On this note most marine VHF antennas do not have any adjustment so if you have a bad SWR reading it’s because the ground or ground plane isn’t good or you are coupling to something else. Ham antennas have adjustments for SWR. If as others have said that antenna uses the mast as a ground or ground plane and the connection is corroded that would throw the SWR through the roof. Why you lost receive sensitivity and didn’t blow out the transmit side of the radio if it is the antenna or cable is amazing. Must be a very good protection circuit on that radio.
I know it costs a bit of money but with the fact that you are a ham as well you really should buy an MFJ antenna analyzer. I am pretty sure that you can get one that will get close enough to marine band to get you good readings. I would have to pull mine out and check to see how high it goes. I have the one that goes to 2M there is also one that does 440. Of course I also have several big beasts of test equipment like an old HP signal generator that goes up to like 480 and my service monitor which goes from DC to 1 gig. The MFJ antenna analyzers are very nice to have. You can use almost anything as an antenna and figure out where it is resonant without having to risk messing up your radio. Vern From: [email protected] [mailto:[email protected]] On Behalf Of Ron Rogers Sent: Sunday, November 22, 2009 11:24 AM To: [email protected] Subject: Re: [Liveaboard] FW: VHF ant 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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