Topband: Eznec/ 4sq
For many years I have run 4sq on both 80m and 40m - I currently run an 8 element vertical array for 80m and the centre mast is a top loaded vertical 85 foot vertical. When resonating my 4sq verticals I have always disconnected three and resonated one vertical at a time to the target frequency for example 3.795 - this has worked well and without problem - I have used home made Hybrid and Llewyn phasing networks. I first started using Eznec and modelling to understand how the 8 Element array prior to Tony's article in NCJ and during the development of the 80m version - Tony originally used 40m for his design. Back to the 4 sq this leads me to my dilemma - If I model one element of a 4sq array and resonate it at 3.795 - using SWR to check no problem. I then bring in the other three element and enter sources of 0 degrees 2 elements at -90 and the front element at -180 when I check the resonance of the array the frequency drops far below 3.795. - at this point I would add that I was modelling a reduces height element of 41.5ft with 4 11ft 10inch top loading, could this be caused by the top loading increasing the mutual coupling and lowering the array frequency? The end result is that the achieve an array resonant target of 3.795 I have to resonate the individual element at 4.105. So the first question is WHY Second question - is how do I phase two four squares? do they have to be in line for my preferred direct NW from the UK which gives me in line SE for LP. I am looking to achieve more forward gain than my 8 element array and two shortie type 4 sq's would be a good start. If I can get to the bottom of all this then Shortie 160m 4sq will be possible. If I have stated anything stupid or silly - remember I have been a ham for 51 years experiment experiment and more experiment is how we learn. Thanks to everyone who helps me - from Dave in the UK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Using grommets to create additional leakage/creepage distance is clever! I never would have thought of that! Best is to turn the material on a lathe, but in a pinch you can use a bolt as a mandrel in a drill press and do it that way. Not as nice, but lots more people have drill presses than lathes. -Bill That problem can be cured with rubber ribs, or by using a larger insulator and turning ribs or skirts in it. Next time, just find rubber panel grommets that fit tight and string them over the rod. They make shrink to fit sealing grommets that are 5 OD. They make dandy skirts, or you can improvise with other materials like you did. They put polymer ribs over fiberglass rod insulators for good reason. :-) http://www.victorinsulators.com/polymerindex.htm 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Eznec/ 4sq
I then bring in the other three element and enter sources of 0 degrees 2 elements at -90 and the front element at -180 when I check the resonance of the array the frequency drops far below 3.795. - at this point I would add that I was modelling a reduces height element of 41.5ft with 4 11ft 10inch top loading, could this be caused by the top loading increasing the mutual coupling and lowering the array frequency? When you couple multiple elements in a unidirectional array, the elements will considerably shift reactance and impedance. What you see when you test one element is nothing like what you have when they are driven. There is no way to stop this, other than swamping the elements with a very high loss resistance. (The passive receiving arrays I developed work this way. They have so much element loss the effects of mutual coupling are diluted to the point of being meaningless.) I'm assuming you built an uncompensated textbook hybrid. Since you have no compensation for the effect of mutuals, you should expect a very noticeable frequency shift. Since the impedance changes and the hybrid is not terminated in the design impedance, phase shift is not actually -90 and 180. It is something other than that, because elements are reactive with very different impedances. The only two elements with the same impedance are the center two elements. That pair is different than the front element (that shifts up in impedance) and the rear (that shifts down in impedance). With a forced 90 shift, which the 4 square you built really does not have, the impedances are roughly: Rear element Impedance = -1.696 - J 15.96 ohms Middle 1 Impedance = 39.35 - J 19.69 ohms Middle 2 Impedance = 39.35 - J 19.7 ohms Front Impedance = 59.58 + J 54.55 ohms Notice the rear element is a negative impedance, which means it puts more power back into the feedline than it takes from the feedline. Since the impedances are not what you planned on having with a hybrid, you do not have the current distribution you think. The array also does not have the phase shift you think, because the impedances are not even close to what the hybrid calls for. Second question - is how do I phase two four squares? do they have to be in line for my preferred direct NW from the UK which gives me in line SE for LP. The highest