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Reviews Categories | Antennas: VHF/UHF+ Omnidirectional: verticals, mobile, etc | Comet GP-9 dual band base antenna Help

Reviews Summary for Comet GP-9 dual band base antenna
Comet GP-9 dual band base antenna Reviews: 40 Average rating: 4.5/5 MSRP: $200 about
Description: Ultra High Gain Dual Bander for 146 & 446Mhz
Product is in production.
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You can write your own review of the Comet GP-9 dual band base antenna.

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KA7EII Rating: 5/5 Mar 7, 2010 06:16 Send this review to a friend
Great Antenna  Time owned: more than 12 months
My Comet GP9 has been in use for over 15 years and has always performed perfectly. Currently it is up 30 feet and is being fed with about 100 feet of 9913. Run 50 watts on 2m and 20 watts on 70cm with a Yaesu FT-100. I can work simplex (other base and mobile stations) up to 50 miles away and am able to work some repeaters over 100 miles away.
N2SLO Rating: 5/5 Mar 2, 2010 16:44 Send this review to a friend
Still Kicking 8 Years Later  Time owned: more than 12 months
I did an initial review back in June 2002. Since that time I have added an 8 Element Quad, and mounted the beam in the GP 9's place. With over 400+ watts, and the beam my signal is at least 4-5S units higher for distant stations. The GP 9 is now mounted on our house vent pipe, for repeater use and hears well. No issues, no rust, very good condition. I use the 9913 which is prone for water leaks. I must have used good "stuff" to seal, since no SWR issues. 1.1 145-147....
KG4OHH Rating: 4/5 Mar 2, 2010 16:16 Send this review to a friend
Fixing the GP9  Time owned: more than 12 months
After having no problems for over 4 years with this antenna in service, we moved from Fl to WA about 6 months ago, and now the antenna (GP9) had a SWR of 1:1:1 now has SWR of 3++

Rain water in the Antenna:
After looking over the antenna (GP9) again, I found 2 tiny Allan grub screws (hex), i pulled them out, slid the ground plane out of the way I was able to pull the entire so239 and connecting element the hole thing, and slid it out of the tube via the bottom, on the co-lininer elements they have used sponges used and insulators to stop the elements from bouncing around inside the tube of the antenna, well these where soaking wet!!!

according to the MFJ 269, the resonant Frq is now 165.500 with SWR of 1.3:1 anywhere above or below this (in Vhf) SWR reads 3++, one thing i did notice is that when i wiggled the base of the antenna (so239 end) the SWR was jumping around 2 to 3 to 2 in the 2 meter band

I have now de coupled the bottom end of the antenna (see pic); and have it in my hand, I also have sprayed it with CrC Switch cleaner, to get out any unwanted water residue I have used a DVM to check for connections as follows:

Center to Center before the blocking cap, good short

outer to outer before the 2nd blocking cap good short

Center to outer no short before or after cap

both caps are ceramic types labeled as:

(C1) 10J, 1kv and reads on DVM set to cap mode 0.215 Nf

(C2) 1.5c, 1Kv and reads on DVM set to cap mode 7.61 Nf and then meter reads O.F (over flow)?

I am using the radio shack DVM model/cat number: 22-811

I am going to re heat up the solder joints as i can see some type of powder residue and then clean it up with a fine file

dose anyone, at this point, recommends doing anything else while i got the antenna in bitz ?

thank you for all who have helped
and will post an up date if this works out
N1MJF Rating: 5/5 Feb 22, 2010 12:26 Send this review to a friend
Couldn't be better  Time owned: 6 to 12 months
My only complaint is that any frequency that I tune in I can hear 2 or sometimes 3 repeaters. I have it mounted 20' above ground and I have no issue getting into a repeater that is 50 miles away on 5 watts daily.

The receive gain on this antenna is almost too much for an omnidirectional antenna if you plan to use it for local repeaters.

