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Amplifiers

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bird704

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So if a person gets a 100 watt amplifier, does the CB need to to dead key below 4 watts (be tuned down)? A lot of confusing info on the web. And you believe these things are shhhh .... illegal?
 

mmckenna

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Depends on the amplifier. The input wattage will effect output, but if you are putting in too much power, it can damage the amplifier.

Since "Peaked and Tuned" radios are often done by guys who have little knowledge and even less test equipment, it's best to not go the peak/tune route. A CB putting out a clean 4 watts will work better than one that Cletus down at the single wide trailer behind the truck stop messed with. Often the peak/tune is done by a guy looking at just a watt meter and cranking adjustments to get the most "swing" while completely ignoring any spectral purity.
In other words, a CB that has been jacked with that spits out all kinds of noise will just get all that noise boosted by the amplifier and piss off the neighbors.
 

DaveJacobsen

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So if a person gets a 100 watt amplifier, does the CB need to to dead key below 4 watts (be tuned down)? A lot of confusing info on the web. And you believe these things are shhhh .... illegal?
All amps are different. For me, I try to dead key are 2 watts, unless the amp is specifically designed for high input.

Better too low than too high. Even an amp designed for 4 watts, it would last longer if you pushed 2...

What amp do you have?
 

prcguy

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You kinda have to map out an amplifier with your radio using a peak reading wattmeter or oscilloscope and an average reading wattmeter will not tell you what you need to know. Take for example a perfectly working, stock, non modified radio should put out close to 4 watts dead key no modulation. At 100% modulation, if it will reach that, the radio will be putting out 12 watts peak. This is normal and every radio should do this, otherwise its not working properly. With AM modulation, the sidebands will add 6dB of power at 100% modulation, or an increase of 4X the power.

Now take an amplifier that's rated at 100 watts, that's all it will do no matter what you drive it with and its saturated at 100 watts. If your 4 watt radio runs it up to 100 watts or 90 watts or somewhere close to its maximum power with a dead carrier its not going to work properly when you add modulation. If the amp dead keys at 100 watts with no modulation, it will need to put out 400 watts peak when the radio is fully modulated, otherwise you get a bunch of distortion and only a fraction of the range increase that you would have if its working properly.

In this case where you have an amp that does 100 watts max and its saturated, then you would want to adjust your radio to produce about 25 watts dead carrier when the amp is on so that it will reach 100 watts under full modulation, getting the full 6dB increase when modulation is applied. I would say 90% of all amps used on CB are not used properly and dead key near full power and when you modulate it has nowhere to go but down (the toilet).

If you just want to jam people out and never talk, then by all means adjust your radio so the amp puts out full power with a dead carrier. You will cover up more people that way. If you actually want to talk you will talk further reducing your drive level so the amp will achieve that 4X increase in power when talking.

Don't be one of the dummies that doesn't know how to drive an amplifier and pick one that is appropriate for your radio and drive it with the right level. In the end you will be running much less dead carrier power than you think is right, but when you get that 4X peak power increase fully modulated the end result is the radio will sound identical with the amp on or off but the power and range will be much better with the amp on. Listen carefully to most amps out there being used wrong and when the amp goes on, the radio sounds different, it lost a lot of punch and clarity, gained a bunch of flat topping and distortion and some people think that sounds ok, but its not. Its pure trash because its owner is clueless.
 

bird704

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What about the cooling fans? Do the RM Italy need them? Only asking cuz I see some are sold with and without. Easy to wire up? Thanks for all the help.
 

slowmover

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You kinda have to map out an amplifier with your radio using a peak reading wattmeter or oscilloscope and an average reading wattmeter will not tell you what you need to know. Take for example a perfectly working, stock, non modified radio should put out close to 4 watts dead key no modulation. At 100% modulation, if it will reach that, the radio will be putting out 12 watts peak. This is normal and every radio should do this, otherwise its not working properly. With AM modulation, the sidebands will add 6dB of power at 100% modulation, or an increase of 4X the power.

Now take an amplifier that's rated at 100 watts, that's all it will do no matter what you drive it with and its saturated at 100 watts. If your 4 watt radio runs it up to 100 watts or 90 watts or somewhere close to its maximum power with a dead carrier its not going to work properly when you add modulation. If the amp dead keys at 100 watts with no modulation, it will need to put out 400 watts peak when the radio is fully modulated, otherwise you get a bunch of distortion and only a fraction of the range increase that you would have if its working properly.

