-----Original Message----- From: Charlie Cunningham [mailto:[email protected]] Sent: Monday, September 02, 2013 7:21 PM To: '[email protected]' Subject: RE: Topband: Nested Loops with one feedline results
Hi, Herb Well, the quad was built in "delta" fashion, and I just brought all the delta drivers together at a common feed-point at the bottom of the driver array. That resulted in Deltas that were somewhat reduced height for 12 and 10m. The elements do interact a bit, and I just spent a lot of time adjusting the dimensions for gain, VSWR and a little fit for F/B. Net result was great. I did most of that work IN EZNEC. BTW - one "bugaboo" that you may have to contend with, is that your 160 delta will approach 2-wavelengths on 80m and can really screw up the pattern on 80m. That was a problem for me with 20 and 10m and is not directly related to the single feedline. The way that I solved it was to reduce t.he dimensions of t.he 20m delta to less than 2 wavelengths on 10m, and I then added horizontal wires at the ends of the 20m driver and reflector deltas to bring them back to resonance. When building the antenna, I adjusted the horizontal wires with a well calibrated Millen grid dipper that I kept an eye on with the FT-1000MP. Usiln split bolts while tuning the elements makes things a lot easier. Then solder them when everything is tuned up! :-) Regards, Charlie, K4OTV -----Original Message----- From: Herb Schoenbohm [mailto:[email protected]] Sent: Monday, September 02, 2013 7:02 PM To: Charlie Cunningham Subject: Re: Topband: Nested Loops with one feedline results Charlie, Very interesting as it seems you were able to bring all 5 band feed wires together at a common feed point via a 4:1 Current Balun. did you you have to change any of the wire lengths to achieve the match on all five bands of was the fomula 1005/f sufficient? Herb, KV4FZ On 9/2/2013 6:48 PM, Charlie Cunningham wrote: > Hi, Herb > > Something you might consider is feeding the paralleled loops via a 4:1 > current balun. I used this very successfully on a 2 el 5-band quad (my > own > design) fed with RG-213 through a 4:1 current balun. Net result was > that, while the VSWR wasn't 1:1 anywhere, it was below 1.6:1 across > all 5-bands 20-10m. Worked great for me, and the antenna was a > wonderful stellar performer! I did spend some months of modeling and > working with interactions in EZNEC, but it was well worth it, and the > antenna tuned up and performed just as the model predicted! A big part > of the success was the use of the 4:1 current balun to feed the paralleled drivers. > > 73, > Charlie, K4OTV > > -----Original Message----- > From: Topband [mailto:[email protected]] On Behalf Of > Herb Schoenbohm > Sent: Monday, September 02, 2013 6:09 PM > To: TopBand List > Subject: Topband: Nested Loops with one feedline results > > Several replies to my inquiry on having a closed 80 meter inverted > delta loop inside a 160 meter delta loop brought me some nice replies. > So I decided to build one for 18Mhz and 24Mhz with the feed going to > the outside Delta loop hoping this would properly allow dual band > operation with a single feed. The inside 24 Mhz delta was closed and > hung inside the fed 18 Mhz antenna. The results showed that it had no > impact on the > 18 Mhz antenna but the VSWR on 24.9 was unusable. Then I decided to > open the 24 Mhz Delta and connect the two wires to the 18 Mhz feed and > now have both bands working with a VSRW below 1:2 to 1 on either band. > The feed-line for the antenna is RG-213 with a 1/4 wave piece of RG-11 > cut for 18 Mhz. I am surprised that the 1/4 wave matching piece did > not seem to impact the antenna on 24.9 at all. > > I will now proceed to build an 80 meter full wave delta inside my 160 > meter one and rely on the simulation on 18/24 Mhz to get a good match. > I trust it will work although the ground proximity might have some > impact on everything. > > > Thanks for the replies on this. > > > Herb Schoenbohm, KV4FZ > _________________ > Topband Reflector > _________________ Topband Reflector
