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One - Do- Tree... Tests with the 2x2x2 40M Yagi stack




 
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Author Topic: One - Do- Tree... Tests with the 2x2x2 40M Yagi stack  (Read 156849 times)
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Steve - WB3HUZ
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« Reply #325 on: October 11, 2009, 12:18:55 AM »

Those lengths were chosen for two reasons. The first length provides the proper inductive reactance for the reflector element when shorted. The second length was to added to the first length when connected to the driven element to produce a 50 Ohm impedance at the end. I didn't worry about whether it was a quarter-wave or not. The match was the important part.

But don't get too wrapped around the axle on those numbers anyway. They were based on models. I did not even need the extra matching section when I built the loops. The impedance was close enough to 50 Ohms. Adding any more 75 Ohm coax to the mix would have only made the impedance lower than 50 Ohm. Since your installation is different, you will need to find the correct lengths for your site.
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WA1GFZ
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« Reply #326 on: October 11, 2009, 06:40:38 PM »

Steve,
Just got it working again. I have 2- 20 foot lengths of RG11 hanging off the loops. I had to extend the driven element and now both are about 135 feet. I have a 9 foot stub hanging off the reflector hunk of RG11. Hope to add the transfer relay next and dial in the stub. I'm flat at 7.1 so close. Seems to play worked and listened to a few stations. proof will be when I flip it.
My VSWR came up the other day when I made the driven element shorter which was a mistake. So I agree you may not need the RG 11 at 20 foot spacing.
The 20 foot feed lines make it possible to work on the the switching close to the ground.
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WA1GFZ
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« Reply #327 on: October 11, 2009, 10:12:08 PM »

Steve,
I went back and looked at the simulation and find when you reduce the size of the reflector to the same size as the driven the input z of the driven goes up and wants the 70 ohm section. This makes me want to revisit the 3 element after I get this thing working. I'm not surprised that you didn't need the second section of RG 11 in series, since I got a good match with 18.6 feet of RG 11. I just need to dial in the reflector shunt since my simulation showerd it needed another 8 feet and you got away with just shorting the 18.8 foot line.
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WA1GFZ
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« Reply #328 on: October 12, 2009, 11:01:37 AM »

JS transfer relay set up at the tower and it looks pretty good. I'll dial in the stub when the band gets a bit longer. Loops are about 5 feet shorter than HUZ design and need to switch in a 8 or 9 foot stub on the reflector. RG-11 ohm sections are about 20 feet long. Covers the band at 2:1 VSWR. West a tad wider.
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WA1GFZ
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« Reply #329 on: October 12, 2009, 07:55:47 PM »

Here is one to think about. I get on tonight and get a few good reports with a little help from HUZ. But there is just one issue. The switching is backwards. I carefully rang out the transfer relay so power off points East but I have to power the relay to get a stronger signal to EU. So either I was brain dead this morning or I have a driven element director. Looking at the stub side I have 20 feet of RG11 with about 9 feet of RG8 as a shorted stub. This adds up to less than a half wave electrical which may be tuning in in the wrong direction. Last night  before I installed the relay I couldn't raise anyone in EU running 100W
But do I mess with 3 s units FB. Or take this as a stepping stone to 3 elements.
More simulation dumbo maybe the stub needs to be over 1/2 wave to be a reflector. It has me dreaming of a driven center element and 2 stubs flipped +/- 1/2 wave..  One othe clue when I shorted the 20 foot RG11 the VSWR was way off. It wanted at least 4 feet of additional coax to play.
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Steve - WB3HUZ
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« Reply #330 on: October 12, 2009, 08:45:21 PM »

Did you get the direction thing straightened out Frank? You got one report tonight of a 3 s-unit difference when you switched. That's pretty good!
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Steve - WB3HUZ
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« Reply #331 on: October 12, 2009, 09:02:20 PM »

Jack and Tom stopped by later. You should have come back after dinner.
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #332 on: October 12, 2009, 09:32:05 PM »

Jack and Tom stopped by later. You should have come back after dinner.


We had a great time again tonight. 

Yep, we all worked a new one on 40M -  Billy, YC6NE in Indonesia.  I didn't think it was possible this early in the year. He was about a 5X6, not real loud but not PW. Billy is a big DXer as shown by his webpage.  That's a rare one.  (As I bury it in my notebook and forget about it by tomorrow... Grin)

T
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Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
WA1GFZ
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« Reply #333 on: October 13, 2009, 08:20:17 AM »

I must have missed you guys. I got back to the shack about 8:15. Sounds like you had a good time. No I didn't climb up the tower and check the relay.
It was dark and I didn't feel like going out.
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Steve - WB3HUZ
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« Reply #334 on: October 13, 2009, 05:20:14 PM »

Yes, the band was better earlier in the evening. I listened later on and most of the signals were down about 10-15 dB. Same for 80 meters. Still worked a mobile in the UK though.  Cheesy
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WA1GFZ
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« Reply #335 on: October 13, 2009, 07:25:22 PM »

