On 10/1/2015 11:56 AM, Brian Howie wrote:
In message , John S
writes
On 10/1/2015 3:29 AM, Brian Howie wrote:
In message , Wayne
writes


"Ian Jackson" wrote in message
...

In message , rickman
writes
On 9/30/2015 12:57 PM, John S wrote:
On 9/30/2015 10:12 AM, Ian Jackson wrote:
In message , Jeff
writes
On 29/09/2015 14:31, Jerry Stuckle wrote:
On 9/29/2015 4:40 AM, Jeff wrote:


So let's get back to the original question. Was it ever really
answered? I think it was made slightly more complicated by the fact
that the antenna feedpoint impedance was not purely resistive, but
was actually around 20-j130 (at 14 MHz),

Was there any advantage in having the coax paralleled (both for 20
ohms resistive, and for 20-j130)?

A quick model.

A vertical antenna about 4.2m long with a wire radius of 0.5mm
approximates to what you have . The devil is in the j130 If you use a
1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a
bad match over the band

Expanding on the original question.... Antenna feedpoint
approximately 20-j130
The ATU drives the antenna through about 15 feet of coax.
Assuming that the ATU provides a +j130 conjugate match, does that
leave the coax with a SWR of 50/20= 2.5:1?
If so, then I will not bother with considering 2 parallel coax.

No the line SWR is still about 36:1. If you run a bit of poke, you might
melt the coax.

If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+
j87) and use a series C ~130pf to take out the the +j87. You have to
do this at the antenna end.

It goes without saying you need a good ground.

Brian

What do you think of this while leaving his antenna unchanged?

2.3uH
___
'-----o-----UUU---------------
.-. | ^
| | | |
20 | | C| '
'-' C| 4uH
| C| 50 ohms
| |
--- | .
-130--- | |
| | v
'-----o------------------------
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)


Yes that works too. Lots of ways to do it.

Brian

Oh, yes of course. I try to avoid capacitors as much as I can because
one end can float with static voltage while an inductor does not. I've
had issues with nearby static lightning discharges.

Just my paranoia. To each his own.