[ARC5] Balanced antenna coupling...

[David Bock]

I have made very good use of the "small" and low horizontal loops fed by
simple balanced couplers right at the radio. Years ago I used an Argonaut
with about 1.5 watts SSB output on twenty meters and checked into the county
hunters net from Emmet county Michigan with but a simple loop taped to the
ceiling of the log cabin with but masking tape and a small MFJ tuner. The
net refused to believe that I was running a hair over one watt output. I
have many examples over the last fifty years of such things. So, just get a
nice roll of enameled magnet wire and string it up as high as you can. A few
feet high does well enough for around the country. Of course you can run
more than 1.5 watts output!

In short, the loop tends to work much better than any other compromise
solutions that seem to present themselves for general purpose NVIS or single
hop propagation in my opinion and long history with field antennas. No
issues with the ground radials and the like with the low loop--none are
needed. Just my considered opinion, but use a true balanced coupler and
forget the use baluns or balun ratios. Do not concern yourself with the use
of balanced line. Just keep the lines a few inches apart and where you bring
them into the window use shrink tubing and close the window assuming wood
sashes. Otherwise just get one of the window feed window inserts.

The tuning will be very sharp but very effective. Do not expect to be able
to move much more than a few KHz without touching up the coupler. The length
is not very important respecting resonance.

If you have a split stator variable capacitor, build your own on the cheap.
Mounting it on a wood base such as you can get from a hobby or craft shop is
just fine--if you want to varnish it, fine. Crocodile clips can do yeoman
work in place of an expensive coil switch set. I either wound my coils on
tubes of wood cut from stair rail stock and soldered finishing nails every
couple of turns of insulated wire or used coil stock suitable for up to 100
watts output.

I once ran the Great Lake Emergency net and MIDCARS from Louisville, KY
simply loading up the gutters of an apartment building with the earth ground
connection (center screw) of the power outlet as the counterpoise with a
HW-101. These were on 75 meters and 40 meters respectively and all with the
same antenna. Of course, it was dry outside.

And yes, I have run ARC-5 transmitters the same way (simple wire loops) to
very, very good effect. Again, just use a balanced coupler. Cheap and
effective.

Dave
W8OHS

-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net]On Behalf Of Kenneth G.
Gordon
Sent: Friday, December 26, 2014 12:20 AM
To: AKLDGUY .
Cc: ARC-5 List
Subject: Re: [ARC5] Balanced antenna coupling...


On 25 Dec 2014 at 20:39, AKLDGUY . wrote:

>
> Hi Kenneth
> Sorry for the delayed reply (been out all afternoon).

No sweat: we've been traveling all day anyway. ;-)

> > You might consider making that an inverted-vee dipole,
>
> Nope, there are tenants on the next floor above me. The 5 foot fence
around my
> property is the practical height limit.

Oh, yuck. You're VERY "Antenna Challenged" !!! Gee...

> > However, if you make the link tunable by adding a fairly high
capacitance
> > tuning cap in series with the coil to ground, it will make it
considerably
> > quicker to set up for a particular frequency or band.
>
> Very good suggestion.
>
> > You may wish to make the link coil adjustable for inductance, less
inductance
> > for higher frequencies.
>
> Nope, it's too much like hard work to make something like that, especially
if
> the much easier link tuning cap suggestion above is already implemented.

Yes. I never had to "adjust" my link-coil's inductance either: the "series"
cap
to ground did everything I needed it to. Adjusting that link is a real PITA
(Pain
In The A**) anyway.

> > Actually, if you diagram the entire link-coupling system, including the
coax
> > and the final tank Pi-network circuit, you will find that it is actually
two
> > parallel-tuned circuits that only LOOK series tuned where two of the
tuning
> > capacitors in the link circuit (the Pi-network loading cap and the
> >link-tuning  cap) are in series across the link coil, with the
> >center-connection of those two  capacitors grounded.
>
> But the BC-230 doesn't have a pi-network output. It has a parallel tuned,
series
> fed tuned circuit with an antenna coil wound over the top. The antenna
picks off
> from a movable tap. I see your point though.

Well then, using that "series-tuned" link coil works exceptionally well with
circuits like yours. I use the the link capacitor as the loading capacitor,
and
the final tank capacitor as the plate tuning cap. The action is very similar
to
the use of a modern pi-net. Dip with the final tank tuning cap and load with
the link cap. Works like gangbusters.

>The aim is to have
> fun and play with the BC-230.

Well, believe me, I envy you. I have more or less lusted after those or the
RU/GF set. They look like they would be very serious fun.

Merry Christmas, Neil

Ken W7EKB
______________________________________________________________
ARC5 mailing list
Home: http://mailman.qth.net/mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html