The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

"Gordon Wedman" wrote:

The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

Standoffs are highly recommended to eliminate coupling/signal loss between the
leadin and the backstay below the insulators. I made mine by running plastic
wire ties through shrink wrap tubing-a loop around the backstay, through the
tubing, a loop around the wire. About 2" long is good. Not coax at this point,
but High Voltage wire, BTW. Easy to do, and does help performance.

I see this all the time on cruising boats not most, not many but a
few. I always try to argue with the person that installed it on the
pros and cons but never get anyone that can talk rf to me. best I had
was an extra class ham that just said it works better because I can
hear the difference.

Distributed capacitance should be taken care of by the antenna tuner
(all random length end fed vertical wire antennas on boats have tuners
I think) So I guess the reason is to keep stray rf from coupling and
reflecting back from the backstay. I would think that a ¼ wavelength
distance from the backstay to the gto-15 should be good. But since you
will be using it on many bands I would guess that at least 1/8
wavelength at the lowest frequency would be someplace to start from.
Maybe about 10 meters separation between backstay and gto-15 may make
a measurable difference. 2 inches of separation, less then 1
electrical degree ROTFLMAO at anyone who says it makes a difference.





sded wrote in message . ..
"Gordon Wedman" wrote:

The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

Standoffs are highly recommended to eliminate coupling/signal loss between the
leadin and the backstay below the insulators. I made mine by running plastic
wire ties through shrink wrap tubing-a loop around the backstay, through the
tubing, a loop around the wire. About 2" long is good. Not coax at this point,
but High Voltage wire, BTW. Easy to do, and does help performance.

In article ,
says...
I see this all the time on cruising boats not most, not many but a
few. I always try to argue with the person that installed it on the
pros and cons but never get anyone that can talk rf to me. best I had
was an extra class ham that just said it works better because I can
hear the difference.

Distributed capacitance should be taken care of by the antenna tuner
(all random length end fed vertical wire antennas on boats have tuners
I think) So I guess the reason is to keep stray rf from coupling and
reflecting back from the backstay. I would think that a ? wavelength
distance from the backstay to the gto-15 should be good. But since you
will be using it on many bands I would guess that at least 1/8
wavelength at the lowest frequency would be someplace to start from.
Maybe about 10 meters separation between backstay and gto-15 may make
a measurable difference. 2 inches of separation, less then 1
electrical degree ROTFLMAO at anyone who says it makes a difference.





sded wrote in message . ..
"Gordon Wedman" wrote:

The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

Standoffs are highly recommended to eliminate coupling/signal loss between the
leadin and the backstay below the insulators. I made mine by running plastic
wire ties through shrink wrap tubing-a loop around the backstay, through the
tubing, a loop around the wire. About 2" long is good. Not coax at this point,
but High Voltage wire, BTW. Easy to do, and does help performance.


If you are talking coax, and it is properly impedance "matched" at both
ends, proximity to objects (metal or not) will have no effect. There is
(should be...) no RF on the outside of the shield.

OTOH...
Most comments reference a single feed wire to the stay. In that case
isolating the wire from nearby objects is very important for proper
function.

Woody

It is practically impossible to match coax cable to an end-fed antenna for
various bands, without traps or impedance matching tricks at the end of the
coax. The outer insulation and even the core insulation of coax is normally
not high voltage proof, so don't rely on it, certainly not near an "earthed"
wire.
Special marine antenna cable can be bought but is expensive. I used
multicore green earthing wire and spacers. These can be made of 5cm pieces
of white conduit pipe (UV stabilised) with two holes on each side to fix a
tag to the feeder wire and the backstay. Wrapping around both, fixes it
well. Perhaps shrink tubing would even make it more "professional". The wire
has been there for more than 5 years and the plastic has not deteriorated.
The inside wires were getting black, so soldering on both ends is necessary.
I am now going to replace it by special multicore UV stable HV cable, neatly
tied to the backstay.
It is still the question if spacers are electrically better than tying a
cable close to the backstay. The coupling between the feeder and the rest of
the backstay makes the antenna anyway into an a-symmetrical off-centre fed
thingie that may radiate well on one frequency but miserable on another. The
tuner will make the whole system resonant but that does not guarantee good
radiation or prevent RFI. Sometimes a dummy load would perform the same way.
With spacers, a 600 ohm feeder could be created (at least for some length)
to keep stray radiation at lower levels but it must be symmetrically fed and
commercial tuners don't do that.
Probably the best is trying it out, as there is not much calculation that
can be done. Thick marine antenna cable tied to the backstay makes the
system at least wind and foolproof. And pray for no RFI into the GPS and
mobile phone antennas.
----
Kris
VK4CPG s/v Marin Hedon

I doubt the boat in question was using coax. I just didn't know the
correct term to use for this type of wire and used "coax". Subsequent to all
the original discussion I had a closer look at the wire used on my boat
(installed in 1983) and I see that it is, in fact, GTO-15. Says so right on
the insulation.
Now I just need to buy a decent SSB to hook up to the backstay after
selling the old Motorola 11 channel unit.

"Woody" wrote in message
tt.net...
In article ,
says...
I see this all the time on cruising boats not most, not many but a
few. I always try to argue with the person that installed it on the
pros and cons but never get anyone that can talk rf to me. best I had
was an extra class ham that just said it works better because I can
hear the difference.

