Frank,
That is true but a 1/2 wavelenght at 160 meters is quite long, about 260 feet;
shorter with the velocity factor.
Mike N2MS
----- Original Message -----
From: donovanf@starpower.net
To: topband@contesting.com
Cc: jim@audiosystemsgroup.com
Sent: Fri, 13 Jun 2014 20:01:13 -0000 (UTC)
Subject: Re: Topband: 50 ohm direct burial coax cable
You can easily make the 75 ohm coax essentially "invisible" in a monoband
application by using some RG-11 to extend the total length of the 75
ohm feedline to any multiple of 1/2 wavelength.
73
Frank
W3LPL
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: topband@contesting.com
Sent: Friday, June 13, 2014 8:33:35 PM
Subject: Re: Topband: 50 ohm direct burial coax cable
On 6/13/2014 12:17 PM, Donald Chester wrote:
> I think you're being overly picky. The 75-ohm cable would be at worst a 1.5:1
> mismatch. Probably a fraction of a dB loss at most, particularly with foam
> type hard line. If you have a source of good, low-loss 75-ohm coax that will
> safely handle the power you intend to run, and which will hold up for an
> extended period under direct burial, use it.
Yes. Assuming a suitable matching network at the transmitter, worst case
excess loss due to a 1.5:1 mismatch is 0.18 dB, no matter how long the
line. Curves showing this have been in every edition of the ARRL
Handbook since I've been a ham (59 years).
73, Jim K9YC
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