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I have 10W U/V transceiver.
Some of same transceiver users reports burnt after change 3rd party antenna.
-'Don't use 50 Ohm matched aftermarket antenna. This transceiver not matched 50 Ohm'
-'Burnt after even genuine Nagoya/Diamond antenna'


Almost RF designed 50 Ohm( Attenuators, Filters, Antennas, Couplers, ... ) But, How about in the wild?


I don't want spending times to trial/error(watching remotely mounted RF monitor & trimming antenna)
Any genius/proper methods of measuring over 30dB powered source impedance?

Objective: Measuring 10W transceiver's SMA port impedance -> Making custom load calibration kit for VNA -> Making good quality(matched) custom antenna for my transceiver.
Items what I have:
- RF Explorer(6G combo)
- SDR(Lime, RTL)
- miniVNA Tiny
- Oscilloscope(2D72)
- Several 50 Ohm load/terminator(1~15W)
- Several 30dB attenuator
- Kinds of directional coupler( , , Chinese cheap others... )
- VSWR meter for U/V band(SureCom)
Knowledge what I know:
- Audio output port's impedance measure with fine resistor & multimeter ( But, My transceiver is 1W even at LOW mode! I don't want let my transceiver burn without antenna )
- Basic skills of using VNA( Measuring load impedance of unknown antenna/filters, measuring reflection/attenuation )

This sounds more like poor engineering than any actual design goal.
Any HT I have used will happily transmit into a large mismatch with no adverse affects.The fact that this is a 10W HT would lead me to believe that it is probably operating on the fringes of capacity anyhow, and probably hard pushed to dissipate all that heat, even in a perfectly matched situation.
I don't think you'll be able to measure the impedance of the transmit path in place. If you had schematics you could calculate it though.
/ Gerry

wait. what is 'burnt' (damaged) here? the 10W U/V transceiver? or the 3rd party antenna?

10W U/V output impedance not 50 ohm is not a good explanation for damage to the transceiver and not a good explanation for a damaged antenna.

before trying to figure out how to measure output impedance, let us know more and know precisely what has happened.

- \0111 -

AND... Some of FB group users reports/Vendor official account also confirmed '50 Ohm is theory. Anyway our stock antenna matched our transceiver. If you want more ranges, use stock antenna'
-'3rd party antenna's loading coil parts burnt': Photos/Videos
-'poor reception ranges when I change antennas'
-Screenshot of professional lab gear and descriptions that 30 Ohm source impedance he said( I remember. he/she did not answered 'how to measure source impedance of 10W RF output port' )

I don't want '20 Ohm is not a problem/VSWR over 2.x that will be acceptable/Transceiver burnt? lie!'
I already addressed 'for better ranges and eliminate heat as far as I can' - Without trial/error

Now. Its your turn 'How can I measure output impedance of 10W RF source right/correct/safe way?'

Do not try to measure the source impedance of an active device using a VNA. It is possible but it is not a straight forward measurement and requires additional devices to complement the measurement. This is particularly problematic at large RF power levels. If you wish to measure the COLD non RF output power level that is certainly safe but of course only an estimate as the active device is OFF.

There is a rather simple method for measurement of an active device source impedance and it is defined by the LOAD PULL METHOD. It requires a variable line stretcher, that is a transmission line with adjustable physical length, a known load impedance, for example 100 ohms, a directional coupler and a spectrum analyzer. The heart of the method is based on the principle that if I sample the ratio of the power change between the incident and reflected power from the directional coupler for a known load pull range, I can deduce the magnitude of the source impedance. If this is of interest, I can try to find the details of the measurement system.

Alan

Thnx, Alan.

I saw someone introduced 75Ohm load side's VSWR with 50Ohm matched VSWR measurement gear
- Easy formular, but it does not suitable for measure sourceZ I think.
Also I already thought coupler that has reference load connectors(4 port with 1:1 balun)
- Coupler input port circuit was already 50 Ohm matched( If unknown sourceZ not matched 50 Ohm, power will reflected before reaching coupler circuit I think ), I already know my loadZ(antenna) through 50 Ohm calibrated VNA.

