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Comet CA-712EFC VS CommScope DB404

drake1792

Member
Premium Subscriber
Joined
Sep 8, 2021
Messages
13
Location
Montour Falls
Hello all,

I am looking at purchasing either a Comet CA-712EFC or CommScope DB-404 for a GMRS repeater site. I see that the DB-404 is much more expensive than the CA-712EFC and has less gain but obviously has two sets of dipoles versus the Fiberglass construction of the Comet. Are there any advantages over one or the other that would make a difference in my instance? The height of the antenna would be about 50ft off ground level right on the edge of a hill at just over 1000ft elevation. Is the DB-404 worth the extra $300+???

Thoughts?
 

prcguy

Member
Joined
Jun 30, 2006
Messages
14,497
Location
So Cal - Richardson, TX - Tewksbury, MA
The Comet is rated 9dBi gain or 6.86dBd. The DB-404 is 3.8dBd omni or 5.8dBd bi-directional. In my experience the gain numbers on Comet, Diamond and similar antennas is inflated. For one example I did a lot of range testing on a 70cm repeater with a Comet GP-9 rated 9.76dBd gain on 70cm then replaced with a DB-411 rated 9.0dBd elliptical In the exact same spot, same height. Within it’s elliptical pattern the DB-411 kicked a$$ over the GP-9.

Another potential problem is dissimilar and or plated metal junctions in the Comet antennas that can create IMD in full duplex systems. My recommendation is to get a DB-408 rated around 6dBD omni or maybe a DB-404. These are proven performers and you can believe the gain numbers.
 

jeepsandradios

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Feed Provider
Joined
Jul 29, 2012
Messages
1,756
Location
East of the Mississippi
Personally I put antenna's in the same light as radios. Quality costs. I run the DB404 on all my GMRS repeaters. I have a couple that are at least 20 years old and are still ticking away in CNY. I think for a $500 antenna they can't be beat for true repeater use.
 

pandel

Member
Joined
Jun 21, 2005
Messages
124
Here is a simple way to look at any antenna. Is it an AMATEUR antenna, or is it a COMERCIAL antenna?
Then fill in your own blanks.
 

drake1792

Member
Premium Subscriber
Joined
Sep 8, 2021
Messages
13
Location
Montour Falls
The Comet is rated 9dBi gain or 6.86dBd. The DB-404 is 3.8dBd omni or 5.8dBd bi-directional. In my experience the gain numbers on Comet, Diamond and similar antennas is inflated. For one example I did a lot of range testing on a 70cm repeater with a Comet GP-9 rated 9.76dBd gain on 70cm then replaced with a DB-411 rated 9.0dBd elliptical In the exact same spot, same height. Within it’s elliptical pattern the DB-411 kicked a$$ over the GP-9.

Another potential problem is dissimilar and or plated metal junctions in the Comet antennas that can create IMD in full duplex systems. My recommendation is to get a DB-408 rated around 6dBD omni or maybe a DB-404. These are proven performers and you can believe the gain numbers.
Okay, thanks for your thoughts!
 

drake1792

Member
Premium Subscriber
Joined
Sep 8, 2021
Messages
13
Location
Montour Falls
Personally I put antenna's in the same light as radios. Quality costs. I run the DB404 on all my GMRS repeaters. I have a couple that are at least 20 years old and are still ticking away in CNY. I think for a $500 antenna they can't be beat for true repeater use.
Thanks for the feedback!
 
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