SSB Antenna

[Jerry Peters]

I have been researching SSB installation issues and am left with a couple of
questions.

First, antenna installation. I intent to use a long wire through a tuner to
operate on HF. I intend to use an insulated shroud (I have a cat with no
backstay) with a short feed from the tuner. I have always believed that the
feed wire should be seaparated from the rigging before it reaches the
connection point to reduce capacitive reactance. I have accomplished this
in the past with 2" spacers holding the wire off of the shroud until it
reached the connection point. Recently, I read a credible opinion that
separation of an inch or two is irrelevant at high frequencies because to
eliminate all capacitive reactance the seaparation would have to be meters.
The capacitive reactance that does exist can be accomodated with the tuner.
If this is true I would prefer to directly attach a long insulated wire to
the shroud - perhaps tape it over a 25 foot length. It would be out of the
way, safe from rf burn risk and would not require the installation of
rigging isolators which introduce mechanical weakness and expense.

My second set of questions relate to ground plane/counterpoise installation
but I'll hold of on those quetions for the moment.

Thanks for your help.

 

[Jerry Peters]

Hi Chuck,

No you didn't miss the boat but I need to clarify. My intent is to have a
permanent long wire antenna installed without having to "break" the rigging
with insulators. I know I can haul a wire up with a halyard but I want it
permanently available. I think that the most out of the way place to
permanently raise a longwire is along the shroud. I'm not very worried
about rf burn because I can be careful and/or insulate the shroud at the
level that is likely to be touched. I am more concerned about loss of
effective power due to reactive interaction with the grounded shroud.

Any thoughts?

 

[Bruce in Alaska]

I have been researching SSB installation issues and am left with a couple of
questions.

First, antenna installation. I intent to use a long wire through a tuner to
operate on HF. I intend to use an insulated shroud (I have a cat with no
backstay) with a short feed from the tuner. I have always believed that the
feed wire should be seaparated from the rigging before it reaches the
connection point to reduce capacitive reactance. I have accomplished this
in the past with 2" spacers holding the wire off of the shroud until it
reached the connection point. Recently, I read a credible opinion that
separation of an inch or two is irrelevant at high frequencies because to
eliminate all capacitive reactance the seaparation would have to be meters.
The capacitive reactance that does exist can be accomodated with the tuner.
If this is true I would prefer to directly attach a long insulated wire to
the shroud - perhaps tape it over a 25 foot length. It would be out of the
way, safe from rf burn risk and would not require the installation of
rigging isolators which introduce mechanical weakness and expense.

My second set of questions relate to ground plane/counterpoise installation
but I'll hold of on those quetions for the moment.

Thanks for your help.

Jerry,
You have designed the system correctly for most situations by having
the feedline standing off the grounded part of the shroud line, to
eliminate a big output capacitance for the tuner to deal with. The
addition of external Capacitance to modern autotuners will cause them to
"Thrash around" a lot more while trying to tune anywhere close to the
1/2 wave resonace of the antenna. Autotuners just don't have the brains
to do this tuning job well if they are presented with external output
capacitance. I would worry more about that than having a crewperson
"burned by RF" while transmitting. It just doesn't happen if the crew
is properly trained and instructed. On most plastic vessels they just
become part of the antenna and detune things a bit, because they aren't
really grounded if they are just standing on the deck, and happen to
grab the antenna shroud while the transmitter is active.

Goggle this group for a complete course on designing a LOW IMPEDANCE
RF Ground System for MF?HF Operations.


Bruce in alaska