[Elecraft] Re: Portable Antennae

[T. David Yarnes]

Hi All,

I would question the assertion that a resonant dipole is the 
absolute best choice.  First of all, I think the original 
query included the condition that the antenna needed to fit 
within "the footprint of the campsite".  Now, we don't know 
how big that footprint is, but I can certainly envision that 
such a footprint wouldn't be that big, particularly in a 
crowded campground.  Putting up a resonant dipole there 
could easily be a problem.

I would concede that a resonant dipole alleviates lots of 
"issues".  But conditions at hand don't always make it the 
best choice.  A dipole that can only be elevated a short 
distance is going to be pretty "NVIS" as a general rule. 
Perhaps that's sufficient, but generally it isn't.  If you 
can get it up in the air a fair amount, all the better. 
Furthermore, if you use balanced feeders and a tuner, you 
have the makings for a nice little multiband system.  But 
again, you may not be radiating in all directions very 
effectively, so maybe that's a problem too.  But clearly a 
dipole that you can elevate somewhat is a good choice.

I find vertical systems to be quite beneficial in many 
situations.  True, there may not be super efficient, but 
sometimes that is really your only option.  Verticals don't 
have to be elevated either, although if you can elevate one 
you might be better off.  And it doesn't have to be elevated 
nearly as much as a dipole--just enough to start chipping 
away at the ground loss issue.  I think the "rule of thumb" 
is to elevate it at least 1/10 wavelength to start getting 
some real benefit.

Vertical antennas tend to have lower take-off 
angles--particularly compared to a dipole at a relatively 
low height.  So, you might work stations closer to you 
better with the dipole, but stations farther away may hear 
you better on the vertical.  For certain you need some 
radials, but they don't necessarily have to be all that 
long.  As we have been told by those more knowledgeable, 
more shorter radials are often better than just a few longer 
ones.

Vertical systems like the MP-1 and PAC-12 are darn good 
little systems.  Admittedly, they could be better, but you 
can also make them better.  You can add more length below 
and above the coil for starters.  Also, you can spread more 
radials than are supplied.  But even as supplied, these 
systems do work, and work fairly well.  I've used both 
systems enough times to attest to that.  Furthermore, I can 
use these systems in lots of situations where a dipole just 
isn't possible.  It's not that I prefer using 
verticals--actually when I can I put up a multiband dipole 
system--but it all depends on circumstances as to which type 
of antenna works better.

I would conclude my comments by posing a hypothetical 
situation to you.  I'm not sure I know the answer, but I 
think I do.  Let's assume you want to work some "DX" on 40 
meters from your campsite.  You are in a situation where you 
could put up a dipole at 30 feet, maybe even 35 feet. 
Alternatively, you could use a limb, or something like that, 
to elevate an MP-1 (enhanced maybe with an extra rod or two 
under the coil, and maybe one or two more on top as well) 
about 20 feet with 4 tuned radials sloping downward.  Which 
antenna has the smaller "footprint" with regard to your 
campsite?  Which one is apt to perform better at working DX? 
Is one substantially harder than the other to put up?

Anybody want to play the game?  Sorry, no prizes for the 
"correct" answers since I can't say for certain what they 
are!

Dave W7AQK


----- Original Message ----- 
From: <jjbbl2 at bellsouth.net>
To: <elecraft at mailman.qth.net>
Sent: Monday, March 03, 2008 4:49 AM
Subject: [Elecraft] Re: Portable Antennae



Ken wrote:

>...I would like to construct a good portable antennae to 
>use while camping

Mike responded:

>...I have played around with multi-band HF antennas for 
>camping and backpacking
for more than 30 years.  I've tried resonant dipoles with 
and without traps,
untuned dipoles fed with balanced line, simple and complex 
verticals, fed-fed
wires, etc.

I have never found anything that works as well as the 
least-expensive of the
above...the resonant dipole.  I have never found anything 
that works as poorly
as verticals....."
......................

Ken, I would agree with Mike! I built this very antenna in a 
short time after Mike sent me a simple diagram/link. I built 
the antenna probably four or five years ago and still use 
it. I used it immediately after Hurricane Katrina with my K1 
and solar panel set up for nearly two weeks after the storm.
I just use a light weight painters pole and bugie cord it to 
a suitable, but stationary anchor. As Mike said, it's easily 
adjustable and it works great given it's simpicity.

Thanks Mike for sending those plans several years ago! And 
Ken, I'd try it. You'll be surprised!

73,
John-KD5EJA
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