SGC coupler to Dipole feedling question
 

Antenna tuners 'like' antennas that are 'too long' better than
antennas that are 'too short'. That doesn't say anything about how
well that 'too long'/'too short' antenna will perform, just that the
average tuner will find it easier to deal with one that's 'too long'.
(Easier to 'cram' more capacitance into a tuner than inductance.) If
this antenna is a doublet, 'balanced', why would you need a
'groundplane'? And while I'd guess that it'll never be 'ideal', the
building is acting as a 'groundplane' anyway, sort of.
- 'Doc

(What am I not understanding about the situation?)


I don't think you are missing anything; your comments sound
reasonable to me. The building is the nearly new local firehouse HQ.
The Chief and staff have outlined very strict parameters for our antenna
location and setup. They fabricated the aluminum mast and will install
it on the side of the building per their own design. Even at that, they
gritted their teeth at the visual impact it has. No stand-off
supported open ladder line for us! We must work with this and I don't
see any feed alternative than coax. The only thing we 'may' have some
flexibility with is the length of the antenna. ( Sorry Cecil, I guess
I should have mentioned that up front ). We are limited to the length
of the side of the building, which I estimated would give us up to 40
feet of element from the top of the mast. However, in hindsignt, I
believe we could at that end point drop some additional length down off
the end for a longer antenna.... would probably give us better operation
on 75 & 80.


Ed

SGC coupler to Dipole feedling question
 

In article . 196,
"Ed_G" wrote:

we will be using an SGC-237 antenna coupler.

Comments?
Ed K7AAT

Ok, first thing, NONE of the Lumped Constant Binary Switch Tuners like
SGC's Knockoff of the SEA Design, will tune ANYWHERE within a few
percent of the Natural Halfwave Point of the antenna. So you must design
the Antenna, so as to move that Halfwave Point to a section of the
HF Spectrum that you NEVER plan on using. Second thing, none of the SGC
Employees around today, were around when this Tuner and it's Operating
software was designed, and most don't have much experience with actual
operational considerations.
Thirdly, After a lot of experimentation with the SEA1612b Series Tuners,
from which the SGC's were plagiarized, when using them to drive a
dipole, there are two schools of thought. One school says that you
should add a 1:1 Balun on the output of the tuner between the RF Ground
Stud, and RF Output Connection to make your Balanced Feed. Second school
says to take the Feedline Coax, Dc Power Lines, and Tuning Feedback
Wire, and wind them, in a Bifilar fashion on an appropriate Torriod
to decouple the Tuner from Radio Feed and connect the dipole to the
RF Ground Stud, and the RF Output Connection.
I have used both Systems on Maritime Mobile Limited Coast Stations,
around Alaska, and find that they both work about Equally Poor. It
should be noted here, however that Alaska is notorious for not having
any kind of decent RF Grounding Soil, so usually this type of Antenna
System works much better than an type of Longwire antenna that needs a
good RF Ground, to work against. Where a GOOD RF Ground is available,
(Salt Water) the Longwire Antenna outperforms the Tuner Driven Dipole,
ever time, but without that GOOD RF Ground, the Tuner Driven Dipole
works better than just about anything else, especially over a wide range
of Frequency Bands available, in both the Maritime and Amateur Radio HF
spectrums.

Bruce in alaska

--
Bruce in alaska
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SGC coupler to Dipole feedling question
 

Ed_G wrote:
They fabricated the aluminum mast and will install
it on the side of the building per their own design.

Get them to fabricate a piece of fiberglass tubing
and all your problems will disappear.
--
73, Cecil http://www.w5dxp.com

SGC coupler to Dipole feedling question
 

Get them to fabricate a piece of fiberglass tubing
and all your problems will disappear.



I fully agree, but we have absolutely no input in regards to the mast
they have provided, and to attempt to persuade them otherwise would only
jeopardize the situaion, so we must accept what they have provided and work
with it.


Ed

SGC coupler to Dipole feedling question
 

Ed_G wrote:
Get them to fabricate a piece of fiberglass tubing
and all your problems will disappear.

I fully agree, but we have absolutely no input in regards to the mast
they have provided, and to attempt to persuade them otherwise would only
jeopardize the situaion, so we must accept what they have provided and work
with it.

There is someone, somewhere, who has the authority to
change the mast from aluminum to fiberglass for the
purpose of multiplying your radiation efficiency by
a factor of 7. I would seek that person out and bend
his/her ear.
--
73, Cecil http://www.w5dxp.com

SGC coupler to Dipole feedling question
 

There is someone, somewhere, who has the authority to
change the mast from aluminum to fiberglass for the
purpose of multiplying your radiation efficiency by
a factor of 7. I would seek that person out and bend
his/her ear.

Believe me, Cecil, that is not the case here. This is a very
small community. The Fire Chief and his Deputy have ultimate authority
over this building. Besides, to attempt to go over his head would
merely jeopardize the good relations we already have which allowed us to
get this far anyway. We'll leave well enough alone and work with what
we have. If it weren't for the fact that we need operation on 3589 &
3980, ~7090 & 7248, and hopefully 60M, we'd probably have just gone with
a trapped wire antenna off this mast instead of using the SGC-237 (
which we already possess).



