A combination of antenna designs, namely the J‐Pole and Zepp along with Alpha Antenna’s matching network technologies, are utilized to achieve a fairly resonant antenna design that can be tuned on 6, 10, 12, 15, 17, 20, 40, 60, 80, & 160 Meters. Relatively low SWRs are achieved as the Alpha J-Pole Jr Antenna utilizes the solid state matching network in the Alpha Match that is specifically made for the J-Pole Jr antenna. Plus the whole system is rated IP69K. (Reference: https://en.m.wikipedia.org/wiki/IP_Code)
Optimum* installations have reported a Maximum SWR across each band as follows:
160m – 5:1
80m – 2:1
60m – 2.5:1
40m – 1.7:1
30m – 1.4:1
20m – 2.2:1
17m – 1.4:1
15m – 1.5:1
12m – 2:1
10m – 2.7:1
6m – 3.3:1
*An optimum installation would be where the antenna is deployed as a sloper with the high (feed point) end at 30 feet or higher and the low end at 10 feet or higher. We do not recommend installing this antenna as a Vertical due to users experiencing high noise (RFI) and unpredictable radiation patterns due to proximity of coax, which also allows for common mode feedback to increase.
Please note that many operators are reporting lower SWRs than we have presented. This is because they are mounting the antenna higher than the 6 1/2 foot high feed point that we used for our tests.
The 34 foot long Alpha J-Pole Jr Antenna can handle 500 watts PEP and is designed for 6-160 Meters. No tuner is typically needed on 15 or 20 meters, however if a tuner is necessary, the unique design characteristics of the antenna enables it to present a SWR on these and all other HF bands that is low enough for your antenna tuner to achieve a perfect match.
RG58-AU coax should be limited to runs that are 50 feet or less. RG-213 coax is great for runs more than 50 feet. See our coaxial reference chart: CLICK HERE for more information. No Balun or air choke coil should be used at the antenna. If you find that more filtering from common mode current is required, we recommend that you wrap and tie off a ground wire around the eyebolt on the Alpha Match (do not loosen the nut that holds the eyebolt in place, as you might not be able to tighten it again). We also recommend that you ground your tuner and rig, do not attach it to the same ground point as the antenna is attached. The manner in which coax is run from the feed point does not matter, as long as it does not run within 18 inches and in parallel to other components of the antenna system. For maximum effectiveness, keep your feed point as high as possible and run the antenna as a sloper for good NVIS and DX results, as a flat top for good NVIS results.
How it all works together – We calculate the J‐Pole wire lengths, spacing of the wiring in their respective sheaths, size & number of the strands of the wire used from a combination of J-Pole and Zepp antenna formulas. From the Zepp is the feeder type design, and although significant, is by no means the only factor in matching the antenna. The Alpha Match allows for the antenna to be fed with 50 ohm coax at the antenna. This makes for an important design characteristic when feeding a tuner, as it keeps the RF voltages low at the base feed point. Your tuner then performs the final matching for resonance once you connect your coax with a PL259 connector.
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