COLD method I will try with shorter than 1/10F cable lengths :-)
I wish to know further more knowledge about 10W powered sourceZ proper/right measurment method.

There is a rather simple method
for measurement of an active device source impedance

Measuring nonlinear devices
(e.g. ferrite cores, diodes and active devices) can be problematic
with non-sinusoidal stimulation e.g. nanoVNA.
While nanoVNA DSP can sort harmonics,
DUT "sees" full stimulation.
Nonlinear DUT response at harmonic of interest
is confounded by amplitude of others,
unlike e.g. ideal transmission lines, capacitors, resistors and inductors.

On Tue, 3 Sep 2019 at 09:36, -- <gpdxdveil@...> wrote:

I have 10W U/V transceiver.
Some of same transceiver users reports burnt after change 3rd party
antenna.
-'Don't use 50 Ohm matched aftermarket antenna. This transceiver not
matched 50 Ohm'
-'Burnt after even genuine Nagoya/Diamond antenna'

This sounds a combination of

1) Marketing rubbish to get you to use their antennas.

2) Poor engineering

The output impedance of this transmitter is likely to be considerably less
than 50 ohms. If the output impedance was 50 ohms and it connected to a 50
ohm antenna you would get maximum power transferred, but an efficiency of
only 50%.

The impedance of any antenna on a handheld transceiver will vary
*considerably* depending upon the position one holds it. So any handheld
device that is properly engineered will tolerate any degree of mismatch.

You would not be able to measure the output impedance of the transceiver
without a system called “load pull” If you connect the NanoVNA to the
output of the transceiver, would very quickly destroy the NanoVNA.

Depending on how much the transceiver cost, I think you should either

1) Throw it in the bin
2) Seek a refund.

Dave

-

--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

i believe Google Translate is part of this conversation loop.

progress! your transceiver is a Retevis Ailunce HD1 VHF/UHF DMR handheld.

you report 3rd party antennas being damaged when used with this handheld.

you must first realize the typical handheld output power is 5W. the Ailunce HD1 output power is 1W or 10W (selectable).
it is no surprise to me 3rd party antennas are being damaged when the Ailunce HD1 is set to 10W out.

the damage is caused by the power level, not the output impedance of the HD1. it is just that simple.

- 3g (base 19) -

On Wed, 4 Sep 2019 at 13:58, kb3cs <kb3cs@...> wrote:

the damage is caused by the power level, not the output impedance of the
HD1. it is just that simple.

- 3g (base 19) -

The marketing hype specifically says its the impedance, not the power
level.

I somewhat doubt any walkie talkie antenna would be damaged by 10 W of
power. Certainly, the ones I have seen are just basically a coil of wire,
with no matching components.

I would also be a bit concerned about 10 W of RF close to my eyes - the
part of the body most likely to be damaged by high levels of RF.

--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

the hype seems entirely misleading to me.

the typical basic rubber ducky is quite robust, i agree.
however, higher gain multiband aftermarket antennas may well not be as robust.

- 67 (base 11) -

Why you guys talking about 'YOUR HT IS SHIT' or 'BURNT? THIS IS NOT IMPEDANCE ISSUE', 'ANTENNA WILL DAMAGE' or WORRYING ABOUT MY VNA?( I am not stupid, I know right way to connect LNA)



Please stop to talking about OFF-TOPIC issue



FOLLOWING ADVICES ARE VERY WELCOME
-Introducing your 'HIGH POWER CAPABLE IMPEDANCE TUNER' or 'UHF/10W OUTPUT IMPEDANCE MEASUREMENT CONFIGURATION' - X/Y plane adjustable tuner( attached photo )
-Even F/Vrms/Iout same condition, 'Audio amplifier output impedance measurement(Two known load state's Vdiff)'method not suitable for RF measurement?
-You can make via xxx.yyy.net/thread?zzz

