On 2019-10-02 12:41 PM, Mark - N5OT wrote:
Actually if it was me, given that you only need two resonant radials
to make a complete system when they are above ground, and from what
I understand this works when the two radials are symmetric about the
feedpoint, I would not be able to stop myself from digging out some
ribbon cable and cutting it so that I had one wire in the ribbon
cable per band per side that was the right length. then I would have
everything I need in a single assembly with a single attachment point
at each end, per each side of the feedpoint.
If you do that, be sure to pull back about 18-24" at the end of each
wire and let it hang down. Otherwise the shorter wires will "disappear"
due to the capacitive coupling. I learned that the hard way when
trying to make a cheap multiband dipole for 80/40 (15)/20/10 meters
using the old 4-wire rotor cable shortly after upgrading from novice.
Now I prefer individual wires spaced 12-18" using schedule 120 (very
light) 1/2" PVC.
> On 10/1/2019 9:52 PM, ed_richardson@shaw.ca wrote:
I was then planning on using 2-3 resonant radials on each band
(40/30/20/15 forget about 10m).
You should only need three wires. 30 will work on 10 meters, 40 will
work on 15 meters if you tweak the antenna length slightly.
>> I was considering mounting the antenna about 13-15 above the ground
>> and above a 7 foot high chain link fence.
I would not go any higher than necessary (say 9') as the take off angle
will rise on the higher bands until you get a couple wavelengths above
ground (high enough to lose the ground reflection). I know 10/15 are
probably not very useful given the current solar conditions but you
don't want to handicap yourself any more than necessary.
73,
... Joe, W4TV
On 2019-10-02 12:41 PM, Mark - N5OT wrote:
Hi Ed,
Do I understand correctly that you have two antennas and you are asking
about making changes to one of them? If the other antenna does not
change, then you could compare the new unusual design to the other
design that has not changed, and you would know the answer. If it was
me, I might be inclined to "put it up and see what happens" but be
advised that this approach is slovenly and without merit to some, which
could open you to disparaging public comment, regardless of how loud
your signal becomes because of the new antenna.
For the humor impaired, that was a little bit of a joke really.
Actually if it was me, given that you only need two resonant radials to
make a complete system when they are above ground, and from what I
understand this works when the two radials are symmetric about the
feedpoint, I would not be able to stop myself from digging out some
ribbon cable and cutting it so that I had one wire in the ribbon cable
per band per side that was the right length. then I would have
everything I need in a single assembly with a single attachment point at
each end, per each side of the feedpoint.
Then, I would mount it so that the radials were also symmetric about the
fence.
Some wax poetic about tuning the radials for resonance, but I, being
confident the system was symmetric, would not look back at that, I would
cut the radials to approximate a resonant dipole, feed the whole thing
with a matching network located for my personal convenience, I would
make the radio happy with a swell SWR, and get on the air and work other
radio operators. Comparing it to the other antenna could yield
confidence or concern, a not-inappropriate currency in my way of looking
at it.
Bear in mind, it's possible the exact ribbon cable one uses might turn
out to be too small. This is easily determined without math as
follows: Put it up. Use it. If the ribbon cable heats up, it is too
small. If the ribbon cable does not heat up, it is not too small.
Flames could be an indication too. Watch the SWR while doing the
experiment.
You might be able to do it differently than I have described and achieve
what some would call "better" results, which would be an arguable
statement, and then the argument about the results and how to measure
them (seasoned with comments about engineering practices), would occupy
the posts of this email reflector in the grand style to which we have
become accustomed.
Or, you could do what I have described and get on the air and enjoy
radio contacts from your warm cozy shack during the cold winter that
will soon be upon us.
And thanks for getting me thinking. I might have to go outside and try
that.
73 - Mark N5OT
On 10/1/2019 9:52 PM, ed_richardson@shaw.ca wrote:
Getting ready for another contesting season from my Postage stamp size
City Lot. In previous years I have installed a winter antenna
(Steppir Vertical) in the rear yard as a second antenna to the tower
mounted beams. In the past I have had had so-so success laying out
50-60 radials around the base of the antenna.. The problem is there is
a lot of ground clutter such as trees and wooden fence in close
proximity to the antenna.
I was considering mounting the antenna about 13-15 above the ground
and above a 7 foot high chain link fence. I was then planning on using
2-3 resonant radials on each band (40/30/20/15 forget about 10m).
Has anyone had any experience with a similar configuration? Obviously
keeping the radials away from the fence would be important.
Thanks for the bandwidth!
Ed VE4VT
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