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SWR meter for VHF/UHF

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twinsen

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uhf swr meter

Hi all

What do commercial UHF capable SWR meters use as a sensing element - a 50ohm stripline or "coax" made with a rod and tube with a 50 ohm D/d and some sort of sensing element?

I have looked for some designs on the web but most are for HF using torroids....
 

eirp

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microstrip swr meter

I think they are used microstrip coupled lines, it's cheap and easy to design.
It isn't difficult to design and build your own SWR meter this way. More than design of lines there can be problem with loading resisotors (due to reactance ...)
Eirp
 

klug

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vhf swr meter

Hi twinsen!

I have made a lot of SWR meters - all of them lack precision, and at once have stopped on very original construction of UA9ACZ (he even has patented it). It is made on thick cable, but without additional turn under sleeving. You will need some segment of thick cable, ten low freq ferrite torroids, 40 or 50 resistors, and some textolite for box. The size of box is 180x80x30 mm for 75 Ohm version. It is precise on wide band - from 0.3 to 500 MHz. I was amazing - precision near 2 % on 30 MHz and near 5 % on 500 MHz. I have not scanner and can not scan article with construction, but if you will need it, I will search scanner on my friends, or will try to explain it.

Happy New Year! klug.
 

flatulent

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vhf directional coupler

You can also buy ready made directional coupler modules, such as the Xinger models and use them in your design. This way you will have a known performance. In general, the coupled line is the only way to do it in TEM tansmission line methods. Waveguides can use holes in the wall.
 

goxy

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toroid swr meter

Hi to all !
I'm find some datasheet for 2.4GHz POWER/SWR meter with microstrips lines on the web, but I can't find them on my HDD.
I remember they are three microstripe lines and two diode detectors .Central lines is transmisions, others are detectors. Detector
line is coupled with R and C on the one end and other end is attached on simple diode detector (R, C and diode).With lines which detector is near transmiter you will detect POWER and with lines which detector is near antenna you will detect SWR.
With exactly shematics I'll help you when I find them.
Best Regards
 

toonafishy

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uhf swr bridge

At these frequencies, I would use microstrip. Just design a microstrip coupler with tight coupling, say -3dB. A coax/toroid combination has too much stray capacitance/inductance to be flat over this range.
 

flatulent

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swr meter circuit 500w

Sage company http://www.sagelabs.com/components/wireline.html makes specialized coupling lines that you could probably make a copy of if you do not want to buy them. You adjust the coupling with the length via their equations or by the following spread sheet. Their site also gives directions on stripping the line and construction techniques.
 

g579

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swr meter vhf

If there is no need of higher power transfer and 6-7 dB through loss can be tolerated, the simplest way is to make a directional bridge.
Very simple construction, you can find a lot of references to that.
 

goxy

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swr meter construction

Check this locations.
h**p://www.pollak.sulinet.hu/elektro/hidak/bridge/how_to.htm
and
h**p://www.qsl.net/n9zia/wireless/pwr-mtr-pics.html
 

goxy

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how to make a coaxial uhf swr meter

Check this locations.There are some interesting about SWR-Meter.
h**p://www.pollak.sulinet.hu/elektro/hidak/bridge/how_to.htm
and
h**p://www.qsl.net/n9zia/wireless

***ADMIN, Please delete this post*******
 

goxy

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cable reflection wave swr

Check this locations.There are some interesting about SWR-Meter.
h**p://www.pollak.sulinet.hu/elektro/hidak/bridge/how_to.htm
and
h**p://www.qsl.net/n9zia/wireless

***ADMIN, Please delete this post*******
Something is wrong with server.
 

klug

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swr bridge vhf/uhf

Hi Twinsen!

I have scanned that article with original UHF/VHF wide band (0.3-500 MHz) SWR meter with good precision. It is on Russian, but I will add some translation and explanations later.

Good Luck! klug.

There are 3 pages on DjVu file, you need to allow color in viewer.
 

g86

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digital swr meter costruction

How to open it ? ACDSee is giving a blank screen.. :(

:!: :idea: :?:

klug said:
Hi Twinsen!

I have scanned that article with original UHF/VHF wide band (0.3-500 MHz) SWR meter with good precision. It is on Russian, but I will add some translation and explanations later.

Good Luck! klug.

There are 3 pages on DjVu file, you need to allow color in viewer.
 

twinsen

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uhf swr diagram

w w w.planetdjvu.com/get_djvu.htm

Its a browser plugin
 

Borber

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swr meter transformer

DJVU is most effective picture compression. Look at:
http://www.lizardtech.com/
There exist program DJVU SOLO 3.1 which is free for noncommertial use.
You will be able to manipulate djvu files.
 

g86

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construction swr meter

Its a nice software i see. How to use it to scan papers ?? How dose it seperats picture and text? Very interesting.. :roll:

But could not understand the attached paper. I have to learn Russian to read it :twisted: Can some russi come forward to teach me russian .. I am interested.

:!: :idea: :?:

Borber said:
DJVU is most effective picture compression. Look at:
http://www.lizardtech.com/
There exist program DJVU SOLO 3.1 which is free for noncommertial use.
You will be able to manipulate djvu files.
 

klug

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swr meter design 2.4 ghz

Hi Friends!

There is my translation of this article. Sorry friends, maybe there are a lot of grammatical errors in translation, but I will explain any question about this construction. All language and terminology corrections are welcome.

----------------------------------------
Coaxial Directional Coupler.

