View Full Version : The FET project

04-05-2012, 08:51 AM
We it doesnt look like the economy is getting any better any time soon - so I am going to start playing around with mosfets. Need to find the best possible bang for the buck that runs efficient!

I had an old skywalker 300 fet amp that i got on ebay a few years back. It has 4x irf520's which is what some of these export rigs are using in the little mini built in amps- and now more and more people are using for final mods on their radios.
So after smoking this amp several times (by testing it to see if it will do what skywalker claims- which it did not - I recently revived it from the scrap heap.

Originally - this thing did 150-200w. Nice little driver. I used it to drive my 400hd. Since i rebuilt it my way, Im seeing 250-300w now and it runs way cleaner and more efficient - max amp draw so far has only been about 15a. So im using this on the base at the moment to drive my 2100b. So far so good!

Now im going to try to build an 8 fet box using the irf520's (cause theyre only $.89/ea)- if i smoke em- who gives a ratts ass.. If this turns out good, then we will strip it back down and rebuild it with the ERF7530's and see where that goes..

I also have a 50v project going on simultaneously with another friend- but this is going to be a multi-band hambone thing that I will somehow adapt for 11m use as well.
Will keep everyone posted!

04-13-2012, 09:15 PM
So hows the 8 fet box coming along

04-13-2012, 09:54 PM
rmitaly makes a 1 driving 8 520 amp but the driver isn't needed with modern cb radios and certainly not with exports so your straight 8 makes more sense with them .


04-13-2012, 09:58 PM
Good to know. Well ill try it out straight 8 and see where its at first.

04-14-2012, 08:09 AM
Doughboy- I'm waiting for some shoulder washers from mouser. As soon as they get here I can finish this thing up and start beating on it.

05-08-2012, 10:20 AM
Update - Last night i got this thing singing. Had to change some tranformers and re-wrapped em and some tuning- but here is the results for 8-FETs (@ $.89/ea). Using my kenwood rig on AM, I drove it @ 50w and saw 450w DK come out of the fet box and ONLY a 20a Draw @ 13.2v. The kenwood is a dog on AM and doesnt talk worth a dam - so that was flat out carrier - no audio. maybe tonight ill put it behind the viking and see what she swings.
If time permits this week, I will make a driver section with 2 FETs and drive it with either my 29 or S9 and see what she does. If all goes well, I think we might just say F-it and build a 4 driving 16 next. Theyre cheap enough to experiment with.

Gordon Gekko
05-08-2012, 02:03 PM
Good job Noisemaker. Stay with it. Fets the future of the hobby, especially considering the price of them.

05-08-2012, 02:26 PM
Good job Noisemaker. Stay with it. Fets the future of the hobby, especially considering the price of them.

You got that right! They went up from $.89 to $.96 unless you buy a bunch.. Just bought 30 more @ $.74 ea.. lol

hey you still have same phone # gg?

Gordon Gekko
05-08-2012, 04:07 PM
hey you still have same phone # gg?

yes I do....

05-08-2012, 09:43 PM
Ok- did some more tinkering. Got 500w off the kenwood (no driver)- straight 50w carrier, no audio. Took a grant xl that DK's 2w and swings 10, put a TS Vmod in line and she swings 600w. We might be on to something here :)

05-13-2012, 09:59 AM
I cant wait to see the 16 mosfet model

05-13-2012, 08:41 PM
Think we may skip that and go straight for the 32 :)

05-22-2012, 11:21 AM
Ok. Added driver section since i had a couple hours to do nothing today. Still need to tune a bit, but from the excalibur base im getting 650w swing outta this thing- radio dead keys 2w swings about 20. Little thing is screamin!

High Voltage Mobile NJ
05-22-2012, 02:33 PM
way to go Noisemaker !!!!!! Noisemaker Amps and Antenna's . com breakaaaaaaaaaaaa:loyal:

05-22-2012, 03:35 PM
Ha! Not! But considering the amp draw i will be building a monster one for the lil motorcar

High Voltage Mobile NJ
05-22-2012, 04:38 PM
nice. your amp draw will be at least half of a pill amp . :pizza:

07-05-2012, 04:27 PM
so hows the mosfet amp going is it still working??

07-06-2012, 12:41 PM
It still works - didnt blow it up just yet. Have to do a little tuning still (clean it up some).
Just havent had any time to play with it.

09-20-2012, 09:05 PM
well i built a 6 irf520 one with a galaxy 77 it does 175 watts

09-22-2012, 10:19 PM
Ok- update. Its not very stable in the mobile.. It acts all wonky with the slightest swr change. much better on the base. Still have to get some time to tune it some more- but i thought i would throw this out there.

10-08-2013, 08:17 PM
noise maker, what transistors are you using in your amps, looking into building a mosfet amp myself, been eyeing the erf7530 transistors, but what i have for a scrematic, as down the irf510s and didnt know if the 7530s would just drop in and work. thanks in advance for any info.