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.

[Socalgmrs]

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.  

[SteveShannon]

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!

 

[CudjoeCane]

Since my September 8, 2023 post above we've grown from 1 repeater in the Florida Keys to 5.  And all of the gear for number 6 has been purchased. 

Comet 712EFCs have remained our antenna of choice here in the Keys.  We have one up the Key West (mile marker 0), Cudjoe Key (mile marker 23) and Marathon (mile marker 50) locations.  We have a J-pole up at mile marker 68, but we're sticking with the Comet 712EFCs for our repeaters in Tavernier and then further north in Key Largo.  

The "Grand Pooba" antennas of our repeater network are a couple of CommScopes up in Miami.  Those cost 10 times as much new.  We are regularly hitting Miami on RF from both the Marathon and Cudjoe Key QTHs.  Occasionally, Key West will also hit them.  SWRs are well within acceptable ranges on all of the Comet 712s.     

Bottom line: the Comet 712EFC are lightweight, easy to set up, easy to take down and good talkers that deliver bang for the buck.

 

 

 

[Socalgmrs]

Totally agree.  I’ve seen many people waste a load of money on all kinds of other antennas in the price range and every single one of them finally got a 712 and ended up very happy.  Now as stated if your budget allows yea get a commercial antenna but for the average operator $135 for a very good antenna is the way to go.  Mine does 200miles every day with only 20w base station behind it. 

[WRWI497]

On 3/25/2024 at 9:12 AM, WRXP381 said:

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.  

How high is your antenna, and are you surrounded by a thick forest of pines and oak trees?

[WRYZ926]

We have discussed this many times on the forum. Getting a range of 200 miles is very unrealistic for most people. 30 to 50 miles is more realistic depending on what part of the country you live in and what the terrain, forested areas and structures are like near you.

That being said, the Comet CA-712EFC is an excellent GMRS antenna. I get about a 25 mile range on simplex here in Mid Missouri with our rolling hills and forested areas. The base of my antenna is about 20 foot above the ground.

Also remember that the best antenna in the world won't do any good if you are using the wrong type and/or low quality coax cable. And try to get the antenna as high as you can get it.

[CentralFloridaGMRS]

I'm just south of SeaWorld. Using the Comet CA-712EFC I got the Orlando 700, Orlando 600, Davenport 575, Polk725 in Bartow. The longest Simplex transmission was to someone in Mount Dora. They had 50 mobile and they were located in an open area in a higher elevation area. I can get 20 miles Simplex no problem. I did have the Ed Fong Antenna before this. 

[GreggInFL]

(Slightly off topic but not worthy of its own thread.)  What kind of performance would one expect if they moved the 712  -- or any antenna for that matter -- into the attic?  Between the hurricanes and lightning strikes I'd be willing to give up some farz to keep it in one piece.

I know, I know, it depends.  But is there some rule of thumb we can work with?

[SteveShannon]

4 hours ago, GreggInFL said:

(Slightly off topic but not worthy of its own thread.)  What kind of performance would one expect if they moved the 712  -- or any antenna for that matter -- into the attic?  Between the hurricanes and lightning strikes I'd be willing to give up some farz to keep it in one piece.

I know, I know, it depends.  But is there some rule of thumb we can work with?

No, and there really can’t be. There are too many variables. The answer will always be: Try it. 

[GreggInFL]

I'm surprised no one has tried it and reported.  Time for an experiment...

[WROU959]

On 3/25/2024 at 8:25 AM, 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 apologize for the late response as I'm just seeing this several months later.
I understand the issue of weight pulling down on it and causing it to separate.  To relieve the strain on that joint, tie the knot below it, at the base, below the radials.  To keep the antenna vertical tie a loop in the rope near the top.  This loop won't hold the weight of the antenna and cable, but it will keep the antenna upright.  Diagram attached.

[Riktar]

On 6/13/2024 at 12:20 PM, GreggInFL said:

(Slightly off topic but not worthy of its own thread.)  What kind of performance would one expect if they moved the 712  -- or any antenna for that matter -- into the attic?  Between the hurricanes and lightning strikes I'd be willing to give up some farz to keep it in one piece.

I know, I know, it depends.  But is there some rule of thumb we can work with?

FWIW I have tried my DB-404B outside my house with an approx height of 22 feet as well as placing the antenna in the attic at (roughly) the same height. My house is a 2 story Lanon Stone with Asphault shingles that are doubled up since the last roofing job was not a full tear off.

Is there a difference? Yes but it is so minimal I decided to stay with the attic mount since I can reach out and hit every repeater in the area without a problem and my simplex range with the mobiles was not enough of an increase (We are talking about less than a couple mile(s) difference) to warrant the added work to properly secure and ground/bond the system for the outdoors.

All that being said, how big is your attic? The CA-712EFC is nearly 10 feet tall. Not sure I have ever seen an attic with that kind of headroom.

[GreggInFL]

On 6/22/2024 at 2:38 PM, Riktar said:

FWIW I have tried my DB-404B outside my house with an approx height of 22 feet as well as placing the antenna in the attic at (roughly) the same height. My house is a 2 story Lanon Stone with Asphault shingles that are doubled up since the last roofing job was not a full tear off.

Is there a difference? Yes but it is so minimal I decided to stay with the attic mount since I can reach out and hit every repeater in the area without a problem and my simplex range with the mobiles was not enough of an increase (We are talking about less than a couple mile(s) difference) to warrant the added work to properly secure and ground/bond the system for the outdoors.

All that being said, how big is your attic? The CA-712EFC is nearly 10 feet tall. Not sure I have ever seen an attic with that kind of headroom.

Being new to GMRS I'm hoping to eventually collect HTs, a mobile and a base station/repeater.  I have the HTs and am looking at a mobile with a mag mount antenna, which will be a lot shorter than the Comet.  This is the combo I'd like to test in the attic; curious how much attenuation will occur.

Yeah, my attic, like most, is too short for the Comet so it will eventually go outside.