On 6/19/2011 8:10 PM, Michael wrote:
Thanx for the input... One of the reasons i was considering an OCF
dipole over a ladder fed "ballanced" dipole at first was a matter of
lightning protection. With an ocf dipole, i can use 50 ohm coax as
the feed line. not to much trouble to use a gas tube. Though, i'll
probably stick with my current method and just disconnect the feed
line and hang it out the window even if I use an arrestor. i'm also
told by a few other people that putting a sharp 90 degree bend in the
feedline outside the shack is an old trick that usually helps in the
case of a direct strike. i'd gather that static coming down the
feedline would probably be the more common worry.

Nobody seems to have asked the burning question that's really
important... what's your budget?

As far as kind of antenna, feedline, etc.

You're not going to have an optimum on all bands. For right now, as the
sunspots are coming up, the high bands seem to be working fairly well
(and as a Tech, all you get is 10m anyway, as far as phone.. but when
you get your General or Extra, you'll get the rest.. study and take that
test..)

I'm a huge fan of autotuners *at the feed*. You don't have to spend
your time trying to adjust the antenna, or worrying about feedline loss,
or any of a zillion other things. Sure, there's some loss in the tuner,
but it's pretty easy to get the antenna close, and if the antenna is
"close" then the autotuner takes care of the rest.

Life is too short to try and prune radials for resonance, and then have
it go out of tune when the tree next to the antenna grows, etc.

Folks who have tube amps have the tuner built into to the output
network, and they're used to the whole thing of tuning every time they
change frequency, so for them, open wire line to their rig is fine. Do
the match at the amp end, the loss from mismatch in the line is small
because the line is high Z, etc. But that's not typical of a "brand
new" station: solid state 100W amp, coax feed, etc.



My own preference is for an autotuner at the feedpoint of some sort of
dipole or inverted V. Any of the 10-15-20-40 multi wire band dipoles
will work quite well, and with an autotuner, you don't have to worry
about "pruning to exact length". The two sides don't have to be equal
length, even. Be aware that not all tuners can tune all impedances, and
you generally do NOT want a transformer between antenna and tuner (esp
if there's a lot of reactance to tune out), so going too far in the OCF
direction may be counter productive. Then you can feed with coax,
which is a whole lot more convenient than any sort of open wire line.

Second choice which is less visually obtrusive is some sort of vertical
with an autotuner at the base and an adhoc counterpoise of random length
wires. Higher the base, the better, in general.


Lightning protection..

Where are you located? A lightning alley like mid Florida? Or somewhere
were lightning is an unusual thing (like Southern California)?

Gas tube arrestor is a nice idea. What will you hook the ground on that
arrestor to? A stake pounded in outside where the coax comes in? Make
sure that you run a bonding wire from the stake to the electrical system
ground. A concrete encased grounding electrode is even better (Ufer ground)

Or, if you're not really in a big lightning area, just use the arrestor
as a "receiver input overvoltage protector", for whatever good it might
do. (I don't know what a TS590 input looks like, but the couple hundred
volts from the arrestor might blow it up...). disconnect the coax when
your not using it. BTW, short the coax with something and make sure
it's not close to something that might catch fire if you do get a
lightning hit.



The 90 degree thing is useless.. there's no significant impedance in a
90 degree bend. If you get a direct hit, unless you're spending a fair
amount of time and effort on a good system, you're going to get
damage..You don't want to spend thousands of dollars on a lightning
protection system to protect a 1000 dollar rig.

Static discharge *is* a problem.. but, if you hook the shield to the
third wire ground (or that other grounding system), on a dipole, that
pretty much takes care of it. Maybe a 100k resistor between the legs
(or between the vertical and ground).. Once the center insulator gets a
bit grungy, leakage resistance will solve that problem for you.