110W Radio: Minimum Output?

fogster · Post by **fogster** » Wed Mar 14, 2007 6:58 am

Strange question perhaps... I may be picking up a 110W ASTRO Spectra, but the antenna I'd planned to use is rated at 50W. I often see the 110W listed as "61-110W," but I'm not sure how to interpret it... Without any alignment equipment, can I program the radio for 50W out?

And I'm not about to put 110W into an antenna rated for 50W, but I'm curious what happens and how they come up with the power ratings. Does it start to reflect a lot of power back over 50W, or is it more like I'm going to burn up the antenna? (Can you tell I've never played with higher-power gear?

)

motorola_otaku · Post by **motorola_otaku** » Wed Mar 14, 2007 8:55 am

I believe the default low-power setting is for 50W, but don't quote me on that. You still probably wouldn't want to run it right at your antenna's maximum anyway.

The power rating is for the components in the antenna matching network. If you go over it, you'll likely burn them up, resulting in transmitting your full 110 watts into either an open or a dead short.

I'm going to venture a guess and say that you have a VHF radio that you're wanting to use with one of these antennas. Do yourself a HUGE favor and toss that thing, and go with a 1/4-wave whip minimum. Or if you absolutely have to have a low-profile antenna, go with one of these.

fogster · Post by **fogster** » Wed Mar 14, 2007 9:04 am

Can it go lower? Not that I have reason to use it, but what if I wanted MURS or the like? Will the radio just not support 2-5W?

Can the matching be 'upgraded' to support higher power? (Antennas aren't my forte.)

I'm looking at mounting on the top of an SUV, and I park in a parking garage. :rolleyes: Thanks for the link to that antenna, though, it's pretty spiffy.

Post by **alex** » Wed Mar 14, 2007 9:08 am

I agree with Josh -

The phantom antennas on VHF are really not that great unless your in a area where you are using a repeater, and you have a VERY strong signal. For the most part, they are horrible for use in simplex systems, you can easily hear the receive range difference if you were to quickly swap antenna's.

I had one of those cans on my explorer, and let me tell you - it really just sucked. I put the metal whip back on same day. The quality sucked.

However, if you want to use the phantom's in UHF or any band higher, they are actually a great antenna. I've been using them in UHF and 800 for about 2-3 years now, and I don't notice a difference.

The long white antenna as well will work nicely, and should handle the 110w without issue. I've seen them used primarily in ambulances, and haven't really heard of a performance issue.

Again, make sure you read and double check documentation on everything before you flood the antenna with 110 watts of pure joy.

-Alex

motorola_otaku · Post by **motorola_otaku** » Wed Mar 14, 2007 9:23 am

fogster wrote:Can it go lower? Not that I have reason to use it, but what if I wanted MURS or the like? Will the radio just not support 2-5W?

If you have RSS/CPS and a good wattmeter and service monitor, yes, you can crank the power down. Since it's a high-power radio, though, the minimum you get out of it may still be 10 to 25 watts. When you're looking at the transmit power alignment screen in RSS (or CPS), the numbers reflect power attenuation, not actual power out. So as well as a maximum power limit, you also have a maximum power attenuation limit to contend with. Oh, and the radio will still draw somewhere around 20 amps transmitting in low-power mode.

Can the matching be 'upgraded' to support higher power? (Antennas aren't my forte.)

No, not really, and definitely not in the low-profile antennas. There's only so much wattage you can cram into a few square inches of etched copper.

I kinda figured overhead clearance was your issue, hence the recommendation of the white "sharkfin" antenna. That's probably about as good as you're going to get on VHF without going to a whip.

Post by **alex** » Wed Mar 14, 2007 9:54 am

I have clearance issues in my garage as well, on the old truck, I had two steel whips, and I would just let them knock against the garage... at $4 a whip, if there's an issue, you can easily afford to pay for another one if there's a problem. I'd recommend there be at least 4-5" of clearance between the mount and where it hits on the antenna. I say that because you don't want it bending or flexing the roof if it's too close.

-Alex

fogster · Post by **fogster** » Wed Mar 14, 2007 10:09 am

What I had in mind was similar (but inferior) to one of these: http://www.tessco.com/products/displayP ... ventPage=2. Anyone have experience with them?

My benchmark for performance (on receive) right now is a VHF HT with a stubby UHF antenna on it...

So even unity gain would be a step up.

By the way, are there special electrical considerations with a radio of this power? Can I wire it right into the battery, or is the ~30A too much? Similarly, the owners' manual of my old car warned against installing two-way radios, as stray RF may trigger the airbags... Any truth to that claim?

4n6inv · Post by **4n6inv** » Wed Mar 14, 2007 10:21 am

My "can" lasted about two days. And, only becasue it was raining hard! Suck is not a big enough word. Paying a lot of $$$ for it was even more insulting. I bet Motorola was slapping their knees all the way to the bank...

