25-03-2019, 05:00 PM
In parallel (pardon the pun) to developing a new multi band dipole type wire for my QTH I want to make a portable vertical for use on field days.
I was hoping to use a nice telescoping 7m fibreglass rod I have spare as the main vertical support and this got me to thinking...
When building a vertical like this is there any reason why you cannot use a spiral wind on the wire? It would seem that way I could put up a 80m 1/4 wave by wiring the 20m element onto the 7m pole... right? Is there a reason this doesn't work? It seems to be the approach used by most CB whip antennas...right?
Ideally, what I want is an easily erectable vertical usable on field days that I could use for 80/40/20 via a tuner. This would mean a 9:1 UNUN and 1:1 RF choke at the bottom to stop RF cmoing back into the tuner, an earth stake and a bunch of ground counterpoise wires. Hopefully have a 20m long wire in the air (albeit only 7m up) should allow the tuner to work on these bands at least...?
OK - before he jumps on me I just found his link and am reading it now...
http://www.vk4adc.com/web/hf-projects/45...-whip-calc
OK - so it looks like the major trade-off is bandwidth huh. I wonder though, would a tuner be much help in that case?
Second trade off is the number of turns - 100m of wire on a 7m long pole = about 3000 turns! Ouch, good luck home rolling that beast...
I was hoping to use a nice telescoping 7m fibreglass rod I have spare as the main vertical support and this got me to thinking...
When building a vertical like this is there any reason why you cannot use a spiral wind on the wire? It would seem that way I could put up a 80m 1/4 wave by wiring the 20m element onto the 7m pole... right? Is there a reason this doesn't work? It seems to be the approach used by most CB whip antennas...right?
Ideally, what I want is an easily erectable vertical usable on field days that I could use for 80/40/20 via a tuner. This would mean a 9:1 UNUN and 1:1 RF choke at the bottom to stop RF cmoing back into the tuner, an earth stake and a bunch of ground counterpoise wires. Hopefully have a 20m long wire in the air (albeit only 7m up) should allow the tuner to work on these bands at least...?
OK - before he jumps on me I just found his link and am reading it now...
http://www.vk4adc.com/web/hf-projects/45...-whip-calc
OK - so it looks like the major trade-off is bandwidth huh. I wonder though, would a tuner be much help in that case?
Second trade off is the number of turns - 100m of wire on a 7m long pole = about 3000 turns! Ouch, good luck home rolling that beast...