M120 Power Setting

aussie_battler · Post by **aussie_battler** » Fri Jul 07, 2006 4:50 am

Hi agian everyone

I have one more question for you fine people.

Can someone please tell me the absolute maximum power an m44 model radio on 465-495mhz?

I know the rating is 40watts, but I don't own a swr metre. The guy who programmed it firstly only set it to 25watts and still charged me (even though I paid him to set it to 40).

So I will get to my point now. I don't own a swr metre so I dont want to just set it to maximum and blindly key up. I would like to know what output these radios generally have when set to number 126 in the RSS (highest number)

I know the radio will get hot but if I break it, it's my fault.
Please also don't tell me I won't notice a difference between 25 and 40 or even 50w --- there is a difference, 3dB actually (2dB for 40), which is quite noticeable.

I am sorry to sound rude but I just need to know the maximum power this thing does and if someone could give me a couple of reference points it would be helpful, such as 50 = 20watts, 100=40watts etc..

Thank you very much everyone for reading this

Regards, aussie_battler

kcbooboo · Post by **kcbooboo** » Fri Jul 07, 2006 12:16 pm

I've seen 40w UHF radios put out between 70 and 100 watts. It'll probably reach that or more before you get to a power setting of 126. The setting is not linear. The radio might put out zero watts at 40.

I'll say it before the others do: the radio will not last long running at that power level.

Also, there may be a limit on the amount of power you are allowed to run at that frequency range in Australia, so that might have been why the person who set it up only gave you 25 watts. If he's licensed to adjust the radio in a non-amateur operating frequency, he may be required to follow certain regulations.

Bob M.

Max-trac · Post by **Max-trac** » Fri Jul 07, 2006 2:45 pm

You'll get what you get, and the numbers do not mean anything.
They are designed with some overhead, but each radio is a little different.

Bruce1807 · Post by **Bruce1807** » Fri Jul 07, 2006 3:23 pm

One has to remember twice the distance the old rule of thumb
10 times the power = twice the distance
so 100 watt txer only gets twice as far as a 10 watt transmitter.
Lucky your not using 800Mhz.
I did my theseis on 800Mhz and Australian pines.
They are buggers for signal absorption

aussie_battler · Post by **aussie_battler** » Fri Jul 07, 2006 5:55 pm

thanks everyone im still no better off though lol.

will it really do 70-100 watts??

Also, I realise there is a limit to power over here but if the guy could not or did not want to set it to what I was paying him for, he should not of accepted my job under false pretenses. If someone pays you to do something, you do it the way they ask you, not the way you want it yourself.

thats getting way off topic though all I need to know is how much power an m44gmc can do? on UHF 465-495mhz please??

You say it;'s not linear but surely they all have the same finals and design so they would all be the same in output?

What is the actual technical cause of these radios blowing up when set to say 50 watts? Would it only be in a case of overheating?

Or is this some weak components in there that will die?

Thanks again everyone

aussie_battler · Post by **aussie_battler** » Fri Jul 07, 2006 8:59 pm

please people just tell me what an m44gmc uhf m120 radio can do please

It is rated to 40w but i know they do way more than that'

please someone tell me what output these radios can do

thank you

regards,
aussie battler

RFguy · Post by **RFguy** » Fri Jul 07, 2006 9:31 pm

please someone tell me what output these radios can do

I think that you have already been told.

I have seen them put out 70+ watts.

Just put it to the max and key it up.

aussie_battler · Post by **aussie_battler** » Fri Jul 07, 2006 11:17 pm

I want someone else to tell me as well

I would like a few opinions on the matter.

Thanks

Post by Pj » Sat Jul 08, 2006 4:39 am

Posting the same thing every 2 hours is not going to get you help any faster. I think your question has been answered.

mr.syntrx · Post by **mr.syntrx** » Sat Jul 08, 2006 8:17 am

Yeah, it'll do 100W - for maybe 30 seconds, before it burns out the PA and becomes a doorstop. 40W will kill it quick enough, as others have mentioned.

100W is far, far beyond the rating of the PA module, so it'll let the smoke out rather quickly.

The mechanical design of the radio is such that there's no way to keep it cool enough at 40W for extended periods, no matter what you do.

Unless you're using this on the amateur bands (which I'm pretty sure you're not), it's not legal. If the ACMA takes it away and gives you a big fine (like $165,000 or 2 years in jail)...

aussie_battler · Post by **aussie_battler** » Sun Jul 09, 2006 12:22 am

OMG

I know it's illegal. It's for UHF CB in Australia.

I have the radio so I can get through on the local repeaters due to people living next to it and buttoning.

I know how the inverse square law works.
I know high powered radios get hot.
I know it's illegal to run high power.
I don't care.

I just need to know what this peice of :o can do? What is the PA in an m44 model M120 on the UHF band capable of outputting?

Also, people don't go to jail for things like this. Last time I checked, laws in countries like USA and Australia are not the same as communist china etc.

Please just help me all I want to know is what the maximum output of these radios is. If I know what it does maximum output I can gauge where to put the setting in the software.

aussie_battler · Post by **aussie_battler** » Sun Jul 09, 2006 12:24 am

Also may I ask please, how will 40w kill it when it is designed and marketed as a 40 watt radio? Hence the M44 part of the model number?

Do you mean it will burn out at 40 watts if you have long transmissions all day etc?

How is that possible when it was designed for that power output?

mr.syntrx · Post by **mr.syntrx** » Sun Jul 09, 2006 3:23 am

aussie_battler wrote: Also, people don't go to jail for things like this. Last time I checked, laws in countries like USA and Australia are not the same as communist china etc.

Fraid so. That's the penalty listed in the Radiocommunications Act.

