By David - K3DAV (2/26/2012)
The Comet GP-9 is claimed by many hams to be the best 2 meter vertical on the market. It was designed as a 2 meter antenna, but the three 19 inch ground radials help it to load nicely on the 70cm band too. Three sections of heavy duty double tubular fiberglass house the wire antenna. The length and built-in matching load coil provide a 5/8 wave x 3 antenna on 2 meters, and a 5/8 wave x 8 on 70cm.
One Minor Little Problem.
There is one hitch to this antenna. Most people who buy this antenna have no problems with it out of the box. But a few who have purchased the GP-9 have properly installed it on their homes only to find a very high SWR. After talking to NCG (the Comet antenna manufacturer), they said there have been problems with cold solder joints inside the 2 upper sections. They instructed that if the owner pulled out the wire and capacitence couplers from those sections and re-soldered the poor connections, then put it back together and installed on the roof again, that it would work perfectly. I know a ham that had to do this to his new GP-9, and when he finished, it actually did work perfectly and very well indeed.
Personally, I think Comet should have recalled these antennas and fixed them, or at least take something off the ridiculous $190 price tag for the customer's inconvenience of having to repair a brand new top quality antenna. But of course Comet is a big company that doesn't really have to care about little things like that. And that is a shame because the GP-9 really is the best 2 meter vertical antenna you can get. Even if you don't use it on 70cm.
Here are the GP-9 factory specifications....
Despite the cold solder joint issue, I am planning to get a GP-9 in the near future. The best is still the best no matter what the issues are, and I am willing to re-solder a few connections for the best 2 meter antenna. When I do buy one, I will post in this article any repairs or modifications I had to make to get it to work correctly.
UPDATE: 5/22/2012 I got my GP-9 today from my friend Dan at Associated Radio in Kansas. I pulled the wire out of the tubing and inspected all solder connections. They all look very good and after wiggling them a little, they all appear to be strong. So I completely assembled the entire antenna in my living room and did a quick check with the antenna analyzer. It shows a good flat SWR around 146 MHz and only up to 1.6 at the band edges. It also shows a nice 1.2 SWR at 446 MHZ. So I guess it is safe to say this antenna came off the assembly line in perfect condition. Hopefully it goes up on the roof tomorrow, and we will see how well it performs on the air. I will post the update here.
UPDATE" 5/27/2012 I have had the GP-9 up for 2 days now and I had a bit of time to play with it and monitor the performance. The improvements are noticeable, but somehow I expected better.
The VHF 2 Meter Side
The SWR is flat at 1.1 from 144 to 147 MHz. then it has a slight rise to 1.3 at 148 MHz. So I have no complaints about SWR or the good soldered connections inside the antenna.
Signals seem about the same for most repeaters up to 20 miles from me. But the more distant repeaters show an increase in signals of 1 to 1.5 "S" units. The one difference I am pleased about is, I seem to hear and get into repeaters a little further away than I used to. I now hear repeaters I never heard before. If you look for me on a map, I am in Middletown PA, about 10 miles SE of Harrisburg, our PA state capitol. The Maryland border is about 45 miles due south of me. I could always hit a few repeaters just a few miles into Maryland, But now I am hearing repeaters about 20 to 30 miles beyond them, and I can key them too. The area of Williamsport PA is 90 miles north of me. I could barely notice them in the noise level before, but now I can hear the QSO's on them. The same with a couple of repeaters from the Altoona area which is about 90 miles west of me. I had a conversation with a ham on the Blue Knob repeater just a few miles south of Altoona. I barely heard peoples voices before. Another repeater in the NE part of the state in Delano about 60 miles away, gave me an S-5 before but is now an S-7 with a little less steam under the signal.
And UHF Too
As for the UHF side of the GP-9, I am not as impressed with this band as I thought I would be also. With a big 11.9dB/i (9.75dB/d) gain on UHF, I thought it would do much better. But the GP-9 doesn't seem any better than my old GP-15 with much lower gain. The SWR on UHF goes up and down a few times across the entire 30MHz of 440. But the SWR peaks are never above 1.6 and the lows are near flat in between. So again, the SWR is exactly as it should be and works great.
As time goes on, I will look for other distant repeaters and see if I can hit them. I can't wait to hear some 2 meter SSB to see if that part is improved. The thing is, I know of several hams who found the GP-9 to be a big improvement over their older antennas. TV stations just 15 miles away from me are not that strong on a good set of indoor rabbit ears, but they should be. I can only come to the logical conclusion that just maybe I am in a crappy area for radio and TV, and I shouldn't expect the big improvements that others see. So take from my review what you will. I still think the GP-9 was worth getting, and I would recommend it highly. I do see improvements, just not as big as I thought they would be. But that is just from my location, and of course your mileage may vary.
Dave - K3DAV