UNIDEN PC76XL MOSFET

newradioguy · Post by **newradioguy** » Monday 24th Mar 2008, 4:18

Anyone do this mod with mosfet 2030 and companion parts? Im going to try it but wanted to hear others opinions on it
http://www.cbtricks.com/miscellaneous/f ... /index.htm
thanks

Pioneer621 · Post by **Pioneer621** » Monday 24th Mar 2008, 7:33

newradioguy,

Hello, I have installed the MOSFETS in a UNIDEN PC76XL & they worked great, you will have no problems if your careful when soldering & don’t create any solder bridges or install anything wrong, just take your time on each step if you have never done it before. Once installed & you are tuning the output, try with & without the tuning slug in L14. Sometimes when you remove the slug it looks good on the meters at first but if you stay keyed down for a little while with modulation you will start to lose output power, so tune L14 for maximum power without it dropping back. Or you could just tune L14 for a 4 watt Carrier.

Again I have installed many of these kits & never had a problem & they do work very well, I think it is well worth the time. Hope this info helps. Take Care. Pioneer621

newradioguy · Post by **newradioguy** » Tuesday 25th Mar 2008, 11:34

Im new to modding what do you mean by tune for a 4 watt carrier

Pioneer621 · Post by **Pioneer621** » Tuesday 25th Mar 2008, 15:27

Hi, what I meant was after you get the new parts installed and you are adjusting the output power (wattage) of the radio on a wattmeter you can tune “adjust” L14 for a 4 watt carrier, the carrier is when you hold the button on the MIC & do NOT speak into the MIC, you transmit just a silent dead key “carrier”, so while holding the MIC button & transmitting a silent carrier adjust L14 for a reading of 4 watts on your external set of watt meters, that is if you are trying to keep the output power at the 4 watt limit.

If you are just trying to get as much power out of the radio as possible, then adjust L14 for maximum power on your wattmeter. Incase you still do not understand when I say “tune” L14; L14 is an adjustable inductor, it is a coil with an adjustable slug in the center that screws in & out, you simply adjust this slug to adjust the output power (be careful while adjusting, as the slugs are delicate & can easily be damaged).

I hope this helps. Take Care. Pioneer621

newradioguy · Post by **newradioguy** » Tuesday 25th Mar 2008, 23:33

Thank you for the explanation,I have tuned 1 radio and everyone says it sounds very good,so now I will see if Im as successful (LUCKY) with my pc76xl,by the way the part I wasnt sure about was the 4 watt carrier part but now understand

Pioneer621 · Post by **Pioneer621** » Wednesday 26th Mar 2008, 4:56

I am glad to hear the info helped! If you have any problems & can't get the radio modded right, I would be more than willing to try & help you out to get it working right; there are many other people here that would most likely be willing to help you out as well, though as I said before, if you are careful & take your time, you should have no problems. Take Care. Pioneer621

newradioguy · Post by **newradioguy** » Thursday 27th Mar 2008, 3:39

the mod went well except the slug broke and I had to use a pick to spin the pieces out,but otherwise it works great.so far people say it is very clear and seems to have good power thanks again for your help

newradioguy · Post by **newradioguy** » Thursday 27th Mar 2008, 3:40

on another note , is there a way to boost the receive or is that part of what I did?

Pioneer621 · Post by **Pioneer621** » Thursday 27th Mar 2008, 11:26

Good to hear the mod went well! Yeah, the slugs are delicate and can easily be damaged if not removed very carefully.

As for the receive: No, you did not do anything to the receive, you only modified the transmitter section. I have never personally done any receive mods to the Cobra 29 LTD other than installing internal preamps that I build.

I have heard of people changing the transistor in the front end of the receiver as well as some diodes with a high gain low noise transistor (2SC2999 I think) & some Schottky diodes (I can't remember which diodes you would need), though as I said I have never done this and I don't know what the improvement would be if any, you would have to try it and see.

I hope this info helps! Take Care. Pioneer621

Peddler_431 · Post by **Peddler_431** » Saturday 21st Jun 2008, 15:15

Not to be the one who kills the parade, but...
Why would you bother doing this to a pc76? A pc76 out of the box with the right tune will sound louder and clearer than any mos-fet final radio.
I hope you're not intending on running a box that has a driver section in it with that.
What did you acheive? 40 watts peak i'd guess.A 76 will do 40 peak watts on a stock 2166 final and a variable 0-5 watt dead key with 9-11 watts on a bird.
I can see doing this with a newer cobra 29 or something, but to butcher a 76 up when theyre becoming harder and harder to come by is just wrong.
Hey it's your radio and if it worked for you and you like it then that's great.
Mos-fets are garbage, More heat, more power usage, it takes more current to make the same output as a bi-polar transistor, you will have more harmonic garbage coming from your radio. Especially when you are keying 2 watts swinging 40 watts, thats way over modulation.
But hey this is cb radio, who said you have to sound good?