Topband: 1000 feet 5/8" hardline or 600ohm True Ladder lin

[k1fz]

----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <topband at contesting.com>
Sent: Tuesday, April 29, 2014 12:22 PM
Subject: Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder lin

 Exactly right -- it's because the current is much smaller for the same
 power.


Correct Jim.

With an RF amp meter  5.477 amps squared times 50 ohm coax equals
1499.8764 watts

With 1.8 amps squared times 450 ohms  the power is 1458 watts

Higher impedance,  higher voltage,  lower current.

Its the currents that limits the wire handling capacity.

Power companies tranform to a very high voltage for their cross country 
lines
to minmize current loss.

They also call their cross country wires  'transmission lines' and their end 
transformers are
wound for 60 Hz

Milt paralled two 75 ohm coaxes to get half the impedance for his vertical 
antenna base impedance.
Match the impedance -lower loss.

I run three in line vertical antennas on 80 meters.  The current requires is 
a 1-2-1 ratio. I use one 75 ohm coax to
towers 1 and 3. Tower 2 has paralleled 75 ohm coaxes to get half the 
impedance and twice the current. A common practice.
Exact currents and phase are controlled with tuning networks using a 
Nems-Clark model 108-E monitor.


As you said Jim, not new information,  most of this goes back to the 
beginning days of radio


73,
Bruce-K1FZ
www.qsl.net/k1fz/pennantnotes.html








> On 4/29/2014 8:49 AM, Milt -- N5IA wrote:
>> For my 160 Meter, 1/4 WL vertical, which is more than 400 feet from my 
>> operating position, I use 1/2" CATV hardline X 2.
>>
>> Since the feed point impedance of the vertical measures ~ 39 Ohms, I 
>> parallel two of the 75 Ohm cables for a near perfect match to the 
>> antenna.
>>
>> The 420 foot long run of paralleled cables dampens the slight mismatch 
>> between the presented impedance of 37.5 Ohms and the desired 50 Ohms for 
>> the amplifier such that the Alpha does not light a single reflected power 
>> segment from 1.800 to 1.880.
>
> Exactlly right again.
>
> Many of the "best" solutions for antenna problems depend on which of them 
> are readily available to us.  If you have that CATV hard line, it's a 
> great solution once you know how to use it.
>
> Another great way to use 75 ohm cable in a 50 ohm system is to use some 
> multiple of half waves of it, coiling up any excess, or using 50 ohm coax 
> to add length.
>
> None of these solutions are "new" or particularly innovative. All have 
> been used since the earliest days of radio.
>
> 73, Jim K9YC
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
>