Post by **alex** » Wed Mar 14, 2007 10:27 am

fogster wrote:By the way, are there special electrical considerations with a radio of this power? Can I wire it right into the battery, or is the ~30A too much? Similarly, the owners' manual of my old car warned against installing two-way radios, as stray RF may trigger the airbags... Any truth to that claim?

What kind of car is it?

fogster · Post by **fogster** » Wed Mar 14, 2007 12:01 pm

This is an SUV (2003 Toyota Highlander). (The airbag reference was to the old one, a POS minivan.)

bellersley · Post by **bellersley** » Wed Mar 14, 2007 12:05 pm

motorola_otaku wrote:Or if you absolutely have to have a low-profile antenna, go with one of these.

Pfft.

That'll take your 110 Watts and come back for more!

Post by Pj » Wed Mar 14, 2007 12:54 pm

Just paint some flames on that bad boy..

Post by **alex** » Wed Mar 14, 2007 1:09 pm

bellersley wrote:
motorola_otaku wrote:Or if you absolutely have to have a low-profile antenna, go with one of these.
Pfft.

That'll take your 110 Watts and come back for more!

I've seen those used in a lot of subway cars.

Post by **escomm** » Wed Mar 14, 2007 1:11 pm

if you put on a Motorola sticker will it increase ERP by 10watts?????

tvsjr · Post by **tvsjr** » Wed Mar 14, 2007 7:34 pm

escomm wrote:if you put on a Motorola sticker will it increase ERP by 10watts?????

No, you use the Type R sticker for that.

Spectra power outputs should NOT be turned not without observing the overall efficiency of the amp. Also, you need to check the output with a spectrum analyzer... most X9000 and Spectra PAs get wonky when the power output is backed down too far.

And, the Antenex Phantoms suck... they're narrow as hell (like 250KHz wide for 1.5:1 SWR... I have the NetTek output to prove it) and they won't hold up to high power for long.

cbus · Post by **cbus** » Wed Mar 14, 2007 8:45 pm

tvsjr wrote:
escomm wrote:if you put on a Motorola sticker will it increase ERP by 10watts?????
No, you use the Type R sticker for that.

Spectra power outputs should NOT be turned not without observing the overall efficiency of the amp. Also, you need to check the output with a spectrum analyzer... most X9000 and Spectra PAs get wonky when the power output is backed down too far.

your not wrong, a high power spectra will very rarely keeps its power output steady under 50w. the power level jumps all over the place.

Why don't you just buy a mid power 45w radio ?

motorola_otaku · Post by **motorola_otaku** » Thu Mar 15, 2007 10:03 am

alex wrote:
bellersley wrote:
motorola_otaku wrote:Or if you absolutely have to have a low-profile antenna, go with one of these.
Pfft.

That'll take your 110 Watts and come back for more!
I've seen those used in a lot of subway cars.

They're used exclusively on the Union Pacific for locomotive radios, and probably most, if not all of the other Class 1 carriers.

I personally like the AS sharkfins. You can paint them to match the color of the vehicle, or paint 'em black for night stealth.

A lot of school districts around me use them for bus radios too, and while I'm sure they'll break if you hit them with a big enough tree branch I haven't seen it happen often.

Elroy Jetson · Post by **Elroy Jetson** » Sun Apr 15, 2007 4:24 pm

When I put my A9 high power VHF Spectra into service, I started the PA power settings at minimum and worked my way up. In low power, I was able to get the power under 2 watts, which is where the shop service monitor is no longer giving a reading. I didn't leave it on that setting, though,
but it certainly could be tuned as far down as you wanted to go. No comment on stability or harmonic emissions, I didn't check that low.

But at 25 watts, it's good to go. So I tuned low power for 50 watts and
high power for 110 watts. I don't seen any overwhelming need to back
down the power unnecessarily.

CJ

sglass · Post by **sglass** » Fri Apr 20, 2007 4:43 pm

I run the w3 and w9 with low 20, high 100.

Seth

mr.syntrx · Post by **mr.syntrx** » Sat Apr 21, 2007 8:32 am

motorola_otaku wrote:
alex wrote:
bellersley wrote: Pfft.

That'll take your 110 Watts and come back for more!
I've seen those used in a lot of subway cars.
They're used exclusively on the Union Pacific for locomotive radios, and probably most, if not all of the other Class 1 carriers.

I personally like the AS sharkfins. You can paint them to match the color of the vehicle, or paint 'em black for night stealth. A lot of school districts around me use them for bus radios too, and while I'm sure they'll break if you hit them with a big enough tree branch I haven't seen it happen often.

ACTION Buses (Canberra's public transport) ran them on their buses when they were on 82MHz. They use a quarter wave UHF whip now on the ActewAGL MPT-1327 system. If you hit a tree, either the tree branch will break, or the bus roof will get Auto-Moderated right up when the antenna is ripped out intact, but the antenna will be fine.

Anyway, I find the Antenex Phantom and similar antennas to stand out and look way more obvious than a nice skinny whip.