Wind your own transformers
Discussion on which matching transformers are best suited
for Flag and Pennant antennas.
Flag and Pennant Antenna mail list,
George Maroti: An option for matching your Flag or Pennant
is a Mini-circuits transformer.
I use a Mini-Circuits 16:1 transformer, purchased from Nebraska
More info on this product may be found at the Mini-Circuits
Tom Rauch, W8JI: Mini-Circuits transformers are very easily
overloaded and damaged.
They also can't handle any DC bias on the windings.
They are good small signal transformers in controlled environments,
but I wouldn't use them on antennas in general applications.
Just wait til you get a little 60 Hz AC voltage across the windings!
The Mini-Circuits transformers will cross-modulate the desired
signals. On the 4:1 transformers, as little as 20mA current will
cause core saturation.
While common mode on the feedlines may not be a problem in all
installations, I'd still opt for a much isolation as I could manage.
That goes for Beverages as well as terminated loops (and ground
return half-loops like the Ewe).
An ounce of prevention is better than missing some DX signal close
to noise floor because the system had conducted noise you didn't
know about, or because it decreased directivity of the antenna.
I use ABS boxes for almost all of my stuff, because it is easier
to keep the shield of the cable isolated from the antenna and/or
the antenna's ground.
"Shielding" is not required, and can actually only increase common
mode problems, so the only argument for using metal is life and
the "warm fuzzy feeling" of a mechanically tougher box.
I'm still using ABS boxes from the 70's.
Earl Cunningham, K6SE: I was aware of the Mini-Circuits
16:1 transformer, but I didn't recommend it mainly because of
its tiny size -- even if the windings are not one on top of the
other, they can't be widely-separated.
Tony, N2TK mentioned that also they were useless in the strong
RF environment.at V26B.
K0FF: I have a fine 4 x 4 inch box that has a gasketed
cover (all plastic), and the binding posts can now be replaced
with simple brass screws.
One other point then Earl, is a rope eye still needed?
K6SE: Rope attachment at the feedpoint end of the antenna
is necessary for the Delta configuration of the antenna and for
the point-fed Pennant and Diamond.
With the Flag and the point-terminated Pennant, the box can be
simply taped to the wooden support mast.
The feedpoint end of any of the antenna configurations should
be near the support where the box can be secured with short leads
to the feedpoint.
A short rope tied from the feedpoint insulator to the support
can secure that end of the antenna. This eliminates any strain
on the box which would be present if a rope tie on the box was
The rope should be attached to both holes in the feedpoint insulator
to reduce strain on that item.
Last winter, during our "DXpedition" to a nearby (60 miles)
salt lake bed for the CQ WW 160-meter CW contest, we used a Delta
receiving antenna. A small plastic refrigerator box housed the
transformer, and the rope at the feedpoint corner was tied to
a the hole in one end of the feedpoint insulator. The box was
taped to the insulator. There were no problems with this arrangement
while using the antenna and rotating it. Of course, taping the
box to the insulator was only a temporary arrangement and might
not hold up for a long period of time.
The beauty of the Delta configuation is that it needs
only one 20-foot support and two stakes driven into the ground
and can be easily rotated. It lends itself extremely well to portable
operation and is becoming popular as a receiving antenna for DXpedition
Consideration should be given for the placement of the connections
on the box, so that the box can readily be used with any configuration
of the antenna (Flag, point-fed Pennant, point-terminated Pennant,
Diamond and Delta).
W3DQ: ICE makes a model 185 balun and 180i terminator that
they claim is good for pennant and flag antennas.
The only ones making the correct transformer to my knowledge are
K0FF and K1ZV.
The 180i has taps up to 800 ohms, not the 900+ ohms that people
are suggesting. Likewise the balun taps are different than what
I'd have expected, considering that they are saying these devices
are for pennants and flags.
When I spoke to ICE, tehy said "don't worry, the difference is
only 10 percent" .
The ICE transformers are made primarily for Beverages and are not
well-suited for use in Flags and Pennants.
The 180A is a UN -UN design which has isolated windings for primary
and secondary BUT they tie the "ground" ends together. There is
a lightning discharge suppresser in there as well and a large capacitor
in series with the input winding for DC block - this is all for
static and lightening suppression.
Since the 300 ohm winding is not needed, just open the box and unsolder
the ground connection for the secondary winding. Also unsolder the
300 ohm connection and put the ground connection you lifted onto
the 300 ohm terminal. You now have a BAL-UN 450, 600, and 800 ohm
winding with isolated windings.
If you don't wish to do this yourself ICE will send a new version
to you, the 180I which I think I convinced them to make as a standard
product based on what we just learned.
If you have
any additional questions, contact Mike Koss at ICE (1-800-423-2666)
directly. He is truly interested in the application (for Flags and
products can be ordered on-line at the official
ICE web site Here you will find datasheets as well
as free publications on grounding and beverage antennas.