Waiting

Is my "Unknown 1W source impedance calculation" theoretically correct?
-Please ignore real measurement problems below-
* My measurement gear still poor
* Mismatch reflection happens front of -60dB attenuator
* Simulation/Correction required ( Even my test path/cable lengths as short as 1/10f lengths still causing loss and influence RF characteristics )

you initially waved around a complaint which might as well be a surrealist's dream: your HT will be un-burnt when you fill your bathtub with brightly colored screwdrivers. and now you make rude demands? consider yourself lucky the group may respond kindly to you.

back to the matters at hand: a technique for measuring output impedance of an audio amp may not at all be used with the Ailunce HT for the simple fact the audio amplifier will happily operate open circuit, while the HT may be very unhappy indeed and release all the magic smoke from its power amplifier.

except for the aforementioned magic smoke release warning, the simple and direct method of measuring output impedance (or "source impedance") is to compare the open circuit operating voltage with operating voltage under load.

the load value will be equal to the source value when the operating voltage under load is one-half of the open circuit operating voltage.

- 1001001 (base 2) -

Output impedance can be calculated (estimated, at least) from the (complex)
incremental change in output voltage and current after a small change in
load impedance.
No need to run anything open circuit.

Den tors 5 sep. 2019 12:51kb3cs <kb3cs@...> skrev:

On Tue, Sep 3, 2019 at 11:36 AM, RFy wrote:

Any genius/proper methods of measuring over 30dB powered source impedance?

In order to measure source impedance, you're needs to measure amplitude for different loads. Since many RF PA cannot handle open output properly you will need to use two different loads which impedance is compatible with PA output. For example 25 Ohm and 75 Ohm. If your PA has very limited range for load impedance, use something like 40 Ohm and 60 Ohm. The goal is to get more different load to get more precision.

So, you have load R1 and load R2.
Just connect R1 and measure amplitude U1.
Then connect R2 and measure amplidue U2.

Now you can calculate source impedance:

Z = (R1 - R1*(U1/U2)) / (U1/U2 - R1/R2)

The only problem here is to measure RF signal amplitude on the load properly. This is not so easy task. You can use wide bandwidth oscilloscope for that.

PS: there is no difference if your equipment measuring RMS voltage or amplitude voltage, just use the same voltage type for both measurement.

PPS: you're needs to measure voltage on the load. But note, you cannot use random wires to do that. The better way is to use high impedance RF probe from oscilloscope. The other way is to use attenuators with 50 Ohm output and RF voltmeter with 50 Ohm input. The main goal is to measure voltage on specific load.

qrp.ddc,

Thanks for confirmation( #1831 ) and additional advise.

Output impedance of a transmitter is not simple thing. Transmitter outputs are not matched to the output transistor or fet collector impedance. That impedance is usually very high. Usually matching circuits are made so that efficiency is best, that is the output device does not get too hot. So if you really measure output impedance of a transmitter, you get strange results. Besides, you may burn your transmitter or measuring device.

And of course, the real answer to your question is the following: If you want a reliable radio equipment, buy reputable a ham radio =radio amateur products or even professional radio products. They keep their promises, no need to worry or guess anything. They'll cost something but quality costs.

On Fri, Sep 27, 2019 at 04:56 PM, sala nimi wrote:

Transmitter outputs are not matched to the output transistor or fet collector
impedance. That impedance is usually very high. Usually matching circuits are
made so that efficiency is best, that is the output device does not get too hot

max efficiency happens when you match output impedance with the load on the output connector.
More hot on the load means better match and better efficiency. This is pretty easy.

For maximum efficiency and maximum match you're needs to tune it in such way to get maximum hot on the load.

So if you really measure output impedance of a transmitter, you get
strange results.

I do that many times and never got strange results. The result is always expected - about 50 ohms for good equipment