Ssb + end fed antenna

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marcot

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I have purchased an end fed antenna complete with a 9:1 Unun . It must be used with an ATU to get a perfect match on all bands. The end fed has a pl 259 but the ATU Icom 130 has a wing nut on top for the antenna.
How can I couple the two?
 
I agree with VIc. I am not familiar with the term Unun. But I imagine it is an unballanced (to antenna) to unballanced (to coax cable) matching device for an antenna that it tuned to a specific frequency. Hence no good for the wide range of frequencies you need for marine or ham long range HF communication. As Vic says discard the Unun and connect the ATU with plain heavy wire to the antenna. This wire should be as short as possible as it will become part of the antenna. it needs to be well insulated and use stand off insulators to keep it clear of any structure with insulators where it goes through the deck. The inner and insulation of heavy RG8 10mm coax is good having high voltage insulation.
When Op describes the antenna as "end fed" one imagines a piece of wire with insulators each end. It is likely that the antenna is itself not much use on a boat. You will more likely use the back stay in some form as the antenna. ie the stainless steel wire with insulators or more modern approach is dyneema backstay with a thin wire fed in under the sheath and emerging before the bottom attachment. Stopping short of the top end of the dyneema. The wire antenna is usually about 10 metres long. The length can be too long for some frequencies with some tuners. So if you get problems on some bands try a shorter or longer antenna.
If OP means a base mounted whip (pole) antenna which can be less efficient than a backstay but works a lot better if mast comes down. Then that antenna should be fine connected to the ATU.
In my limited experience in boats it is the earthing of the ATU that is most often neglected and most critical. A friend with some radio skills fitted a HF SSB set. When he transmitted it lit up all the LED light indicators on the panel with his speach. He thought it must be working well. In fact RF power was not getting out so much as buzzing around inside his gRP boat. It had very poor performance. good luck with the installation olewill
 
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An UnUn is an impedance transformer, in this case between 50 and 450 ohms.
The advice to remove the UnUn and connect directly to the antenna is good, if possible; the tuner (matcher) should take care of the impedance matching.
If you can't remove the UnUn, then a bit of coax connecting the core of the pl259 to the wingnut on top and the screen to the ground terminal on the bottom will work, but probably not very well.

@marcot, do you have a link to the antenna you've bought?
 
Agree that you don't need an Unun. Our ATU was connected to the wire that goes out the hull to the aerial by copper foil about 8 inches wide, it was folded in a V shape to fit at both ends.
 
The Icom ATU will accept an unbalanced antenna, that's what it is for.

It needs an antenna and a ground. Be sure to have a good ground plane.

There is a lot of useful info on Bob Smiths web sites, yacht com and sail com.

You will need a long range license and a good familiarisation on your kit.

Assume you realise you need to retune the antenna every time you change frequency..

Tony.
 
Yep, bin the UnUn; although you've then spent quite a lot of money on plain wire... c'est la vie
 
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Between the ATU antenna terminal and the long wire ( commonly the backstay) use only wire. Definitely NOT coax with the outer grounded. This will simply add capacitance between ground and antenna terminal. This wire should be well insulated, thick coax inner is not bad, other high voltage cables are often recommended, I would suggest 2.5mm2 as a minimum.
The wire from the ATU to the backstay is part of the antenna. It can carry high or low current and be at high or low voltage depending on the frequency in use and the antenna length.
Connect the ATU to a a good ground with wide copper strip (50mm+).
I am not going to enter the debate on what makes a good ground, that is the radio equivalent of what is the best anchor!
 
Chalker said:
Between the ATU antenna terminal and the long wire ( commonly the backstay) use only wire. Definitely NOT coax with the outer grounded. This will simply add capacitance between ground and antenna terminal. This wire should be well insulated, thick coax inner is not bad, other high voltage cables are often recommended, I would suggest 2.5mm2 as a minimum.
The wire from the ATU to the backstay is part of the antenna. It can carry high or low current and be at high or low voltage depending on the frequency in use and the antenna length.
Connect the ATU to a a good ground with wide copper strip (50mm+).
I am not going to enter the debate on what makes a good ground, that is the radio equivalent of what is the best anchor!
Click to expand...

Bob Smith at yachtcom carries all the necessary cabling, copper strip etc.
 
>I am not going to enter the debate on what makes a good ground, that is the radio equivalent of what is the best anchor!

It's simple a metal boat or we knew and American cat owner who ordered copper foil the built into the length of both hulls when the boat was built. It had a slightly stronger signal than our steel boat. The bottom line is the ground makes up half the aerial so the bigger the ground the stronger the signal.
 
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