Part 2 of making a J pole antenna, tuning, transmit and receive. A coulpe of years since the build video, have you made one since? What are your experiences with J poles..?
That choke coil needs to be 4 windings at 12.7 cm diameter (5"). You've got about 12 windings there. I really think that has adversely affected the other dimensions. Which, by the way, should actually be 147.69 cm for the radiating element, 49.02 cm for the tuning stub, 4.61 cm for the spacing between them, and 4.82 cm for the feed point matching dimension. I think if you make those changes, you should be in the ballpark for a fairly flat SWR across the band, with the lowest reading at 145.5 MHz. Also...the spacing between the two elements needs to be exactly 4.61 cm all the way along. Rather important. I have seen PVC tubing used as a spacer, or heat and bend them to the correct distance. Great video, though, because variations are in the realm of experimentation, and the results were fascinating. Thank you, and 73! NO8Z.
Thanks for your input. I had 4 turns on 2" plastic pipe as a choke as seen when I first measure the vswr which is about right for 2m vhf. 15 turns on 4" pipe is ok for 20m hf, it was the only piece of coax to hand. A coax choke should not effect anything other than common mode current as far as I'm aware. Your dimensions are within 0.5mm of mine initially but it didn't work for me, hence the faffing about, that's radio I guess....
When measuring all the lengths and spacing do we measure to the outside edge of the copper pipe or the inside lengths. He mentions this question in the video and is a very confusing topic as some plans call for outside measurements and some inside but associated calculators generate the same numbers.
DESDE URUGUAY ,, MONTEVIDEO ..EXELENTE TRABAJO ,,GRACIAS ,, BUENOS ,,DX .73 CORDIALES .. 1... 3 ,,,, 2023
That choke coil needs to be 4 windings at 12.7 cm diameter (5"). You've got about 12 windings there. I really think that has adversely affected the other dimensions. Which, by the way, should actually be 147.69 cm for the radiating element, 49.02 cm for the tuning stub, 4.61 cm for the spacing between them, and 4.82 cm for the feed point matching dimension. I think if you make those changes, you should be in the ballpark for a fairly flat SWR across the band, with the lowest reading at 145.5 MHz.
Also...the spacing between the two elements needs to be exactly 4.61 cm all the way along. Rather important. I have seen PVC tubing used as a spacer, or heat and bend them to the correct distance.
Great video, though, because variations are in the realm of experimentation, and the results were fascinating.
Thank you, and 73! NO8Z.
Thanks for your input. I had 4 turns on 2" plastic pipe as a choke as seen when I first measure the vswr which is about right for 2m vhf. 15 turns on 4" pipe is ok for 20m hf, it was the only piece of coax to hand. A coax choke should not effect anything other than common mode current as far as I'm aware. Your dimensions are within 0.5mm of mine initially but it didn't work for me, hence the faffing about, that's radio I guess....
When measuring all the lengths and spacing do we measure to the outside edge of the copper pipe or the inside lengths. He mentions this question in the video and is a very confusing topic as some plans call for outside measurements and some inside but associated calculators generate the same numbers.
just make a flpwer pot antenna,,hahahaha nice vid.. cheers..