Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uunet!pilchuck!ssc!tad
From: tad@ssc.UUCP (Tad Cook)
Newsgroups: sci.electronics
Subject: Re: TV Antennas, the knob
Summary: impedance
Message-ID: <725@ssc.UUCP>
Date: 2 Jan 91 23:17:21 GMT
References: <14239@mcdphx.phx.mcd.mot.com> <6690003@hpcvaac.cv.hp.com>
Organization: very little
Lines: 24

In article <6690003@hpcvaac.cv.hp.com>, billn@hpcvaac.cv.hp.com (bill nelson) writes:
> 
> Absolutely correct - I believe the primary cause of the impedence variation
> is due to mounting height variation.  I know the effect decreases as the
> height (in wavelengths) increases.  I don't think the 25-40 ft above ground
> level is enough to minimize this factor.

Maybe at HF, but at VHF 25-40 feet above ground without nearby obstructions
should be just fine for minimizing impedance variations.  I have seen
charts in the ARRL Antenna Book which shows impedance variation based
upon height above ideal ground, and they are talking about at a wavelength
or less.  One wavelength at lowest frequency (TV ch2) is something around
17 feet.



Tad Cook
Seattle, WA
Packet: KT7H @ N7HFZ.WA.USA.NA
Phone: 206/527-4089 
MCI Mail: 3288544 
Telex: 6503288544 MCI UW  
USENET:...uw-beaver!sumax!amc-gw!ssc!tad
or, tad@ssc.UUCP