[Boatanchors] Re Feedline Through Wall Post File

[Duane Fischer, W8DBF]

I am looking for away to bring several coax and rotator cable through
a window. I am wondering if there are different solutions than that
offered by MFJ. My preference is a metal device so I can ground it. I
don't like the MFJ because the coax terminates at the boundary - this
introduces additional loss above 6M because of the additional
connectors. Any advice will be appreciated. I will pay for a custom
solution if required. I have 4 coax and one 3/4 inch hardline I want
to bring in. It needs to be an environmental barrier. Best Regards,
Dave

Have the window pane replaced with plexiglass. Install an aluminum
plate over that, drill and install bulkhead connectors. If you use N
connectors loss will be unmeasurable thru 432. Carl KM1H

Or use C connectors, which are like grown-up BNC connectors, the
bayonet lock making it easy to change connections quickly, if you need
an antenna patch panel effect. Now I guess replacing the window pane
with plexiglass is a lot more complicated if you have the modern vinyl
windows that are double or triple paned.  What I did in that case was
just to cut a board to fit into the window opening, close the window
against it, and cut another board to hold the window shut in that
position.  Then run the cables through the board, with or without
using connectors. Where I was sure I wanted to put the radio
equipment, permanently, I had an electrician friend cut through the
wall and install a piece of conduit through the wall and seal all
around it.  Then bring the cables through the conduit, and stuff it
with stuff so the creepy-crawlies can't get in through it. Jim W6JVE

hey heres my idea cut a piece of plexaglass large enuff to put in
window, now wait a minute more to come. Cut the holes large enufff to
let the coax and hardline tru now cover the plastic with a slab of
innertube from a car cut to proper size, just poke a pencil size hole
in each opening over the plastic now slide, with a little lube, the
coax thru the holes  to the proper length you want. after all hooked
up pull back on coax alittle from outside  and rubber will pucker out
side and make a good seal. there you are no connectors to have line
loss and a good weather seal, did I mention close the window over the
plastic and put foam at top between the two panes. Don K8OMO at it
since 1959

I drill holes through the wall and run all feedlines that way. Fast &
easy  :-) A bit of caulking seals up a hole if I decide I don't want
that run anymore. Mike WE0H

The through the wall idea is great *IF* your wall ISN'T 8" thick
reinforced concrete. That's when you look at windows and the like. Bob
- N0DGN

Yea that would be a pain in the ass to deal with. The window mod
sounds a heck of a lot easier with heavy duty walls. Mike

My solution was to buy the 4603 from MFJ - with a back order time of 4
weeks UGG. I plan to build a window metal plate grounded to the tower
and several copper rods. Oh Well FYI Dave

You havent seen my place then Bob. When the 10" thick foundation was
poured I had them install three 4" PVC Sched 40 pipes. Only way to get
the hardline right into the shack for the VHF thru microwave bands.
All the flexible coax, rotator, stacks and 4 Square control lines go
thru also. Carl KM1H

Not knowing the full details of construction but just drill a hole
thru the sill. Regards, Gary

Hole thru the wall (or if the hamshack is in the basement have
foundation core-drilled). Cover hole with a NEMA box (or similar); the
NEMA box is suitable for external ground point, addition of terminal
strips for rotor control, add Polyphasers, etc. Terminate the coax
inside the NEMA box, then add jumpers as needed to run into shack.
This way you can switch antennas/rigs, change connector types/genders,
etc. Balanced line can also exit the building thru this box by using a
pair of coax cables as a short run of balanced line. Once outside the
building, mount a pair of standoffs on the NEMA box, and connect the
two coax lines to the standoffs. I you want to get really fancy, use a
pair of lawn mower sparkplugs as the standoffs, they will also act as
spark gap lightning suppressors if you ground the box. Not as fast &
easy as Mike's approach, but keeps the XYL happy (cosmetics) and is
quite flexible for when you make changes to the shack, rigs, anetnna
farm. 73 Dan K0DAN