Distributed capacitance should be taken care of by the antenna tuner
(all random length end fed vertical wire antennas on boats have tuners
I think) So I guess the reason is to keep stray rf from coupling and
reflecting back from the backstay. I would think that a ? wavelength
distance from the backstay to the gto-15 should be good. But since you
will be using it on many bands I would guess that at least 1/8
wavelength at the lowest frequency would be someplace to start from.
Maybe about 10 meters separation between backstay and gto-15 may make
a measurable difference. 2 inches of separation, less then 1
electrical degree ROTFLMAO at anyone who says it makes a difference.





sded wrote in message
. ..
"Gordon Wedman" wrote:

The other day I was wandering around one of our marinas trying to
steal
ideas from other boats and I came across an aluminum pilot-house
sloop that
may have come over from Europe. I noticed that the SSB coax was
held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers.
I've
never seen this before and the previous owner didn't do it on my
boat. I've
been thinking of upgrading the ancient SSB system on my boat and
was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

Standoffs are highly recommended to eliminate coupling/signal loss
between the
leadin and the backstay below the insulators. I made mine by
running plastic
wire ties through shrink wrap tubing-a loop around the backstay,
through the
tubing, a loop around the wire. About 2" long is good. Not coax at
this point,
but High Voltage wire, BTW. Easy to do, and does help performance.


If you are talking coax, and it is properly impedance "matched" at both
ends, proximity to objects (metal or not) will have no effect. There is
(should be...) no RF on the outside of the shield.

OTOH...
Most comments reference a single feed wire to the stay. In that case
isolating the wire from nearby objects is very important for proper
function.

Woody

I think I read somewhere that the high voltage GTO wire should optimumly
approach the backstay at right angles. Something about when the lead
runs close and parallel to the grounded section some power is leached
off. Not real practical in most cases though. Stand offs about 1 1/2"
long keep the lead wire away from the stay enough to prevent significant
loss and are a pretty good way to keep things neat but probably not the
most electrically efficient.

OTOH, if you have this RF hot wire running up the stay where anyone can
grab it, why have a lower insulator in the first place? I am
considering not grounding the backstay chainplate and feeding the tuner
directly to one of the bolts. Just have to remember to yell "If you
have to pee off the stern rail Don't hold the backstay!" before sending
any e-mail. :-)

Gordon Wedman wrote:
The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

If it is feeding a backstay, coax is not the best solution. GTO-15
high voltage wire is the proper choice. If the lower part of the
backstay is insulated from the rest of the boat then standoffs
are not necessary but the part below the insulator becomes part of
the antenna. Don't touch it while transmitting. If the lower part
of the backstay is connected to the bonding systems or a metal hulled
boat then insulators are necessary. The cheapest ones I have seen are short
lengths
of PVC pipe notched at the ends to nestle against the wire and backstay.
Then
a wire-tie is threaded around the backstay, through the pipe, around the
wire and back. Works well and is cheap. Probably have to replace them
every couple of years due to UV degradation.

Doug, k3qt
s/v Callista

"Gordon Wedman" wrote in message
news:JMfqb.136245$EO3.29023@clgrps13...
The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop
that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat.
I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord

If the backstay turnbuckle were "hot" (energized with RF) this would
be prudent because there can be considerable voltages from the tuner
on certain frequencies, such as near when the backstay is a 1/2
wavelength antenna.

The question arises, why does the coax go to the backstay AT ALL? It
goes to the TUNER who's tuned RF output goes to the backstay. I has
no business going to the backstay.

The wire from the tuner's high voltage post to the backstay shouldn't
be coax, either. Coax has LOTS of capacitance to the shield and if
some idiot grounds it it will decouple the RF off to ground at the
higher impedances.... A heavy wire should hook the tuner to the
backstay as it's just part of the antenna.



On Wed, 05 Nov 2003 23:32:57 GMT, "Gordon Wedman"
wrote:

The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away
from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've
never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord




Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"

It was probably GTO-15. I would hope that who ever went to the trouble
of adding the standoffs would know the difference. GTO is hard to tell
from RG59 from a distance. Neon sign suppliers even have it in
decorator colors.

Larry W4CSC wrote:

If the backstay turnbuckle were "hot" (energized with RF) this would
be prudent because there can be considerable voltages from the tuner
on certain frequencies, such as near when the backstay is a 1/2
wavelength antenna.

The question arises, why does the coax go to the backstay AT ALL? It
goes to the TUNER who's tuned RF output goes to the backstay. I has
no business going to the backstay.

The wire from the tuner's high voltage post to the backstay shouldn't
be coax, either. Coax has LOTS of capacitance to the shield and if
some idiot grounds it it will decouple the RF off to ground at the
higher impedances.... A heavy wire should hook the tuner to the
backstay as it's just part of the antenna.



On Wed, 05 Nov 2003 23:32:57 GMT, "Gordon Wedman"
wrote:


The other day I was wandering around one of our marinas trying to steal
ideas from other boats and I came across an aluminum pilot-house sloop that
may have come over from Europe. I noticed that the SSB coax was held away

from the backstay turnbuckle and wire by ~1 inch plastic spacers. I've

never seen this before and the previous owner didn't do it on my boat. I've
been thinking of upgrading the ancient SSB system on my boat and was
wondering if these standoffs were something recommended.
Anyone know about these? Thanks
Gord





Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com