Topband: 50 ohm direct burial coax cable

[Carl]

For monoband use, use an asynchronous transformer to go to 50 Ohms if you or 
the equipment is that fussy.
http://www.k1ttt.net/technote/matching.html

Carl
KM1H



----- Original Message ----- 
From: <donovanf at starpower.net>
To: <topband at contesting.com>
Cc: <jim at audiosystemsgroup.com>
Sent: Friday, June 13, 2014 4:01 PM
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 at audiosystemsgroup.com>
> To: topband at 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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