Questions tagged [swr-meter]

The SWR meter or VSWR (voltage standing wave ratio) meter measures the standing wave ratio in a transmission line. The meter can be used to indicate the degree of mismatch between a transmission line and its load (usually a radio antenna), or evaluate the effectiveness of impedance matching efforts.

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Voltage along transmission line with scattering parameters and VSWR given

A transmitter is connected to an antenna with a coaxial cable with length \$l=1.5 \:\text{m}\$. The characteristic impedance of the cable is \$Z_0 = 75 \: \Omega\$ and the scattering parameters are \$\...
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1 vote
2 answers
121 views

What are the reasons to use SWR instead of the reflection coefficient?

It seems that using SWR is a tradition (historical legacy). But even in the history of electronics I can't find why SWR was considered more useful compared with the reflection coefficient. What are/...
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2 votes
3 answers
593 views

What does SWR and reflected power mean in terms of power actually dissipated in a load?

I'm struggling to understand the "meaning" of VSWR in the context of power delivered to a load. Say I have a transmitter operating at 10MHz, a short (~1m) piece of assumed-lossless ...
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8 votes
0 answers
513 views

Looking for criticisms for a VNA-like meter I am designing

I would like some help from anyone who could let me know any flaws or improvements in my design they can find and help me reconsider any last minute design fixes before I send my new project off to be ...
0 votes
1 answer
107 views

Is current direction always opposing when signals are reflected on a transmission line

Having read Dave Tweeds excellent description of reflections in electrical transmission lines, I thought I was one step closer to a full understanding of SWR. However, later I was watching w2aew's ...
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1 answer
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relation between reflexion coefficient and power ratio

Assume you have an intermediate input/outpout device connected to a coaxial line. For example, the device may be a DC-bloc, a bias tee, or simply a PCB microstrip transmission line. Using a signal ...
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0 votes
3 answers
3k views

Using a Spectrum Analyzer to measure VSWR

I need to measure the VSWR of a coaxial wire that has a length of 100 metres and a characteristic impedance of 50 ohms using a Spectrum Analyzer (I don't have a Network Analyzer). I found this website:...
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0 votes
1 answer
276 views

Transmission line voltage measurement(visualizing standing wave)

I want to measure voltage across a T-line to visualize standing waves on the line. something like this video min 6:53 and this experiment Measuring Standing Waves on a Microstrip Transmission Line I ...
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2 votes
2 answers
1k views

Determining Power in a VSWR Bridge

I have recently been trying to build an Arduino based VSWR bridge. The final goal is to make it feature rich but right now im having trouble calculating the forward and reverse voltage from the ADC ...
2 votes
1 answer
2k views

How to automatically switch RF path to external antenna

I'm designing a circuit that has 2 antenna options for one transceiver @ 1.6 GHz. One antenna is internal and is the default RF load. Another antenna is external - to be attached by the user if ...
2 votes
3 answers
4k views

Shortening the coax on UHF CB antenna caused SWR to get worse, why?

I shortened the coax cable on my car's 477MHz CB antenna because the braid was frayed at the transciever connector end, and a metre or so of spare coax was coiled up behind the dash. I thought if I ...
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0 votes
1 answer
295 views

High SWR on a new dipole antenna

I'm constructing / moving a low power fm radio station to a new location. The antenna is a new folded dipole mounted on a 2-3/8" steel pole and attached to a new magnetic base. This location is the ...
1 vote
1 answer
490 views

Standing Wave Ratio(SWR) Measurement

I'm trying to find a way to measure SWR digitally. Generally SWR is measured with analogue equipments and it is not practical on self designed PCB. I did not find so much resource on how to do it ...
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4 votes
1 answer
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Explain differences in SWR meter circuits

I am trying to understand the detailed operation of a VSWR meter, and found an excellent account in the article "An Inside Picture of Directional Wattmeters" by Warren B. Bruene W0TTK in QST for April ...
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0 votes
1 answer
860 views

VSWR measuring, directional coupler

I may need to measure reflected power from some PA at 868 MHz with a maximum power of 5W and there are readily available SMD directional couplers to buy. However, I found only 90 deg. couplers on ...
4 votes
3 answers
5k views

How does an swr meter directional coupler work?

How does the directional coupler in an swr meter work? How are the forward and reflected waves separated out from the standing wave on the feeder? I would like an answer in terms of sine (or cosine) ...
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5 votes
1 answer
3k views

Modify SWR meter

I am trying to modify a SWR meter (http://www.mondoplast.ro/Reflectometru-powermetru-Performer-DF2469-pg_ft-3597) and add a new scale (now it has 200W/50W and 20W/5W) for 2W/0.5W. I have made some ...
2 votes
1 answer
963 views

How can i create a SWR meter that works for 0dBm sources @ 2.4Ghz?

I've stumbled upon this, but it only works for outputs between 15db and 20dBm. How can I modify it to work for 0dBm sources? I'm planning to use this to roughly tune my matching circuit for the ...
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