[Elecraft] Why did I purchase this antenna for the KX3?

[Ron D'Eau Claire]

John, IMX any product that uses "Miracle" in its name isn't, Hi!, especially
when transmitting. You can get away with a much reduced antenna when only
receiving more easily than if you want to transmit. 

The efficiency of any antenna drops as it is made shorter than 1/2
wavelength (130' on 80 meters, 66' on 40 meters, 33' on 20 meters, etc.)

An antenna only 1/4 wavelength long can be pretty nearly as efficient if you
pay close attention to minimizing losses in the ground system if end fed.

Below that the efficiency literally plummets. The drop in efficiency is not
linear but accelerates as the antenna is made shorter. In large measure that
is due to the resistive losses in the antenna and matching network
conductors. 

We know how to avoid those losses. Use a super-conductor for the radiator
and in the matching network. Unfortunately, I don't know where to buy
room-temperature superconductors. Until we can, we're stuck with those
losses.

We're not talking about the resistance your DMM might show. RF flows over
the surface of a conductor, not through it. Currents flow only in the very
outer layers of atoms in a conductor so the resistance at RF is far greater
than your DMM indicates. 

We can minimize those losses by plating all the conductors with silver or
gold. But that costs money and only partly helps. Even so, it's what
high-quality RF circuits use. Another critical point is in the sliding
contacts used in switches, variable capacitors and telescoping antennas.
Under the best of conditions they are lossy. 
Sometimes we must put up with them, but we're paying a big penalty in
efficiency.

The issue with the "Miracle Whip" is that it does not address any of the
loss issues very well. It uses a telescoping whip and inexpensive components
in the matching network. 
 
And then there's the height above ground and distance from surrounding
objects. The closer you are to the ground or other objects the more RF
current is induced in them. That RF is simply lost. You'll hear Hams
referring to it sarcastically as "warming the worms" Hi!

Sometimes we simply must accept the losses to get the portability we need,
but there is no "magic" solution, no new technology, no newly discovered
principles, that will help. 

It rather sounds like one can't get out of their own back yard with a tiny
antenna, but it happens every day. Under the right conditions even a few
thousandths of a watt (milliwatts) getting radiated can be heard over a long
distance. But a larger antenna, at least up to one at least 1/2 wavelength
long and well clear of the ground and other objects, will do much, much
better every time. 

Good luck getting your license! It's a fun hobby. 

73, Ron AC7AC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of John Stears
Sent: Monday, March 05, 2012 12:02 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] Why did I purchase this antenna for the KX3?

Good afternoon, I am a very new (receive only/studying for license)
enthusiast caught up in the excitement here and for the loaded KX3 that I
have on order. Could the group please give me some kind of idea as to
whether this purchase
http://www.universal-radio.com/catalog/hamantht/5046.html was a wise one for
this unit given that I now see it has an antenna already attached to it
(doh!).or is this 'improved'(?) antenna as good as any other (in
2012/regardless of cost) for increasing performance while still keeping the
whole package compact and portable? Thanks for any help as I'll stick with
the stock whip if this product isn't a good match and concentrate my funds
on whatever fixed base setup you guys agree on that is still portable and
most importantly the best on the market as of this year. 

 

 

 

 

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