Todd, Thanks for sharing. I've been following your post. I too wondered about sharing the radial field like you did. My situation is somewhat similar in that I feed a 90 foot tower which has a c31 at 95 feet and a two el xm 240 40m beam at 75 feet beneath it on a gate....the antennas should give me some top loading but it has never been modeled. Shunt wire presently comes down from 70 feet about 3 feet out from the tower to the base of my tower. The Tower(AB-105) Is guyed at 40 and 70 feet, guys are broken up with insulators. I have tried to find the resonant freq of the tower and at one time or another I have moved that tap from 40 feet to up 50 60 70 feet in 2 foot increments. (that's a lot of climbing)and never found the sweet spot if there is one. I saw your post and Like you I wondered what would Happen if I ran an inverted L up to 90 feet. (I already had a pulley and rope up there) and run the tail out to the west since I seem to be "deaf" to the west and north west (and really everywhere) and would share The same radial field which has 2 radials that I was able to stretch out to 100 feet (in a very crooked line) and a couple of others that are 60 feet and 56 others of various lengths from 20 to 50 feet. The correct word is probably not "share" as only one of the antennas would be hooked to the xmtr at a time. My salt water swimming pool Is about 8 feet from the base of the tower. Not sure if the pool helps or hurts in any way. In the fall, once I cover the pool,I run out 30 radials of varying lengths which I have to roll back up again come spring when we uncover the pool. I remotely tune the tower with a motorized vacuum variable capacitor to tune the tower for minimum swr. I've only played with this since I saw your post. 5 years ago Before trying the shunt fed tower, I put up the inverted L with 4 buried radials mainly to be able get some points for PVRC in the DX contests. 160m has a way of hooking you in to trying to do just a little more than the bare minimum I then added 6 more radials, then a few more and then a few more after that. I noticed that things got better Up until I had 20 radials or so and then adding more radials didn't seem to help or hurt anything . Bandwidth went down at first and then like it says in the on4un book, leveled out. The real problem for me is RX. I have never heard a KL7 on 160 even though guys locally 3 or 4 miles away hear and work KL7's in every arrl or cq 160 contest. (I'm located 7 miles off the water at Virginia beach) I have managed 1 KH6 QSO (could not hear either of the two I saw spotted last night in the stew) Things are up and down here. Stuff I don't expect to hear. I sometimes get, but other easier stuff I never hear. Example, when I was able to work the ET3 on 160 a while back. I also got Yemen when K1ZM was in sanaa, I got bouvet last time out, the last 2 FT-8's but still no KL7. Never expected to work the VP6 or whatever the latest big dxpedition was a few weeks ago , the one that had to leave early due to weather. Vp6di Ducie? Xmas? Either one would have been new one for me on 160. I just knew I wouldn't hear them so I did not check for them........Until the night before they left, I turned on the rig, I was on 40 m and saw them spotted. Figured ok I'll waste my time and Clicked on the spot. I could actually hear them on my 40 m beam, switched to the shunt fed tower and zip, nada, nothing. Back to the 40m beam and they were still there. Went down to feed point and found that the dogs toy was entangled in the shunt feed and in trying to remove it, the dog had ripped the feed wire off of the top of the vacuum variable with his toy still attached. It was pouring rain so since this expedition was gonna be there 2 more days I figured I'd fix it at first light or as soon as the rain stopped and be ready that night. I was WRONG. The weather apparently got so bad they left early so I never got to call them.
In the Stew I tried out a couple of quick swap outs between the inverted L and the tower on both G4AMT & KV4FZ last night in the stew when both were running em and I could not discern any difference on receive between the L and the tower. I worked both of them with 100 watts. I called N6RK on both antennas. On the inverted L I got an imi, and on the shunt fed tower no response. Lots of qrm. n6rk was not loud but he was the ONLY w6 I heard. N2IC was loud from new mexico all night. When I try to call cq I can hear partial calls and I know there are stations calling me. I know I was called by an EU4, 9A2 and a TF2 last night but I couldn't pull any of them thru. The shunt fed tower seems to radiate pretty well on xmit but on rx its an alligator. I definitely get out better than I hear but its still pretty discouraging to call CQ and to look at dx summit and see.....................spots like these from the europeans N4FX ZZZZ ?????. N4FX no receiver N4fx don't waste your time calling, rx broken N4FX No ears N4FX Unmanned beacon station?? N4FX Big signal does not hear N4fx code reader failure??? N4FX op asleep at key??? N4fx where is he listening?? is he even listening? N4FX working crossband??? I have tried a 200 foot BOG which actually runs across the street and cars drive over it. (I roll it out after dark but not a busy street). And roll it back up when I am finished) It works pretty well sometimes but last night was not one of those times. tried a W2UP rotatable Loop which lost all directivity when I ran some radials out in its direction. A VE3DO loop (no joy at all) I just had my mp1000 tweaked and have a 756 pro II and don't think either of them has an rx problem. Talked to Lee K7TJR about his antennas and because my tower sits almost smack dab in the center of my lot he didn't seem to think it would work well even if I were to detune the tower. I'm not sure that a K9AY or SAL would work for the same reasons. Like you I think I will just take down the inverted L. I learned quite a bit from some of the comments you got. I didn't fix anything but definitely know a lot of things that won't work. It was not particularly reassuring that when AA1K was here last year, I asked him if he thought a choke at the feed point would help anything? He said he didn't think one was needed on a vertical. Then I asked what else I could do he suggested that I might want to consider putting up a FOR SALE sign. Thanks again for sharing your results. 73 Chet N4FX KP4EAJ, VP2A, ZD8W, VQ9Xx, KL7AIZ, KG4ZO, N6Zo/HH9 N6ZO/6Y5 -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Rob Atkinson Sent: Sunday, December 30, 2018 9:52 AM To: topband@contesting.com Subject: Re: Topband: Inverted L improvement question - Part 2 Hmmm....you DID relocate or rebuild your ground system so it converges on a point below the bottom of the 100 foot tall wire right? I mean, you aren't using the 43 foot vert. ground system with the 100' wire? A series fed vertical isn't rocket science so let's not over think this. If it doesn't work well it is probably inefficient. I'd make sure your ground system is adequate. No, you can't use an existing ground system that converges on a point 30 or 40 feet away from the 100' wire. Yes, I've had people ask me if they can do that, so it is worth mentioning. You can go the elevated route, but it is _critical_ that it be constructed correctly to adequately replace a full ground system at or below grade. You need four radials parallel to earth extending out 90 degrees from each other and their lengths must be equal and 90 degrees long (1/4 w.) at frequency. The ends must be h.v. insulated. They should be elevated 20 feet on 160 m. to completely de-couple from earth. 73 Rob K5UJ _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
