[NLRS] 6m rover antennas

[Jon Platt]

Jerry, I usually ignore the absolute (gain) numbers and base any work on
comparison to a base antenna such as a dipole at the same height, etc.    Is
this approach safe given this issue with NEC programs ?

73's  Jon
W0ZQ

----- Original Message -----
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
To: "Jon Platt" <jon.platt@gte.net>
Cc: "NLRS" <nlrs@mailman.qth.net>
Sent: Sunday, October 13, 2002 10:54 AM
Subject: Re: [NLRS] 6m rover antennas


> All the NEC programs have a subtle error in concept. When working over a
> ground their gain figures in what they claim as dBi, are actually dB
> over half isotropic. E.g. the reference isotropic radiator has only a
> hemisphere of radiation and the energy from the lower hemisphere is
> neglected, knocking the reference down to half power, e.g. -3.0103 dB.
>
> This error of concept makes any antenna simulations over ground show
> twice the gain they show in free space, even when the antenna is at a
> very great elevation.
>
> When I had source code for my Apple ][ for NEC-2, I put in a correction
> for that 3 dB error over a ground plane.
>
> 73, Jerry, K0CQ
> --
> Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
> Reproduction by permission only.