Topband: Inverted L improvements - Part 3 (now with data)

[Guy Olinger K2AV]

Hi, Fred. You said:

"Guy K2AV I'm guessing you don't like rg58 because of the center conductor
moving outwards??"

Nope.  :>))   RG58 is not RG400. That's why I don't like RG58.

RG400 is what should be used for winding coax on toroids. RG400 is a
currently manufactured item. It is INTENDED to handle sharp bends as found
in aircraft wiring harnesses (and therefore also handle being wound on
toroids). The center conductor is silvered stranded copper, the dielectric
is PTFE (Teflon), the shield is TWO dense woven layers of silvered copper
braid, and the jacket is PTFE.

RG400 is rated to 7 kW.

RG400 is Mil Spec. MIL-C-17 27478. Which means that if your house blows up
from a gas explosion, the RG400 will still be there working when the fire
is put out.

Essentially it never ever goes bad or weird unless catastrophically
treated, like crushed with a hammer, nailed through, ends submerged in
battery acid, or used as a tow rope for something heavy. I have one piece
of RG400 that was inappropriately used to arrest the fall of and suspend a
linear amp in mid-air. The coax still works, but it looks funny, and it
wasn't 50 ohms any more. A Chinese finger trap on the dielectric.

The silvered copper conductors in the double shields and stranded copper
center conductor will not deteriorate from occasional moist air in the coax
and convert it to many small conductors with performance changes, because
silver oxide is conductive.

The dense silvered copper shield weave, with two layers of shield weave in
RG400, makes for extremely good shielding. A lot of RG58 is cr*p shielding,
sparse enough to see through, sparse to maximize profit.

The PTFE in the jacket and dielectric is a low loss material, will not
deteriorate from ultraviolet. PTFE will not gradually shrink or crack by
leaching its chemical components.

The jacket and dielectric will not melt and ruin a connector when you
solder it, or when you forget it's there and put 1500 watts on it.

PTFE is a highly robust and predictable material. The PVC jacket
formulation on RG58 could be just about anything.

People have discovered that jumpers and leftover pieces of RG400 can be
sold on eBay. So you can pick up a ten foot piece of RG400 for less than
retail. I like the pieces with a male BNC on one end. I hate doing BNC
connectors. Brand-new coils of 100' plus can occasionally be had for as
little as 1.80 USD per foot, and regularly for 2.30 USD per foot, on eBay.

For all intents and purposes, a toroid wound with RG400 is a permanent
device, lifetime depending on the toroid instead of the coax.

You should buy enough RG400 so RG400 is the small coax that's "laying
around" and still good as new to do a project with, even if you bought it
20 years ago.

You can put your lifetime stash of RG400 in your will, and leave it to a
younger local ham, who will appreciate it.  :>))

RG400 is also K9YC's choice in his new
http://audiosystemsgroup.com/2018Cookbook.pdf. Check out the monster common
mode blocking choke wound with 23 turns of RG400 over a 4" OD, 3" ID, inch
thick #31 ferrite toroid. THAT'S a choke. 17K ohms resistive on 160.

73, Guy K2AV

On Sun, Jan 20, 2019 at 12:36 PM <fmoeves at twc.com> wrote:

> Hello everyone.
>
> I also trying to improve things here on 160 and other bands.
> Going to make a few chokes.
> I have wound 8 turns thru 2.4 x2 31 mix but haven't seen any real
> improvement.
> Trying to get rid of some birdies.
>
> Guy K2AV I'm guessing you don't like rg58 because of the center conductor
> moving outwards??
>
> 73 Fred KB4QZH
>
>
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