Topband: trying to tune up 80 meter 4-Square
terry burge
ki7m at comcast.net
Fri Oct 12 21:30:57 EDT 2018
FYI concerning my 80 meter 4-Square using sloping dipoles....
I have now disconnected all four 75 ohm links from the Comtek box. The 75 ohm stubs are just left hanging, not shorted or anything. Comtek box out of play right now. Three of the dipole are laying on the ground with shorts across their feed points. The SE sloper is now back up with only a 110' LMR-400 (50 ohm) coax running to the Rig Experts AA-170. I have removed all changes I had done on each dipole so we are back to the start. It's getting dark and I'm tired out so we'll call it a day.
3597 Khz SWR 1.9
Rl 10.4 dB |Z| 93.0/93.3 ohms
R: 93.2 ohms x: -0.0/0.0 ohms
c: infinity
R|| 93.1 ohms x|| infinity
c|| 0pF/2pF
I plan to adjust the SE sloper to 3700-3725 Khz. That should give me good coverages 3650-3850 Khz which should be idea for contest like CQWWPHN as well as working the SSB DX window around 3795 Khz. Plan is to follow this procedure doing each dipole. Since my ground is pretty rough and it's hard to make accurate measurements of the lengths I will just follow dipping them in this way.
Then I will connect them back up to the Comtek box through the 75 ohm stubs. At that time I should know the dipoles are all approximately equal length and resonant. Once on the Comtek unit I should be able to use the dump power to do any further needed length changes. Any changes will be duplicated on each sloping dipole.
Sound good?
Terry
KI7M
> On October 12, 2018 at 5:09 PM Dick Green WC1M <wc1m73 at gmail.com> wrote:
>
>
> I might have done that. It was 20 years ago… :)
>
>
>
> From: MrToby <mrtoburen7 at gmail.com>
> Sent: Friday, October 12, 2018 7:11 PM
> To: Dick Green WC1M <wc1m73 at gmail.com>
> Cc: Guy Olinger K2AV <k2av.guy at gmail.com>; David Raymond <daraymond at iowatelecom.net>; w3ea at hotmail.com; TopBand List <topband at contesting.com>; terry burge <ki7m at comcast.net>
> Subject: Re: Topband: trying to tune up 80 meter 4-Square
>
>
>
> You dont have to lower them but you need to short them to ground to make them electrically invisible
>
>
>
> On Fri, Oct 12, 2018, 6:07 PM Dick Green WC1M <wc1m73 at gmail.com <mailto:wc1m73 at gmail.com> > wrote:
>
> 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 <mailto:k2av.guy at gmail.com> >
> Sent: Thursday, October 11, 2018 11:29 PM
> To: David Raymond <daraymond at iowatelecom.net <mailto:daraymond at iowatelecom.net> >
> Cc: w3ea at hotmail.com <mailto:w3ea at hotmail.com> ; terry burge <ki7m at comcast.net <mailto:ki7m at comcast.net> >; TopBand List <topband at contesting.com <mailto: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 <mailto: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 <mailto: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 <mailto:topband-bounces at contesting.com> > on behalf of terry
> > burge <ki7m at comcast.net <mailto:ki7m at comcast.net> >
> > Sent: Thursday, October 11, 2018 6:11:37 PM
> > To: topband at contesting.com <mailto: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
> >
> >
> >
> > _________________
> > Topband Reflector Archives - http://www.contesting.com/_topband
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> >
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> > Topband Reflector Archives - http://www.contesting.com/_topband
> >
>
>
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>
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