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vhf radio and swr

Old 10-01-2009, 06:03 PM
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Default vhf radio and swr

I have a question regarding my vhf radio and swr. Is it necessary for me to check the swr and adjust it? If so can it be done with a HF meter like I would use for a CB? There is nothing in the radio user manual that discusses swr.

Thanks for your help
Old 10-01-2009, 06:28 PM
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Originally Posted by geno001 View Post
I have a question regarding my vhf radio and swr. Is it necessary for me to check the swr and adjust it? If so can it be done with a HF meter like I would use for a CB? There is nothing in the radio user manual that discusses swr.

Thanks for your help
You can buy a SWR meter and check it if you like but there's nothing to adjust so what's the point? A good quality antenna from a reputable manufacturer will have a low SWR ratio and it will not change over the life of the antenna unless the antenna is damaged in a way that shortens the length.

Most folks do not bother and their radio/antenna combination serves them well.
Old 10-01-2009, 06:35 PM
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Here's a link to the Shakespeare tester

http://www.shakespeare-marine.com/ac...menupick=ART-3

I like testing mine a couple of times a year just to make sure the radio/antenna setup is functioning properly

Much better than a radio check
Old 10-01-2009, 08:16 PM
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Thanks for the advise. I have a shakespeare and as you mentioned I didn't see any way to adjust it. One less pain in the a.... to deal with. Thanks
Old 10-01-2009, 08:30 PM
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On the tall whips just make sure you DO NOT cut and shorten the coax. There preset with the lenght to vhf Freq from the factory. You shorten the coax by three inches and you have changed the swr. You can still hear but your transmit will be affected.
On the smaller 3 foot steel whips yes, they can be set by moving the antenna up or down in the base but again do not cut the coax. Both must have that lenght that they came with.
Old 10-01-2009, 08:43 PM
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Originally Posted by liveaboard74 View Post
On the tall whips just make sure you DO NOT cut and shorten the coax. There preset with the lenght to vhf Freq from the factory. You shorten the coax by three inches and you have changed the swr. You can still hear but your transmit will be affected.
On the smaller 3 foot steel whips yes, they can be set by moving the antenna up or down in the base but again do not cut the coax. Both must have that lenght that they came with.
Wrong. At VHF, coax length doesn't matter. Coax lengths on ANY "balanced" antenna doesn't make much, if any, difference, for that matter. Marine VHF antennas are all balanced.
Old 10-01-2009, 09:13 PM
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Originally Posted by t3rockhall View Post
Wrong. At VHF, coax length doesn't matter. Coax lengths on ANY "balanced" antenna doesn't make much, if any, difference, for that matter. Marine VHF antennas are all balanced.
I see your a ham and I'll take your word for it but could you explain that. Balanced? I"ve run beams, directional antennas but I would never say I know it all and always eager to learn something new.
Thanks...
Old 10-01-2009, 09:36 PM
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You still can check with your CB swr meter. I think most of them are rated up to VHF, but do not rely too much on it. If high, consider you most likely have a problem, but if low consider you are a happy CBer but maybe not a happy boater. I know Harris will shoot be for saying that ;?
Old 10-01-2009, 10:42 PM
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On the tall whips just make sure you DO NOT cut and shorten the coax.

Shakespeare says it's ok to shorten, but no less than 3'. A factory rep I talked with a few years ago suggested shortening rather than coiling up excess with a twist tie ...
Old 10-02-2009, 04:23 AM
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Default Here we go?? Lol

I have the meter and check the guys I know antenna around here. I"ve heard that to about the 3 foot but have had to add coax and quick connects when lenght was shortened to bring the swr back down. Three foot is the same rule in Cb and you are suppose to have a three foot jumper on the swr when checking behind the meter. The guy that is a ham should be the one to ask but over 2.0 to me your loosing transmit signal. At 2.5 your really cutting it down. I personally dont like to run anyting over a 2. I"ve seen them go right on past 3 when there is more than several foot chopped off but again, the gentleman thats the ham operator should know his stuff. Years ago I was into that cb stuff , liniers, towers with 2000 watt bace stations and played with all types of antennas. You guys had a thread about taking down trees and were having fun about the good old boys that climbed and spitting beer on the counter. I posted a picture of a guy climbing a tree and enjoyed the thread with you. I think I installed every cb antenna that was in a tree for 80 miles around the house back in the 70's and 80's. Use to be good money... On the whips on cb, where they are non adjustable antenna's the coax lenght is where you adjust your swr. Every antenna came with instructions on the lenght you needed.. Start trimming in 3 inchs on that and you could watch the swr slowly change. The gentleman that said three foot? By then and again this is from what I have seen, the swr is at 2 or better up from a 1.3 or 1.5 Thats on 26 to 30 and in the 150's on vhf. I have seen. When I lived in Lake Waccamaw I ran a 150 wattt vhf on of course FM and I had the swr to 1.6 with that much power on a standard Shakespear antenna. Vhf is a shorter antenna for highter freq. and I just want to know what the difference is on the whips. There stright through elements no bace load and non adjustable. Other than the lenght of the antenna which again is made for the freq. to me, and again just asking, I see no difference in how our Marina 156 meg antenna is made. This Balance??? is what has me. How from the bottom of the antenna to the top does it balance when there is no coil. How does it stay matched when their is no bace coil to offset lenght cut off the coax. ? Bace coils or top loaded or coils are wire that is wrapped to shorten the height of the antenna. Making it where the antenna does not have to be extended higher to be at a certain freq. Our vhf whips are not top loaded and thats the same fix as bace loaded but at the highest point. Vhf antenna's are stright through shaft unless I'm wrong, which again I'm asking for a open answer..... In other words, this wondering mind wants to know. ;?
I have called and ask shakespear myself long ago and the "Balance" was the whip and lenght coax together. What has changed???
PS.. Never spit been on a counter.. Snapper head and I got a good laugh on that one.

