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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 08-26-2008
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2:1 Vhf Swr

I just installed a new Raymarine DSC VHF.

I have a mast top antenna with a balun. It looks like it's a 1/2 wavelength, 36 inch antenna.

When I was a HAM radio operator, I always tried for a 1:1 SWR. I measured mine at 2:1 using a SWR Bridge.

Anybody else ever measure their SWR?

I think 2:1 is not bad, but I was just wondering what others are seeing.

Chris
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Last edited by EO32; 08-26-2008 at 05:05 PM. Reason: DCS to DSC
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Old 08-26-2008
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Anything less than 2:1 is pretty good for a VHF unit. Ideally, you'd have it be 1:1, but I don't think that is all that feasible. Using a Shakespeare SWR meter, I found that the setup on my boat is about 1.5:1 or so, varying a bit with the frequency.
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Old 08-27-2008
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Are u sure u have a balun ? and not just a matching coil, a balun does nothing more than change an unbalanced line (ground referenced) to a balanced line no ground reference. You normally use a balun when you have radio op that has the outer cable shield tied on to ground (basically the 3rd prong on your AC power plug) and u want to feed a split dipole antenna. normally used for SSB radios, not VHF . I've never heard of VHF radis having a Balun attached. Just wondering..
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Old 08-27-2008
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Sounds like we have a new Radio Guru......Good I know nothing
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Old 08-27-2008
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Check for water in the coax shield, or if the coax cable got crimped or pinched somewhere along the run. My SWR was so bad due simply to old deteriorated coax that my Uniden VHF was self limiting itself.. What type of meter are you using? Remember they need to be calibrated to whatever frequency you are transmitting on.
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Quote:
Originally Posted by EO32 View Post
I just installed a new Raymarine DSC VHF.

I have a mast top antenna with a balun.
That would be a matching coil. Baluns are used to transform unbalanced transmission lines to balanced antennas. (E.g.: Coax to dipole.) Hence the name: Balanced to unbalanced transformer.

Quote:
Originally Posted by EO32 View Post
It looks like it's a 1/2 wavelength, 36 inch antenna.
That would be about right at 162MHz.

Quote:
Originally Posted by EO32 View Post
When I was a HAM radio operator, I always tried for a 1:1 SWR. I measured mine at 2:1 using a SWR Bridge.
2:1 is usable, but I wouldn't like it. I would want to get that down to under 1.5:1.

Quote:
Originally Posted by EO32 View Post
Anybody else ever measure their SWR?
I've been meaning to. I keep forgetting . Many, many things to do. The list seems to grow longer, as time goes on, rather than shorter. The radio works, so there are much higher priorities. Nothing I can do about it atm, anyway, being as the antenna is a one-piece fiberglass thing.

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Originally Posted by EO32 View Post
I think 2:1 is not bad, ...
I don't regard 2:1 as acceptable, but that's my opinion.

Jim
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Old 08-27-2008
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Wow. You guys are picky sometimes.

Since I have a 1/2 wave antenna, I agree the base is not a balun, but just a means of mounting it.

The connections at the mast top are old, 20 to 30 years, so I plan to run new coax at some point.

I held an advanced class ham license (WA6TZE and KB7KJ) and also a First class Radio license, plus a BS in Electronic Engineering, so I have a pretty good idea of what is going on.

Mainly I just want to bring up SWR (Standing Wave Ratio) as a topic, since it is important in radio commnuications.
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Old 08-27-2008
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Just want to say.........What the Hell are you guys talking about??????
Ya turn the damn radio on, you switch it to what ever channel you want to talk on, you push the friking button on the microphone thingy and you talk into it. It's simple.
Than you listen to what the udder guy be saying.
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Doesn't always work that way TJK... BTW, you forgot to say "stop pushing the microphone thingy button when you're done yakking" so you can hear them. but it does explain why you never seem to hear us when we reply to you hailing us.

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Just want to say.........What the Hell are you guys talking about??????
Ya turn the damn radio on, you switch it to what ever channel you want to talk on, you push the friking button on the microphone thingy and you talk into it. It's simple.
Than you listen to what the udder guy be saying.
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a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Old 08-27-2008
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ok, I'll remember next time to STOP pushing the button thingy.
My radio works and I still have no idea. Never claimed I did.........
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