Good informative video Tim. I think these type of parallel wire antennas have something in common with ‘Morgain’ antennas. I did a lot of reading about them and defo a potential solution for small plots/ small masts etc. Keep up the good work Tim. Cheers, Nick M1DDD
Hi Tim Merry Christmas to you sir have you ever placed a reflector wire on the ground below an inverted V, linear loaded, Doublet dipole antenna? I want to do it to see if it will help to focus the signal upward for NVIS communications. Probably is I just don't know how long it should be! My antenna has 16 ft legs on both side that are made from 450 ohm ladder line with the center wire woven in and out of the windows. What would you recommend for the type of reflector to use and how long should it be
So what about two parallel pieces of ladderline spaced with 1cm or so blocks to give 4 wires? I have a small garden and am thinking - adding more wires could it eventually work on 80m?
AE0TE good thought! I use 45 feet or so of ladderline with the ends shorted and that resonates at 7.1 MHz and when fed with 300 ohm works well on 80 as a doublet. How small is your garden?
The_Radio_Op 2E0TWG-Tim I have about 80 feet between available trees. Are you saying 45 per side or total length? Maybe I could put in some poles for support.
AE0TE that's a decent space there. I have just 2x22.5 feet legs so the whole antenna is 45 ft but as it's linear loaded it's resonant on 7.1mhz therefore electrically it's 66 feet. If you made a 70 ft long doublet in the same manner you would have a doublet which would electrically be around 100 ft long, resonant on around 4.6 MHz and should work pretty well on 80 and up.
The_Radio_Op 2E0TWG-Tim That sounds good and is very doable. I think I’ll give it a go. One other thing - is the ladderline feed length a set length or just a variable piece?
Great job, Tim, but you're selling yourself short. According to your analyzer, your antenna is actually resonant between 21.066 MHz (4:23) and 21.111 MHz (4:27). Your analyzer is showing X=0 between those two frequencies, and X=0 is, by definition, resonance. The SWR in this range is about 2:1, which means it might be worthwhile to try feeding the antenna with some length of 75 ohm coax. It's almost certain that if you used a 2.5 to 3m length of 75 ohm coax at the shack end, you'd be down close to 1.1 SWR for the low end of the 15m band (assuming your analyzer is calibrated relative to the port on the device, and not the end of your coax). It is unclear what that length would do at the antenna end of your feedline, however. Some experimentation might help.
Tim it would be interesting to see if you could derive a formula from the experiment that would allow for a three wire linear loaded dipole to be as easy to calculate as a standard dipole.
Good informative video Tim. I think these type of parallel wire antennas have something in common with ‘Morgain’ antennas. I did a lot of reading about them and defo a potential solution for small plots/ small masts etc. Keep up the good work Tim. Cheers, Nick M1DDD
Enjoyed and learnt watching this. Thanks.
Glad you enjoyed! 73
Hi Tim Merry Christmas to you sir have you ever placed a reflector wire on the ground below an inverted V, linear loaded, Doublet dipole antenna? I want to do it to see if it will help to focus the signal upward for NVIS communications. Probably is I just don't know how long it should be! My antenna has 16 ft legs on both side that are made from 450 ohm ladder line with the center wire woven in and out of the windows. What would you recommend for the type of reflector to use and how long should it be
I haven’t Pat and if I had the room at home I would. I’d love to try that out
So what about two parallel pieces of ladderline spaced with 1cm or so blocks to give 4 wires? I have a small garden and am thinking - adding more wires could it eventually work on 80m?
AE0TE good thought! I use 45 feet or so of ladderline with the ends shorted and that resonates at 7.1 MHz and when fed with 300 ohm works well on 80 as a doublet. How small is your garden?
The_Radio_Op 2E0TWG-Tim I have about 80 feet between available trees. Are you saying 45 per side or total length? Maybe I could put in some poles for support.
AE0TE that's a decent space there. I have just 2x22.5 feet legs so the whole antenna is 45 ft but as it's linear loaded it's resonant on 7.1mhz therefore electrically it's 66 feet. If you made a 70 ft long doublet in the same manner you would have a doublet which would electrically be around 100 ft long, resonant on around 4.6 MHz and should work pretty well on 80 and up.
The_Radio_Op 2E0TWG-Tim That sounds good and is very doable. I think I’ll give it a go.
One other thing - is the ladderline feed length a set length or just a variable piece?
Great job, Tim, but you're selling yourself short. According to your analyzer, your antenna is actually resonant between 21.066 MHz (4:23) and 21.111 MHz (4:27). Your analyzer is showing X=0 between those two frequencies, and X=0 is, by definition, resonance.
The SWR in this range is about 2:1, which means it might be worthwhile to try feeding the antenna with some length of 75 ohm coax. It's almost certain that if you used a 2.5 to 3m length of 75 ohm coax at the shack end, you'd be down close to 1.1 SWR for the low end of the 15m band (assuming your analyzer is calibrated relative to the port on the device, and not the end of your coax). It is unclear what that length would do at the antenna end of your feedline, however. Some experimentation might help.
Thank you for this suggestion. 73
about time
Has anyone tried this with something speaker wire instead of ladder line ? Would the parallel wires be too close?
No it can work, look up the Cobra doublet series of antennas
nicely done... very interesting concept... de NJ4Z
John Gendron thank you for watching and commenting 73
Tim it would be interesting to see if you could derive a formula from the experiment that would allow for a three wire linear loaded dipole to be as easy to calculate as a standard dipole.
John Gendron I agree which I'll cover very soon ... good idea 👍
Hi Tim, trying to contact you , I need the callsign of the EI you talked to at lunchtime today. 73's ON9CJD John.
JD Transport will let you know when I check the log tomorrow if that's ok? 73