gain is with two arrays broadside, ideally at least 5/8th wave apart broadside. In that case you can get roughly around 3 dB gain, depending on the base patterns of each cell and exact spacing. You can get end fire gain with 0 shift between cells, and that would take about 1/2 wave center-to-center cell spacing in line with the target. The array would have about 2 dB gain, but one of the elements would go highly negative in impedance. Since the impedance errors get even nastier than with a regular uncompensated 4-square, you are very unlikely to see any real gain in a typical array. You might even see loss. If you compensated impedances, you could get the ~2 dB. But the array would waste elements and physical space. There are other phasing methods for in-line (end fire) but all of them complicate distribution because the array actually wants a binomial current distribution. I am looking to achieve more forward gain than my 8 element array and two shortie type 4 sq's would be a good start. or a bad start. I'm not sure how the eight element array was planned, but most Ham arrays work far less than optimally. :-) If the eight element is poorly planned or implemented, then a pair of poorly planned 4 squares could be better. If you really want gain, then you might want to start with a better initial directive cell or just improve the eight element. I hate to sound so negative about this, but this is just how stuff really is. Commercial 4-squares, at least those I have had contact with (like the current Comtek and the DXE), are not the same as slapping a 50-ohm 90 degree hybrid on four elements and calling it done. They have some planning to correct for mutual coupling shifting element impedances around. A 4-square built with a perfect textbook hybrid is a dismal performer. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Using grommets to create additional leakage/creepage distance is clever! I never would have thought of that! I'm cheap and lazy, not clever. _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Static charge-Zapped
-9 f. Most DXers know that tap water water is not chemically pure. Got a reminder yesterday. I turned the water on, then got an item from a very close storage area. Returning I put my hand to the running water and drew a large spark. (to the water, not the faucet). A noise pulse on 160 ?, probably not close enough to the antenna. 73 Bruce-K1FZ www.qsl.net/k1fz/pennantnotes.html _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Try here Herb, http://www.surplussales.com/antennas/antennas-6.html http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx I have not purchased from either of these 2 places... Doug - K1ZO - Original Message - From: Herb Schoenbohm he...@vitelcom.net To: topband@contesting.com Sent: Tuesday, December 17, 2013 2:19 PM Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Herb, Try Fair Radio Sales in Lima, OH The catalog I have shows a 5-1/4in diameter thru panel insulator. Ron N9AU -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Herb Schoenbohm Sent: Tuesday, December 17, 2013 1:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Eznec/ 4sq
Even if you have a scheme that successfully drives the elements in quadrature, the problem is that quadrature is not necessarily the optimum phasing. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Thanks Tim. I might try one of these if I can get them to send them in single unit quantities. The one I currently use is a bowl type but about 3 inches on the flange. I guess for a 160 ATU I should be able to punch a new hole through the metal box and get it to work. The one presently there was all that was left of a motorized 2-30 Mhz automatic ATU for which I just retained the Vacuum Cap and put in my own 6 inch flat wound AM coil. It was made in Ft. Lauderdale, FL over 40 years ago but the beehive feed through was made from some glazed bead like material which must soak up water like a sponge although so far has not failed in my tower's wire cage feed tuning box at the base. I had even considered replacing it with a small necked rum bottle glued into the original hole. But the idea of a large porcelain replacement would look so much better. 73, Herb Schoenbohm, KV4FZ On 12/17/2013 3:30 PM, Shoppa, Tim wrote: Some of the old-school ham radio suppliers sell/stock Daburn porcelain insulators, or you can get them direct from Daburn. e.g. Daburn 10-52: http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx Tim N3QE From: Topband [topband-boun...@contesting.com] on behalf of Herb Schoenbohm [he...@vitelcom.net] Sent: Tuesday, December 17, 2013 2:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Some of the old-school ham radio suppliers sell/stock Daburn porcelain insulators, or you can get them direct from Daburn. e.g. Daburn 10-52: http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx Tim N3QE From: Topband [topband-boun...@contesting.com] on behalf of Herb Schoenbohm [he...@vitelcom.net] Sent: Tuesday, December 17, 2013 2:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
