[ICOM] AH-4 Antenna Designs

[David J. Ring, Jr.]

John,

Is the number for the 80 meter 100 foot long dipole correct?

-5.2 dBD for the loss of 20 feet of wire seems a bit extreme to me. 
Wouldn't it be "0" dBD if it were 20 foot longer, or am I missing something?

73

David N1EA
----- Original Message ----- 
From: "JohnD" <wm7a at cox.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Wednesday, November 10, 2004 10:36 AM
Subject: RE: [ICOM] AH-4 Antenna Designs


Jon,

There are a couple of things to consider: gain, noise.

With respect to gain, I did some quick EZNEC simulations on the various
bands assuming average ground (Sommerfield-Norton method)and a 15 degree
elevation angle. The rough results are as follows.

Band Inv L Dipole
80M -6.5 dBd -5.2 dBd
40M -3.1 dBd -1.2 dBd
20M 2.2 dBd 4.2 dBd
15M          4.4 dBd 7.0 dBd
10M 5.8 dBd     7.0 dBd

The vertical (really an inverted L) will probably pick up more man made
noise than the dipole because the inverted L has some vertical polarization.

I will send you some pictures of the patterns for these two antennas so you
can look at the patterns, but it looks like the dipole is the best choice
because of its greater gain and lower noise characteristics.

John DeRuiter, WM7A
http://members.cox.net/wm7a/

-----Original Message-----
From: icom-bounces at mailman.qth.net
[mailto:icom-bounces at mailman.qth.net]On Behalf Of Jon W0AMT
Sent: Wednesday, November 10, 2004 12:28 AM
To: icom at mailman.qth.net
Subject: [ICOM] AH-4 Antenna Designs


Just re-subscribed to the list after being off for awhile.

I am planning to install put up an AH-4 driven antenna in the next week
or so.  I have 2 options:

#1 I can connect the AH-4 ground to about 25 ground radials that are on
average 30 feet long each with 2 that are about 70 feet.  The antenna
would be a 115 ft long wire with about 30 feet vertical and the rest
would be diagonal or flat.

#2 Use the AH-4 to feed a 100 foot dipole at 40 feet with about 30 feet
of 450 ohm ladder line.

Any thoughts on what design will work better with the AH-4?

Thanks for the help

73, Jon
W0AMT


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----
Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
Icom Users Net: Sundays, 1700Z, 14.316 MHz
Icom FAQ: http://www.qsl.net/icom/


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