Dear fellow TopBanders,
I am still struggling for building something that is better than my previous
bottom-loaded 30 meter vertical. (Sometimes I feel I should re-build the old
configuration, which I used on four bands with a matching unit).
Currently I have a 23 meter vertical part (average diameter 3 inches,
telescopic)with two 22 meter wires (diameter 3 mm) attached to the top, at
an angle of about 60 degrees to the vertical.(that is, 30 degrees slope from
horizontal) Dimensions were calculated using ON4UNs latest book (pp. 9.43
through 9.45). When I connected the MFJ analyzer to the antenna (no matching
elements, just a ten-inch piece of coax and inner conductor to radiator,
shield to grounding system of 60 radials), I felt like I have done nothing:
the impedance around 1800 kHz is over 300 Ohms and SWR is close to infinity.
The lowest I could go to about 1750 kHz, where the antenna is some 200 Ohms
and still extremely high SWR. All connections are correct, the MFJ probe is
good, everything is good, except that I had to skip the ARRL CW because the
antenna is practically useless...
My questions are:
Is that a T antenna, or is it a short vertical with a capacity hat? (At the
description of the T antenna one of the books says the horizontal wire
should be about twice as long as the missing vertical part - that is, about
2x17 meters in my case, probably a little longer because of the slope of the
wires)
Where is the problem? I thought the antenna should be about 25 Ohms and
resonate around 1830 kHz (based on calculations), and I even constructed a
high-power 2:1 impedance transformer (S56A system) to match it to 50 Ohm
coax.
Sorry to ask these, but I am absolutely disappointed....
73 Steve HA0DU
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|