KODAN has pretty well described my setup.  Here in Florida  (lightning
capital of the USA)  we really have to watch what comes into the
house.  I installed bulkhead connectors in my outside NEMA box and
therefore I can disconnect my antennas OUTSIDE the house and connect
the antenna leads to SO-239's that are centrally grounded to a 10'
copper-clad rod.  In addition, we follow a general rule to disconnect
the entire shack from the AC mains when not in use and when
threatening T-storms are approaching.  The idea of spark plugs as a
means of providing a "spark gap" is very reasonable indeed.  Of course
their primary function is to provide a means of relieving static
buildup on the antenna system which, in turn, can provide a "leader"
for the formation of a path by which a lightning strike can occur.
Gap them at .020 or whatever is necessary if you're running QRO.  The
most often quoted fallacy is that of a device that provides protection
from a lightning strike.  If a direct strike pays you a visit you're
toast!  So keeping the antennas OUTSIDE the house and the rigs
disconnected from the AC mains is the best insurance one has if the
protection of the rig is the goal.   I have Collins, Eico, Heath, EF
Johnson and the like in my shack.  I want these BA's to survive. As I
write this, we have an approaching T-storm usual for Florida and this
time of year and the NOAA broadcast sez dangerous lightning, hail, 60
mph winds and some rain.  Think I'll go follow my own advice. As
always, YMMV Best 73 de W4MIL Chuck

Dan, what's the advantage of using -lawn mower- spark plugs rather
than automotive spark plugs?  I intend to do more or less what you
have described for my balanced lines.   Thanks and 73  Gary  N9ZSV

The mower sparkplugs are likely non-resistor plugs verses the resistor
plugs run in automotive motors. Mike WE0H

Excellent point.  Although non-resistor Champion N-8 and N-14Y are
still available for the 50's through 70's 4-cylinder Land Rover
engines.  Lawn mower spark plugs are also generally shorter as well.
But how do you connect the coax center conductor to the electrode?
And without disturbing the ground electrode for the spark gap? WA5CAB

I'd use the sparkplugs that have the thread on cap, use nuts instead
of the thread on cap that comes with the sparkplugs. Take some copper
sheet and make a big ring terminal to go on the sparkplug where it
screws into your ground block, solder the braid to this, use small
ring lugs to connect the feedline center conductor to the top of the
sparkplug. Mike WE0H

k0ewu wrote: HI, some sparkplugs have the center electrode modified so
the ground side covers only one half of the center one. This
decreases  the firing voltage.  Champion used to designate this
feature by the "Y" suffix. Jack

Good morning Jack, That is good information to know. I did not know
this. Thank you, Mike WE0H

I believe the lawnmower plugs arc at lower voltages than some of the
fancy new automotive designs. BTW, if you're running QRO, you need to
make sure that your plugs don't arc on voice peaks or during CW
keying! For me this was a trial and error thing. Also, I put a rubber
cap on the bottom of the plug so rain/ice don't short the gap. As
someone else mentioned, these sparkplug "surge suppressors" aren't as
good (quick discharge) as Polyphasers and other gas discharge
suppressors, but are better than nothing so far as large wire antennas
go. They may help bleed off a large static charge which accumulates on
the wire, which could protect your precious gear. This is less of a
factor with boatanchors than with solid state, but HV to the receiver
input is a no-no under any circumstances! GL es 73, Dan K0DAN

Mike's right, i was the presence or absence of a resistor...the arc
voltage may or may not be an issue as I previously stated. All my
comments were related to balanced line feeder. I use nominal 600 ohm
balanced line, approx 6" spacing. The open-wire feed goes straight to
the shack, but at the exterior entry point you drill a block of
aluminum or copper (if you can still afford copper!), thread the
holes, and insert the sparkplugs. Also drill a hole for a bolt, which
connects to your ground system. Mount the metal block on suitable
wall, pole, etc. Inside the shack you can also install a heavy duty
DPDT knife switch (one side to ground system) and/or connect the open-
wire feed to banana plugs, so when you have the big thunderstorms, you
can easily disconnect the equipment from the antenna network. I
wouldn't recommend trying to do this with a coax feed....you'd mess up
the impedance of your system. For coax, Polyphasers, Alpha Delta, or
other gas-discharge surge suppressors are the right choice. GL es 73,
Dan K0DAN

