br0adband
Member
Yes, that's what I was doing: the ground planes on the original antenna I built were 20" long, I had an element cut at 19" for 150 MHz, I had another one cut to 460 MHz, and another for 890-ish and I would just swap those out depending on what I was attempting to monitor. The ground planes at 20" were "permanent" and not swapped, just the main element. I took a pair of needle nose pliers and crimped the top of the SO-239 chassis jack just enough so it would provide a better grip on the elements (made from wire coat hangers) - none of this stuff has been soldered, not even the newer ones I just made that are truly tuned to their respective bands.
When I use the "original" design, I can put the 150 MHz element in place and I still get fairly decent reception all the way from 115 to 940 MHz, so even though it's "tuned" to 150 MHz specifically it's definitely grabbing stuff. It's like a poor man's wannabee discone I suppose.
It can't hurt to build one to the original design (19" main element, 20" ground planes) and then see just how it performs across the entire spectrum for yourself. I was pleasantly surprised that it does so well as a broadband reception antenna - I know it's designed for 150 MHz but it sure does well for me in my area. I decided to build the more properly tuned 460 and 890 MHz antennas just because I have a few extra SO-239 jacks and plenty of coat hangers.
So now I have 3 of these types of antennas:
- the original one with the 20" ground plane elements and the 19" 150 MHz main element
- one cut to 460 MHz (both ground plane and main elements with the ground planes being 5% longer)
- one cut to 890 MHz (same thing, with the ground plane elements being 5% longer)
I just unscrew them as needed (meaning the entire antenna itself, the SO-239 chassis mount screwed into the PL-259 connector on the coax). I found a kiosk stand recently (just a base plate and length of 3" folded steel) that's about 4 feet tall and has a top portion that made it easy to attach a short mast to here in my apartment. I did attach a 2" section of PVC to the top of the stand, and the antenna sits on top of the mast and it's all inside by a window, so far so good.
When I use the "original" design, I can put the 150 MHz element in place and I still get fairly decent reception all the way from 115 to 940 MHz, so even though it's "tuned" to 150 MHz specifically it's definitely grabbing stuff. It's like a poor man's wannabee discone I suppose.
It can't hurt to build one to the original design (19" main element, 20" ground planes) and then see just how it performs across the entire spectrum for yourself. I was pleasantly surprised that it does so well as a broadband reception antenna - I know it's designed for 150 MHz but it sure does well for me in my area. I decided to build the more properly tuned 460 and 890 MHz antennas just because I have a few extra SO-239 jacks and plenty of coat hangers. So now I have 3 of these types of antennas:
- the original one with the 20" ground plane elements and the 19" 150 MHz main element
- one cut to 460 MHz (both ground plane and main elements with the ground planes being 5% longer)
- one cut to 890 MHz (same thing, with the ground plane elements being 5% longer)
I just unscrew them as needed (meaning the entire antenna itself, the SO-239 chassis mount screwed into the PL-259 connector on the coax). I found a kiosk stand recently (just a base plate and length of 3" folded steel) that's about 4 feet tall and has a top portion that made it easy to attach a short mast to here in my apartment. I did attach a 2" section of PVC to the top of the stand, and the antenna sits on top of the mast and it's all inside by a window, so far so good.
