On Sep 5, 3:02 am, wrote:
On Sep 4, 7:04 pm, Highland Ham
wrote:



===================================
A current balun near dipole in the shape of ferrite cylinders or ,when
using RG58 type of coax, 7 - 9 windings of the coax on a larger toroid ,
will ensure no RF interference in the shack /house (eg no RF current
flowing along coax braid)

True. I usually just roll a choke from the coax. You don't need a
toroid for single band use. Or even 20-10 triband use for that
matter.. May have problems trying to do 80-10 well with a single
choke though.

It is even better to use a balanced feeder instead of coax.

Only if one intended to use it for other bands.
For single band use it would probably have a higher system efficiency
using coax, being most that run ladder line use tuners, etc
which add some loss to the system.

You then either need a matching unit for a balance feeder or use a balun
as described above near the transmitter ,connecting coax to feeder
through a dual plastic connecting block .

Dunno, I prefer to keep things simple. I would usually prefer a 50 ohm
radio, feeding a 50 ohm feedline, to a 50 ohm antenna.
Using a 50 ohm radio to a balun or tuner feeding a 450 ohm feedline to
a
50 ohm antenna seems kind of silly to me in comparison, if for a
single
band. But to each his own I guess..
BTW, I have compared the two, and the coax fed always slightly beat
the
ladder line/tuner fed system as far as efficiency on any HF band.
Of course, my coax runs are never over a 100 ft.. Often half that.
But when using a 989c tuner and ladder line, I could never get quite
the
system efficiency vs using coax, even using the most careful tuning
methods.
IE: using the minimum inductance needed to get a match.



Personally I would always use a balanced feeder for any wire antenna.

I'm usually about the opposite. The only time I use ladder line is
if
I intend to use a single wire for multiple bands. In that case, I can
see it.
Or if maybe I had to run a line several hundred feet, but I've
never had to do that yet..
But for single band use, it's going to be very hard to beat the
efficiency of a coax fed system with any type of ladder line system,
unless maybe you use the "Cecil" no tuner method.
And then.. it's more work, and the feedlines have to be off the
ground,
coiled just so, etc..... :/ The coax can be running anywhere. Even
in standing water.. On the lower/mid HF bands where I'm usually at,
the losses using coax are so low as to be a non issue. Trying to
beat the loss by using ladder line is not going to make any noticable
difference as far as the line itself. But.. Adding a matching device
almost always will. I can actually see it on receive just A/B
comparing using the S meter readings as an indicator.
I have no problems with ladder line, but the usual claims of
better performance isn't really true in the majority of cases on HF.
Often, quite the opposite, because of the matching devices usually
used with ladder line systems. Their loss usually overshadows the
slightly lower feedline loss.

Now, on UHF feeding say a TV corner reflector-yagi thing I use for
ATV, I prefer the twin lead.
Unless it gets wet, it's gonna beat most runs of coax as far as the
system loss. In that case, the matching devices don't overshadow
the higher more noticable coax losses at those higher frequencies.
MK

All

Welll once again this proves the theory - two amateurs = three opions.
However, this is a very useful discussion and the 25ft (ish) simple
dipole seems to be the easiest thing to work with and the length is
very achieveable in the space. I therefore have to get to a decision
on what i use in the centre. I estimate from the centre of the antenna
to the shack would be approx 50-75ft max even if i run it neatly
around the walls. I am happy to use an ATU to achieve a perfect match.
So what do i go for?

Secondly, is there an optimal height. My half size G5RV is at the top
of the 30 ft pole so this would need to be below that? Also does it
matter if it is on a slight incline with the lowest part closest to
the house?

Many thanks for all the great advice

Andy