In this case where you have an amp that does 100 watts max and its saturated, then you would want to adjust your radio to produce about 25 watts dead carrier when the amp is on so that it will reach 100 watts under full modulation, getting the full 6dB increase when modulation is applied. I would say 90% of all amps used on CB are not used properly and dead key near full power and when you modulate it has nowhere to go but down (the toilet).

If you just want to jam people out and never talk, then by all means adjust your radio so the amp puts out full power with a dead carrier. You will cover up more people that way. If you actually want to talk you will talk further reducing your drive level so the amp will achieve that 4X increase in power when talking.

Don't be one of the dummies that doesn't know how to drive an amplifier and pick one that is appropriate for your radio and drive it with the right level. In the end you will be running much less dead carrier power than you think is right, but when you get that 4X peak power increase fully modulated the end result is the radio will sound identical with the amp on or off but the power and range will be much better with the amp on. Listen carefully to most amps out there being used wrong and when the amp goes on, the radio sounds different, it lost a lot of punch and clarity, gained a bunch of flat topping and distortion and some people think that sounds ok, but its not. Its pure trash because its owner is clueless.


OP, you’ll also see this referred to as a 1:4 ratio.

I’ve several of the RM Italy amps. The KL203 is an easy choice for Mobile. Size and amp-draw mean that moving up in output is a great deal more involved (wiring voltage loss, coax problems, antenna mount problems, etc).

I’ve run a KL203P (different version) for several years behind a half-dozen radios. Replaced and upsized the amp wiring, and have always had far more wire capacity than it needs (see MARINCO 3% Voltage Drop Chart and size generously).

Knock on wood, no problems. Radios either were untouched or had variable power.

Just don’t be surprised if a mismatch smokes one. The general recommendation is to use 1.5-2.5W. Think of it as a 50-75W amp, and there’ll be no surprises.

The bigger amplifiers start to demand REAL Amp Capacity. 30, 40 or more. That demands a throughly systematic approach.

A power supply for a 30A max draw amp ought to be capable of, say, 45A continuous (headroom) as you’ll find to be a regularly-made piece of advice.

The 203s are easy to use. Give you a chance to learn more about antenna theory and the other thousand details before spending big.

A Uniden 980 + 203 + West Mountain Radio ClearSpeech DSP Speaker = outstanding performance on a budget.

You’ll

Hear & Get Heard

Mobile or Base.

An RF/CMC Choke at the antenna feed point, then checking 12V source for noises you can filter or eliminate

Is the best start I know.

.
 
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bird704

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I know nothing about taking a radio apart to adjust the dead key. But Youtube videos are saying that the President Andy, and newer models can not be adjusted. So, you basically have no choice to drive a linear with 4 watts if you own one of these or just plain old dont. I have heard that people been having good luck but ... I need some feed back before I go blowing stuff up. Just about all info on the net is stating to drive the RM Italy 203 and 503 with 1.5 to 2 watts or the linear wont last long. Thanks.
 

bird704

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All amps are different. For me, I try to dead key are 2 watts, unless the amp is specifically designed for high input.

Better too low than too high. Even an amp designed for 4 watts, it would last longer if you pushed 2...

What amp do you have?
thinking of getting the rm italy 203-p but have a new President radio that cant be adjusted
 

alcahuete

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thinking of getting the rm italy 203-p but have a new President radio that cant be adjusted

I know RM Italy makes some high drive amps, but I'm not sure about the 203. The 503 definitely comes in high drive, which I believe takes 35w input.

Yes, if you run high power into a non-high drive amp, you're going to blow it up.
 

bird704

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Input power - 1 - 6 W for the 503

Input power 1 - 5 W Max for 203

so 4 watts should be ok ... but everyone on the net is stating 1 to 2 watts input or boooom after a while. and again, i have a cb radio that cannot be adjusted, a newer president radio.
 

mmckenna

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You should make sure you check your CB through a reliable watt meter into a 50Ω load to see what it's actually putting out.

