Topbanders,
I spent some time to change my lossy and critcal shunt feed omega match against
a
better one. Maybe someone remember my endless burning experiences last
winter/spring.
Burned 7/8" Coax-dynamite-bundle as a cap, example:
http://www.df9ox.de/pics/20051101_78_burned.jpg
Now I am feeding my 26.5m (88ft) vert with 2 wires, tap point around 19.5m
(65ft). Its a
kind of not normal solution, I had to do.
Due to mechanics of my tower, the tap point can not be lower than now, also
some
other points like spacing apart tower are given, because of vertical design.
Btw, radials are 120 times abt 20m long.
http://www.df9ox.de/pics/20051101_vert.jpg
Vertical is straight, artefacts are from stitching software. 160m Tap-point is
that flying-T
up in the air. For relations, tower part is 11m (35ft), tower-face is 0.7m
(3ft).
Problem is: Now I have a fine AM medium-wave gamma-matched tower. Resonance
frequency is below 1700 kHz, Variabel-cap says abt 130 pF. Bandwith +/- 15kHz
(border SWR 2).... Could be rented by AM-Pirates.... :-)...
Question: How can I bring the QRG up to 1830kHz?
I know the basics, but:
- lower tap point = not possible
- decrease distance of wire = not possible in upper part (detailed: I have
tried that in the
lower part, but it gives me only some 10kHz, SWR 1 was at 1750kHz, at best)
- tnx W8JI-site, PI-filter would work, but 2 more parts than a gamma-cap are
needed,
so lossy ?
For easy matching:
Is the only solution to raise the feed-point ? Would not be that easy, it is a
kind of crank-
up tower. Think, if it is only solution, I need "some"meter... For up/down I
can not use
the tower as box support.
I hope I am missing a simple basic, which gives me a red face, saying
"...ohhh....excuse
my question, Sir..."
vy 73 de André (Andy) DF9OX
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|
