After 5+ years of faithful service, my Alpha J-pole Jr (34ft) HF antenna started misbehaving on higher frequencies.
SWR was high above 12MHz and 20m band (most prolific and useful) wouldn’t even auto-tune with my FT-450 transceiver. It would still transmit at the previous setting but my signal reports were generally weak, even on 30 and 40m.
Suspecting the coaxial cable connector at the antenna coupling, I lowered it to inspect the PL259 connection. Sure enough, rain got in and there was a corroded mess with white powder around the connection. Cleaned it up, added coax grease (waterproofing) and re-applied coax seal tape around the connection. Thinking this was the problem, I raised the antenna back up and tested again. Same bad SWR 😦 , although I made a good 30m contact with it.
Suspecting bad 100ft RG8x coaxial cable, I lowered the antenna again in the morning and connected a 50ohm dummy load in place of the antenna to see if the cable was the issue (thinking moisture contamination or something like that to explain SWR rising with frequency (chart above). Surprised to see that the cable is essentially good with low SWR:
Looks like the antenna itself is the problem. Not sure what I can do to fix it, so fortunately I have a new antenna ready to go. Got an Alpha J-pole Sr (60ft) HF antenna for my April birthday but hadn’t yet put it up. Now that I have an excuse (more like a need), it’s in place for now. Being twice as long it has to take a different sloping path in the back yard. Instead of a more straight 45° angle down to the northwest, it’s now more lazily drooping to the north.
SWR is much better per analyzer. Like the Jr version, it tunes 11 bands from 6 to 160m. With more wire in the air I hope to have better low frequency performance. Made a couple of 20m FT8 contacts immediately (new counties) and PSK Reporter shows good propagation (all over USA + Alaska, New Zealand, South America, and Spain) under poor band conditions, so hope for good behavior in the future. Low end not properly secured yet, and plan to put up on new, taller mast eventually. This one has a smaller, lighter match module which is easier on the mast and less obtrusive.
Well, not as easy on the mast as I had hoped, since the fiberglass mast snapped just above the gutter; antenna wire was drooping in the yard and the match was laying on the roof. More time spent erecting the new, taller, stiffer mast and it’s working well. Still bends a bit but not as much as the old one.
Hoisted end guyed by 3/16″ paracord to CamJam tightener hooked onto fence
Wire element nearly invisible against tree; slopes down to north between big tee on left and little Red Bud.
Wire end secured by paracord into clothes line tightener onto fence hook.
This is the time to document the old J-pole Jr’s performance. Did really pretty well, considering its short 34ft length and barefoot 100W FT-450D transceiver. Oversimplifying it, but looking at QRZ awards is a fair measure of performance. It neglects contacts made which don’t use QRZ or LoTW for confirmation, but those represent a small minority. Long list of awards for the Jr J-pole are pasted below.
WAS on 5 bands, practically all digital mode. Pretty close on 4 other bands, too. 21 states on 160m is amazing to me.
Mixed bands, lacking only Alaska for WAS CW.
Really 12 states; AL and NV were on new antenna and WA was Echolink which I confirmed to make the other guy happy. Note also SSB QSOs in IN, NM, and UT which were not (or yet) confirmed.
126 “countries”, none non-digital mode. Still pretty good for compromise all-band short antenna.
Not a great performer for CW DX, only 7 “countries”, but OK considering these past 5 years of weak propagation. Phone DX limited to USA only.
Another measure of DX; all 6 continents on 5 bands.
Even on CW we got half of the continents on all bands, mainly because Hawaii is designated as Oceania.
753 grid squares around the world confirmed in mixed mode (almost exclusively digital) with 100+ on 7 bands.
Even CW mode has a fair showing with 129 grids confirmed.
SSB (my only phone mode to date) shows 17 grids confirmed, but two of these do not count, since one is Echolink and the other on the new antenna, so really only 15. But I have worked little phone with this antenna, and 13 of these are the unique states worked.
It shows 2095 US counties confirmed in mixed mode, but this includes Puerto Rico, Guam, and Guantanamo, and ignores other forms of confirmation. Real count is 2049 of 3137 (65.3%) per my own tracking spreadsheet, with 8 states completed. Pretty darn good.
CW mode shows 156 counties confirmed but we should subtract one with Puerto Rico, so 155 really.
17 counties by phone is really 15 when we subtract the Echolink one along with one made using new antenna.
In summary, I think the Alpha J-pole Jr is a decent all-band compromise antenna and has served me well. As expected, at only 34ft long, it suffers performance limitations on lower frequencies.
That said, I already see better performance with the longer Sr version raised up higher.
AF5NP 