Power amplifier

[WROA675]

Hello all you out there in radio land...here's my noobie question of the day : Can I use a power amplifier with my mobile unit?

For my base, I'm using the DB25-G. In the owner's manual it states the output power is 5W/25W GMRS...however, at best I'm only seeing 17.9 watts on my meter.

Hence the above question. Would it make a difference? Does anyone use a power amplifier with their mobile unit? Pros/Cons, please...thx

[BoxCar]

Yes, you can use an amp but why? It would be less expensive to just buy a higher power radio without the multiple point-of-failure hassle.

[Radioguy7268]

You would also have to realize that in order to bump up your transmit power by just 3dB - you would need to double the transmit power up to 36 watts.  How high did you plan to go?  Is the transmit power where your system is lacking?

The old GMRS rules specifically ruled out using external power amps. Not so sure that the newer revision still does.

You also need to realize that most cheap amps will amplify noise as well as signal across a broad range. In short - if you're throwing off some spurious birdies  - the amplifier is going to increase those spurs as well as your desired frequency. It's not going to make you popular with your frequency neighbors.

As BoxCar said - invest in a higher power mobile if you truly need more power. Or just get a better antenna. Or better coax. You're probably losing 1 or 2 dB just in your cheap coax - not to mention any poor connectors or adapters you might be using. 

 

[WROA675]

26 minutes ago, BoxCar said:

Yes, you can use an amp but why?

Thanks for your input. As to why, well I have a radio already so there's that. I like my 25 and maybe in the future I could upgrade if needed. I have not done any research into the prices of a compatible power amp, so I'm not sure how much I would be saving or not. Regardless, just looking at my options for using my current equipment. 

[WROA675]

6 minutes ago, Radioguy7268 said:

The old GMRS rules specifically ruled out using external power amps. Not so sure that the newer revision still does.

Thanks for the information, I'll check into the current regs. Great point about the birdies.

My coax is solid, LMR 400, the antenna is the Larsen BSA 450 (gonna try a j-pole next to compare performance).

May consider a higher power mobile in the future, but for now I'm just trying to dial in what I got and use it to it's full potential. 

[tcp2525]

I  believe the rules state 50w maximum. For a base with a good antenna and feedline 5w is more than enough. I have a StationMaster fed with 1/2" Heliax at 50' and I get out just fine. As for an amp, just use what you have as there's going to be no noticeable difference between the two power levels. Invest your time and money into a good antenna system.

[WROA675]

32 minutes ago, tcp2525 said:

there's going to be no noticeable difference between the two power levels. Invest your time and money into a good antenna system.

Thank you for that perspective. Sounds like what I was needing to hear.

The antenna system is a work in progress, exploring different options, as I'm limited by CC&R and trying to stay off their radar.

[MichaelLAX]

2 hours ago, tcp2525 said:

I  believe the rules state 50w maximum. For a base with a good antenna and feedline 5w is more than enough. 

Except that Papatree and I are unable to communicate simplex on one of the 5 watt channels, yet do so fine on one of the 550-725 channels using 25 watts in his case and 18 watts in mine. 

[AdmiralCochrane]

8 hours ago, Papatree said:

Would it make a difference? 

No. No difference that you could tell

[BoxCar]

More  power usually means better coverage in the areas you can already reach. From my experience the amount of area you can cover is increased by less than 5%. Antenna selection and placement usually mean much more than increasing the ERP. There are really 3 power measurements needed to get a true picture of your potential coverage. You need to measure the RF output into a dummy load first then through the antenna feed line and finally, using a field strength meter the actual signal from the antenna. The measurement of the feed line is because line losses published are averages based on samples produced. Your actual loss will probably be higher than the published figures because of adding the connectors.

[tweiss3]

The other problem you will find is getting an amplifier that will match your low power output to 50W. Most have a drive input of 5-10w, outputting 80-150W, over the power limit allowed for GMRS.

[WyoJoe]

20 hours ago, tcp2525 said:

Invest your time and money into a good antenna system.

 

20 hours ago, Papatree said:

Thank you for that perspective. Sounds like what I was needing to hear.

The antenna system is a work in progress, exploring different options, as I'm limited by CC&R and trying to stay off their radar.

I was going to basically echo what tcp2525 said. Optimizing your antenna system will give much greater gains than more power ever could. Given the restrictions you have to comply with, your best bet is to get a good antenna as high up as you're able to without getting in trouble with the HOA.

One option might be to put a "stealth" antenna in a tree, provided it's close enough to run the cable to the radio.

Something else to think about is if you have a friend nearby whose house is on a hill where coverage would be better. If so, perhaps you could talk them into allowing a repeater at their house (of course they will also likely have to comply with HOA restrictions). Of course, that would not help you to reach other repeaters, but it could give you an option for broader coverage in the area around your community, but it would likely be limited mostly to those in your group or family.

[WROA675]

On 11/11/2021 at 7:48 AM, WyoJoe said:

Optimizing your antenna system will give much greater gains than more power ever could.

My current antenna is the Larsen BSA450 with a 4.5 db gain. It's small and discreet. I tried a 2ft j-pole, but found it only had a 2.5 db gain (gifted it to a buddy who had no antenna at his house).

Looking at possibility getting this one:

https://www.amazon.com/dp/B094DNP9PC/?coliid=I176NXRPR3GV03&colid=603H8JI6495Q&psc=1&ref_=lv_ov_lig_dp_it 

Hitting a couple repeaters fine right now with my current set-up, but on  the fence about trying another antenna. I feel it would give me better performance and clarity, but on the other hand, the Larsen is adequate for my needs (not wants).

Interested in any input regarding this matter...

[wrci350]

Amazon is *not* the place to buy antennas.  

That looks very much like a knock-off of the Diamond X50A, which is a pretty good 2m/70cm ham antenna, and does fine on GMRS, at least for me.  If that's the way you want to go, get a real one for $6 more:

https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_193_257_1107_261&products_id=4869

[WROA675]

1 hour ago, wrci350 said:

If that's the way you want to go, get a real one for $6 more:

I appreciate the tip, good looking out.

I'm still on the sidelines about spending another hundred bucks, at the moment, but I think your right about antennas and amazon and will order from a reputable dealer (i.e., Antenna Farm, DX, HRO) if I decide to pull the trigger on this one.

[MichaelLAX]

Get the X50G! 

[WROA675]

1 hour ago, MichaelLAX said:

Get the X50G! 

You got me, Michael...I was searching everywhere for it, could only find the X50 and X50A. 

[MichaelLAX]

Your future is 2 meters and 70 cms, so get the antenna optimized for Ham bands!