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40 Meter Two Element Delta Loop




 
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W9GT
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« Reply #25 on: October 23, 2009, 12:44:42 PM »

Those relays are good for full power. Just don't hot switch them.   Grin  Remember, if everything is tuned up correctly, the impedance is around 50 Ohms, so the contacts don't need to be any larger than those of your TR relay. Ever looked at the size of the contacts in a Dow-Key?

Yes, I agree the contacts should be fine, but the insulation might not be all that great. Might have to use something a little more robust, if you are using it for AM.  I have some latching vacuum relays that I got for another project and never used.  They might be nice also, since they can be switched with a pulse and then remove power.  I'm not sure though if it is politically correct to mount Jennings vacuum relays in a Radio Shack box.   Shocked Grin

73,  Jack, W9GT
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Steve - WB3HUZ
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« Reply #26 on: October 23, 2009, 04:24:23 PM »

LOL. Yes, the Jennings will reject the rad shack box - kinda like a kidney transplant.

I've used mine on full power AM and no problems. JJ has verified this too.
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WA1GFZ
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« Reply #27 on: November 09, 2009, 09:49:21 PM »

Steve,
I reduced the length of my stubs to 19 feet and turned the director into a reflector. I even saw the effect in simulation interesting how a slight length change has such a large effect. I think I got a little water in the transfer relay since the resonant frequeccy shifts 100 kHz down pointing west. When I had a director the resonant frequency only shifted 25 KHz. I didn't add the RG11 stub on the feed line. It is about 19 inches shorter now. Both loops 137 feet and simulation says 135.8. I had the relay in a plastic bag and there was some water in it this morning.  I'll let it sit a couple days before I mess with anything. One corner is down a bit and want to move the support to a higher tree this weekend. The  final relay box will be at about 15 feet and I ran 50 feet of LMR400 into the shack. 50 feet of LMR400 is very close to an electrical 1/2 wave on 40.
It seems to play and worked a couple guys on 40
Do you think I should reduce the stub or loop length to shift the resonant frequency up a bit?
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Steve - WB3HUZ
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« Reply #28 on: November 09, 2009, 09:54:16 PM »

The progression to make the system was as follows.

1. Put up one loop and cut it to resonance at the desired frequency.

2. Take down the first loop and put up the second loop and cut it to resonance at the desired frequency.

3. With both loops up and spaced properly, add the stub length required to get the needed amount of inductive loading.

4. Trim both loops the exact same amount to achieve resonance system at the desired frequency.

5. Then check the SWR and see if any matching is required. In my case none was required. If it were, I would have dealt with it independent of the existing stubs (those would not have been touched). An L network or a series matching section would have been most likely applied.
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WA1GFZ
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« Reply #29 on: November 10, 2009, 08:21:05 AM »

Steve,
I'm sweeping each loop keeping each side equal for wire length and stub. I do have 1 corner a bit lower than the rest of the antenna. This could be effecting the resonance when I swap the pattern. I was just wondering where you ended up with total wire length. My simulation says I'm a foot or so too long. I notice things changed when I pulled the relay up the tower. I think I was pulling the bottom in closer than 20 feet when the cables dropped to the ground.
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Steve - WB3HUZ
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« Reply #30 on: November 10, 2009, 11:09:13 AM »

I made it a little long and then took about three feet off each. So, IIRC, I wound up with about 138 feet of total length. I am using insulated #13 stranded wire.
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WA1GFZ
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« Reply #31 on: November 10, 2009, 12:20:38 PM »

I bet there is some water in the transfer relay since we are so close in lengths. I'm using #12 solid and insulated. The only difference is I have a tower going up the middle.
When facing East the resonant frequency is 7.13 MHz. Time to build the box I bought at Deerfield and mount it on the tower.
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WA1GFZ
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« Reply #32 on: November 21, 2009, 03:44:00 PM »

Success...finally. My simulation showed a slightly longer stub and slightly shorter loop then the HUZ configuration. Steve said something that made me think last night. He said you just have to start trimming the length until something happens. So this morning I went for it. I cut a foot off at a time on the west loop and after 2 feet the resonant frequency started coming up. I dialed it right to 7.160 and then the East loop to 7.160. The longer stub 18.8 feet of RG11 (.66) reduces the Q of the antenna enough that it is under 2:1 across the whole 40 meter band. FB looks good. now back to the afterburner.
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Steve - WB3HUZ
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« Reply #33 on: February 01, 2010, 10:44:42 PM »

The loops at sunset last night.

Click on the image below for a larger view.



* loopsatsunset.jpg (295.35 KB, 768x1024 - viewed 919 times.)
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K1JJ
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« Reply #34 on: February 02, 2010, 12:10:59 AM »

No wonder you're Whirl-wide on 40M!   The lake, slope and swamp in front of it makes it play like it's at twice the height.    Dr. Love advised me not to get any more comparisons with you...

Getting the wire to stand out like that is FB.

T
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WA1GFZ
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« Reply #35 on: February 03, 2010, 07:37:54 PM »

Very cool picture.
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