Hello Guys and Gals,
Recently Tree did some work for me and one of the things was to put up the
Comtek 80 meter 4-Square switching unit and a couple of pulley setups for my
raising of the 80 meter slopers. Lately I've been chasing my tail around to get
them dipped in around 3700-3750 Khz. Been adding or subtracting length of the
slopers to bring them into resonance but it seems the more I work at it the
worse things get. Today I dropped back to punt by rechecking my Rig Experts
AA-170 with a 50 ohm load just to make sure it read right...it did.
The sloper dipoles are MFJ 1779B's 'trim to length' except one I had to rebuild
with a hy-que center SO-239. RG-213 from the switching unit to the Rig Expert
and when put together using a long run of LMR-400 about 175-200' back to the
shack. 75 ohm DXE foam RG-11/u coax quarter wavelength stubs from switching
unit to each dipole center. Each 75 ohm stub has multiple ferrite snap on's 5
or 6 to form current baluns.
Here is an example. SE sloper, read SWR of 3875-3850 Khz of 1.0:1 in the shack
on Elecraft W2 wattmeter. 3799 Khz SWR 1.3, 3775 Khz 1.4, 3750 1.5, 3725 1.5,
3700-3650 1.7...Added 19" each end and it seemed to read close to the same
resonance! Added 24" more each end and this time used the Rig Experts to check
it out. Got two dips but not even where I was expecting them
Resonacne 4680 Khz SWR 1.16
RL 23.3 dB |Z| 57.4 ohm
R: 57.5 ohms X: 10.7 ohm
C: 52000 nF up and down
R:: 57.9 ohm XLL -4878 ohm
second dip at 2169 Khz SWR 1.07
RL 28.0 dB |Z| 46.5 ohms
R: 46.5 ohms x: 0.2/0.4 ohms
L: 2.2 nH
R:: 46.4 ohm X|| (infinity or very high)
L:|| same infinity
And the frequency where I was trying to drop down from when I begain this
morning....
3860 Khz
resonance now 3984 Khz SWR 1.8:1
R: 10.9 dB |Z| 27.9 ohms
R: 27.9 ohms x: -0.1
c: infinity
R|| 27.8 ohms X|| -48000 up and down
C|| 8pF
How can I add almost 4' of wire on each end and not drop the resonance down a
couple hundred Khz? What is with the two dips way above and below where the
128' sloper should be resonating? That is an approximate length since by this
time and several days of adjusting I'm not sure what each dipoles length are.
Since I have a 40 meter dipole near the slopers I tried raising and lowering
about 10-15' up and down but it did not seem to change much. I'm beginning to
instinctively cringe each time I have to tune up an antenna because this is
what I know I'm in for. Especially with dipoles!
After all this I just made another run of the SWR across the band with the SE
sloper.
3550 Khz 1.7:1 , 3600 Khz 1.7 , 3650 2.0 , 3700 1.7 , 3750 1.7 ,
3795 1.5 , 3825 1.3 ,
3850 1.1 , 3875 1.0 , 3900 1.1 , 3925 1.3 , 3950 1.5 …..see what I
mean?
Terry
KI7M
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