A fellow named Salty John provides the answer: “DefaultRe: Checking VHF aerial
_____ VSWR stands for Voltage Standing Wave Ratio. If your antenna and radio were perfectly matched and there was no cabling between them you would have a VSWR of 1:1. When you add manufacturing imperfections and an imperfect cable run a mismatch of greater or lesser degree is introduced. This mismatch gets somewhat significant when it reaches about 1.5:1 and gets really serious at 3:1 and can damage your radio at higher levels. Some radios have a built in VSWR meter and won't allow you to transmit when VSWR is above a dangerous level. If you use the right components - antenna, cable, connectors - and they are properly installed and undamaged you won't lose sleep over what your VSWR is, unless you are a radio fanatic! Also, if you are unfamiliar with the use of a VSWR meter you can get things wrong and convince yourself all is well when it isn't. With a masthead whip antenna you need to check with a multi-meter that the outer shell and the centre pin on your connectors are not shorted and, if possible, that there is continuity between the centre pin at the antenna and at the radio and the same for the outer shell. The whip antenna will usually show a dead short if you measure across its centre socket to outer body so the above tests must be done with the cable disconnected at both ends. The best check is to take the radio to another antenna or another antenna to the radio. Sometimes you can test the antenna by extracting the PL259 connector at the radio end so only the pin is connected and not the outer body. Tune to a radio station. Then push the connector all the way home and the reception should slightly improve. If it doesn't and actually worsens or goes away you have a faulty antenna system. __________________ John http://www.saltyjohn.co.uk” From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Sunday, November 22, 2009 10:12 AM To: [email protected] Subject: Re: [Liveaboard] FW: VHF ant [email protected] writes: Hopefully, someone else can remind us, but the Metz (excellent choice) may have “a designed dead short to ground” in this case the mast. This sort of rings bells as to why an AM/FM splitter wouldn't work with the short mast mounted Metz. Carl
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