[Antennas] A couple antenna and ground questions

[Philip Atchley]

Hi.
After too long an hiatus (about 4 years) I'm returning to the airwaves.  The
last 4 years I've primarily concentrated on SWLing and longwave beacon
chasing.  So, anyway, my modest antenna farm needs some work (don't they
all?).  Been in Radio 45 + years overall but I always have questions 8^)

At the present it consists of a Hustler 6BTV vertical mounted over about
1200 Sq/ft of sheetmetal roof/awning.  That may need new coax again (think I
may have a coax muncher or something).  Last time it was damaged by roofing
tar eating the outer coating.  The Alpha Delta DX-B lowband sloper, FAR from
an optimal installation is also run over the metal roof, attached to a
pushup pole (yeh, I know they "should" have a tophat but this mobile home
doesn't offer many lowband antenna alternatives).  Due to the roof proximity
it resonates below all bands (160, 80, 40 & 30 M).  After being up there 4
years I finally plan on trying to actually "tune" this critter, at least try
to get the bands in closer 8^)

ALSO, while the pushup pole is down I am going to mount a half size G5RV
antenna Inverted Vee fashion on the same pushup pole, mounted as "backstays"
or guy wires for the pole.  These elements will be at about right angles to
the sloper so I anticipate little interaction (I hope).  It'll take some of
the "bow" out of the pole and act as needed buy wires.

Here are my Antenna questions.

1.  The 17 foot ladder line matching section.  I'm using good quality, heavy
duty stranded 450 Ohm cable (with windows).  I have NOT been told what the
velocity factor for this cable is (it was a gift).  Before I cut I would
like somebody to confirm for me that 17 feet is the proper length (for half
sized G5RV).

2.  How far do I need to space this from the metal pushup pole for good
results.  I can get the TV type "strap" twinlead standoffs from the shop but
I'm not sure they're long enough for this application.  Anybody have a
better idea how to secure the ladder line to the pole without spending a lot
of (non existent) money?  Alternatively, I can string it back through "free
space" from the antenna center insulator and tie it off at the roof edge,
but it wouldn't be "vertical" and would also flop around in the wind some.
I don't feel that's a reliable alternative as we do get some good windy days
here.

3.  Alpha Delta DX-B tuning questions.  As mentioned, this antenna is slung
rather low over a metal roof (no choice) and resonates below all bands, 160,
80, 40 & 30M.  The 30 meter element is an individual line, the other three
bands are one 60 foot long element with 2 "Iso-Res" coils splitting it up.
I suspect that all they are in reality are a pair of loading coils!
   A.  Alpha Delta gives no tuning instructions, they say "use a tuner and
enjoy the low bands".  When tuning this critter I suspect that I would want
to tune one band at a time, starting on the highest frequency, 40 meters and
then work down through 80M and finally 160 M (Like I would my Hustler
Vertical).  Does this make sense?  Has anybody tuned one of these?
   B.  How would this critter perform if, instead of sloping down I had both
ends at equal height, fed as a 1/4 wave end fed wire against ground (which
is essentially what it is anyway)?  I believe that raising the far end up a
fair amount would also raise it's resonant frequency a significant amount
without cutting.  It'd mean putting an additional pushup pole (which I have)
in place of the shorter pole now holding it.

Grounding questions.
The station ground system here (which the sloper depends on heavily)
consists of 4 ground rods spaced out and tied together.  Two are quality 8
footers, two are "cheap" 4 footers that were tossed out at the shop where I
work.  I see why they tossed them out.  They were copper plated, skinny
little things and after 4 years the visible part is just a solid mass of
rust.  I hate to think what the underground part looks like.  Plans call for
their replacement.

Questions.
1.  Should I try to pull the 2 old 4 footers out using a car jack (they'll
probably pull) and then drive the new 8 footers in their place (making that
job a little easier)?  Or should I leave these in place and just add two
additional 8 footers nearby tying the new ones in to the system.  In other
words, will those old rusted rods be of any benefit at all?

73 from the "Beaconeers Lair".
Phil, KO6BB

In daily combat with QRM & QRN.
We may lose a battle but we'll win the war!
beaconeer@elite.net
Merced, Central California
37.18N  120.29W  CM97sh



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