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- Subject: Split SuperLoop variant
- From: Mark Connelly <markwa1ion@xxxxxxx>
- Date: Tue, 5 Sep 2017 00:38:36 -0400
- Delivered-to: irca@xxxxxxxxxxxxxxxx
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The following is a variation on the Split SuperLoop design that I may actually be able to install and test here soon. I have attached a drawing. If it can't be accessed directly from the email, please see:
http://www.qsl.net/wa1ion/pictures1/split_superloop_201709.gif
This differs from the conventional layout in that it is designed for two available supports (one on each side) so some allowance needs to be made for droop in the center.
Each top wire drops in height (referenced to base) from 8m / 26 ft. at the side supports to approximately 6m / 20 ft. at the center.
At the crossing point of the near-center drop wires, a wooden garden stake cut to 0.4m / 16" with holes drilled 2" from each end (one for each wire) is used to keep the wires separated.
As in the notes on the drawing:
Wire used = #14 AWG insulated stranded THHN from Home Depot.
Height of bottom wires above ground is approximately 1m / 3.3 ft.
Looking at the antenna drawing as I would actually view the antenna from my back deck, the left (Side 1) is west and the right (Side 2) is east, approximately.
I am soliciting Neil (and/or others proficient in EZNEC) to model this layout and see if it has merit for good F/B ratio and reasonable pest reduction at bearings +/- 45 deg. off max null, e.g. at least 10 dB down (relative to forward pick-up) at all bearings between southwest and northwest if the main null axis is west.
How finicky is termination resistance and would a high band station need a different setting from a low band one on the same axis?
If I do install the antenna, there will be several different stages of testing.
Stage 1:
9:1 transformer each side with speaker wire or CAT-5 runs back to operating position. Feedline lengths approximately 27m / 90 ft.
4PDT rotary switch sends one feedline to 500 ohm pot (in-shack termination adjustment), other feedline to 2:1 transformer to coaxial cable that either goes straight to the receiver or through a DX Engineering RPA-1 amplifier (or similar) en route to the receiver.
Switch can be reset to flip the connections of the two feedlines to allow nulling in the opposite direction.
Stage 2:
The Stage 1 set-up except that common-mode choke boxes are inserted in the feedlines a short distance (under 3m / 10 ft.) from connections to each 9:1 transformer.
Choke assemblies per page 1 of:
https://www.okdxf.eu/lankford/Half%20Size%20Dual%20Active%20Delta%20Flag%20Arrays.pdf
or similar.
Stage 3:
The east side of the antenna gets an at-antenna amp (Clifton Labs, Wellbrook, or homebrew). West side either stays with 9:1 transformer / speaker wire / in-shack pot or goes over to a Vactrol (or motorized pot) scheme. This, of course, takes away the reversibility feature and would only be retained if the Stage 1 and 2 set-ups did not provide satisfactory results.
The location where this will be installed has just had an upgraded TA SuperLoop (width: 20m / 66 ft., height base-top: 9m / 30 ft., base above ground 0.3m / 1 ft.) installed. It is presently set up per the Stage 1 connection method above so it is reversible.
Day and night tests (Perseus spectrum captures) will be done with that antenna first to establish performance baselines and then the Split SuperLoop variant will be dropped into the same space using existing support ropes into the adjacent black locust trees.
Mark Connelly, WA1ION
South Yarmouth, MA
On Sun, Sep 3, 2017 at 9:44 PM, Neil Kazaross <neilkaz58@xxxxxxxxx> wrote:
> My new Double Corner Fed Flag antenna is up but needs some more and very
> careful dimensioning I think. A huge willow tree isn't making this easy. It
> has more signal (EZNEC says 7 dB) than a DKAZ requiring the same space and
> height since the two loops are rectangles rather than triangles and
> therefore have more area underneath them. However, I am not getting as good
> F/B as I'd like or as I could get from the DKAZ, but it seems adequate for
> sunrise work to the west.
>
> LSR here was 11:20 today so I started DXing just a few minutes prior to
> 1100 in hopes of Tonga but little trace and bad slop from NM. Over to 1098
> and V7AB had audio and did so much of the time til about 1131:30 when it
> seemed it was cut. Music, mostly island mx and ancr in island lang at
> times. Bothered by slop from KKLL on early and even KEXS running day rig at
> night clobbering KAAY 1090.
>
> I had weak audio at times from 4QR 612 and 2NR 738 but 702 was more
> interesting usually with 2BL which is just a bit low of 702 sometimes
> audible but often mixed with NZ which is almost on 702 and had mx and a
> different ancr. NZ rose atop around 1125 for a bit. A third considerably
> weaker carrier is a bit above 702.
>
> My apologies for sending the again, but Gary hasn't learned to keep off the
> keyboard.
> http://www.universal-radio.com/catdir/cuscb333.html
>
> 73 KAZ Barrington IL Perseus and DCFF aimed west.
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