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VSWR Test setup help

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abicash

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Hi

I am about to build a VSWR meter and have researched a bit about the same.

Now i need to know low level requirements of a VSWR measuring setup.
Like what kind of dummy load i need to buy and the cables required and the signal to be fed and where can i buy these peripherals.

Any help is appreciated
 
Hi

I am about to build a VSWR meter and have researched a bit about the same.

Now i need to know low level requirements of a VSWR measuring setup.
Like what kind of dummy load i need to buy and the cables required and the signal to be fed and where can i buy these peripherals.

Generally such aerial system are 50 ohms, so you need a suitably rated 50 ohm dummy load, the only signal you need if that from your transmitter.

However, VSWR meters are cheap enough to buy, why not just buy one? (I've just thrown one away).
 
Now i need to know low level requirements of a VSWR measuring setup.
What are you trying to measure the VSWR of?
The obvoius conclusion would be that you are trying to match an antenna to a transmitter.
But from the way your question is phrased, you could be trying to do something else, a bit of detail please.
What frequency are you trying to measure this at?

JimB
 
Hello and thanks for replies.
This is for a regulatory requirement in measuring some parameters including vswr of a connector.
I found some suppliers for 50 ohms.
But beyond that I know very little, like what connectors, cables,i/p generator and amount of power to be fed.
Can someone share a descriptive photo, preferably with suppliers names

Would be very helpful.
Awaiting reply
 
Well, you seem to have drawn the short straw!

Measuring the VSWR of a connector is not exactly a trival task, especially for someone who has no experience in this area and has only been given a vague description of the requirements.

What sort of connector is it? You don't even know that!
Is it supposed to be a constant impedance connector? Don't know!

I suggest that a good start would be to find out what type of connector, what are the requirements, and then ask the manufacturer of the connector.

Maybe not what you want to hear, but this is more than can be accomplished by an simple SWR meter.

JimB
 
Laboratory precision measurement of VSWR requires a calibrated Vector Network Analyzer, phase stable test cables, a calibration kit designed for the connector type you are measuring (which includes a precision 50 ohm load within it), and a test fixture for the particular connector type under test. If microwave frequencies, 100,000 USD is a rough price for that equipment. A little less for lower frequencies. If you don't do this sort of stuff a lot, better to send it to a Precision Measuring Equipment Lab.

For somewhat less precision, a Scalar Network Analyzer with directional bridge and calibration kit and Signal Generator is most often used. In both cases, the items in the calibration kits are traceable to a primary standard. They are housed in handsome, well crafted hardwood cases with custom foam inserts.
 
Hello and thanks for replying

I am attaching a photograph or 2 of the earlier setup which was used for this.

The frequency for which this is required is 250 MHz.

I want to know some stuff as follows...

1) Will it be sufficient if i were to build a 250 MHz, +5v square wave out (preferably from a Microcontroller) which is then given as i/p signal to the setup?
2) What type of cables are required?
3)What type of connectors are required?
4)What type of probes or detectors are required? I have read that various probes with different impedance are available and we have to calibrate the meter according to the matched impedance.

The info on the setup in the photographs is limited to the photographs only.

Please guide
 
what you need is a directional coupler and a 250Mhz signal generator (sine wave, not square wave) and some way of measuring the reflected energy at the reverse port of the directional coupler. the forward port is used as the reference.

another way to do this using fast rise-time pulses is this:
https://en.wikipedia.org/wiki/Time-domain_reflectometer
 
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