Monday, June 3, 2019

Build your own VSWR meter

A handy test instrument for HF operators is the VSWR (voltage standing wave ratio) meter. It basically tells you how far the load presented is away from 50 ohm resistive. Many transceivers have them built in. They can suffice as indicators but there are times when you want a VSWR reading at or near the antenna. Or you might be using older or homebrew gear that doesn't always have an inbuilt meter. 

Probably the easiest way of getting a cheap stand-alone VSWR meter is to visit a hamfest and find a used on. Often 27 MHz CB type meters come up. They should be OK on HF. Their main problem is that although they're fine for 4 watts on 27-28 MHz their sensitivity drops at lower HF frequencies. Which could be a limitation if you run QRP. 

Another thing you could do is make your own. The moving coil meter is probably the hardest part to obtain. You will also need some germanium diodes, and, for some designs, a toroid. You can often save time and money by buying a used CB type VSWR meter and building your own circuit inside that.  The fancier VSWR meters have two meter movements so you can view forward and reverse power simultaneously while more basic ones have one meter movement and a switch to monitor these one at a time. 

Anyway, here are a some ideas for VSWR (sometimes abbreviated as just SWR) meters you can build. 

PS: Want to read more about antennas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.


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