Comet CA-712EFC 460-470Mhz base atenna review

[arctodus]

Anyone using the above base antenna ? I would like to know how it is working for you. Will be putting it up today as soon as it arrives.

 

Thanks

[BoxCar]

If you asked me I'd say it's a little late to be asking others how his antenna would perform if you have already bought it and will be installing it as soon as you can. It'sa question you should have asked before committing.

[n4gix]

Odd question now or not, I have had mine up on the roof @42' for the past six years. It has performed wonderfully for me. I did run 1/2' heliax cable from the antenna to the polyphase arrestor, which was then bonded to my ground system.

[mbrun]

Anyone using the above base antenna ? I would like to know how it is working for you. Will be putting it up today as soon as it arrives.
 
Thanks

I use the antenna. Currently installed at 40+ feet. LMR400 into the radio shack, then adapter cable to radio. Excellent SWR at the antenna and in shack. No complaints.


Michael
WRHS965
KE8PLM

[SkylinesSuck]

Very happy with mine. Noticable performance improvement over my Jpole and Ed Fong.

[oldtech]

I have been building a portable repeater based on the Retevis RT-97. I was using a 5/8 until I received my Comet CA-712EFC. While it didn't extend my range appreciably, it did provide a very nice S/N improvement and helped fill in some 'holes' in coverage. My son lives 5 miles away in an apartment building with a lot of metal siding. He was able to find some spots in the apartment where his 4 watt handheld could hit the repeater reliably, but at best the signal was barely tolerable, lots of annoying fade.

With the Comet, he can talk from most spots in his apartment and sounds 'good', not great, but certainly a whole lot better with little fading (he still tends to forget to hold the antenna vertical).

While not in the professional, commercial, industrial duty antenna category, I would certainly rate it in the 'Prosumer' category. Easy to assemble and mount, with shrouded N connector, only a little more weight, and about the same wind load as my 5/8. My old antenna exhibited a 1.4:1 SWR attached to the RT-97. While the Comet is advertised as being 1.5 or less, when I tested it I could not see the return loss needle on my meter budge... so I rate it as 1.1 or less for my particular antenna (within my eyeball resolution of an analog SWR meter).

So all in all I am currently very pleased. We'll see how it ages.

[Wdsracer]

On 7/21/2021 at 5:40 PM, oldtech said:

I have been building a portable repeater based on the Retevis RT-97. I was using a 5/8 until I received my Comet CA-712EFC. While it didn't extend my range appreciably, it did provide a very nice S/N improvement and helped fill in some 'holes' in coverage. My son lives 5 miles away in an apartment building with a lot of metal siding. He was able to find some spots in the apartment where his 4 watt handheld could hit the repeater reliably, but at best the signal was barely tolerable, lots of annoying fade.

With the Comet, he can talk from most spots in his apartment and sounds 'good', not great, but certainly a whole lot better with little fading (he still tends to forget to hold the antenna vertical).

While not in the professional, commercial, industrial duty antenna category, I would certainly rate it in the 'Prosumer' category. Easy to assemble and mount, with shrouded N connector, only a little more weight, and about the same wind load as my 5/8. My old antenna exhibited a 1.4:1 SWR attached to the RT-97. While the Comet is advertised as being 1.5 or less, when I tested it I could not see the return loss needle on my meter budge... so I rate it as 1.1 or less for my particular antenna (within my eyeball resolution of an analog SWR meter).

So all in all I am currently very pleased. We'll see how it ages.

Just wondering how you like the rt97 for local comms? I have one on order and plan on setting it up on our hunting lease. I can put that comet antenna up about 30 ft on the peak of the cabin.

[MichaelLAX]

52 minutes ago, Wdsracer said:

Just wondering how you like the rt97 for local comms? I have one on order and plan on setting it up on our hunting lease. I can put that comet antenna up about 30 ft on the peak of the cabin.

What will you use for power; or is the property connected to the grid? 

[Wdsracer]

On 10/8/2021 at 12:37 PM, MichaelLAX said:

What will you use for power; or is the property connected to the grid? 

The property is on the grid

[WREY478]

Comet 712EFC is a great choice for a base antenna.  I have mine mounted on a tripod on the roof of my house.  Approx 30' or so off the ground.  Works great, light weight, no tuning, priced right.. what's not to like? 

[CudjoeCane]

Our radio club installed a repeater in Marathon, Florida in the Keys.  We considered a whole laundry list of antennas in our search for a high performing antenna that would be easy to maintain and simple to take down when a hurricane approaches.  The Comet CA-712EFC fit the bill and got the nod.  We're happy enough with it that we've purchase two more for the next two repeaters we'll put on-line.  I went ahead and purchased one for my home QTH, where the Comet far outperforms my old Laird CRX 450 and the 11 dbi gain Yagi I previously used.

