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Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 6:41 pm
by Dennis David
I will be living in an apartment in San Diego on the weekdays. How capable is a screwdriver antenna set up on a balcony?
Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 7:49 pm
by cruiserlarry
Dennis David wrote:I will be living in an apartment in San Diego on the weekdays. How capable is a screwdriver antenna set up on a balcony?
Difficult to answer a generic question like you have presented. Much would depend on the exposure to the sky you're balcony affords, and what interfering objects and clearance you have. It is possible the balcony might not work well for any antenna, depending on its location....
Are you on an upper level unit with roof access ?
For specifics, I think Randy (xtatik) might be better informed than I...
Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 8:34 pm
by xtatik
cruiserlarry wrote:Dennis David wrote:I will be living in an apartment in San Diego on the weekdays. How capable is a screwdriver antenna set up on a balcony?
Difficult to answer a generic question like you have presented. Much would depend on the exposure to the sky you're balcony affords, and what interfering objects and clearance you have. It is possible the balcony might not work well for any antenna, depending on its location....
Are you on an upper level unit with roof access ?
For specifics, I think Randy (xtatik) might be better informed than I...
If your antenna is going to be above ~6' from the ground, you'll nead to put 1/4 wave tuned radials under it, 2 for each band to complete the other half of the antenna.
Are you familiar with the principles of a dipole? If not, it will be hard for me to convey the screwdrivers' (or any vertical) functions and needs in order to radiate properly.
Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 9:17 pm
by DaveK
Without knowing exactly what your balcony looks like, it is a little hard to know what's best. For general home mounting of a screwdriver antenna, see the Scorpion website for some ideas of what you will need and what it will cost. See:
http://www.scorpionantennas.com/scorpio ... ll-package
Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 9:25 pm
by Dennis David
Are you referring to a counterpoise? It will have that. I have not rented the exact apartment yet. It will be in the same complex though.
It will look something like this scorpion

Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 9:43 pm
by DaveK
Dennis:
That would be it.
Re: Screwdriver HF Antenna for home use.
Posted: Tue Apr 20, 2010 11:11 pm
by xtatik
Dennis David wrote:Are you referring to a counterpoise? It will have that. I have not rented the exact apartment yet. It will be in the same complex though.
It will look something like this scorpion

Isn't that a Hi-Q?
Unfortunately, those counterpoise systems are not optimal. It'll work, but it's a huge compromise to an already compromised antenna being that it's physically short and loaded for most bands. The radials used are loaded as well, and are essentially hamsticks. Also, they are perpendicular to the antenna which is not ideal. It's not likely it will outperform even a unity gain dipole. My Dad was using the one from Scorpion and looks like the one in the pic. I made him a radial plate and cut 4 ea. 1/4 wave wires (flexweave) for radials. The gain increase was like night and day, and his signal reports have shot up as well. He mounts the antenna higher so that the radials depart the base of the antenna at approx. a 45 degree angle (down and away) from the base of the antenna for the first 20 feet or so. This raises the feedpoint impedance and pulls the take-off angle down so that it actually functions as an elevated vertical should.
If you're up a couple floors and you're not going to be using power above 250w you might want to consider an End-Fedz. You can just hang the wire off the balcony and you're in business. This would be the simplest and cheapest way to get on the air....but, it would require you be up a few floors. About 40ft for 20m and about 70ft for 40m.
Re: Screwdriver HF Antenna for home use.
Posted: Wed Apr 21, 2010 3:36 am
by Dennis David
It is actually a scorpion. I know it will be a compromise. But I wanted to use the same antenna as I would use in the field. I guess that my not be possible. It does seem though that it will take some experimentation to get the best results which I guess is part of the fun.
Re: Screwdriver HF Antenna for home use.
Posted: Wed Apr 21, 2010 10:31 pm
by xtatik
Dennis David wrote:It is actually a scorpion. I know it will be a compromise. But I wanted to use the same antenna as I would use in the field. I guess that my not be possible. It does seem though that it will take some experimentation to get the best results which I guess is part of the fun.
The radial kit is a Scorpion but, I'm certain the antenna is a Hi-Q 580.
Re: Screwdriver HF Antenna for home use.
Posted: Wed Apr 21, 2010 10:46 pm
by Dennis David
Yeah I think you're right, either a 5/80 or 5/160. In either case I was thinking of an Antenna I could use at, home, in the field and on the road. Maybe that's not possible. I'll still probably get the antenna and if it works in the apartment then great, if not then I'll have to go to plan B.