[Antennas] Ladder fed antenna questions. (Long post, several questions)

[Philip (KO6BB)]

Hi,

FIRST:  As a ham for 15 years AND radioactive since the early '50s, I 
realize that the BEST antenna is the one you can put up, not what you'd 
"like" to put up.  Life is often full of compromises and I certainly have to 
make some here!

I'm asking so many questions because I can no longer man-handle the push-up 
poles etc by myself.  I'll have to get help, precluding repeatedly taking 
the antenna up/down for experimentation.  Once Up, it will stay put until it 
"breaks".  Budget constraints also enter the picture (I'll be making the 
wire antenna myself, not buying ready-made).

To lay the groundwork for my questions, I've lived in this 14x60' mobile 
home with a sheetmetal roof for over 9 years now, and have tried a number of 
different antenna configurations.  There is almost NO yard space, so all 
skyhooks reside above the roof.  This past week a tree came down, damaging 
two wire antennas (not to mention a support now missing) has prompted a 
complete re-think of my antennas here (changes were on the agenda anyway)..

For the "low bands" I used first an Alpha Delta Shorty sloper for 160-30M. 
This antenna was NOT very satisfactory, primarily because I couldn't get it 
high enough above the metal roof.  So I did some changes.  Here is what I 
presently have.

1.  A Butternut HF-2V vertical for 75/40M.  With about 1200 sq/ft (counting 
awnings) of sheetmetal under it, it performs VERY well.  This one will 
REMAIN in service.

2.  A couple years or so back I replaced the Alpha Delta mini sloper with a 
Alpha Delta DX-EE shorty "fan" dipole 40 feet long (not enough room here for 
full sized 40M dipole).  This one uses two "Iso-Res" loading coils on the 
longer wire for 40/20 meter loading isolation.  The coils are close wound on 
PVC pipe.  The antenna performs moderately well on all bands, 40-10M, using 
a tuner for the WARC bands.  (Antenna performance of course is all 
relative).  BUT, anytime there is even a slight rain storm, or even heavy 
dew, the antenna detunes so badly that even the wide range auto tuner sits 
and "chatters" trying to tune it.  THIS ANTENNA IS COMING DOWN!

3.  A 20M Vee that was held up by the tree that came down (as well as 
serving as a back-stay for the Alpha Delta).  When the tree came down this 
one, as well as the Alpha Delta were stretched tighter than a drum head for 
a couple days.  Now it is no longer resonant, and even the Alpha Delta will 
no longer tune 40/20M without a tuner (before I didn't need a tuner on 40, 
20, 15 & 10M).

Here's what I plan for the "new" antenna farm. . .

1.  Eliminate the 20M inverted Vee  completely since it now has to be tied 
down at too sharp of an angle to be effective.

2.  Replace the Alpha Delta Mini Fan dipole  with EITHER a G5RVjr (51 foot 
flat-top fed with 16' of ladder line), OR just a basic ladder line dipole as 
long as I can make it.  From the center support Push-up pole I have room for 
25 feet on the North leg and 35 feet on the South leg (I'd make both legs 
equal length).

3.  The 300 Watt MFJ993B auto tuner I have has a true internal 4:1 "current 
balun" on much larger ferrite cores than most of the lower cost MFJ tuners. 
With a matching range of 6-3200 Ohms (150 Watts) or 6-1600 Ohms (300 Watts) 
the tuner should be up to the task (I have a FT-2000 running 100 Watts).

ANTENNA QUESTION:
1.  Would I be better off configuring the antenna as a "G5RV jr" (51' 
flattop and 16' ladder line) fed with the "suggested" 35 foot length of 9913 
coax for "matching".  I understand that the G5RV jr often get's it's "match" 
from the SWR loss of the coax, this isn't good!

OR. . .

2. Run the ladder line all the way to the tuner (it'll be over the 16' 
length of a G5RV jr) and just let the tuner do it's job?

BALUN and LADDER-LINE  QUESTIONS:
1.  Would I be better off, both from an "RF in the Shack" in the shack 
standpoint to obtain an external balun, put it outside the shack at the 
roofline (metal roof, remember) and complete the run with a SHORT section of 
coax to the tuner (about 5 feet), OR just bite the bullet and run it right 
to the tuner?

2.  For a ladder-line feeding a 50-51 foot flat-top (or whatever consensus 
says would be best available length), would a 4:1 balun (whether internal or 
external) be optimum, OR would a 1:1 balun be a better choice (would have to 
be external)?

3.  And Finally, 450 Ohm Ladder Line choice:  I've noticed that 18ga copper 
clad steel is significantly cheaper (~.29 ft) than the 14ga stranded copper 
(~.69 ft).  I DON'T mind paying the price for the premium stuff if it either 
lasts longer or is lower loss!  Ideas???

73 de Phil,  KO6BB
http://ko6bb1.multiply.com/ (My OTR Blog)
http://www.qsl.net/ko6bb/   (Web Page)

DX begins at the noise floor!
RADIO/Antennas: Yaesu FT-2000, Two Modified Mini-whips.
Homebrewed 6Hz Filter, Modified MFJ-1040C Pre-Amplifier.
Merced, Central California, 37.3N 120.48W  CM97sh