Wonderful discussion! :-)


you just shoot a lot of amps though wire that was NEVER
meant to take the amps, this is obvious by the manufacturer
saying not to run 5 watts though it.

No, I didn't do that. I agree, it might have fried the wire or
magnetized the toroid. The problem was all between the outer shell and
the ground lug-washer on the SO239 side of the device. That contact
was not accessible as it was potted in resin. I had already removed
the magnetics. The 15A flowed only through lug-washer and the outer
conductor.


Isn't there a little factors like cutting the Antenna
Wire to the 'right-length' and having the 'correct
length' of Coax Cable that contribute to a good
"Match" : At least for one SW Band ? ~ RHF

The MLB is meant to give a good-enough, install-and-forget, receive-
only match between a 50 ohm line and a random wire whose Z wildly
gyrates between 30-1000 ohm in and out of the complex field. Any RF
transformer turning 50 ohm into 300 to 600 ohm is vastly superior to a
direct connection.

There are receivers that include exactly that kind of transformer
between the inputs for "50 ohm" and "600 ohm" or "wire". I have seen
such transformers working reasonably well all the way between .1 and
30MHz. The MLB is nothing special but works like that, on a 300/1
bandwidth. The Lowe 124-225-250 etc. contain such a transformer, and
work OK down to 30 (thirty) kHz, a 1000/1 bandwidth. By "working" I
just mean that a given signal from a wire antenna produces
dramatically better results when fed via the transformer than direct
to 50 ohm input. That improvement geverally jibes with the source
being hi-Z.

I've never been able to reproduce such broadband behavior in a toroid
I wound myself. The Palomar Associates MLB clone was OK but weaker on
MF-LF. The ICE ununs come in lower and higher frequency range
versions. I have no idea what the trick is in the transformers used by
Lowe and RF-Systems, but it must be very simple, e.g. a mix that
compromises by having a somewhat higher loss all over or by saturating
at low power levels [over 5W ], but that's just a guess. It has to
be smtg that normal 1:9 ununs made with the usual HF mixes don't do
terribly well.

As for transmission: go on a ship, and if it's old enough you might
still even see a nice chunky metal case with the leftover transformer
matching the MF or low-HF random wire to a coax, complete with anti-
flashover insulator. Every time the radio room was removed from the
wire antenna, it made economic sense to deliver the 100-1000W RF by
standard radio guide (coax) than via a special high-voltage, high-
impedance line made wire suspended inside a large copper pipe.

In the real (professional) world NOBODY in at least the last 30 years
tried to cut MF or HF antennas to resonate on a special frequency.
Broadcasting dipole arrays were ~ 2:1, MW (AM) towers (and even VHF-
UHF antennas in space applications back in the day) are roughly sized
for radiation angle requirements, not for natural resonance. A 5/8
lambda vertical is like that.

Professional broadband dipoles normally "guarantee" a SWR mismatch
under 3:1 over 2-30MHz, and I remember UHF space applications with
1:10 SWR on short coax lines that were compensated at the radio end of
short low power and low loss coax runs. In many applications antenna
mismatch is practically irrelevant as long as it does not multiply
losses in the transmission line.

It's a consideration that corresponds to the cos-phi concern in
electric power transmission. A wild mismatch may generate extra
current or voltage that will cause additional Joule loss in conductor
and dielectric. In power transmission, 50-60Hz wavelength is so large
that you don't really get localized voltage peaks and throughs due to
reflected and direct power interference patterns, but at RF you see
that too, so you get both added losses and extra insulation breakage
risk. But if the run is short, and the power is low, both losses and
overvoltages can be safely ignored, and reflection and Z mismatch can
be addressed at the radio end.

In a long coax run, the huge mismatch of a nonresonant wire to a lo-Z
coax is nontrivial, and a transformer can actually nicely cooperate
with an ATU at the other end.

Today's AUTOMATIC ATUs are now routinely placed at the antenna end.
Not needing human attention, it makes sense to move them over there,
in which case a RF transformer becomes irrelevant. Antenna-side MF
transformers on ships are a thing from the indoor manual ATU and early
automatic ATU era.

But even today, antenna side transformers are the rule in the HF
market. That's what you do to improve match between a generally-high
impedance antenna and a low impedance coax of a broadband dipole. The
few rhombics still in use either have a Z-transforming balun or an
extremely low loss and broadly Z-matched balanced HV line. Ditto for
beverages - you could just connect coax and wire, but it would be
lossy, and nobody does it.

The broadband no-transformer no-ATU alternative exists. In practice,
only the military can afford the metal masses of large HF antennas
that have no clear resonance and reasonably narrow Z range without RF
transformer [and w/o resistor... :-P ], like inverted-cone on ground
plane, double-cone dipole, discone. Also (few) hams use log-periodic
rotatables. An MIT dorm used to have a fixed LP all-wire ham antenna,
never heard of a ham using a fixed "half-LP" vertical wire curtain.
Even with such antennas I'd still leave an automatic ATU in line if
already available. And, not coincidentally, such antennas are
generally sized for 13 MHz. Below that it's mostly broadband wire &
transformer country.


"Toss the piece of cr*p and get/wind something decent ... "

Yes, one can surely do that!

((narrower response or you tell me the simple trick for practicable
300:1 width) and/or (heavy, ground level or masthead commercial unit)
and/or ((buying toroid, casing, connectors, strain-relief, sealant)
and (winding, drilling case, installing strain relief, connectors,
soldering, sealing)))

vs.

(solder, glue, seal, use