Topband: Would like info on "Snake Antenna"

[Fred Hopengarten]

From:
Fred Hopengarten  K1VR               781/259-0088
Six Willarch Road
Lincoln, MA 01773-5105
permanent e-mail address:  fhopengarten@mba1972.hbs.edu
if sending attachments:  k1vr@gis.net

KV4FZ writes:

>I don't know if the snake antenna is used today at all but I would 
>like some basic construction information. 

From: Ward Silver <hwardsil@wolfenet.com>

Because I got a lot of request for details of the W0CM Snake antenna...


The W0CM Snake is described in detail in the August 96 issue of the
Lowband Monitor.

To summarize:

			coax				  coax
	_____________________________________    ____________________
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
    |	_____________________________________   
____________________
    |   1 				    2    3                  4
    |			"A"				   "B"
    |
    |
    |                      125' ground radial
    o----------------------------------------------------------------
    G
    G
    G - ground rod
    G
    G
    G

The antenna is made from coax...I used RG-58C/U.

		Foam	Solid	Dielectric
Section A -     100'     88'    

Section B -      25'     37'

Total		125'    125'


At points 2, 3, and 4...solder the braid and shield together.  Yes, that
makes section B look like a big fat piece of wire...just do it :-) 
Solder sections A and B together at points 2 and 3.

The feedpoint (point 1) is tricky - connect the center conductor of the
coax to your receiver to the SHIELD of the section A coax at point 1. 
Connect the shield of the coax to your receiver to the CENTER CONDUCTOR
of the section A coax at point 1.  Ground the CENTER CONDUCTOR of the
section A coax at point 1 to the ground rod.

Support the whole thing 8' or so above the ground and enjoy!

I haven't got the theory figured out yet, but it works for me.

Ward N0AX
===========================================================
From: Ward Silver <hwardsil@wolfenet.com>
Subject: TopBand: Snake Ant Errata & Clarifications

On Wed, 8 Jan 1997 W7lr@aol.com wrote:

> Some questions.
> 1) If foam coax, a= 100', B= 25'?  If solid dielectric coax, A=88',
B=37'?

Right.

> 2) you say at points 2,3,4 solder braid and shield together.  Doesn't
braid=shield?

Ack!  At points 2,3,4 solder *center conductor* and shield
together...sorry, flying fingers in a hurry...mea culpa.

> 3) What does the ground radial connect with, if anything?

The single radial wire connects to the ground rod, runs along the ground
under the antenna (mine's not buried, the orig. article says to bury, but
not deeply), and is open at the end away from the feedpoint.

> 4) How well does it work, or compare to tx ant, or other types of rx
ant?

It has a much better s/n ratio than my inverted-L, and compares about the
same to my hardline loop, with higher signal levels than the loop.  I'm
building a preamp for the loop and will have a better comparison later.

> Do you know its pattern, and "gain"?

No.  The original article indicates directivity off the "ends", so I
assume it's bidirectional.  Mine runs E/W and hears JA's and VK6HD just
fine.  I'm going to install another to the NE, so will report further
results when available.  Look for an article in one of the magazines,
eventually.

> I've tried several rx antennas but mostly go back to my tx ant abt
99.9% of the time.  The only rx ant that has helped at all is the K6STI
square loop.  I have one 50' on a side, and at times it really helps in
the morning. In the evening it is worthless.  I have a 300' Beverage but
doesn't seem to  hardly ever help.

I'm finding that sometimes the loop is better (stateside to the East) and
sometimes the snake is better - long haul stuff.  The loop heard GM3POI
with better s/n ratio.  Given the discussion on modes of propagation,
it's clear that one "needs" high-angle and low-angle antennas to cover
the changing arrival angles, especially as the band opens and closes,
which is of particular interest in marginal conditions.

Of course, what all this rx antenna improvement leads to is the need for
more tx signal to work the new stuff that I can hear.  Or more patience
to put up with getting stomped :-)

Ward N0AX


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