T&T: Wiring question

[Ken Bloomfield]

For what it is worth, normally boats of the vintage of mine (1984) did have 
the 3 inch wide heavy foil running along a stringer from one end to the 
other to serve as a good low resistance common bonding ground bus.  I think 
that the HF Radio use as a kind of  Ground Plane is likely a very secondary 
use.  I know that my boat has never had an HF radio, but came from the 
factory with the copper grounding bus.

There is one question that has perplexed me, however, for many years now. 
My background is in telecommunications and I realize the need for a ground 
plane for antennas. I have often seen the recommendation for copper strips 
installed in the bilge ostensibly for this purpose, and it doesn't seem to 
make engineering sense to me, but I am likely missing something?  I would 
love to understand what that is.

On the other hand, it seems to me that the sea itself ought to be a 
wonderful ground plane, as long as there is a good low resistance contact 
between the R/T chassis/common-rail and the sea.  It would seem to me that 
the typical distance between the R/T's antenna to the bilge (where the 
copper foil is located) would make the surface area of the foil almost 
inconsequential to the performance of the antenna.  More years ago than I 
care to admit to, aircraft that were engaged in Electronic Counter Warfare 
missions would cover all the bands and had multiple antennas, and they would 
use (among other antennae) a long-wire antenna.  This required a device 
known as an "antenna coupler" to properly "load" the antenna to keep the 
VSWR (voltage standing wave ration) low to ensure that the transmitter power 
was "getting out" and not just bouncing back to the set.  When we would do 
design changes on these couplers, we had to set up a simulation of the 
airborne circumstance, and we found that ground planes required substantial 
surface area relative to the antenna to get a good VSWR.  In actual use of 
course, the aluminum body of the aircraft served this purpose.  When the 
surface of the sea is so close to the copper strip, and since fiberglass is 
essentially virtually transparent to HF-RF, other than the bonding/grounding 
purpose,  I can't imagine what other good the copper strip would do.

Ken Bloomfield
Cell# 865-293-2174
MTOA# 2062
AGLCA# 3529
M/V Tellico Lady, 50' Marine Trader-Walkaround
Maryville, TN


>I agree that if the wire was either a green insullated wire or solid copper
> wire, it was bonding.   The 3" wide foil is for a HF radio ground--and 
> this
> the normal way it is run.