EMRFD Message Archive 6091

Message Date From Subject
6091 2011-04-11 16:38:36 ka3j12 5 Watt Amp Opttions
Hi - I'm attempting to design a rig that will put out 5 watts SSB/CW through 21 MHz running on 10 volts. Available drive will be about 300 mW or less. Is there any chance that an IRF510/512 would work as a final or would I be better off going with a real RF Mosfet like an RD06HHF1? Other suggestions and specific designs also would be appreciated.

Ron (KA3J)
6092 2011-04-11 18:31:43 kb1gmx Re: 5 Watt Amp Opttions
6093 2011-04-11 19:44:07 Adi AM Bls: [emrfd] Re: 5 Watt Amp Opttions
that is right allison.
the irf 510 below of 12v very low output.
in indonesia can not get the type of RD.........
with the 2sc1969
6095 2011-04-12 08:43:03 Tim Re: 5 Watt Amp Opttions
IRF510 will be running out of oomph at low voltages and 21 MHz.

At low voltages like 10V and 5 watts - perhaps some "stacked and combined" or "paralleled" 2N7000's/BS170's would work nicely.

By "stacked and combined" I mean several parallel final stages each with output transformer, and the secondary winding snakes between them.

e.g. KD1JV's Simple PSK rig gets 3.5 watts from 3 BS170's in parallel but that's class C. http://kd1jv.qrpradio.com/PSKTX/SIMPLEPSKTX.HTM

I've made class AB 2N7000 push-pull stages that I've been quite happy with at the 1W level. Combine 5 of them?

I still feel slightly guilty if I fry an IRF510 on the workbench (not that I haven't fried a lot.). I have no guilt at all frying a little 2N7000 or even a stack of them :-)

Other designers go as far as designing SWR protection for 2N7000 class finals. Probably makes sense for field use where no soldering ir
6096 2011-04-12 08:49:58 n7ve Re: 5 Watt Amp Opttions
I used to like 2N7000s before I found out about the BS170. 300 mW for a 2N7000 vs. 800 mW for a BS170.

- Dan, N7VE

6097 2011-04-12 08:52:19 Tim Re: 5 Watt Amp Opttions
Thinking from a different direction:

I am not in the public service mobile radio repair business. But it seems to me that 10V and HF use, ought to be able to use whatever part is comm
6098 2011-04-12 14:46:35 kb1gmx Re: 5 Watt Amp Opttions
6099 2011-04-12 14:54:23 kb1gmx Re: 5 Watt Amp Opttions
6100 2011-04-12 22:27:44 victor Re: 5 Watt Amp Opttions
The IRF510 can be used at low voltage PA when it is used as a single band tuned matched PA.
I built and used a 10m PA with single IRF510 at 13V giving close to 10W
6121 2011-04-14 01:50:00 Ashhar Farhan Re: 5 Watt Amp Opttions
have you considered jbot?
it is a pretty stable amp. i am quite happy with it. though, i haven't
performed any IMD measurements on it.

- farhan VU2ESE