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I am planning on getting a Comet antenna for my first base antenna but I'm not sure which one.


WRPH745
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I am looking to get my first antenna for my base.  Comet antenna have been recommended several times.

The CX-333 was recommended and the Comet Original CA-712EFC.

The CX-333 is a triple band antenna for 2m /  1.25 m / 70 cm. 

The CA-712EFC is for 460 -470 MHz

I am brand new to all this.  I have my GMRS license and I am taking the test for Technician next week.

My area has a GMRS repeater which connects to The Midwest GMRS Repeater network.  It also has a 2 m repeater where the local Ham group has weekly on air meetings.

I spend most of my time on GMRS but once I get my Technician license I want to participate in the local Ham group.

There is a repeater on the 1.25 m band but I have not listened to it.  I do not have a radio for that band.

I also have heard the 6 m band is interesting.

I also found:

The Comet GP-15 is a triple band on 6 m / 2 m / 70 cm.

The Comet GP-6 is a double band on  2 m / 70 cm.

I know the best thing would be to get a GMRS antenna and an antenna that would cover the 2 meter band.  To keep down expense and only running one line into the house I would like to just get one antenna to cover both GMRS and the 2 meter band.  It is my understanding I cannot put a GMRS antenna and a 2 m antenna on the same mast.  If I could I would be tempted to get a separate antenna just for GMRS.

So I am leaning towards a double or triple band antenna and trying to pickup GMRS using the 70 cm band.  All the antennas listed have similar price points and similar specs for similar bands.

Is there any reason to get the double rather than the triple?

If I should go with the triple which triple?  At this point I don't have enough knowledge about 6 m or 1.25 m to know which way to go.

Thanks

 

 

 

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I have a 333 at about 35 feet.  My nanoNVA says its tuned slightly better for 65cm than 2m.  As a simple matter of convience I am not using it on 1.25 right now, but the nanonva shows its tuned very well there as well.  If I recall, the readings were 1.27 on 2m, 1.1 on 1.25 and very close to 1.19 across the parts of 70cm and 65cm that I use

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Comet CX-333 is not terribly expensive, but it's all relative, depends on one's budget. If you plan to be on 1.25m, sure, go for the tri-band. Otherwise, many of ham dual-band will cover 2m, 70cm and GMRS for less money.

I use Diamond X50NA, it works great on 2m and 70cm, and has acceptable SWR on GMRS band (below 1.8).

6m is a sort of monkey wrench here. 6m is more popular than 1.25m, but everything depends on local situation. SSB or CW on 6m would prefer horizontally-polarized antenna and a different rig. Local FM on 6m would be of vertical polarization, but still a different rig, from 2m/70cm/GMRS. There are transceivers that cover 6m, 2m, 70cm, and GMRS, but they are not legit in the eyes of FCC (for transmitting), and this tidbit might be important to you.

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If your housing situation is one that will last for years, be sure to consider different operating plans for the future:

For example, maybe 220 MHz (1.25 meters) will become more active in your future and a tri-band antenna once is cheaper than a new additional antenna later.

That is what I did and although I still do not do 220 MHz all that often, I am glad I have that capability into the future.

I plan to get more active again on 6 meters (both FM and SSB) and HF and my antenna for those bands is a HyGain Vertical.  For years I spoke to Hams on HF who were horizontally polarized with a rotatable beam antenna and it always worked fine for me.  Maybe if I had a beam to switch to, they would hear me better, but it has always worked cross-polarization.

I used to use one rig for all: Yaesu FT-857d - 80 meters to 440 MHz, but now with my Anytone AT-779UV (Radioddity DB-20G), I use that rig for 2 meters, 70 cms and GMRS into my Comet CX-333

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17 hours ago, WRPH745 said:

I have my GMRS license and I am taking the test for Technician next week.

Good luck on getting your ticket next week. Great to see you're expanding your horizons in the world of radio. 73

de WROA675/KN6SDM

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  • 2 weeks later...
  • 2 months later...
On 2/18/2022 at 5:33 PM, WRPH745 said:

I also found:

The Comet GP-15 is a triple band on 6 m / 2 m / 70 cm.

The Comet GP-6 is a double band on  2 m / 70 cm.

