance. The pylon was far from the ? wave

When we study an antenna project on EZNEC, we can clearly see that the resonance only acts on the impedance and quay only on the reactive. The real part of the impedance varies little in the vicinity of the resonance
--
F1AMM (Fran?ois)

-----Message d'origine-----

De la part de Ray
mercredi 10 ao?t 2022 16:40

You are all missing the message, Resonance has no effect on antenna performance so it’s not a concern if an antenna is resonant or not. I don’t think I ever saw an US AM broadcast antenna that was resonant.
Ray
W8LYj

What one wants to avoid (with some transmitters) is too much reactive
component - sure, you can cancel it with a passive component, but that
component will have some loss AND the required value changes with frequency.

I thought, at one time, that by not using the antenna at resonance (zero reactive) the bandwidth of the antenna would be widened. After adaptation (filter in 'L'), I note, by calculation, that it is not so.

Can you confirm this statement for me ? (or not)
--
F1AMM (Fran?ois)

-----Message d'origine-----

De la part de Jim Lux
Mercredi 10 ao?t 2022 01:29

H4_REV4_3.pdf

Would you have the same for my nanovna-F I don't understand anything in github to treat this myself.
--
F1AMM Fran?ois

-----Message d'origine-----

De la part de Roger Need via
mardi 9 ao?t 2022 18:17

On 8/9/22 4:03 PM, Brian D wrote:

"Dave W6OQ via groups.io" <david.hostetler@...> wrote:

On Tue, Aug 9, 2022 at 12:16 PM, Ray W8LYJ wrote:

The only reason amateurs like to operate an antenna at or NEAR resonance
is because the feed point impedance is low so it’s easier to match.

Exactly! But not just amateurs, everyone!

Resonance could be a paralell resonance, as with a full wave dipole, which
is high impedance.

What one wants to avoid (with some transmitters) is too much reactive component - sure, you can cancel it with a passive component, but that component will have some loss AND the required value changes with frequency.

So if you have a transmitter that wants to see High Z, then you might choose that full wavelength doublet. If your transmitter wants to see low Z, then maybe a 1/4 wave over a ground plane (~35 ohms at resonance).

For a practical system engineering solution, leaving aside a regulatory constraint (like 1500 W PEP), you want to trade mismatch (not getting as much power to the antenna as you might with a match) vs loss in matching components vs loss in a passive pad (if the transmitter can't tolerate mismatch).

Lots of people (non-amateurs) use a terminated folded dipole as a very wide band low gain antenna, because they have RF power to burn, and they don't have to worry about (auto)tuning a matching network.

Many collinear arrays are also high-Z. That quoted statement from ARRL is
a gross over simplification! Dipoles, Yagis, yes. But there are many
common radiating structures that do not offer low-Z to match.

For my long doublet (half-wave resonance is about 950 kHz) fed with
parallel conductor transmission line I use for 160 through 6-meters the
real part of the measured impedance ranges from 12 to 1160 ohms in the
shack. After measuring the complex impedance in the shack and spending a
lot of time on SimSmith, I designed and built my own antenna matching unit
(a.k.a., "antenna tuner").

Dave - W?LEV

--
Dave - W?LEV

"Dave W6OQ via groups.io" <david.hostetler@...> wrote:

On Tue, Aug 9, 2022 at 12:16 PM, Ray W8LYJ wrote:

The only reason amateurs like to operate an antenna at or NEAR resonance
is because the feed point impedance is low so it’s easier to match.

Exactly! But not just amateurs, everyone!

Resonance could be a paralell resonance, as with a full wave dipole, which
is high impedance.

--
Brian D
G3VGZ G8AOE G3T
IO94im

On Tue, Aug 9, 2022 at 12:16 PM, Ray W8LYJ wrote:

The only reason amateurs like to operate an antenna at or NEAR resonance is
because the feed point impedance is low so it’s easier to match.

Exactly! But not just amateurs, everyone!

Thanks, but still a problem.

Wouldn’t download with Chrome, but as advised I used Edge. Initially said it wouldn’t download because of malware risk, but ignored that and downloaded.

When clicked to open, it advised a version 4 was available. Clicking ok then led to the programme opening, but clicking connect, with correct COM port, led to no data showing.

David

On Tue, Aug 9, 2022 at 11:02 AM, Kyle Claisse wrote:

Awesome, that schematic looks correct! Its definitely not the cable, theres no
current draw when the switch is off but when the switch is on the USB port
draws around 300mA but doesn't charge the battery no matter how long the
device is left on that way.

You should be drawing current when the NanoVNA is off if the battery needs charging. The battery has a protection circuit in it to prevent over and undercharge. Perhaps that has failed. You can see it through the yellow Kapton tape.

Try taking the battery out of the nanoVNA and see if it will take current from an adjustable power supply. Start with a low voltage and then move up slowly to 4.1 Volts.

Roger

thank you

martin
n6qlh

On Tue, Aug 9, 2022 at 12:14 PM Larry McElhiney via groups.io <lmcelhiney=
[email protected]> wrote:

Hi Martin,
I do not use any Malware protection on my iPads, but a search for iOS
Malware should give you options.

Larry AC9OX

Sent from Yahoo Mail for iPad

From ARRL antenna book many editions:
Resonance has no effect on antenna performance. The only reason amateurs like to operate an antenna at or NEAR resonance is because the feed point impedance is low so it’s easier to match.
Ray
W8LYJ

Hi Martin,
I do not use any Malware protection on my iPads, but a search for iOS Malware should give you options.

Larry?AC9OX

Sent from Yahoo Mail for iPad