I run an aluminum mast at 2 inch "OD" at 60 feet with 106 feet of 10 gauge
wire connected at the top to make the "L". Three guide wires that are
active for the first 5 feet, from the 5 foot mark I added an insulated to
break it up from there. Also I drilled three wholes through the top of the
mast in three different directions and inserted three 3/8 tubing into the
holes, adding a small 5 foot top hat.
Its being fed with a 1100pf air variable in series with 50 ohm cable.
It has roughly 25-30 ground radials connected to a 10 foot ground rod that
is tied into the shield of the 50 ohm cable. With a Black and Decker
electric screwdriver attached to the air variable, I can use the whole 160
meter band.
Keep in mind, the distance the horizontal wire is to ground can change the
S.W.R.
Raising or lowering the horizontal wire can change the swr curve. This is
something one might want to try before cutting the wire to achieve 1.1 swr.
It works great!
Good luck. (and don't forget to search the web!)
Ken
K3YI
-----Original Message-----
From: topband-bounces@contesting.com
[mailto:topband-bounces@contesting.com]On Behalf Of i4jmy@iol.it
Sent: Tuesday, January 06, 2004 11:02 AM
To: k9kl
Cc: Topband
Subject: Re:Topband: 160m int L
Inverted L does not necessarily need a cap (a reactance) to work and to be
properly matched.
It may be matched with a capacitor with when its feed-point is looking
reactive (inductively), as well as it may happen with any other antenna.
If the inverted L is not quarter wave resonant, but longer, its impedance
looks higher, and inductive.
At a certain lenght, and taking into account also ground losses, feed point
impedance can be something like 50 ? J. Putting in series a capacitor whose
reactance is +J the SWR goes 1:1.
Moreover, if the capacitor is variable some adjustment is possible when the
operating frequency is changed.
Note anyway that the higher impedance has nothing to do with efficiency
while inverted L length may change substantially radiation patterns, as well
as the energy radiated in the H and E planes.
If what you want is a medium and long distance antenna, an improvement over
your dipole, I don?t suggest the inverted L is above a ¼ electrical in
length.
73,
Mauri I4JMY
> Well the snow is finally starting to fly here in Wisconsin so it is time
to
> put up a 160 antenna.I have used an inteverted v here for years with the
> apex at 70 feet and the ends at maybe 30 feet,pretty poor.......I would
like
> to try an inverted L.It is my understanding that they need a cap. to tune
> them into the freq that you want.I have an 80,70 and 2 60 foot towers to
use
> as supports,and lots of room for radials.Are L's directional?What would be
a
> good starting point in length for say 1.85 mhz.Are they broadbanded?Any
> ideas???? Gregg K9KL
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