My new UHF / GMRS antenna

  I got a new antenna, and it's "different". No, it's not some cheap Chinese antenna that's deceptively marketed and doesn't work. It's the Italian-made Sirio GP 430 UHF antenna that I bought from DNJ Radio. It's a lot like a beer can with three radials sticking out of the bottom, and an SO-239 on the bottom. A tube is supposed to go in the bottom and allow you to mount it to a mast, but that mount is out-of-stock at the moment. So I set it up on a table on my balcony and tried it out like you see below.

  I got this antenna because I was tired of switching between my UHF (440 MHz) ham antenna and my GMRS antenna while using my UHF TYT TH-9000. As you can see from the label, this antenna covers both.

Okay, if you can't read it, it says 380 - 480 MHz. That's pretty wide-band, and it's possible because of the large OD of the radiating element. It's a 1/4-wave folded dipole, which means "unity gain". But the idea of "gain" from vertical antennae is sort of deceptive to begin with. The angled radials help to keep the angle of radiation lower than what I get from my 1/4-wave whip mag-mounted on the balcony's steel cap. 

I didn't get it for "gain", anyway. Aside from allowing 440 and GMRS operation with the same antenna, I was looking for a ground-plane antenna. My other gambles on UHF ground-planes have been disappointing, and the balcony's steel cap is not an ideal ground for a mag-mounted whip. I'd expect "gain" over my dual-band mobile whips just by virtue of having the ground radials. And it looks as if that steel cap will be gone next year when they renovate the balconies, so I need a real ground solution.

The other reason that I got this antenna was for stealth. I live in a condo, and antennae aren't really allowed. Much of what comprises the concept of stealth is merely placing antennae in plain sight, while making them appear (to a non-ham) as something other than an antenna. For example, a length of PVC pipe conceals a roll-up J-pole. Most hams would immediately recognise this as an antenna if it were mounted on a condo balcony. Non-hams just see a piece of PVC pipe, which isn't against the HOA regulations. Horizontally-strung wires, with the tell-tale centre conductor and coax running out, are a dead give-away, on the other hand. You could put an upside-down flower pot over a mag-mounted 1/4-wave UHF whip on your steel patio table. Nobody would think twice about it, except perhaps to think that you're slightly untidy. With this UHF antenna, all that I need to do is conceal the radials -- perhaps with cloth or nylon to make it look like an umbrella. Sure, it would look a bit stupid...but it wouldn't look like an antenna to a non-ham. That stupid-looking umbrella-thing opens up all of the 440 MHz repeaters to me, plus GMRS, and nobody's going to know but me. 

View from the bottom

The SWR was virtually flat on both UHF and GMRS just setting it on the balcony table. Setting it on the floor inside, or on top of a metal rack outside, produced higher mismatches but not high enough to warrant concern. Once it's mounted on a piece of PVC or wooden dowel, I expect that SWR won't be an issue. 

Just because it tunes up, that doesn't means that it performs well, though. I set it near the window in my home office, and the received signals from repeaters were generally lower using the GP 430 than using a Browning BR-180 dual-band mag-mounted on top of an old stereo receiver. But I don't plan on using it indoors. 

Sirio makes another UHF / GMRS antenna that has more gain, is cheaper, but is not quite as stealthy.