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Gary Schafer
 
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Default SSB Antenna connection

On Wed, 26 May 2004 11:38:26 -0400, "Jack Painter"
wrote:

"Steve (another one)" wrote in message
...
Dear Folks,

What is the recommended wire to connect my insulated backstay to my
AT-120 tuner ? I see references to GTO15 for this purpose in American
publications, but no-one here in the UK seems to know what GTO15 is.
Could someone please suggest an equivalent, or at least a description !

Also if the ground connection has to be broad copper strip because RF
won't run down a wire like a conventional dc current, how can the
antenna be wire ? Doesn't RF have to run along the cable to the base of
the antenna and then up the antenna wire itself ? I'm confused !

Thanks for your help.

Steve


Steve, you have asked about two distinctly different forms of connection
that require equally different conductors. Additionally, within your
grounding questions there also are two different issues, addressed below:

1. RF feedline from ATU to antenna.

This should be coaxial cable with dialectric and shielding designed for RF.
Never improvise with something such as spark plug wires.

2.(a) Grounding: RF

This does not have to be wide surface area copper, but doing so will not
hurt, and it will allow the combination-use of the RF ground connection to
serve as a lightning protection ground. RF ground does not require a dc-
connection to ground, and is often designed to use capacitive coupling to
ground for sailing vessels and other marine applications where isolation for
galvanic protection is adviseable.

2. (b) Grounding: Lightning protection

Also does not require a dc-connection to ground, but may not use low valued
capacitors such as would be acceptable for RF ground. Lightning protection
DOES require the widest surface area possible, this provides a lower
impedance path to ground. But your radio and auto-tuner and other equipment
are most importantly bonded to each other, and that may be of any standard
braid, #8 wire, etc. Only the single connection of all your bonded equipment
to ship's ground must be of the highest surface area possible. If more than
one connection from bonded equipment to ground must be made, then each of
those connections should be wide surface area conductors.

Hope this helps,

Jack Painter
Virginia Beach, VA



A good lightning ground is also a good RF ground. But a good RF ground
is not always a good lightning ground. (as in the case of elevated
radials)

Most lightning energy is concentrated in the DC to 1 mhz range with
some energy going much higher in frequency. So the ground conductors
and ground system must be treated the same as an RF ground system with
with regard to low impedance leads (large surface area) and, in the
case of lightning, low DC resistance connections. Even a low
resistance connection can develop many thousands of volts across it
with the high current lightning.

An RF ground requires a low impedance conductor as well.

Regards
Gary