"EMERGENCY FIELD" Design Comments:

 1/2 WAVE COLINEAR "EMERGENCY FIELD" 2 METER 146 MHz FM J-POLE
   Date: Wed, 12 May 1999 16:47:19 -0400
   From: Famille Magnan <famille_magnan@infoteck.qc.ca>
 
I have just about finished the construction of the above mentionned antenna. I have a couple of questions that I'd like
answered.

1- You mention that it is a low power antenna.  What do you mean by low power ? 5, 10, 50 watts ?

2- You mention is performs like a small beam. Please define (in dBd) "like a small beam".

3- What formulas did you use to calculate the different dimensions (coil, 300 ohm twin lead, etc...) ? If this design works
the way you mention, I will probably want to build a UHF version.

4- Speaking of UHF, is there a way to build a dual band colinear antenna like this one ?

Thanks for the cooperation.

--
Stay safe !

73 de VE2JPT

Jean-Pierre
________________________________
Jean-Pierre Magnan
Firefighter
VE2 JPT
Notre-Dame-du-Mont-Carmel FD,  Québec,  Canada   G0X 3J0
email: famille_magnan@infoteck.qc.ca
URL: http://members.tripod.com/~Famille_Magnan/ (Brand new page. Go take a look)

The opinions expressed above are mine, all mine.
But I love to share them  8-)
 

 
        To: famille_magnan@infoteck.qc.ca

1- You mention that it is a low power antenna.  What do you mean by low power ? 5, 10, 50 watts ?{This antenna dose not
work well at power levels above 7 watts.  Will work well with a HT.}

2- You mention is performs like a small beam. Please define (in dBd) "like a small beam".{This statement is somewhat
speculative.  The performance of this antenna design is greater than that of
a normal 1/2 wave, 2 meter, j-pole antenna.  Because of the nature of the mutual impedance between collinear elements the
radiation resistance is increased, but the power gain is not in direct
proportion to the number of elements.  The design of this antenna makes it better than a 1/2 wave but the performance is
not twice that of a 1/2 wave; a little less then twice the power gain.
This antenna dose not perform as well as a 3 element Yagi beam antenna, as far as gain in one direction.  But it is an
omnidirectional antenna with good gain and very portable.  I am unable to
provide you with exact dBd information because of limited resources.}

3- What formulas did you use to calculate the different dimensions (coil, 300 ohm twin lead, etc...) {It is much easier to
steal shamelessly then invent something.  This design is something of
a collage of ideas and "things that just work"  from several sources.  Some from on the WWWeb.  Others from the "ARRL
Antenna Book.  I came up with the idea of the "weed whacker line trick" and
the "steel nuts and wire ties" to put it up in the trees.}

4- Speaking of UHF, is there a way to build a dual band collinear antenna like this one ?{Try this antenna on 70cm!  It
might work.  I have seen several designs of collinear 1/2 wave antennas
that claim to work on both 2 meter and 70cm.  See what happens.  I have not tried this...}

Steve   KB1DIG