Essential point that might be missed: each one of the elements, one at a
time, must be tuned independently with the other three elements down. This
is the initial tuning. If when everything hooked up characteristics are OK
then you’re done.
Finish initial tuning and it's *not* OK? To slide the ARRAY center freq up
or down, there are several methods:
1) Redo the initial one at a time tuning with an opposite-to-the-error
adjustment to the one at a time tuning target frequency.
2) make *small* identical wire length changes to all four elements at the
same time.
3) If you're an engineer and have the equipment and design software,
redesign the box to work with what you have. ☺
Just remember that the elements of a four square are very heavily coupled
to each other, regardless that all are driven from the control box. The
final result is a complex function of the driven current AND the effects of
the heavy mutual coupling between elements.
73, and good luck,
Guy K2AV
On Thu, Oct 11, 2018 at 8:15 PM <daraymond@iowatelecom.net> wrote:
> Yes, install ONE sloper. . .measure and cut to resonance. Duplicate that
> measurement for the other three. 73. . .Dave, W0FLS
>
> -----Original Message-----
> From: Wayne Kline
> Sent: Thursday, October 11, 2018 6:03 PM
> To: terry burge ; topband@contesting.com
> Subject: Re: Topband: trying to tune up 80 meter 4-Square
>
> Terry,
>
>
>
> I assume you only installed ONE sloper and made your measurements ?
>
>
>
> With all 4 installed there is way to much mutual coupling to get a
> meaningful reading.
>
>
>
> If your readings were from only ONE antenna tuned with a length of 50 OHM
> cable at it’s feed point and trimmed to your desired freq. and that FREQ
> will rise about 80 to 120 KC when the 4 are installed .
>
>
>
> Wayne W3EA
>
>
>
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows
> 10
>
>
>
> ________________________________
> From: Topband <topband-bounces@contesting.com> on behalf of terry burge
> <ki7m@comcast.net>
> Sent: Thursday, October 11, 2018 6:11:37 PM
> To: topband@contesting.com; terry burge
> Subject: Topband: trying to tune up 80 meter 4-Square
>
> 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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> _________________
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