Comet CX-333 opinions needed

[n4dbm]

Greetings,
I am looking for honest opinions on the Comet CX-333 2M/220 MHz/440 MHz tri-band vertical antenna. I have my own opinions on cheaper fiberglass "ham grade" antennas. I have plenty of commercial stuff that will cover what I need but it would take three antennas and my mast probably wouldn't appreciate three antennas and three transmission lines going to the top, plus other stuff on the side.

The antenna will be out the top of a short tower, around 50 feet. Very high winds are rare, and in 17 years I've never taken a lightning strike on this tower (but it could happen tomorrow). I'm prepared to risk the $179 if it gets blown up, though. I truly do need omni-directional coverage on all three bands, and also truly need at least some gain over a 1/4 wave on all bands, fairly regularly.

The antenna will not be duplexed (not going to be used for repeater service) nor will it ever see more than 40 watts on any band at a time. Aside from a lightning strike blowing it up, I need dependability and longevity.

If you have or know someone who has a CX-333 antenna and would share their opinion, please let me know. I'm getting lazier by the moment, and really want to be able to monitor and use all three bands with one stick if possible.

Thanks in advance.
N4DBM.

 

[prcguy]

I have two CX-333s and think they are fine for their size and compare favorably to other dual band antennas of a similar size. Its a much better antenna for putting a signal out at the horizon than something in the 5-6ft tall range. Not counting 220MHz, the Comet GP-9 series puts out a noticeably better signal than the 333 but its over 17ft tall.

 

[n4dbm]

I have two CX-333s and think they are fine for their size and compare favorably to other dual band antennas of a similar size. Its a much better antenna for putting a signal out at the horizon than something in the 5-6ft tall range. Not counting 220MHz, the Comet GP-9 series puts out a noticeably better signal than the 333 but its over 17ft tall.

I have a DB-411 for GMRS. I intend to keep that one, but just for the asking, how does the CX-333 match up on 467 MHz?

 

[n4dbm]

I have two CX-333s and think they are fine for their size and compare favorably to other dual band antennas of a similar size. Its a much better antenna for putting a signal out at the horizon than something in the 5-6ft tall range. Not counting 220MHz, the Comet GP-9 series puts out a noticeably better signal than the 333 but its over 17ft tall.

Also, the CX-333 would replace the spot where the DB-411 is currently at. How disappointed will I be in the 440 MHz band performance of the CX-333 vs the DB-411?

 

[prcguy]

Ok, now we're talking something that I'm real familiar with. I've tested lots of antennas here and the Comet GP-9 is rated 2dB higher in gain than the CX-333 in the 440MHz band and that's about what I have noticed. I've done testing here swapping a GP-9 with a 450-470MHz DB-411 in 9dB cardioid mode, antennas in the exact same spot on a 440 amateur repeater. Before I swapped antennas I took precise receive levels from several 440 repeaters and I don't remember the exact numbers but the DB-411 was around 4-6dB better than the GP-9 depending on the direction from here. Going from the GP-9 to the DB-411 on the amateur repeater was like moving the repeater to a higher site, it just got out further and users had less noise.

This is not good news for you because the CX-333 is about 2dB worse than a GP-9 in the amateur band which was 4-6dB worse than the DB-411 and you are looking at using the 333 for GMRS where it doesn't work very good at all, GMRS is way out of band for that antenna. So going from a DB-411 on GMRS to a CX-333 will be a drastic, probably 10dB or more degradation in my opinion.

The DB-411 I'm referring to here is actually a split DB-413 where there are two DB-411s on a single 18ft mast. I have one 4-bay set on an amateur repeater and the other on a GMRS repeater and its working great. I also have a normal DB-413 with 12dB of gain in cardioid but I'm out of tower space. I just realized your DB-411 might be set for omni mode and that would have 3dB less gain than cardioid I tested but it will still outperform a CX-333 in the amateur band and and even more on GMRS.

Also, the CX-333 would replace the spot where the DB-411 is currently at. How disappointed will I be in the 440 MHz band performance of the CX-333 vs the DB-411?

 

[AK9R]

I'm prepared to risk the $179 if it gets blown up, though.

Plus your time and exposure to risk if you need to replace the antenna.

 

[n4dbm]

This is about what I thought you would say, so it doesn't really surprise me. I have always figured antenna gain (in dBd) with approximate "capture area" as in a 22-foot Stationmaster would have 10 dBd gain on UHF, a Comet GP9 at 18.5 feet might actually have 9 dBd gain.. If the DB-420 has 9.2 dBd and the capture area is about that of the GP9 then I guess it should make sense. In theory, the CX-333 being 10 feet should have perhaps 3 dBd on 2-meters and 6 dBd on UHF. We did real range testing on multiple antennas in a controlled field study and found that the Hustler G6-144 actually had 3 dBd of gain - fitting, because the 10-foot capture area is similar to that of a DB-222 which also has 3 dBd.. I could open a can of worms on how disillusioned some of these antenna companies are with their advertised gain, but that's another subject.

