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2 Meter Slot-Cube Antenna (QST Jan 2019)

Feb 13th 2019, 09:28

jimvw57

Joined: Dec 16th 2017, 15:23
Total Topics: 0
Total Posts: 0
I believe different brands of the copper connectors are not all the same length.

kmikemoo did that change the gap between the vertical tubes?
Feb 16th 2019, 23:06

jimvw57

Joined: Dec 16th 2017, 15:23
Total Topics: 0
Total Posts: 0
did some more playing around today and found that by moving the feed point to 4 inches back from the vertical l, I get resonance at 148 Mhz with SWR at 1.3. I attached wire directly to the horizontal tube without using the short stubs with the tee connectors

UPDATE
I took it outside and stuck it in a tree about 6 1/2 ft off the ground, reports from other stations say it is much better than my od J-Pole and lots less background noise, I noticed it also doesn't feedback into my computer speakers.
Feb 26th 2019, 20:32

kmikemoo

Joined: Jun 15th 2018, 21:54
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jimvw57 I didn't change the vertical spacing (which I assumed was the 7" pieces). I just expanded the two squares. I also tried moving the t stubs away from the verticals with the original lengths and I'm pretty sure that my resonant frequency went up. I have yet to put mine on the air. Snow and cold are winning.

Mar 2nd 2019, 16:31

jimvw57

Joined: Dec 16th 2017, 15:23
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Total Posts: 0
same as what I found.
Mar 11th 2019, 06:04

hartford

Joined: Nov 15th 2013, 19:29
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Total Posts: 0
I built the antenna over the past couple of weekends and found that mine also was resonant at 152 MHz. I lengthened two of the horizontal pipe sections 1 1/4" each and the resonant frequency dropped to 146 MHz. The SWR is below 1.3:1 across the band.
I also abandoned the CPVC coupling for two copper end caps, this gives a little more metal to tap into for the coax connection.

I would also like to try this antenna as a mobile as suggested by AD6ZH, and would like to know if anyone has tried it over a ground plane.
Apr 17th 2019, 00:01

KC6ZBE

Joined: Jul 16th 2010, 02:31
Total Topics: 0
Total Posts: 0
Quote by N7LT
KC6ZBE, your initial resonance at 152Mhz is a LONG way off from the ham band. Did you readjust the size to reach resonance on 2 meters? if so, what are your final measurements?

Thanks for your help guys! de N7LT


Sorry for the late response, OM.

I see a lot of other people got their cube resonant somewhere in the 150mhz range as well with the original specs.
I tried the heating up/hammering out method but gave up. I decided to try to make a new one using K1TGF's dimensions. I like the idea of how he added some length on some sides.

Got a few more pieces to solder and we will see how it goes.
Apr 17th 2019, 19:56

KC6ZBE

Joined: Jul 16th 2010, 02:31
Total Topics: 0
Total Posts: 0
SUCCESS!

Using K1TGF's dimensions, the new one I built came out resonant enough in the 2 meter portion with an SWR of 1.4 at 146.500 mhz which is just fine by me.

Also, instead of screwing in the feed line to the stubs, I used 3/4in copper pipe strap and wraped it around the 1/2in stubs and secured it with a bolt (if that makes sense).

73
Dave.
Apr 21st 2019, 18:13

jimvw57

Joined: Dec 16th 2017, 15:23
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Total Posts: 0
I used hose clamps so I could adjust where they are positioned. Easier to tune
Apr 30th 2019, 10:19

KG7QJB

Joined: Feb 7th 2015, 15:55
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My swr came out 1.4 at 146.520 using 50 feet of LMR 400 and 5 wraps of choke using a smaller coax on the plastic gray pipe (electrical pvc) . Very impressed with it , works as it should. My pictures are on QRZ.com not sure how to get a picture on here. KG7QRZ Curtis in Pasco, Washington. P.S. some of the lengths were wrong on the copper pipe, figured it out pretty quick that something was wrong.
Jul 15th 2022, 15:25

jimvw57

Joined: Dec 16th 2017, 15:23
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Total Posts: 0
after over 3 years of weekly use, the only thing I found needed was to clean up the contact points and added a hole to drain water out of the tubes. Not sure how it gets in there but it has a way out now. When i see the SWR go up, it is time to clean up the contact points for the cable connections.
Jan 28th, 14:01

jimvw57

Joined: Dec 16th 2017, 15:23
Total Topics: 0
Total Posts: 0
Update** Still using this lil guy at least weekly, I did change and added it to the top of a 40 ft tower, Still getting reports of clear transmissions up to 50 plus miles away.

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