Topband: trying to tune up 80 meter 4-Square

[terry burge]

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