Like me get my cobra 148 gtl made in philipines to 28500 and RF power 25 watts ¿ what I need?

check driver voltage

need to get a watt meter hooked up to then go the where the final is and look aroung for a tuning slug marked L38 and that is the baby you have to turn in order to power down this radio.

best way is to leave the radio in piece and obtain a linear amplifier to do the job a 10 meter ham radio amplifier will do nicely but you must re-tune it for the 27 mhz band 10 meter band is 28 mhz.
RF amps work best using side-band mode.

Have you checked the 2sc2166 or the 2sc1969? Those are the RF Driver and the RF Final output transistors.

you would probably want at least a 4watt continuous power supply or better. do not use as switching power supply.

Hi
try replacing the transistor just before the last on the rf pa output.

Hope this helps

Ray

Sounds like you may have a bad mic

On the meter you are using, does it mesure Average power or peak envelope power?

This is very important to know when you are measuring.

AVG measures basically your dead key. It usually will very little if at all.

PEP measures your peak output, or swing. Modulation.

So even if you have a radio that has been peaked, on a meter that reads AVG, it will still read around 3 to 4 watts. And, if it has a swing kit in it, it will read even less. A swing kit lowers the dead key it increase modulation. Higher PEP.

For example. I peaked my cobra 29 and it does some where around 22 -25 watts PEP. I have variable power in it as well, but usually run the dead key at 2 watts because I have a linear. The Radio alone, when mesureing on PEP with key up at 2 watts, and then when you talk, swings to about 22 -25 watts.

If I flip the meter to AVG, it stays at 2 watts even with talking.

If you have one of those cheap pyramid meters, etc, they usually only read AVG.

Get a meter from radioshack. They have a fairly decent radio for the money. It reads both PEP and AVG and has SWR as well.

If the radio has been peaked and it has a swing mod, it will most likely be swinging to some where in the 20 watt range.

On a side note. According to FCC regulations, a CB radio is only allowed to transmit with 4 watts of final power. Most times the manufacturer will have it a hair under so that they are leagal.

Basically it is illegal to use a CB that puts out more then 4 Watts.

But its a free for all these days. There is no more funding to the FCC for monitoring CB radio, so they do not want anything to do with it. As long as you don't over do it, have over 50000 watts and terrorize a small community with RF, you can do what you want.

Now a days most cb radio's bought have already been peaked if you got it from a cb shop, or off a website that does it.

for more power replace the 1969 with mrf455 be sure the pins are inverted big power gain about 50 watts

try adjusting the L36,L38 to the highest reading on the external meter and then adjust VR10 TO 4 watts. If this doesn't cure the problem, you have a weak final transistor. Good Luck