[K6BW] Re: 3/8" feedline

[David Mueller]

I've CCed our conversation to the reflector....

My replies are in your email...

73, Dave
PS - If anyone has W2FMI's book on transformers and
baluns, I'd love to borrow it!




--- ab6mt <ab6mt at sonic.net> wrote:

> You could make a coil out of #18 solid wire, slip
> the coil on each end of the center conductor, butt
> the cable together and solder.   The outside is more
> difficult.  I have aluminum solder, but the melting
> point is very high, a torch is necessary, and its
> application would likely damage the cable.  Hose
> clamps may be the best idea. 

Your idea for the center conductor is exactly what I
was going to do.  I think that soldering the shield
would be extreme overkill, and would damage the foam
core.  A couple wraps with the aluminum flashing,
NOALOX, and hose claps would make a good, long-lasting
connection.  Again, the Beverage antenna is a loss
antenna and feeding it with hardline is overkill
enough!  VE1ZZ is one of the top dogs on 160M and he
uses CATV hardline for EVERYTHING.  He simply brings
both ends together vertically, hose clamps the shields
together, and solders the center conductors together. 
He waterproofs the connection by sliding a coke bottle
with the top cut off over the whole thing.  He's even
built yagis with 1/2 inch CATV hardline taped to
bamboo for elements!

> 
> How thick is the aluminum outer shield (you
> mentioned two of them).  Is it possible to strip a
> section of cable and bare back a section of
> aluminum?  If so, it might possible to spot solder
> the shield.

The cable is flooded (waterproof) but it's pretty easy
to get the jacket off with a box knife.  The shield is
pretty thick, solid aluminum, that I cut with a tubing
cutter.  The center insulation is flooded foam so I
think we might do more harm than good by trying to
solder it.  Again, this is a loss antenna.

> 
> I'd seal the splices with silicon rubber.  Though it
> is no good when liquid, after it sets and dries it
> has excellent insulating properties, is durable, and
> makes an airtight joint.

This sounds like a good idea

> 
> I wonder if there isn't PVC pipe or something
> similar which might have an inside diameter that the
> cable could just slip through.  Perhaps some of the
> surplus aluminum tubing might work.  If so, perhaps
> a section could be slipped over the heliax joint. 
> Sealed with silicon rubber, it would make a great
> mechanical joint, something akin to a giant
> shrink-tubing splice.  I have large shrink tubing if
> you need any.

This is a pretty good idea also.  I'll look around for
something to use since I didn't think about it when I
was at the Home Depot earlier.

> 
> Agreed, you can make almost any physical connection
> without introducing much loss.
> 
> We ought to carry this conversation on the
> reflector, I'm sure other members would be
> interested, and may be able to assist with their
> previous experience with handling heliax.
> 
> Can you re-use 7/8" connectors?  If so, I'd like to
> remove the connectors from the coax I brought up and
> reinstall them on new 7/8 cable at the school.

I'm almost certain that hardline connectors are
reusable.

I got another thousand feet of wire so I'm ready to
string some Beverages if the rain ever stops! 
Fortunately 160M has been "Broken" the past few days
so I haven't missed much.  Once I get the 315 degree
antenna installed I may get up early to try working
some of the deep asian countries.  Apparently the guys
in the Northwest were worked EU long path on 160 a
couple mornings ago!