Y. Kurinyi (UA9ACZ), V. Pilskii.

There are a lot of directional coupler circuits, but all of them have big disadvantage in relatively narrow frequency band. It compels to use adjustment of sensivety, for example in SWR meters.

This SWR meter allows to measure SWR in wide frequency band (1 to 500 MHz), to measure power in cable (without dependency from SWR level), to explore HF modules for unmatches in connectors and coaxials (with precision up to fractions of percent), to find with big precision positions of shortage or break in cable and other elements of HF lines, to use in half-duplex systems, and so on.

This Directional Coupler (DC) consists of current and voltage sensors and summator. The simplified circuit of the DC is shown on Fig.1, where "+-Ic" means current in cable (sign depends of wave direction), "p" - impedance of a cable, R1 R2 - resistors at voltage sensor, R3 - resistor in current sensor. If R1>>R2=p>>R3 , then mathematical description of this circuit is greatly simplified. In result, we have V(tap)=(V(cable)+-V(cable)/(2*K), where K=p/R3=R1/p - coefficient of attenuation to tap output. Thus, V(tap)=V(cable)/K for direct wave, and V(tap)=0 for reflected wave.

Wide working frequency band of this DC is achived by original construction. Current sensor is realized as one-turn current transformer with central wire of cable as primary coil and special cavity on shield together with cable sleeving as secondary coil.
...

The secondary coil have load made of resistors which are uniformly located on perimeter of sleeving gap. They are named as R3 on simplified circuit diagram. The parasitic inductance of this shunt is much lower then inductance of a cableon this construction. We need to have R3=<(w*Ls) on lowest working frequency, where w - lowest frequency, Ls - inductance of secondary coil. We use a number of ferrite toroids weared to cable to increase this inductance.

Voltage sensor consists of resistive divider R1R2, it is connected between central wire of a cable and output of current sensor. Divider R1R2 is connected in parallel with a cable, current sensor R3 in series with a cable.
...

The practical construction of SWR and Power meter is made as two back-to-back connected couplers (look at color picture #2). Shield, that is used as a box at the same time, is made of textolite. The sizes of this shield/box is free. This construction was designed for 50 Ohm cable with maximum power near 200 Watts with SWR<=4. The maximum allowed power is increased for little SWR and decreased for big SWR. The coupler attenuation is chosen as K=100.

R1 consists of 4 resistors in serial two 1.2K and two 1.3K (all are on 1W). R3 is made of 15 resistors 7.5 Ohm (0.5 W), they are located uniformly on gap of cable sleeve (look at color picture #4). R2 consists of two 100 Ohm resistors (0.25 W) in parallel, they are located above current sensor resistors on distance 1.5 - 2 mm between these two resistors. All resistors are needed to be without parasitic inductance in their construction. Distance from R1 to shield needs to be more than 15-20 mm. Torroids are made of low frequency ferrite core. You need to fix tightly cable sleeve to dielectric on whole lenght, so use wire or thread winded above it.

This construction becomes simple if you use cable connectors, but you can use panel connectors. Look at b/w picture #2, (a) is for 30 MHz upper frequency, (b) and (c) for 500 MHz. Cone in third variant is made with cable sleeve or from tin. The biggest circle of this cone has no critical diameter and it depends of used connector size. You need to solder it accuratly on all perimeter.

If you take all resistors with 1% precision then you have no need to adjust it. In other way you need to correct one of current resistors for minimal signal of reflected wave. (Anyway all this adjustment is needed only for SWR precise measuring less than 1.05).

Our first construction was made without component selection or any adjustment with these parameters:
Frequency Band = 0.3 - 500 MHz,
K = 100 +- 5
There was worsening 2% of directional coefficient on 30 MHz, and 5% on 500 MHz.
There were taken 30 ferrite toroids with 20x10x6 size. As amateur band has lower border on 1.8 MHz, the number of toroids could be 6-7.

You can use double-beam oscilloscope to find inhomogeneity in cable, with sending square pulse you can find time delay between direct and reflected pulse, as wave speed in cable is near 2*10^8, you can calculate distanse to inhomogeneity.

If you are planning to use this SWR meter only on VHF (where powers are not so big), then you can extend frequency band to high. For this, take K=10-20, R3 (1/8 W) in one line, change R1 to one resistor (1/2W) and make some frequency compensation to avoid parasitic capacitence of R1. In this case you can extend upper frequency to 1 - 1.5 GHz.
-------------------------------------------

Best Wishes! klug.
 

S

sick_man

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vhf uhf swr bridge

SIMPLE ANSWER

USE AN ABSORBTION WAVE METER
MEASURE YOUR CABLE AND RADIATORS TO GIVIN QUANTA

RELATE THESE TO PI TAGANOL RF ALGIBRAIC EQUATI

AND OCTAGONALISE YOUR RESULT
INCLUSIVLY UTILISING AN LCD VOLTMETER TOO QUATIFY THE WAVE GEOMETRIC ORIGIN POINT WHICH IS ALWAYS 1-1.5 FOR A VERTICAL
IF A HELAXICAL TUNEL IS AC ON A RADIATOR


IF YOU VERTICALISE RF THEN RMS = PEP *1.707
BUT PEP IN A SQUASHED TUNNEL EVEN FOR A SECOND IS RMS * 1.707
BECOUSE .707 * RMS = PEP IN A SQUARE VECTER

RF IS THE RESVERSE OF DC RELATIVE TO THE ORIGIN IN A GIVEN TIME FRAME
 

phongwiroon

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vhf power ham meter

i've seen it all on pcb and it look easy to build
 

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