Thanks.

Ed

SGC coupler to Dipole feedling question
 

Ok, first thing, NONE of the Lumped Constant Binary Switch Tuners like
SGC's Knockoff of the SEA Design, will tune ANYWHERE within a few
percent of the Natural Halfwave Point of the antenna. So you must
design
the Antenna, so as to move that Halfwave Point to a section of the
HF Spectrum that you NEVER plan on using. Second thing, none of the
SGC
Employees around today, were around when this Tuner and it's Operating
software was designed, and most don't have much experience with actual
operational considerations.
Thirdly, After a lot of experimentation with the SEA1612b Series
Tuners,
from which the SGC's were plagiarized, when using them to drive a
dipole, there are two schools of thought. One school says that you
should add a 1:1 Balun on the output of the tuner between the RF
Ground
Stud, and RF Output Connection to make your Balanced Feed. Second
school
says to take the Feedline Coax, Dc Power Lines, and Tuning Feedback
Wire, and wind them, in a Bifilar fashion on an appropriate Torriod
to decouple the Tuner from Radio Feed and connect the dipole to the
RF Ground Stud, and the RF Output Connection.
I have used both Systems on Maritime Mobile Limited Coast Stations,
around Alaska, and find that they both work about Equally Poor. It
should be noted here, however that Alaska is notorious for not having
any kind of decent RF Grounding Soil, so usually this type of Antenna
System works much better than an type of Longwire antenna that needs a
good RF Ground, to work against. Where a GOOD RF Ground is available,
(Salt Water) the Longwire Antenna outperforms the Tuner Driven Dipole,
ever time, but without that GOOD RF Ground, the Tuner Driven Dipole
works better than just about anything else, especially over a wide
range
of Frequency Bands available, in both the Maritime and Amateur Radio
HF
spectrums.

Bruce in alaska


Bruce,

Thanks for the response to my query. I have a couple comments to
these. One, we already own a new SGC-237 coupler, so that is what we
will use. Two, thanks for the info on the SGC personnel.... that
might explain why some of their responses to my emails didn't seem to
make sense... especially their comments about NOT needing any balun.
Three, and more direct to my initial questions, it appears we will be
using coax between the coupler output and the antenna feedpoint.... up
to 20 feet of low loss... we'll just eat the loss. But more
importantly, I had intended, and will proceed along the lines of your
comments on baluns, by installing a 1:1 balun at the input to the
tuner. This will, at least, keep the RF out of the building and our
station location.

thanks.

Ed

SGC coupler to Dipole feedling question
 

Ed_G wrote:
There is someone, somewhere, who has the authority to
change the mast from aluminum to fiberglass for the
purpose of multiplying your radiation efficiency by
a factor of 7. I would seek that person out and bend
his/her ear.

Believe me, Cecil, that is not the case here. This is a very
small community. The Fire Chief and his Deputy have ultimate authority
over this building.

If the goal of those guys is to sabotage amateur
radio communications, they have probably succeeded.
It's like them going to fight a fire with big holes
in the hoses.
--
73, Cecil http://www.w5dxp.com

SGC coupler to Dipole feedling question
 

Thanks for the feedback, John. I imagine that we will end up doing
as you suggested. We WILL test the antenna on the ground with a
temporary mast to see if there are any issues, but we also realize that
things can, and probably will, change when it is permanently mounted on
the building. One of the reasons I am posing these questions here now
is that once the antenna is up, it will be difficult to get the
building personnel ( its a firehouse ) to lower the mast for changes.
Its a rigid one piece aluminum mast that will be bolted at its base to
the building.
===============================
Suggest you fit a pulley at the top of the mast such you can lower and
subsequently change the antenna using a halyard.

Frank GM0CSZ / KN6WH

SGC coupler to Dipole feedling question
 

In article . 196,
"Ed_G" wrote:


Bruce,

Thanks for the response to my query. I have a couple comments to
these. One, we already own a new SGC-237 coupler, so that is what we
will use. Two, thanks for the info on the SGC personnel.... that
might explain why some of their responses to my emails didn't seem to
make sense... especially their comments about NOT needing any balun.
Three, and more direct to my initial questions, it appears we will be
using coax between the coupler output and the antenna feedpoint.... up
to 20 feet of low loss... we'll just eat the loss. But more
importantly, I had intended, and will proceed along the lines of your
comments on baluns, by installing a 1:1 balun at the input to the
tuner. This will, at least, keep the RF out of the building and our
station location.

thanks.

Ed


Ed, you would be Much Better Off, if they would allow you to use (2)
runs of Coax, side by side up the mast, and connect only the Center
Conductor of each, to the tuner, with the shield left open on each end
and sealed against water intrusion. Even if taped to the aluminum mast.
This would provide a much better situation than a single coax feed.
Also if you are stuck with a single coax, then make SURE, that the
shield side of the coax is connected to the Ground Stud of the tuner.

--
Bruce in alaska
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