> 
> Bill
>   ----- Original Message ----- 
>   From: David Mueller 
>   To: ab6mt 
>   Sent: Friday, December 30, 2005 11:24 AM
>   Subject: Re: 3/8" feedline
> 
> 
> 
> 
>   --- ab6mt <ab6mt at sonic.net> wrote:
> 
>   > The new cable certainly attracted my attention,
> it
>   > just didn't look like 3/8" line, and couldn't
>   > believe that it could be larger cable.  Would
> like
>   > to hear of your splicing technique.  Is the line
> 75
>   > ohm cable?
> 
>   Yes, it is 75 ohm cable.  At 80 and 160M, I could
>   splice it any way I wanted without having to worry
>   much.  I'm basically going to solder the center
>   conductors together end-to-end by wrapping some
> #14
>   stranded copper around them (and soldering), wrap
> with
>   electrical tape, then get some aluminum flashing
> to
>   wrap around both shields (which are aluminum also)
> and
>   attach with hose clamps.  Water proof with liquid
> and
>   regular electrical tape, and tape a length of 1.5"
>   angle aluminum over the joint for strength.  
> 
>   > 
>   > FB on your Sister's visit, the antenna projects
> will
>   > be there when you have time.
>   > 
>   > Alan mentioned the tower the other day, he is
> still
>   > interested in putting it up. 
> 
>       I looked at the tower again.  It's designed to
>   mount a rotator atop the section of mast that
> sticks
>   out the top of the tower.  It was never designed
> to
>   mount a rotator inside the tower section with a
> thrust
>   bearing at the top.  None of our rotators have
> base
>   mast adapters.  I wouldn't want to mount a TH7
> that
>   way even with a tailtwister rotator.  Unless we
> want
>   to put up a small 3el tribander or VHF antenna,
> it's
>   not that much use.  We could attach the TH7
> directly
>   to the mast, but it wouldn't be rotatable.
>       I'm also somewhat concerned if we put the
> tower up
>   simply to hold wire antennas that it would screw
> up
>   the radiation pattern of the roof-mounted TH7. 
> It's
>   not really at the top of the list of projects I'd
> like
>   to do....I'd like to try putting up a 1/4 wave 80M
>   vertical on the water tower first.  The LMR-600
> would
>   be perfect for that.
> 
>   HNY,
>   Dave
> 
> 
>   > 
>   > Happy New Year!
>   > 
>   > 73 de Bill, AB6MT
>   > ab6mt at sonic.net
>   >   ----- Original Message ----- 
>   >   From: David Mueller 
>   >   To: ab6mt 
>   >   Sent: Friday, December 30, 2005 8:32 AM
>   >   Subject: Re: 3/8" feedline
>   > 
>   > 
>   >   Hi Bill,
>   >     The feedline you see to the north of the
>   > driveway is
>   >   actually 7/8" CATV hardline!  I finally ran
> into
>   > one
>   >   of the cable employees at the fenced area (by
> the
>   >   dumpsters on the housing area) and begged him
> for
>   > any
>   >   short sections he had laying around.  The
> feedline
>   >   runs about 450 feet from the back of the
> building
>   > to
>   >   the new NE Beverage feedpoint location.  It's
> 3
>   > pieces
>   >   and I still need to splice them together when
> the
>   > rain
>   >   stops (I have a good method that works).
>   >     My Sister is visiting until early next week
> so
>   > time
>   >   is somewhat limited, but I hope to get the new
> NE
>   > and
>   >   NW Beverages installed by the end of next
> week.  I
>   > got
>   >   the Amidon transformer material and have been
>   > building
>   >   the 50-450 and 75-450 ohm transformers.
>   > 
>   >   73, Dave
>   >   PS - 160 has been "broken" for the past few
>   > nights.
>   >   PPS - my FT1000MP has the new roofing filter
>   > installed
>   >   and it seems to help reduce the BCI quite a
> bit.
>   > 
>   >   --- ab6mt <ab6mt at sonic.net> wrote:
>   > 
>   >   > Hi Dave,
>   >   > 
>   >   > Picked up 85' of 7/8" Heliax and nearly 500'
> of
>   >   > LMR-600.  It has a couple of
>   >   > spots where cable clamps crushed the cable
> (not
>   > good
>   >   > for SWR), but is
>   >   > otherwise like new.  Also picked up a small
>   > amount
>   >   > of hardware, e.g. clamps,
>   >   > eyebolts.
>   >   > 
>   >   > Also, have installed two new shelves in the
>   >   > workshop.  Books are all over
>   >   > the place, we need to sort through them and
> put
>   > them
>   >   > in the Library.
>   >   > 
> 
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