I know the best thing would be to get a GMRS antenna and an antenna that would cover the 2 meter band.  To keep down expense and only running one line into the house I would like to just get one antenna to cover both GMRS and the 2 meter band.  It is my understanding I cannot put a GMRS antenna and a 2 m antenna on the same mast.  If I could I would be tempted to get a separate antenna just for GMRS.

So I am leaning towards a double or triple band antenna and trying to pickup GMRS using the 70 cm band.  All the antennas listed have similar price points and similar specs for similar bands.

Is there any reason to get the double rather than the triple?

If I should go with the triple which triple?  At this point I don't have enough knowledge about 6 m or 1.25 m to know which way to go.

 

 

 

 

I have a Comet SBB-15 mobile tri-band antenna (2m/70cm/6m) that I am trying to use as a base unit (camping, etc) utilizing a Tram 1465 mobile-to-base bracket.  The Tram bracket came with ~20" radials which work fine on 2m/70cm but not 6m.  I'm currently beginning work on cutting longer radials (first trying 1/8" aluminum rods at around 60") to use on 6m then run through an antenna analyzer to see if they'll work at all on 6m and, if so, whether they will on 2m/70cm as well.  I kind of doubt it, which then kicks me back into the possibility of taking two sets of radials along which is a real pain if I'm going to want to work anything beyond 6m.  I have a mobile in those bands, so I thought I'd try setting it up as this base, too, but it's feeling a little like a pipe dream at this point.

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  • 2 months later...

I'm in the same position as WRPH745   where I've got my GRMS license and will be working on getting my ham technician license so I want an antenna that will work on 2 meter, 70cm and GRMS.  I am thinking about the Comet GP-9 dual band (no plans for 6 meters).  Is this antenna tunable or will it have good SWR for GMRS band out of the box.  Anyone else using this antenna for GMRS?  Thanks in advance for the input.

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1 hour ago, TXFitz said:

I'm in the same position as WRPH745   where I've got my GRMS license and will be working on getting my ham technician license so I want an antenna that will work on 2 meter, 70cm and GRMS.  I am thinking about the Comet GP-9 dual band (no plans for 6 meters).  Is this antenna tunable or will it have good SWR for GMRS band out of the box.  Anyone else using this antenna for GMRS?  Thanks in advance for the input.

Not really... It may be tunable, but you'll need to shorten it a fair amount but you won't be able to use it for 146MHz, 445MHz (I'm picking mid range of most repeaters), AND 463MHz (rounding up) even if you use a reversed antenna selection switch (instead of picking from two antennas, sharing one antenna with two radios -- a bit of a risk as they aren't perfect and some signal leakage can feed back down the "off" side... and with 100W out, that leakage might be enough to damage the receive input of the other radio. I really need to modify my shack by using four switches to allow for || with two antennas, and then X with the two [bottom are radios, top are antennas])

463MHz is ~65cm. Assuming quarter-wave whip, you are looking at cutting 1.25cm off the antenna (half an inch); most don't have that much adjustment range using set screws and shifting the whip.

Looking at the manual for the GP-9... It is NOT tunable, it is manufactured "tuned" for the 2m/70cm bands, and appears to be phased/stacked half-wave antennas (2m half-wave is 1m and this antenna is 5 of those in length, 14 for 70cm unless trapped internally to a shorter length).

(nice, but pricey... I'm halfway through installing an MFJ ground-plane 2m/70cm that I've had for half a decade onto the end of the garage... Need to get suitable hex-head wood screws for the five attachment points -- and a day when the temp&humidity aren't so high! Running a "wire rope" with adjustment turnbuckle between the house eave and garage eave did me in today [this is for me to loosely spiral the coax around, rather than have 10-15ft of coax dangling between buildings])

I suspect 445 and 463MHz are close enough that fitting a GMRS antenna in parallel (on the other side of the mast) is going to cause problems -- detuning of both, possible reflector/director effects making the pattern of the antennas somewhat directional... AND OVERLOADING the receive circuits of a unit when the other is transmitting.

 

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On 5/15/2022 at 2:47 PM, fremont said:

The Tram bracket came with ~20" radials which work fine on 2m/70cm but not 6m.  I'm currently beginning work on cutting longer radials (first trying 1/8" aluminum rods at around 60") to use on 6m then run through an antenna analyzer to see if they'll work at all on 6m and, if so, whether they will on 2m/70cm as well.  I kind of doubt it,

Yes -- old post, OP may not be reading and has solved the matter by now, but...