Post by Pj » Sun Jul 09, 2006 3:25 am

Dude, chill.

The radio is not rated to be used with the mic keyed for long periods of time. Most most mobile radios are rated at 50% duty capacity if that. If you use mobiles for long periods of times the heat cannot be dissapaited quite enough so either the power cuts back by internal protection or the radio fails. Simple as that. If you are running the radio higher than designed, then the run times are even less.

Its a simple matter of heat.

aussie_battler · Post by **aussie_battler** » Sun Jul 09, 2006 5:28 am

okay thank you.

mr.syntrx if I needed a f'ing lawyer I would ring legal aid.

I don't care about the "act", alright?

Thank you PJ but I am still at a loss as to how much power the radio can output?

so far i've been told 40, 50, 70 and 100.

does ANYONE know what the maximum power of an M44 model M120 UHF radio can do?

................thanks..

Bruce1807 · Post by **Bruce1807** » Sun Jul 09, 2006 6:30 am

You must be from the North but here we go.
There is no way to know what the maximum power the radio will put out is short of testing it till it blows.
Sure it won’t put out 1Kw but maybe you can crank it to 150 Watts if you run your power supply at 20 or 24 volts. The identical radio in the same test environment might only make it to 70 watts before the smoke comes out.
Motorola doesn't do destructive testing of this type. They only do destructive testing to for water, dust, smoke, strength and vibration and a few others.
Might I suggest you buy a wattmeter off EBay.au, I see they start at about $20.00 for a nasty one.
The alternative if you have a decent true RMS RF voltmeter and a tap you can measure the RF voltage and I can send you the Correlation Theorems using Fourier techniques that will let you convert it to watts. You may need to run Mat lab to get a decent plot though as the full formulas are pretty complex. (Ah. Brings me back to the RMIT (Aussie University) days).
Hold the TX button in for 10 minutes and that should give you a good benchmark.
Personally please video the turning up to full power and post the link for entertainment purposes.
As I said earlier crank up the voltage and you’ll get your 100 watts or whatever you are trying to achieve but we don’t want your next post to be
“Help needed for PA dead on M120”

Max-trac · Post by **Max-trac** » Sun Jul 09, 2006 6:55 am

The finals (and other parts) are NOT all the same in all these radios.
There have been production changes, supplier changes etc over the years. And as mentioned, the supply voltage etc....

So there is NO WAY to answer your question!

Do a search on "maxtrac manual power control" and put your own pot in it and you can set it yourself.

aussie_battler · Post by **aussie_battler** » Sun Jul 09, 2006 8:15 am

13.8v supply

lol you guys are good value, thanks.

okay i might borrow a swr metre and test it

kb0nly · Post by **kb0nly** » Sun Jul 09, 2006 11:54 am

I don't understand why this crap keeps coming up, this is the second post about this in the last month.

M44.. 40W radio, PERIOD!! GET OVER IT!!!

You asked why they would market it as a 40W radio if it couldn't handle it. You have to realize their intended use. How often does a PS (public safety) or local utilities user transmit for? Not long, usually short and sweet and to the point. Hence why they have abbreviations and codes for everything. The radios are 40W but with a low duty cycle, hence the small heatsink size on them. If you could improve the cooling then you could run it at a higher duty cycle at 40W. The main problem with the Maxtrac/Radius mobiles is the small contact area under the final transistor in the PA. It sits on a small bump up from the cast heatsink, if you ever pulled one apart you would see what i mean. It would take a complete redesign to increase the cooling effeciency of these mobiles.

If you set it for 40W or more, then you better buy more radios to keep on hand for spares as you burn them up. It's a plain and simple fact, i have seen plenty of them with dead PA's, solder melted from the final and dripped inside the PA section, etc. A lot of hams buy the 45W VHF models and crank them to 50W and they last a couple long winded chats and it's dead. Plenty of them also buy the 40W radios and push them right at 40W or higher and end up with the same thing. Can't count how many Maxtracs i bought of eBay with the solder melted from the final and all over the place inside, think of how hot it needs to be to melt that solder and then you understand what we are talking about with heat being the problem.

You can force air cool them, i have taken 40W radios and set them to 25W and then put fans on the heatsink so they can be used to build a repeater, but they still get warm, just not hot enough to destroy themselves.

And for the last and final time, no offense to you, but it's been asked a few times now recently, the number in the RSS is not linear in any way and does not have anything to do with the power output. You need an accurate wattmeter to set it, and you also need to go to the alignment section of the RSS and adjust the power output across the entire range of the radio with the frequency steps provided. Also, NO TWO RADIOS ARE ALIKE, each one will be different, one might need a setting of 80 for 40W and the next might only need a setting of 65 for 40W, etc..

Will · Post by **Will** » Sun Jul 09, 2006 3:32 pm

aussie_battler wrote:
I know it's illegal. It's for UHF CB in Australia.

.

You know it is against the law, but you continue to violate the law. It is persons like Aussi Battler that make it bad for the rest of us.

BTW, UHF CB in Australia is limited to 5 watts, period.

W3ZR · Post by **W3ZR** » Sun Jul 09, 2006 6:06 pm

I smell a troll.

kb0nly · Post by **kb0nly** » Sun Jul 09, 2006 6:07 pm

May i make the suggestion that this is locked and any further discussions pertaining to illegal power levels on the UHF CB band in AU is treated in the same manner?

It's the same as if someone here in the US started a thread about running more power on FRS or MURS than allowed, or the 11m CB band, etc.

Technical info aside, illegal is illegal.

Enuf Said...

Post by **wavetar** » Mon Jul 10, 2006 3:49 am

Yes, I believe the thread has run it's useful course. Locking...

Todd