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Old 21 November 2010, 11:51   #31
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Originally Posted by Richard Selman View Post
New aerial bought.

With the height extended by the A-frame, the coax does not reach the set. Problem with these aerials is that the coax is captive in the aerial. Would there be any major problem with extending the length by 2m or so on top of the 6m ish it comes with providing I do a decent splice or does this unbalance the aerial?

Richard
You could try a BNC-BNC join or a PL259 join if need be. Don't use spit and tape else all hell will break loose. In any case, cover the join in Sekafix and make sure it stays in the console or out the elements somewhere.
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Old 21 November 2010, 11:54   #32
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Quote:
Originally Posted by Richard Selman View Post
New aerial bought.

With the height extended by the A-frame, the coax does not reach the set. Problem with these aerials is that the coax is captive in the aerial. Would there be any major problem with extending the length by 2m or so on top of the 6m ish it comes with providing I do a decent splice or does this unbalance the aerial?

Richard
No problem at all. I have to do the same. What did you buy in the end?
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Old 21 November 2010, 12:26   #33
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Quote:
Originally Posted by Richard Selman View Post
New aerial bought.

With the height extended by the A-frame, the coax does not reach the set. Problem with these aerials is that the coax is captive in the aerial. Would there be any major problem with extending the length by 2m or so on top of the 6m ish it comes with providing I do a decent splice or does this unbalance the aerial?

Richard
This type of aerial has always been a pet hate of mine. Apart from the PITA of not being able to disconnect the aerial from the cable, they don't lend themselves to good performance.

The cable you have there is called RG58, it's just about the worst performing 50 ohm coax available. The reason the aerial comes with such a short length is because it's generally accepted that any longer length would have an unacceptable amount of signal loss.

For me personally, I like to get the maximum possible performance from my VHF which is why I use a good quality antenna with a connector at the base, coupled with a good quality mini-RG8 coax.

You could extend the cable you have, it won't damage your equipment or anything, but don't expect to get the kind of range your radio is actually capable of.
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Old 22 November 2010, 03:17   #34
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Quote:
Originally Posted by Richard Selman View Post
New aerial bought.

With the height extended by the A-frame, the coax does not reach the set. Problem with these aerials is that the coax is captive in the aerial. Would there be any major problem with extending the length by 2m or so on top of the 6m ish it comes with providing I do a decent splice or does this unbalance the aerial?

Richard
I was always told at Transmission School (Comms) that each connected break in the cable created a 3db loss. This is the same as changing your 2.7metre ant for a 1m ant. Breaks also cause reflections again. However it is acceptable to put one in. I would put it in a IP68 box or such.

My wife bought me a 2.7 metre whip with 12m of cable and they delivered it to her office. Bit of a job getting it home though.

Gary
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Old 22 November 2010, 04:04   #35
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My wife bought me a 2.7 metre whip with 12m of cable and they delivered it to her office. Bit of a job getting it home though.

Gary
Be popular with that at rush hour on the Tube
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Old 22 November 2010, 09:55   #36
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Martini - what aerial would I be better using?

Cheers

Richard
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Old 22 November 2010, 11:50   #37
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Originally Posted by Richard Selman View Post
Martini - what aerial would I be better using?

Cheers

Richard
Richard, mines made in Norway by a company called Comrod, bulletproof but expensive!

If you're thinking about taking your new one back and replacing it with something else, my advice would be to speak to Malthouse on here. He's quite knowledgable on antennas and can do you a very good deal on a new one. You might not get a reply for a couple of days though, he's meant to be on a yacht delivery at the mo.

As for the cable, the most suitable would be mini-8 (aka RG8x), very low loss for it's size, RG213 performs better but it's half inch diameter and doesn't like going round corners and through conduits! After much searching the best one I've found is made by Ancor. It has 96% braid which is better than most and reduces the signal loss. It also has a tinned centre conductor as well as tinned braid which improves corrosion resistance. It's available at various places but I buy all my cable from a US company called Genuinedealz.

Moving on to connectors There's a small UK firm called WH Westlake that do a good quality PL259 and can supply a reducer to suit the Mini-8 cable. They also do a PL259 that's specifically for mini-8 but don't buy this as it's the screw on type which is no good. Connectors really need to be soldered, if you're going to all the trouble of sourcing the right components, you don't want to spoil it by using screw-ons.

As for the soldering, there's a right way to do it and several wrong ways. Sounds extreme but if you don't feel up to it and don't know anyone who does, you could run the cable, cut to length, then post it with connectors to me. I'm happy to solder them for you FOC. In fact I'm fairly sure I've got some 259's in stock, I'd just charge you what they cost me plus postage back.

Seems like a lot of work for something you may hardly use but IMO apart from your lifejacket, your VHF is probably the most important bit of safety equipment onboard.

A very wise, old engineering tutor once told me "All things are only as strong as their weakest point." Remembering this statement has served me well throughout my career as a steel fabricator as well as many other circumstances!
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Old 22 November 2010, 12:42   #38
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My drystack broke mine for me trying to fit my boat into a different (smaller) slot ... didnt even attempt at fixing it as it wasn't worth it, replaced it at a cost of 60.
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Old 23 November 2010, 06:11   #39
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Thanks for the offer but the cable will be run through the A-frame which is now a part of the boat......

Ok with a soldering iron and my dad's an expert (built electronic gear for a living).

Does this cover the technique?

http://www.scribd.com/doc/8511808/PL...lation-on-RG8X

What diameter is RG-8X?

Cheers

Richard
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Old 23 November 2010, 07:58   #40
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That's the way, excellent article there

Note the comment re soldering iron size, I've got a 100w and really struggle. Bigger the better.

RG8x is 6.1mm iirc
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