[BC] Re: Cutting Vs Matching Antenna Vs no code

[DANA PUOPOLO]

A discone covers a very VERY wide frequency range. Essentially, it goes on
forever once past its cutoff (critical) frequency.

-D


------ Original Message ------
Received: 
From: "Richard Fry" <rfry at adams.net>
To: "Broadcast List" <broadcast at radiolists.net>
Subject: [BC] Re: Cutting Vs Matching Antenna Vs no code

Larry Bloomfield:
>As for Antennas, we all know that an antenna is resonate at one
>frequency only. If you intend to change from that frequency, you MUST
>change the electrical length so the transmitter thinks it is the correct
>length - shorter or longer as the frequency you're putting to it is
>higher or lower.
_________________

This can be true-ish for a simple wire dipole or whip, but even then they 
have an acceptably low VSWR over a small range of frequencies with no 
physical change to the antenna, or needing a "matcher."   And even a simple 
dipole can have a fairly wide VSWR bandwidth if the radiator outer diameters 
are suitably large.

Other radiator designs can have a very wide VSWR bandwidth.  Recall that FM 
broadcast Master antennas can have a measured VSWR of 1.1:1 or less across 
the whole FM band (20% bandwidth), using radiators with fixed mechanical 
dimensions.  Some UHF TV transmit antennas cover the whole UHF TV band with 
low VSWR.

RF 



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