Well I had a bit of light when I got home and checked the transfer relay. Yup it is a director. Element lengths are quite close to 140 feet and flipping  the pattern shifts the CF by about 20 KHz. the RG11 stubs are close to 20.5 feet and the switched stub adds about 9 more feet so just over a quarter wave electrical. Maybe the slightly longer stub then Steve has if flipping the thing when I go past 90 degrees. I need to dump some numbers in my 3 element simulation and let it loose and see what it wants. I have the center element fed so the reflector and director can have stub lengths as variables.
Tom remember old W1JF. Dick always thought that if spacing was under a quarter wave use a director rather than reflector. It works so not sure I want to change it just yet. I'm thinking I'll need to add more coax to the stub to make it a reflector....or make it a lot shorter. I like working from the ground, getting too cold to climb. 
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Steve - WB3HUZ
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« Reply #336 on: October 13, 2009, 09:24:00 PM »

You'll want a reflector.
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WA1GFZ
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« Reply #337 on: October 13, 2009, 10:26:51 PM »

I want to figure out what is going on. I may have to add another 45 degrees of length to flip it back to a reflector. I don't want to cut the RG11 much shorter but hope to find some quality N connectors Friday. If that is a director and I can make it a reflector than it will be 3 elements shortly after that. You are about 11 feet shorter than me for the reflector stub which is darn close to 45 degrees. Our loops are within a foot of each other total length. My loops not quite as tall about 30 feet and you are around 40 feet so I would think I have a slightly higher input z, but I'm closer to the ground so that may pull it back down.
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WA1GFZ
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« Reply #338 on: October 15, 2009, 09:12:04 AM »

Steve your 18 feet is a good number even in simulation. I'm playing with a 3 element that wants 32 X VF for director and 22 X VF for reflector. I started at about 20.5 feet so adding more length flipped it. I have a 3 element simulated so it will take 50 ohm feed with a 1.3:1 VSWR on a 20 foot boom.
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ei9ju
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« Reply #339 on: January 22, 2010, 03:25:03 PM »

I've been on the receiving end of Tom's 2x2x2 and can hear nothing else coming out of the States even close, it's head and shoulders above the rest. Wink

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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #340 on: January 22, 2010, 06:22:11 PM »

I've been on the receiving end of Tom's 2x2x2 and can hear nothing else coming out of the States even close, it's head and shoulders above the rest. Wink

Nice to work you the other night on 40M, Gerry!

You were ceratinly the Euro-ChannelMaster in here from the Land of Ire.  It's always good to see our big efforts pay off.  Thanks for the report, OM. Hope to get on sometime this weekend on 40M.  Be sure to give me a call if you tune in.


73,

Tom, K1JJ

A picture of Gerry's multi-band quad:


* latest_quad_6m_element_002.jpg (88.08 KB, 800x600 - viewed 805 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
w6xr
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« Reply #341 on: January 22, 2010, 07:48:40 PM »

Tom,

Your story about the low 40 array opening the band into Europe is fortunately a common one.  Once, in a galaxy far, far away I was the 40 meter op at W2PV in Schnectady NY and I do so vividly remember the low (60') forty meter yagi grossly outperforming the stacks on forty until the sun was set.  The low 40 outdid a stack at 60 and 120 on one rotating pole and the single low 40 made a fool of the stack at 220' and 110'.  All of Jim's 40 meter antennas were Telrex three element beams on very strong booms.

Jim, W2PV, explained to me the wave theory that caused the low antenna doing so well and it all had to do with the high angle antenna (the low one) getting through a specific layer quickly, while the low angle signal dawdled in this region and lost its amplitude on it's way through.  It all made sense!

Get the driven elements set up correctly and you will have a ball with the big array.  Just be sure you can switch your lowest 40 meter yagi so it's all by itself until well after sunset.

73

Natan W6XR
Freeville, NY 
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #342 on: January 22, 2010, 08:44:27 PM »

Interesting info, Nathan.

Good going -  you associated with the master, W2PV. Many still refer to his famous writings on Yagis.

Since posting the results using a lower reference Yagi against the stack, I now use a simple isolated dipole at 45' as a reference against the stack.  I  see at least  12db in favor of the stack until an hour before sunset. Then as time gets closer, the stack really starts to perform and can be as loud as 20db (or more) better than the dipole an hour before and after sunset.   I'm sure a lot depands on the time of year and band condix, of course.

Last week I wanted to see how early in the day I could generate a pileup into Europe on 7133 khz. At 12:30 local (afternoon) the sun was high and I could easily hear Euros talking, however most were beaming VK and east. I got on and called a few. Some thought I was a Euro playing games and others had their antennas facing the other direction. It was not the norm for USA, I found. I then called CQ and slowly drew in a good pileup. I found I could barely hear them on the dipole and contacts would have been few. But on the 2x2x2 stack it was cake and quite a thrill. The best part was hearing Euros say they never worked USA that early in the day on 40M.  Next I want to try it at 9AM local when it's still full daylight in Europe to see what happens.. Cheesy.  I think the lowest angle possible will be best then, but will have to find out.

The take off angle is down around 13 degrees, a single focused lobe on the horizon - so it is always interesting to see what a lobe that low will do with the ionosphere.

I hope to put in a homebrew in-phase / out of phase switcher next  summer to try some higher angles. As the sunspots come back, I will wish for higher angle lobes, I am told.

73,

T

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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
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