"Tom Horne" wrote

Thanks to the generosity of a fellow radio club member I now have the
use of a Yaesu FT-1000 (no Suffix). Since it has a built in antenna
tuner, that I'm hoping to use, I need to ask what the best way is to
couple the window line that feeds my folded dipole antenna into a
short; say twenty feet; coaxial feeder from the radio. I used an Icom
AH4 antenna coupler with my FT-857D on this antenna with very good
results. I would guess that I need a balun but which type is a
mystery to me.

So is a balun a good solution to this challenge or should I resort to
the two pieces of coax in parallel that I have read of elsewhere?
When you use the two parallel coax leads do you ground and/or bond the
two shields at the transceiver end? Further since the FT-1000 does
not have obvious balanced feed line terminals would I connect a
balanced feed line to the ground terminal and the the center pin of
the SO239 connector by using say a banana plug.


Tom, I looked up the AH-4. It appears it is to be used only with a
random-length single wire antenna. You cannot feed a ladderline transmission
line to it. So as you already may know, that's out. And you cannot connect
the referenced two pieces of coax directly to the FT-1000. What you must do
is use a transmatch (erroneously called an "antenna tuner") such as any of
the various MFJ "tuners," or those from Palstar, etc., between your
ladderline and your FT-1000. The transmatch you use must accommodate a
balanced line. It can have coax inputs, too, but it must have balanced line
terminals as an available option. The ladderline is fed through your wall
(more on that later) to the transmatch; a length of coax connects the
transmatch to the FT-1000. I run 100 watts and use RG-8X from my transmatch
to my FT-950.

The other way is to use a balun outside your shack. (I think DX Engineering
sells some of these. You would normally find a 4:1 balun, in a weatherproof
container, for this purpose.) The ladderline connects to the balun, and from
the balun you run a SHORT LENGTH of RG-8 type coax (any RG-8 size coax will
do -- but definitely not anything smaller) through the wall to your
transmatch. The swr's can be very high on various bands at the balun, so you
have to use one rated for many thousands of volts to be sure it can handle
the heat. And because the swr's can be high, you want the coax lead through
the wall to be as short as possible -- maybe five feet or less, or try to
keep it under ten to reduce losses as much as possible. By the way, I tried
this method 20 years ago using a Radio Works 4 KV "current" balun to work
with my then MFJ-948 transmatch. Running just 100 watts, that balun heated
up so badly that it was destroyed. So I do not recommend this method.

In any case, you *have* to use a transmatch because your FT-1000 tuner can
handle swr's of only up to 3:1, and, unless you're really lucky, your
transmission line is going to present swr's far higher than that. Thus the
need for the transmatch.

If you want to run the ladderline through the wall, the way I did mine was
to cut a 3" diameter hole in the side of my house, through the vinyl siding
and all that, and insert a 3" PVC tube. I made holes in 3" PVC end caps to
tightly accommodate two lengths of RG-8/U coax of *identical* length (five
feet each, in my case). Outside the house, the ladderline is soldered to the
center conductors of the two lengths of coax. Inside the house, the center
conductors of the other ends of the coax connect to the balanced line
terminals of the transmatch. For good measure, I inserted fiberglass
insulation into the PVC tube. On each end of the PVC, the end caps are
secured, and bugs can't get through. (Also note I attached a 45 degree PVC
elbow to the tube on the outside of the house, pointing it down. That way,
any water that gets on the coax will drip DOWN away from the 3" tube
itself.) OK, what to do with the coax shields? Solder them together at both
ends. Now you have "ladderline" running through the wall, but shielded from
any electrical influences that might be inside the wall. Finally, attach a
length of coax from the transmatch to the FT-1000, and you're all set.

For lightning "protection" I installed, within the ladderline outside, male
and female pairs of banana connectors. One housing contains two plugs, the
other housing contains two jacks. That makes for a nice and quick connect
and disconnect. I think I got them from Mouser Electronics. The width is
just right for 450 ohm line. This makes it easy to disconnect the ladderline
outside the house when I know a storm is approaching, or for times I go away
overnight.

Howard N7SO