Originally Posted by fireflimoon
Was wondering if people measure the SWR on their home built antennas to see how well the build went? Buying an SWR meter seems a little pricey and I guess if it works then why sweat the details right - but I'm just wondering if there are simple ways of checking on the efficiency of the antenna and whether it is performing as it should. The GH/M8 models by Nikiml and Mclapp have swr and gain info, so I was wondering if a build of one of those antennas could be measured against that information to see if there were errors in the building of them.
Although stand-alone SWR Analyzers are readily available for Ham radio bands,
the test signal is ONLY output over fairly narrow bandwidths and is NOT
available over the TV & FM bands....probably due to FCC interference rules.
Unfortunately, the fol. wide-band IN-LINE Bird SWR Meters need quite a
few watts of INPUT power to measure SWR < 2.0 (Return Loss = 9.5 dB).
Which interferes with reception of TV & FM signals in your neighborhood.
LEGAL test signals need to be no more than about 10 mW (100 mW EIRP):http://www.rfparts.com/bird.html
I did come across the fol. $695 AEA-140-525 Antenna Tester, which might
get the job done (I didn't see a manual available for download), except it
only covers the Hi-VHF and lower half of the UHF TV bands. With a very
low output of +5 dBm (3 mW), it might even be legal outdoors:http://www.aeatechnology.com/products/swr/140-525
AEA also makes 600-999 MHz Cellmate EX and 100 kHz - 54 MHz VIA models:http://www.aeatechnology.com/swr-meter/
Since it's a 50-ohm device, you'll also need a 50-to-75-ohm Low Loss Pad.
PS: Antenna Under Test needs to be mounted well away from other objects,
otherwise you'll be measuring reflections more than actual SWR.
Network Analyzers and some Spectrum Analyzers can measure Forward
Power and Reverse (Return) Loss, from which SWR can be calculated.
Unfortunately, they cost 10's of thousands of dollars new and several $1000 used.
Which puts them out of the reach of amateurs.....and even many pros,
who rely on electronic rental companies to bring the cost down....
From time to time I've see DIY projects for a Ham Radio "SWR Bridge",
which could be readily adapted for TV and FM Band if someone has the
requisite skilzzz....but I wouldn't undertake this redesign effort without
having access to the above expensive test equipment to verify the design:http://ludens.cl/Electron/swr/swr.htmlhttp://www.qsl.net/n9zia/wireless/appendixF.html#10http://pe2er.nl/wifiswr/