Exactly! Yes, some plugs have a threaded post; get these and throw
away the round ignition wire nut and replace with a stainless nut of
same thread. Also include some stainless flat washers and star
washers. Find ring lugs of suitable size for your open feed wire,
crimp AND solder), then torque down "just so" onto the plug's "anode".
Careful, the plugs will strip without too many ft-lbs torque. Coat the
whole connection with KOPR-SHIELD or other anti-oxidant goo. BTW the
wire that grounds the metal block to your ground system should be
BIG...#4 or bigger, OR use a big fat piece of the copper strap your
mention. 73, Dan K0DAN

Place a 1 to 2.5mH RF choke from each feeder to the ground plate. With
a DC resistance in the 25-75 Ohm range it will bleed off voltages that
dont cause an arc. Experiment with fuses in series or expect to
replace them now and then. Carl KM1H

Wow perfect!!! I was thinking you guys were talking coax. I wonder how
bad the impedance bump would be with coax using the sparkplug sparkgap
method? Might be neat watching the 'plugs with nearby thunderstorms.
Wonder if they'd spark blue or what color? GM all, Mike WE0H

Funny now reading my post this morning, I can see it as a open wire
feeder connected to the tops of a pair of 'plugs. I was thinking coax
last night. oops! The anti-oxide goop is good stuff. I've been using
it for many years on everything inside & outside. Never any connection
issues. On my outside connections I also add high voltage self fusing
rubber tape to seal the connections. Tough stuff to remove but those
connections look as new as the first day I put them together, several
years later. BTW, I am not seeing these replies that have multiple
address's in the 'TO' field as getting posted on the reflector. I get
a copy but they are not on the reflector. I delete personal address's
and send only to the reflector address. That's why I am replying to
all these to get the info on the reflector for all to see. This is a
darn good discussion about antenna stuff. 73's, Mike WE0H

The LF guys have mentioned this before. I am using a toroid
transformer coupling to my 600 meter vertical so it is DC grounded
through the secondary winding (12g copper) similar to the choke
bleeders but using 12g wire for the inductor. I have not heard, felt
or seen any static charge on this antenna. So far so good. But many LF
guys use the sparkplugs. I just haven't tried it yet. Mike WE0H

Putting a resistor from the center conductor to ground (between 4.7 K
and 47K) of coax and when using open wire from each side to ground
(between 10K and 100K) will "bleed off" the static charge that builds
up due to wind action.  A 2 watt "non inductive" (i.e. don't use a
wirewound resistor) will work fine even with full legal power and will
not affect the feed line impedance in any measurable amount. I have a
composite photo showing a couple of ways of doing this that I can E-
Mail to those who request it.  I still haven't put it up on my
website!  Since the reflectors do not allow any attachments I cannot
include it in this message. Of course the resistor cannot take a
"direct" lightning strike.  But, bleeding off the charge will
definitely help keep a "feeler" from being formed (as well as
protecting the "front end" of the receiver) and no "feeler" means no
lightning strike. Glen, K9STH Website:  http://k9sth.com

The Cushcraft Blitz Bug of the 50's and 60's used the spark gap idea.
Many hams adapted a regular sparkplug since they were free and non
resistor types were still in wide use. Carl KM1H

The Wireman in Landrum, SC has a spark plug device with two plugs on a
bar with a mount for the end of a ground rod.  See:
http://www.thewireman.com/prodpix5.html
  . I've had a couple of these.  They're strongly made and come with
copper straps for the plugs in a couple of different lengths for 450
ohm window line or 300 ohm twin lead. Harry, KT4AE Maryville, Tennessee

Dang that saves a guy the work right there. Thanks for showing us the
link. Mike WE0H

Coax is why Polyphaser, TransiTrap, etc., were invented. They do the
same thing, only shunt the charge faster/better, and also have
negligible loss and constant impedance. Mister Natural says, "Use the
right tool for the right job"! K0DAN

You wouldnt even see the bump at LF thru HF as the transition is such
a small fraction of a wavelength. It would have about as much effect
as a PL-259. Carl KM1H

Note: Special thanks to W5JT, James Thayer for taking his time and
talents to edit all the original posts and assemble the above material
on said topic.
Tuesday August 5, 2008
Duane Fischer, W8DBF -

WPE8CXO
E-Mail: dfischer at usol.com
Hallicrafters web site: www.w9wze.net
HHRP web site: hhrp.w9wze.net