Last edited by liveaboard74; 10-02-2009 at 04:54 AM.
Old 10-02-2009, 06:12 AM
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a quarter wave on CB is 102" and a quarter wave on marine VHF is about 18". A balanced antenna essentially has a quarter wave to the center conductor and a quarter wave to the shielding, creating a dipole (although there are many other types of balanced antennas). That's the entire antenna.
A marine radio is designed to "see" a 50 ohm load. The antenna is manufactured to present that 50 ohm load. The 50 ohm coaxial cable becomes nothing more than an invisible extension of the connector on the back of the radio.
Old 10-02-2009, 06:39 AM
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respect your answer, understand it and thank you but have you personally never seen the swr rise when the coax has been shortened. ? ; Also something in my experence when someone has cut it way back, the first thing I notice is there not receiving as meny weather stations as I am but that has to do with the receive.
It would be wonderful if you didn't have to have but 3 to 4 foot of line to the radio mounted in the top e box , and your saying it does not affect the trans, or receive?
There have been a few as mentione that I had to add line back to bring the swr down. Was that a bad antenna?
Old 10-02-2009, 06:50 AM
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Originally Posted by liveaboard74 View Post
There have been a few as mentione that I had to add line back to bring the swr down. What that a bad antenna?
Without using an antenna analyzer, you can't tell. Because there ARE soldered connections inside the antenna shell, they certainly can fail.

Almost all problems I have seen with marine radios have been caused by bad PL-259 connections. Cold solder joints, hairs from the shielding shorting to the center conductor, corrosion of the shielding, no solder to the center conductor, melted dielectric from too MUCH heat... It's the first place to look when there's a problem.

YMMV.
Old 10-02-2009, 06:58 AM
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Originally Posted by t3rockhall View Post
Almost all problems I have seen with marine radios have been caused by bad PL-259 connections. Cold solder joints, hairs from the shielding shorting to the center conductor, corrosion of the shielding, no solder to the center conductor, melted dielectric from too MUCH heat... It's the first place to look when there's a problem. .
Yep. Reinforces my post on another thread about electrical connections. The average Joe does not know how to solder. Not enough heat, too much heat, failed to clean the surfaces, used the wrong kind of solder, no flux or the wrong kind of flux ..............

That highlights the one advantage of the "Digital" brand antennas - a pre soldered "mini plug" that connects to a standard plug after the cable is installed.
Old 10-02-2009, 07:14 AM
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Originally Posted by t3rockhall View Post
Without using an antenna analyzer, you can't tell. Because there ARE soldered connections inside the antenna shell, they certainly can fail.

Almost all problems I have seen with marine radios have been caused by bad PL-259 connections. Cold solder joints, hairs from the shielding shorting to the center conductor, corrosion of the shielding, no solder to the center conductor, melted dielectric from too MUCH heat... It's the first place to look when there's a problem.

YMMV.
What you call center I call grounding and yes that I have seen a lot with no solder.
What are your personal view on the digitial antennas. ?
Old 10-02-2009, 07:45 AM
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Originally Posted by liveaboard74 View Post
What you call center I call grounding and yes that I have seen a lot with no solder.
What are your personal view on the digitial antennas. ?
Well, if you call the center conductor on a PL-259 plug "grounding", you have a lot to learn about electronics.

The center conductor will not be soldered on a "solderless" connector. Personally, I don't think much of these, but they are better than a soldered connector installed by someone who does not know how to solder correctly.
Old 10-02-2009, 08:37 AM
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Originally Posted by rwidman View Post
Well, if you call the center conductor on a PL-259 plug "grounding", you have a lot to learn about electronics.

The center conductor will not be soldered on a "solderless" connector. Personally, I don't think much of these, but they are better than a soldered connector installed by someone who does not know how to solder correctly.
Where you solder the ground wires where the several holes are around the plug. Thats what we call the grounding. RELAX amego. It will be ok. hahah
Old 10-02-2009, 04:18 PM
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Originally Posted by liveaboard74 View Post
Where you solder the ground wires where the several holes are around the plug. Thats what we call the grounding. RELAX amego. It will be ok. hahah
Well, that's not what you posted above.

Perhaps English is not your first language? ;?
Old 10-02-2009, 04:51 PM
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Originally Posted by rwidman View Post
Well, that's not what you posted above.

Perhaps English is not your first language? ;?
Carolina. farm boy. but we are different. Have a great evening....
Old 10-02-2009, 04:57 PM
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Years ago I was into that cb stuff , liniers, towers with 2000 watt bace stations and played with all types of antennas.
says it all.

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