[WRWI497]

I bought one of these about 9 months ago to use with my repeater built from 2 Wouxun KG-1000G 50W radios and a Fumei mobile 50W notch duplexer.  I initially used it to replace a TRAM 1486-B with 6.5dBd gain; the Comet has 6.85dBd gain.  The installation was at 45 feet above ground and the results were marginally better.  I could only get around 5 miles range with either antenna.  I live a swamp in southeastern Louisiana so there are many 80+ foot trees over flat ground.  I used an EZ-Hang slingshot to place a rope 75 feet above ground.  Didn't get much of an improvement in range and I had to use 126 feet of KMR-400 coax.  I measured 62% insertion loss through the coax.  I bought a professional spectrum analyzer and tuned a used Phelps-Dodge 6 cavity BP/BR duplexer I found on eBay.  I detected another slight improvement.  What seemed give me a more solid range was inserting a NooElec ultra low noise amplifier between the receiving radio and the duplexer.  Suddenly, I had a fairly solid range at 7.5 miles radius, and 19 miles while driving on top of overpasses.  i conducted range testing with a 20W (that transmits 16W) Btech 20V mobile radio.  I also used a Surecom simplex repeater with an HT to parrot the full duplex repeaters output because I was testing by myself while driving around.

Anyway, after 2 weeks of excellent repeater coverage, a rainstorm cause the two halves of the Comet CA-712EFC radome to separate.  The top half of the radome is now permanently 75 feet up in the tree!  Realize that I have a rope tied to the top of the antennas that hang off a branch.  I replaced the Comet antenna with the TRAM again.  Under the same conditions, the range is about the same, but not with solid coverage.

I will probably buy another Comet CA-712EFC and pull it up the same tree, but before I do so I will epoxy the two halves of the radome together.  The compression connection between radome halves isn't designed or strong enough to mount the antenna from the top with all that coax hanging below.

I do recommend this antenna.  It works well, but I wish there was a way to tune it.  It is made with a collinear coax design.  Mine came center tuned at 465mHz, but the VSWR on the input frequency of 467.55mHz was about 1.5:1 VSWR and higher than the output frequency of 462.55mHz at 1.3:1 VSWR.  I would prefer better tuning on the input because if the repeater is deaf, it will also be mute.

[WRXP381]

Wow might be something wrong with your set up.  I get well over 200miles from my comet 712efc with a 20w base station on all frequencies with a low swr.   Most of our radio club is running them as well. Many have switched over and love them.  

[Sshannon]

1 hour ago, WRWI497 said:

I bought one of these about 9 months ago to use with my repeater built from 2 Wouxun KG-1000G 50W radios and a Fumei mobile 50W notch duplexer.  I initially used it to replace a TRAM 1486-B with 6.5dBd gain; the Comet has 6.85dBd gain.  The installation was at 45 feet above ground and the results were marginally better.  I could only get around 5 miles range with either antenna.  I live a swamp in southeastern Louisiana so there are many 80+ foot trees over flat ground.  I used an EZ-Hang slingshot to place a rope 75 feet above ground.  Didn't get much of an improvement in range and I had to use 126 feet of KMR-400 coax.  I measured 62% insertion loss through the coax.  I bought a professional spectrum analyzer and tuned a used Phelps-Dodge 6 cavity BP/BR duplexer I found on eBay.  I detected another slight improvement.  What seemed give me a more solid range was inserting a NooElec ultra low noise amplifier between the receiving radio and the duplexer.  Suddenly, I had a fairly solid range at 7.5 miles radius, and 19 miles while driving on top of overpasses.  i conducted range testing with a 20W (that transmits 16W) Btech 20V mobile radio.  I also used a Surecom simplex repeater with an HT to parrot the full duplex repeaters output because I was testing by myself while driving around.

Anyway, after 2 weeks of excellent repeater coverage, a rainstorm cause the two halves of the Comet CA-712EFC radome to separate.  The top half of the radome is now permanently 75 feet up in the tree!  Realize that I have a rope tied to the top of the antennas that hang off a branch.  I replaced the Comet antenna with the TRAM again.  Under the same conditions, the range is about the same, but not with solid coverage.

I will probably buy another Comet CA-712EFC and pull it up the same tree, but before I do so I will epoxy the two halves of the radome together.  The compression connection between radome halves isn't designed or strong enough to mount the antenna from the top with all that coax hanging below.

I do recommend this antenna.  It works well, but I wish there was a way to tune it.  It is made with a collinear coax design.  Mine came center tuned at 465mHz, but the VSWR on the input frequency of 467.55mHz was about 1.5:1 VSWR and higher than the output frequency of 462.55mHz at 1.3:1 VSWR.  I would prefer better tuning on the input because if the repeater is deaf, it will also be mute.

I am impressed!  You’ve certainly gotten the most out of that combination and in a heavily wooded, high humidity area with an antenna lower than the canopy.
The use of the amplifier is something I haven’t seen others do; good job!
 

The 200 mile range mentioned by wrxp381 is  highly unusual except between high elevations and across deserts, which bear no resemblance to your swamp at sea level. 

As long as you’re epoxying the radome, you might consider drilling and epoxying (or screwing) in some pins to prevent the halves from separating. 
I would not worry about tuning that antenna. You’ll truly never notice the difference between a VSWR of 1.5:1 and 1.3:1. 
As you know, your feedline is attenuating quite a bit of signal though and in both directions.  That’s your most easily identifiable avenue to getting more power, but it could also be expensive. 
Again, I’m impressed!