Diamond SG-7900-A-NMO on GMRS Frequencies?

[marcspaz]

I am wondering if anyone has used a Diamond SG-7900-A-NMO on their vehicle, on GMRS frequencies?  If so, how did it go?

 

I am looking at getting a better mobile antenna.  A radio I just ordered covers 2 meter, 70 cm and GMRS frequencies.  I am thinking about getting a Diamond SG-7900-A-NMO for 2m/70cm use.  I had one before and it worked great for its intended use.

 

The antenna is pre-tuned and not adjustable.  The Ham UHF frequencies stop at 450 MHz.  I am hoping the antenna will be tuned close enough to get good performance and have a good SWR on GMRS frequencies as well.  It will make life easier if I don't have to swap antenna's as I move between Ham and GMRS.

 

Any feedback on your experience on this is much appreciated.

 

Thanks,

Marc

[coryb27]

I have not had or seen anybody have good luck running a dual band ham antenna on GMRS, In my personal experience the trusty NMO UHF 1/4 wave has given me the best performance for repeaters and hwy simplex use and most will cover 440 to 480. No issue with repeaters 30 miles away and regularly see 10 miles simplex on the hwy. 

[marcspaz]

That's good to know. If that's the case, I'll likely keep both antennas in the truck and just swap them as needed.

 

I appreciate the reply.

[WRAF213]

There's a 1/4 wave dual-band whip on my car, even that simple construction cuts off right at 450 MHz. Most of those dual band antennas are based on 70cm being around the third harmonic of 2m, and 467 MHz is quite some distance from the third harmonic of 148 MHz.

 

Most of those multi-band ham antennas are designed to give good SWR inside 144-148 and 440-450, and SWR will rise very quickly above 450 MHz. As a good rule of thumb, higher gain antennas are narrower-bandwidth than lower gain antennas.

[WRCR872]

Check out these two Comet antennas, CA-2x4SR & CA-2x4SRNMO.

 

1.5:1 or less SWR:

144-148/440-450MHz
2:1 or less  SWR:
140-160/435-465MHz
Gain: 3.8/6.2dBi

[marcspaz]

I just wanted to take a moment to follow-up on my research and testing.  Just so everyone knows there is no bias, I do not work for, nor have any connections to Comet or any other two-way radio communications companies.  This is a totally unbiased opinion.

 

I actually found a great, multipurpose antenna (Thanks KD2NCN / WRCR872 !).  I bought a Comet CA-2x4SR NMO and its performance exceeds my expectations.  Comet advertises this antenna for this very purpose and they did not let me down.

 

My dedicated GMRS antenna (Midland MXTA11) had a 3:1 SWR on channels 1 through 7 (shared FRS/GMRS) and 15 through 22 (GMRS only).  On the FRS channels it had a SWR of 2.5:1.  Likely due to the extremely low power of the handheld, otherwise it would have be 3:1, too.  On the 70cm frequencies, that antenna actually did very well, with a 1.5:1 SWR.  On 2 meter, it was over 5:1. 

 

The Comet antenna has a 1:1 SWR on 2 meter, 1.2:1 on 70cm, and a 1.5:1 on all FRS and GMRS frequencies.  In my simplex testing on channel 15, while using the old antenna, my mobile to mobile between my two trucks was a max of about 2.6 miles in the suburbs.  The new max is 8.3 miles in the same suburbs.  Also, I got a signal report that I was "full quiet with loud audio" on a repeater that was 28 miles from my test location, while using a full 50 watts.

 

If there are any Hams looking for a good 2m/440/FRS/GMRS antenna, I highly recommend this one.

 

Hope this helps someone.

Spaz

[WRAF213]

Just remember that while simplex operation happens down at 462 MHz, duplex operation transmits at 467 MHz and SWR / return loss should be checked at 467 too.

[TheMD]

Marc,

 

Marc,

Can you share what radio you purchased, and what are your thoughts on how well it works. 

Finding it difficult to find 2M/70CM/GMRS rigs, and understand for obvious legal reasons.

Thanks
MD

[MichaelLAX]

1 hour ago, TheMD said:

Finding it difficult to find 2M/70CM/GMRS rigs...

Check out the Anytone AT-779UV a/k/a Radioddity DB-20G available for retail $99, $129 respectively:

Mobile, 18 watts

Fits in the palm of your hand

Cigarette lighter plug

Certified FCC Part 95

Transmits on GMRS, 2 meters and 70 cms. 

[MichaelLAX]

On 3/16/2019 at 7:40 PM, marcspaz said:

Any feedback on your experience on this is much appreciated.

Let's Get Ready sold me a $20 mag-mount for the Anytone AT-779UV they also sold me (the Anytone is not listed as for sale on their website; you have to contact them to buy it) and it works well on all 3 bands.

I also use it with my Comet Tri-bander installed up on the roof when I use it in the shack and it really gets out -- hitting a Santa Clarita 70 cm repeater from my San Fernando Valley residence, which impressed the repeater OP!

[WyoJoe]

5 hours ago, MichaelLAX said:

I also use it with my Comet Tri-bander installed up on the roof when I use it in the shack and it really gets out -- hitting a Santa Clarita 70 cm repeater from my San Fernando Valley residence, which impressed the repeater OP!

Nice to be able to talk into SCV from SFV. Is the repeater you're using on Magic Mountain (not the amusement park)? It overlooks both valleys, more or less.

[MichaelLAX]

30 minutes ago, WyoJoe said:

Nice to be able to talk into SCV from SFV. Is the repeater you're using on Magic Mountain (not the amusement park)? It overlooks both valleys, more or less.

No, actually it's not 147.735 (while known historically as the Magic Mt repeater, it moved to Oat Mt).

On the map here on myGMRS.com, I found the SCV550 repeater for Santa Clarita.  But if you look at its details, it says:

"Effective 12/10/2020 this repeater has been moved to 70cm Ham.  If you're a Ham, please join us on 446.860 - PL 100.0hz"

So I drove up to Santa Clarita and had a nice chat will Bill KJ6EO, the repeater OP.  He actually owns and operates a low power FM station up there too: 103.5 and is a very interesting guy to chat with.

AND he made me aware of a Dickie's BBQ not far from where I was driving off Hiway 14 and its a real find!

So later that night, I brought my Anytone up into the shack, connected to the Comet and consistently hit this repeater.  

Later I also discovered my Yaesu FT-857d also hits it well on the Comet; I was just on the wrong PL when I tried before. 

Are you based here in SoCal, too?

[WyoJoe]

22 hours ago, MichaelLAX said:

Are you based here in SoCal, too?

Yup! Near the top of the Grapevine, not all that far from you. I've listened to a few of the repeaters around SCV on occasion, but usually I'm focused on other things, so I don't turn my radio on to listen to them.

[MichaelLAX]

I enjoy taking "drives" and one of them is up to the Pilot Flying J Truck Stop up at the top of the grapevine in Frasier Park.

I get a big order of their spicy hot wings and bring them next store to the Wendy's where I add a baked potato and their Summer Strawberry Chicken Salad.

I note that there is a repeater just to the West in Mt. Pinos.

I have already programmed it into my Anytone and I look forward to testing its coverage the next time I get up there.

[WyoJoe]

1 hour ago, MichaelLAX said:

I enjoy taking "drives" and one of them is up to the Pilot Flying J Truck Stop up at the top of the grapevine in Frasier Park.

I get a big order of their spicy hot wings and bring them next store to the Wendy's where I add a baked potato and their Summer Strawberry Chicken Salad.

I am a fan of hot wings, but I've never tried them at "the J." I'll have to give them a try some time, since I go by there almost daily.