The few CB's I've tested never came close to 4 watts. Most of them were anywhere from 2.5 to 3 watts. That was with a Bird 43 and a Bird 50Ω load.
 

bird704

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Thats what Im hoping. Yeah I do need to get one of those, but what has me worried is most of the people on youtube say say come 4 watts cuz that adjustment is "sealed". And they say they hook em up and they are 4 watts. But again the box of most of these RM Italys are stating 1 -5 watts input, so hmmmmm. I know nothing, and thats why Im here.
 

ForestRunner98

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Input power - 1 - 6 W for the 503

Input power 1 - 5 W Max for 203

so 4 watts should be ok ... but everyone on the net is stating 1 to 2 watts input or boooom after a while. and again, i have a cb radio that cannot be adjusted, a newer president radio.

Which President radio? I have a brand new McKinley and it has adjustable RF power. Running it at 2w into a KL203. Amp on deadkeys at 25w and PEP’s to 125w on AM.

If you put 4w into that amp it WILL get warm/hot fast if your long winded. I have a fan on mine just for precaution.
 

bird704

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I have a McKinley and a Andy. So if I adjust the RF on the McKinley screen itll take down the wattage? Without opening it? Im so new.
 

ForestRunner98

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I have a McKinley and a Andy. So if I adjust the RF on the McKinley screen itll take down the wattage? Without opening it? Im so new.

Ya..you can adjust power off the function key. If I remember you key up press and function key and your RF power meter will starting blinking. Turn the channel adjust to where you want it and then long press the channel adjuster until it stops blinking.

Do as much research before you jump into an amp seeing that your new. I pretty new too but did a lot of reading and taking advice from experienced members. But remember to have fun with your new hobby!!
 

slowmover

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At (2) for $105 shipped worldwide from 88Radio, it’s like any other experiment.

Radio is — if nothing else— an experiment. Some gear works, some doesn’t.

The system into which you plug a component far outweighs in importance any one piece of gear no matter its’ price.

Mag-mount on a car? Cigar lighter power? No RF Bonds? That’s a joke.

Cheap, low-amp power supply at home into an antenna system a 6th grader would build? That’s a joke.

An inexpensive amp like the 203-series makes any ol’ radio a potential talker. Without the inflated price of an internal amp radio.

Over-build, and oversize, the capacities of the radio system.

I had HD power wiring installed to replace the xtra-light OEM stuff on the 203. At the other end are Anderson PowerPole connectors. Wherever I use it, it’s NOT a permanent radio system feature.

At $50 it’s disposable (if need be).

A Uniden 980 + KL203 is sub-$200 for 50-75W output. AM/SSB.

Put the effort (worries) into the SYSTEM, not any one component.

A few years from now maybe today’s components are just sitting in a box on a closet shelf as “better” meant a (complete) system capable of Amateur-quality gear in place being installed.

I’ve A LOT MORE than $50 into gear & supplies just sitting in boxes, unused.

Gonna use this at home or in car? Make the 12V power capable of a 30A continuous draw with headroom. As one may have (as I do) 5-6 items drawing power. Research and build that SYSTEM.

I could, “get away with”, a power system ideal for 15A-intermittent and maybe never look back. But why take the chance when the upgrade is only a percentage $ increase?

Approach this from another angle.

.
 
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Cmillz31

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Bamminjammin, in my honest opinion i would suggest getting a texas star amp rather then the rm Italy boxes. I would look for an older texas star that has toshiba transistors in it. They are a much better transistor and can take way more abuse than the rm Italy boxes. If your only looking to achieve a few hundred watts of peak.power a texas star 350 would be perfect for you.
 

slowmover

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Bamminjammin, in my honest opinion i would suggest getting a texas star amp rather then the rm Italy boxes. I would look for an older texas star that has toshiba transistors in it. They are a much better transistor and can take way more abuse than the rm Italy boxes. If your only looking to achieve a few hundred watts of peak.power a texas star 350 would be perfect for you.

You should really do more research. Reliability is not a strong suit. TX Star just another cheap amplifier, and maybe not “better”.

My KL203P has close to 900-days of being in use 8-10/hrs day in rough-riding big truck mobile. As reliable as can be (knock on wood as with any gear).

$350 buys maybe (1) used, unknown TX Star or six (6) brand-new KL203

If one can’t get the job done with 75W, then the problem is elsewhere.

A 7405 is a step up, but Amp Draw gets a good deal higher.

.
 
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