As for power handling, it handles my 100w FM amplifier just fine with a dead flat 1:1 SWR on 2 meter simplex. I have not ran anymore then 25 watts on 440MHz.
M6SIX Rating: 5/5 Jan 28, 2010 11:24 Send this review to a friend
SUPERB!!!!  Time owned: 6 to 12 months
I have owned and used this aerial for the past 10 months, it has withstood high winds, we live on the east coast, it has proved to be the very best fm/uhf dual band aerial that I have ever used, fantastic transmit and receive reports. Well done Comet, very well made and the highest of quality build. By the way, the base of the aerial is only 5'6" above the ground. SUPERB!!!!!!!!!!!!!!!!
K5PRT Rating: 5/5 Jan 20, 2010 10:43 Send this review to a friend
Pricey but worth it  Time owned: 0 to 3 months
Awesome antenna. Very flat SWR. Instruction sheet is just barely adequate and mostly broken english, but drawings make up for it. Very good construction and a real signal grabber.
M0TTB Rating: 5/5 Oct 21, 2009 05:38 Send this review to a friend
excellent perfomer, erect & forget  Time owned: more than 12 months
Up at 30ft to base for 18 month or more. QTH asl is no more than average for my area but my rx & tx considerably better than neighbouring radio amateurs on 2/70cm fm. SWR effectivley flat on 2m from 144-146, and a similar story on 70cms.

Simple enough to construct, although the internal elements were pushed down in some sections and required a bit of fiddling to pull them up to mate with the section above.

basically, erected and forgotten about.
COWBOYBOB Rating: 3/5 Jul 2, 2009 23:11 Send this review to a friend
dissappointed at first.  Time owned: 0 to 3 months
at first i was dissapointed, actually shocked. wasnt sure what the swr of 6 was about. yes i said 6. my setup consists of a yaesu 897d, belden 9913 (and yes i know about its problems, another story though)and the antenna in question, the comet gp9.
after calming down, reading reviews and information from this site and others on the gp9 and the belden 9913 i decided to just take the antenna down and treat it like i was doing it for the first time. part of doing this was completely disassembling the antenna and inspecting the insides. turns out i saved myself a good deal of trouble. it was a cold soldier between the copper and the brass tube in the bottom section. i had planned on making a whole new coax with ends, always by in bulk when you can, not just for the deal either-B prepared! that wasnt necessary though. my "engineer" (the buddy of mine thats older and smarter than me) and i were pleased to see there was virtually no standing wave! receive is exceptional as well as the transmit.
we used pl connectors, they seem just fine, especially if you are on a budget. we also used approximately 60 foot of belden 9913. take your time with the soldering! antenna is only up 16' at the base, however our elevation is 700+ feet above sea level. sealed the connection to the antenna well, was carefull not to cover drain hole either.

even though im extremely pleased with my gp9 preformance, i cannot ignore the fact that i had to repair my new antenna, also didnt care for assembly or instruction sheet (sorry some of us require a little more detail, they also dont have to jam it all on a single sheet of xerox paper either). i have owned a gp6 for a year now, have noticed considerable difference between antennas, gp9 is definitely an improvement.

in the end though, it gets a 3 and next time i will be looking around before i go to comet.
W2TMA Rating: 5/5 Jan 15, 2009 22:30 Send this review to a friend
Almost 13 Yrs and Still Great!  Time owned: more than 12 months
Antenna has been up for 13 yrs come March. Besides changing feedline once and tightening the radials once, it is going strong. Got my moneys worth out of it, for sure. I wouldn't put more than 100 W FM through it, though.
N2OEL Rating: 3/5 May 19, 2008 05:20 Send this review to a friend
Low Power Antenna, do not use over 50 watts FM  Time owned: 0 to 3 months
The package brags that the GP-9 antenna is rated for 200 watts. As an omni-directional antenna, it is obviously aimed at FM Simplex and Repeater users. However, the instruction sheet rates it at 200 watts SSB, not FM. It was my impression that SSB ratings are about 4 times that of a AM or FM rating. I would then assume that a 200 watt SSB rating would give a maximum FM power rating of about 50 watts.

I asked the US Distributor that type of question via email. Their reply email is below. The only change I made in copying this email, was in my changing my email address to protect me against spam.

-----Original Message-----
From: MickStwernik
Sent: Tue, 13 May 2008 2:07 pm
Subject: Re: GP-9 Data Sheet

The FM rating of the GP-9 is 100W FM, 200W SSB.

Depending on the duty cycle, 160W will probably damage the antenna.

Mick Stwertnik
NCG Company
15036 Sierra Bonita Lane
Chino, CA 91710-8901
Fax 909-393-6136

----- Original Message -----
Sent: 2008-05-12 07:27 PM
Subject: GP-9 Data Sheet

What is the FM Power Handling capability of the GP-9? The data sheet says 200 Watts SSB, which is about 50 Watts FM power. I want to use the antenna with a 160 Watt Mirage amplifier on FM Simplex at 146.58 Mhz. Is this wise, or will I be melting the antenna?

Noel Spears N2OEL

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