Try modelling it... https://www.eznec.com/

If the vertical component has loading/trap coils, you are on your own (EZ-NEC handles them) -- I've only modelled simple stuff, like an MFJ OCFD [40/20/10/6 meter] for purposes of required RF Safety evaluation). HTs and Mobiles aren't commonly required to be evaluated -- they are low enough power OR transient enough that the "uncontrolled environment" [people passing by without knowing about radio exposure] doesn't apply, and the operator is in the "controlled/occupational environment" which allows higher exposure limits. I have to reduce power on 6m as the uncontrolled safe distance just reaches the neighbor's upstairs bedrooms. Going to have to model the 2m/70cm I'm putting up on the garage -- but that is basically the center of my lot, so should have a long safe zone.

20" radials is about 1/4 wave on 2m. I suspect longer radials won't affect the higher bands too much (I've not modelled your situation). 1/4 wave on 6m would be 1.5m, or 59 inches, so your estimate looks about right -- not counting velocity factor of the metal (which, again, may not be critical if they are longer than actual wave fraction -- after all, they provide an apparent ground plane to the vertical, and real ground is doesn't vanish an N-inches from a vertical).

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18 minutes ago, KAF6045 said:

Not really... It may be tunable, but you'll need to shorten it a fair amount but you won't be able to use it for 146MHz, 445MHz (I'm picking mid range of most repeaters), AND 463MHz (rounding up) even if you use a reversed antenna selection switch (instead of picking from two antennas, sharing one antenna with two radios -- a bit of a risk as they aren't perfect and some signal leakage can feed back down the "off" side... and with 100W out, that leakage might be enough to damage the receive input of the other radio. I really need to modify my shack by using four switches to allow for || with two antennas, and then X with the two [bottom are radios, top are antennas])

463MHz is ~65cm. Assuming quarter-wave whip, you are looking at cutting 1.25cm off the antenna (half an inch); most don't have that much adjustment range using set screws and shifting the whip.

Looking at the manual for the GP-9... It is NOT tunable, it is manufactured "tuned" for the 2m/70cm bands, and appears to be phased/stacked half-wave antennas (2m half-wave is 1m and this antenna is 5 of those in length, 14 for 70cm unless trapped internally to a shorter length).

(nice, but pricey... I'm halfway through installing an MFJ ground-plane 2m/70cm that I've had for half a decade onto the end of the garage... Need to get suitable hex-head wood screws for the five attachment points -- and a day when the temp&humidity aren't so high! Running a "wire rope" with adjustment turnbuckle between the house eave and garage eave did me in today [this is for me to loosely spiral the coax around, rather than have 10-15ft of coax dangling between buildings])

I suspect 445 and 463MHz are close enough that fitting a GMRS antenna in parallel (on the other side of the mast) is going to cause problems -- detuning of both, possible reflector/director effects making the pattern of the antennas somewhat directional... AND OVERLOADING the receive circuits of a unit when the other is transmitting.

 

Thanks KAF6045 I did find the GP-6NC GP-9NC that are dual band and tuned for GMRS so that appears to be the best route for me for when I include 2 meters to my set-up.

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Neither GP-6NC nor GP-9NC will cover 2m (nor 70cm)... They would cover MURS (and 8dBi gain might be an impressive effect on a 2W HT connected to it 😱 ).

I really don't think you will find one antenna that is tuned for both 2m Amateur AND GMRS. They will either be Amateur 2m/70cm OR commercial 155MHz/465MHz.

In many cases, the higher band is harmonically linked to the lower band. 146MHz * 3 => 438MHz (low end of 70cm repeater range -- US 70cm covers 430-450). 155 (MURS 4&5 are 154.x) * 3 => 465MHz (splitting GMRS 462 primary/simplex and 467 repeater inputs).

Note that the FCC regulations for the half-watt 467 interstitials are in ERP, so don't feed those to an 11dBi antenna (even if the FCC is in dBd, you'd have over 8dB gain on that half-watt -- effectively between 2 and 5 watts ERP in the antenna beam). Also for the 5W 462 interstitials -- you'd have between 20 and 50 watts ERP...