QSL on your "dual" DB411. I have similar dual 408's up on repeaters, on the same mast, using one for TX and one for RX with appropriate pass filtering.

Your reply already confirmed my suspicions that I probably won't be satisfied with the performance on the CX-333 vs the DB-411 even on the ham band, let alone GMRS. Some of the repeaters I maintain and need to work are 40 to 50 miles away and I'm on very flat terrain. I only have 50 feet of vertical height to deal with, so I need the gain, as some of these repeater signal strengths I'm working are already in the -100's to begin with. I don't need to lose any signal, especially in the direction that it's aimed, that's for sure.

I will probably leave the DB-411 as is and then pick and choose my 2M and 220 MHz antennas. For test purposes, I have mounted a G6-144 and a PD-200 Super Stationmaster cut for 224 MHz on the tower. Even just above roof level both 2M and 220 antennas work very well but have a noticeable null through the tower, of course, which I don't need in any direction. Like everyone else, I want my cake and eat it, too. And, if I leave the DB-411 as is, then I'll probably never get a lightning strike. The minute I put the CX-333, the sky will turn black and a storm out of nowhere will throw a strike at it and pulverize it.

Low-quality pic of my tower before I even got the feed-line hooked up on the 220 MHz antenna. Excuse the shabby loose cabling, it's a work in progress, along with moving the G6 to the opposite side of the tower.

Thanks for posting your experience.

 

[prcguy]

I would want to get side mounted antennas at least 2 wavelengths out from the tower to reduce some of the pattern distortion. That would be about 12ft 9" for the 2m band. Since the G6-144 is not that large or heavy, why not stick it on top of the DB-411? Worst case you could get a new thick wall galv steel mast another foot longer for the DB-411 and transfer the dipoles to that then put the Hustler on top.

 

[n4dbm]

It's funny you mention that. I sourced a good piece of 1-1/4" galvanized threaded conduit (the real deal, the dull gray galvanized, not the cheap China crap), also a 1-1/4" to 1" stainless reducer and a 1" stainless nipple for a 146 MHz DB-201 ground plane to mount, with coax inside the conduit. I was planning on mounting the DB-411 dipoles to the 1-1/4" conduit and the DB-201 out the top. Since the DB-411 dipoles are the old style, with the worm clamp, they will fit on the conduit where the clam shell type would be too loose. The problem is the sheer mass of the conduit. I could find a way to mount the DB-201 to the aluminum mast the DB-411 is already on. I would rather not put the G6 out the top, because I have had two of them blown away by lightning - the fiberglass coil actually exploded.

More than likely, I will shorten the tower 10 feet, and put a four-way mount at the top, so that four antennas can be mounted out the top in the clear, and all be 6 or 8 feet away from each other. Losing 10 feet of height won't amount to a hill of beans' worth of difference, just so long as I am above the roof line.

There is currently 25 feet of tower above the house bracket. I don't feel very comfortable with multiple antennas at that height. Shortening it down to 15 feet above the house bracket will allow me to (comfortably) mount multiple 10-foot arrays out the top. Thanks for the ideas.

 

[prcguy]

Loosing 10ft of height on a tower in the flat lands will reduce your range noticeably.

It's funny you mention that. I sourced a good piece of 1-1/4" galvanized threaded conduit (the real deal, the dull gray galvanized, not the cheap China crap), also a 1-1/4" to 1" stainless reducer and a 1" stainless nipple for a 146 MHz DB-201 ground plane to mount, with coax inside the conduit. I was planning on mounting the DB-411 dipoles to the 1-1/4" conduit and the DB-201 out the top. Since the DB-411 dipoles are the old style, with the worm clamp, they will fit on the conduit where the clam shell type would be too loose. The problem is the sheer mass of the conduit. I could find a way to mount the DB-201 to the aluminum mast the DB-411 is already on. I would rather not put the G6 out the top, because I have had two of them blown away by lightning - the fiberglass coil actually exploded.

More than likely, I will shorten the tower 10 feet, and put a four-way mount at the top, so that four antennas can be mounted out the top in the clear, and all be 6 or 8 feet away from each other. Losing 10 feet of height won't amount to a hill of beans' worth of difference, just so long as I am above the roof line.

There is currently 25 feet of tower above the house bracket. I don't feel very comfortable with multiple antennas at that height. Shortening it down to 15 feet above the house bracket will allow me to (comfortably) mount multiple 10-foot arrays out the top. Thanks for the ideas.

 

[n4dbm]

Well then, before I go through the effort, I'll side mount two DB404's on the same side of the tower, one at 45 feet and one at 35 and check the difference with a spec-an.

 

[n4dbm]

The 440 MHz difference from 45 to 35 feet according to Radio-Mobile online. Now, this is from my tower to a vehicle on the road, not a repeater tower way off in the distance. It doesn't look like much, but I still want to know what it is in "real world" conditions. Instead of hassling with the DB404's, I might see if I can borrow a friend's X-50 and mount two of those on the tower (easier) 10 feet apart so I can check 2M and 440 also.