Tuning.
Tuning the matching network was achieved with help of AEA
HF SWR Analyst and transceiver Yaesu FT-990AC with a priority
of CW parts of HF bands. All initial adjustments were made without
feed line, right at the out connector of the matching box. The
Analyzer was used in general adjustment and selection of circuit
types. It is necessary to bear in mind that the analyzer makes
measurements at very small signals, accordingly, it is very sensitive
to even greater signals coming from the air, so that can result
in chaotic distortions of diagram of SWR. The adjustments of SWR
were checked with transceiver finally, but they only have confirmed
that all have been properly adjusted by means of the analyzer.
The measurements with coax feed line showed even lower (approximately
10 percents) SWR due to the coax losses. It always is possible
to adjust SWR down to 1:1, it only depends on how accurate you
are and time spent. In my case SWR was down to 1:1.1/1:1.2, which
seemed to be quite sufficient for the time being, hoping to improve
it to best SWR later on, but this time hasn't come yet :-) Results.
Though the theory predicts of low efficiency (especially on 1.8Mhz)
and rather high radiation patterns in a vertical plane (on 18Mhz
and above), operating experience has proven (I operate all HF
bands since 1997 with this antenna) to be a success! It's hard
to make impartial assessment to the quality of the omnidirectional
aerial because it depends on too many factors, for example: propagation,
output power, experience of a HAM and so on.
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But those who used to chasing DX up to 2004 (I am not
too active since than due to non HAMRADIO reasons), should remember
my callsign, their assessment would be more convincing than my
own... A direct comparison with other aerials in my case is impossible,
since I have only one. However, indirect comparisons while poking
pile-ups show high efficiency on all HF bands. 322/CW out of 325
countries by DXCC are worked with this
aerial and 100W (> 90 % QSO, the others by means of 3xGU50-200W
out amplifier only on 3.5/7/14MHz) since 1997 and up to 2004.
Here (http://www.feerc.obninsk.org/rw3xa/ant/rw3xa.txt)
is
my LOG quote. On lower bands the near field certainly is weaker
(in comparison with the neighbour HAMs using horizontal antennas).
The difference was especially appreciable at indirect comparison
with R7000+, not in favor of the last. I took the matching box
several times during field test with me, connecting it to the
mast of similar size, but different diameter aluminum tubing (approximately
in 1.5 times less). The aerial was erected right on the ground
with an insulator and same radials as I use "on the roof
position". In comparison with the aerial set up on the roof
of 9 stores block of flats, SWR differed by 20 to 30 percents
due to insignificant shift of its resonance. SWR tables of the
aerial (on top concrete roof cover of the 9 stores block of flats)
on separate HF bands are resulted below. In addition, lowering
the signals by 10-20db of the other bands (i.e. if the network
is switched to the other band) makes additional attenuation much
useful: especially when the heavy QRM from my neighbour RA3XO
while he is operating even the other band but his vertical is
near my antenna, 12 meters apart. Here
(see page 38) is RW3XW matching network box picture. This is the
same idea, but his antenna is 18 meters high, though more effective
on lower bands, but LC network is different, of course.
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