VHF antenna recommendation

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Scubadoo

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Can anyone recommend a VHF antenna to fit onto my radar arch, so far I have come across various makes including Glomax, Vtronix etc. but simply no idea which is best in terms of quality and performance.
 
Scubadoo said:
Can anyone recommend a VHF antenna to fit onto my radar arch, so far I have come across various makes including Glomax, Vtronix etc. but simply no idea which is best in terms of quality and performance.
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Glomax are good although most of them are similar in construction. Whichever you buy, make sure it is installed properly and it's checked with a swr bridge. It's an important part of the setup.
Dave
 
I have had 2 glowmax areials and they are good for the first 2 years then they slowly loose there range. I would recommend Shakespeare aerials you will have to buy on line as I have never seen them in a shop. Very big in America these aerials if you look on line there is plenty of info . I had a 17ft boat with one on and I was at the back of the isle of Wight just off bembridge and I could here Portland coast guard and also that same day I heard a transmission from one of the channel islands . I doubt that I could transmit that far but it just shows that these aerials are good.
 
jamie langstone said:
I have had 2 glowmax areials and they are good for the first 2 years then they slowly loose there range. I would recommend Shakespeare aerials you will have to buy on line as I have never seen them in a shop. Very big in America these aerials if you look on line there is plenty of info . I had a 17ft boat with one on and I was at the back of the isle of Wight just off bembridge and I could here Portland coast guard and also that same day I heard a transmission from one of the channel islands . I doubt that I could transmit that far but it just shows that these aerials are good.
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Vertical antennas (based on the good old dipole) are simple in design and have very little to go wrong unless they are damaged or have moisture ingress. For an aerial to 'lose range' there must be something significantly wrong with the installation and is usually damaged feeder with subsequent moisture ingress although very easy to check. Never had problems with glomax and I test mine every year (in all fairness only one of the two is a glomax) although all feeders are through stuffing glands so no way to get damaged, something people are often not aware of. There are a significant number of factors which can affect propagation so I'm sorry but the comments above are probably nothing whatsoever to do with the aerial but more to do with propagation. I've been a radio amateur for the last 38 years and used to be a radio engineer and aerial rigger (radio masts) so a little meticulous in the respect I show my VHF!
Therefore in answer to the original Op, get a good quality product, install it correctly, keep the feeder as short as possible and if it needs to be long don't use the usually UR43 that peeps often use, the insertion losses significantly outweigh the additional gain from the extra height. Regularly check the installation with a power bridge or swr bridge.
 
boatingdave said:
Vertical antennas (based on the good old dipole) are simple in design and have very little to go wrong unless they are damaged or have moisture ingress. For an aerial to 'lose range' there must be something significantly wrong with the installation and is usually damaged feeder with subsequent moisture ingress although very easy to check. Never had problems with glomax and I test mine every year (in all fairness only one of the two is a glomax) although all feeders are through stuffing glands so no way to get damaged, something people are often not aware of. There are a significant number of factors which can affect propagation so I'm sorry but the comments above are probably nothing whatsoever to do with the aerial but more to do with propagation. I've been a radio amateur for the last 38 years and used to be a radio engineer and aerial rigger (radio masts) so a little meticulous in the respect I show my VHF!
Therefore in answer to the original Op, get a good quality product, install it correctly, keep the feeder as short as possible and if it needs to be long don't use the usually UR43 that peeps often use, the insertion losses significantly outweigh the additional gain from the extra height. Regularly check the installation with a power bridge or swr bridge.
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I can only go on my experience with glomax. The interesting thing in your comment on installation is that the Shakespeare was installed on the same boat and on the same way but lasted for 7 years but I then sold the boat .
 
jamie langstone said:
I can only go on my experience with glomax. The interesting thing in your comment on installation is that the Shakespeare was installed on the same boat and on the same way but lasted for 7 years but I then sold the boat .
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Shakespeare are good quality Jamie, can't dispute that ;-). Maybe I've just been lucky with glomax I've had? Metz are also popular it seems. My point to the op really is don't skimp, there are some obviously poor quality ones out there and they need to be checked, not fit and forget. The Shakespeare 6' colinear gives 9dB gain (applies to transmit power and receive signal) so for 10w in should be around 80w Effective radiated power (ERP) less feeder and connector losses so maybe you could have spoken with the stations you heard! Theoretically if two stations have balance receiver versus output, if you can hear them they should be able to hear you.
 
For a power boat that doesn't enjoy the benefit of a mast on which to mount the antenna you should still try to get the antenna as high up as possible - height trumps everything. Use good quality tinned cable in a marine environment and make good connections. Most antenna problems are caused by water ingress and dodgy connections.

A tall fibreglass antenna has higher gain than a shorter stainless whip but it also has a focused radiation pattern that is not really suitable on the rocking, rolling base that is a boat at sea. The broad radiation pattern of a 1m whip on a pole is the best of both worlds.

Here's some light reading matter on antennas for boats:
http://www.saltyjohn.co.uk/resources/Marine%20VHF%20Antennas%20aerials%20and%20their%20installation.pdf

We're the European distributors for Metz antennas - so I declare a commercial interest in this subject.
 
That's why fibreglass high gain antennas are better close to the pivot point on a fibreglass power boat and a simple quarter wave with low loss feeder (that's the bit people forget) on a metal mast (ground plane) is better for an omnidirectional generality. You could also get in to the discussion around phased stacks and polar diagrams, thermal ducts, temperature inversions and all the other myriad of influences, picking the right antenna is quite specialist as you know but a good rule of thumb as above will suit most people.
Height is important as you say, an increase from 15' to 30' may give gain of 6dB but then it's reduced by feeder losses. Of course at circa 165MHz it's not so critical but still important. Most antennas come with RG43 or similar. This could be a long thread which wasn't the intention :-)
 
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Dave,

Not really the place for this but why do they use RG43, I wasn't familiar with that coax and only found one site listing spec's and it listed rg43 as having a nominal impedance of 95 ohms. My antenna theory is rather rusty, why not a 50 ohm coax? May be I'm off base and found duff information.

Richard
 
I like the look of the Metz although its a lot cheaper in the USA so might pick one up that way. However, my previous aerials have had the cable moulded to the aerial so that the connection is waterproof. The Metz needs a separate cable and then has the connector in an exposed location. Would the connector (and eventually the co-ax) fill with water?.

Martin
 
whichever one you choose, keep the antenna upright for the best possible performance. The number of boaters who see an antenna as a fashion item to be swept back from the radar arch to make it look streamlined is ridiculous
 
RIN said:
whichever one you choose, keep the antenna upright for the best possible performance.
The number of boaters who see an antenna as a fashion item to be swept back from the radar arch to make it look streamlined is ridiculous
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+1.
Re. brands, if you look at Glomex, consider also their professional line.
Not cheap, but you get what you pay for, both in terms of performance and durability.
 
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