Topband: trying to tune up 80 meter 4-Square

Fri Oct 12 19:07:06 EDT 2018

Interesting. This is not how I tuned my 40m 4-square, albeit with tubular elements not slopers.

Anyway, my understanding is that you disconnect all four elements from the control box and measure at the feedpoint, not through the phasing lines. I did it that way and had no trouble tuning the elements. I did, however, tune them to a frequency that was something like 5% below the target resonant frequency. I can't remember the exact frequencies now, but I think I wanted the array resonant at 7.025 MHz, so I tuned them to about 6.700 MHz. Might have been a little higher than that.

I've not heard that you must lower the other elements to do the tuning. Certainly a pain with nesting tubular elements.

73, Dick WC1M

-----Original Message-----
From: Guy Olinger K2AV <k2av.guy at gmail.com> 
Sent: Thursday, October 11, 2018 11:29 PM
To: David Raymond <daraymond at iowatelecom.net>
Cc: w3ea at hotmail.com; terry burge <ki7m at comcast.net>; TopBand List <topband at contesting.com>
Subject: Re: Topband: trying to tune up 80 meter 4-Square

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 at 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 at 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 at contesting.com> on behalf of terry 
> burge <ki7m at comcast.net>
> Sent: Thursday, October 11, 2018 6:11:37 PM
> To: topband at 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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