 

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The 467 interstitials are restricted to HTs, are they not?

I appear to have lucked out with two Diamond antennas, as far as working on 2m/70cm and GMRS.  The X50NA I've been using for almost two years has a SWR just under 2.0 on the GMRS repeater inputs.  Not great, but OK for limited use.  I just put up a V2000A and it has an SWR< 1.5 all across the GMRS 462 and 467 frequencies.

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21 minutes ago, wrci350 said:

The 467 interstitials are restricted to HTs, are they not?

Yeah, but the calculation still applies: FCC regulations for 0.5W NFM 467 interstitials AND the 5W FM 462 interstitials are stated in terms of ERP while repeater inputs (467 primaries) and output/simplex (462 primaries) are stated in transceiver output power.

Nothing prevents one from connecting an HT to these antennas but for the adapters needed (since the industry seems to have standardized on SMA -- though the chinese radios use the opposite gender -- from the 80s/90s common usage of BNC). And with gain of those, exceeding regulation ERP levels. I suspect I have at least one HT that /might/ be in violation -- at least on the 467 group; the 462 group on high power is nowhere near 5W -- so the tall whip's gain may not be enough to counter the lower "high" power output.

 

21 minutes ago, wrci350 said:

I appear to have lucked out with two Diamond antennas, as far as working on 2m/70cm and GMRS.  The X50NA I've been using for almost two years has a SWR just under 2.0 on the GMRS repeater inputs.  Not great, but OK for limited use.  I just put up a V2000A and it has an SWR > 1.5 all across the GMRS 462 and 467 frequencies.

Did you mean SWR < 1.5 ? (L <  less; G >  greater [one needs a G with the squared/tail on the lower right to make the association work]).

 

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2 minutes ago, KAF6045 said:

Did you mean SWR < 1.5 ? (L <  less; G >  greater [one needs a G with the squared/tail on the lower right to make the association work]).

OMG really?  I don't need an explanation of the less than and greater than signs.  It was a typo, and I fixed it.

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  • 2 weeks later...

I have had the CX-333 on gable end of house (35’ off ground) for almost a year. I have been extremely happy with it. I can’t share any measurements as I don’t have any meters but have had nothing but good sound checks using a BTech UV-50x3 mobile.

Repeaters 50 miles away are easy to hit. I can get some folks on VHF in simplex at over 20 miles. I have had no bad experiences with the antenna.

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  • 5 weeks later...
On 8/4/2022 at 3:40 PM, KAF6045 said:

I really don't think you will find one antenna that is tuned for both 2m Amateur AND GMRS. They will either be Amateur 2m/70cm OR commercial 155MHz/465MHz.

Tram 1181 may get you close.  (SWR) from a fender mount:

VHF     144.000 (1.34) climbing up to (1.62) at 148.200

UHF     (2.05) 440.000 / (2.29) 443.333 / (1.82) 446.800 / (1.55) 450.000

GMRS     (Approx. 2.00) in 462.xxx frequencies and (1.36) in 467.xxx repeater Tx frequencies

MURS    (2.06) Channels 1-3; (2.35) for Blue/Green (Ch 4-5)

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  • 2 weeks later...
On 8/19/2022 at 12:22 AM, flashover52 said:

I have had the CX-333 on gable end of house (35’ off ground) for almost a year. I have been extremely happy with it. I can’t share any measurements as I don’t have any meters but have had nothing but good sound checks using a BTech UV-50x3 mobile.

Repeaters 50 miles away are easy to hit. I can get some folks on VHF in simplex at over 20 miles. I have had no bad experiences with the antenna.

I get similar with and Diamond X200a it's abou 8.5 feet tall in my attic about 35 feet up, with LMF400. HIt Warrenton GMRS repeater from Potomac, MD. which is about 37.4 aero miles as well as Towson GMRS repeater (41.9 mies) at 50 watts.

No swr readings, to hand off.

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I already had the Comet CX-333 tri-bander installed on my 2nd story roof (for my ham radio) and I am amazed at how well it works for GMRS and limited testing on MURS:

With my 18 watts on GMRS, I find that I can communicate simplex to about 35 miles and hit repeaters (with elevation) on a radius of 60 miles (and 80 miles on 2 meters).

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