Re: ND6T AGC implementation for uBIT-X

Jerry Gaffke

Exactly where did you find this data?

Most of the forum posts about dead IRF510's seem to be from people who twiddle bias pots for no particular reason.
A fuse or polyswitch in the PA-PWR line to the IRF510's would catch that before anything catastrophic,
and would be a good idea for the RD16HHF1's as well.

Other than that, I'd find it hard to imagine that a pair of IRF510's giving 5W each in a final on 12v would blow.
They are quite hardy even at 24v and 4x the power if you give them an adequate heat sink.

In post 22597, KB1GMX reports:

My experience with IRF510s is extensive and much different.  I rarely kill one even during experimenting.  I use them for RF power though 6M.  How much 8 in a parallel 4x4 push-pull at 6M running 225W!  My favorite is two in a push pull amp (K500r/wa2eby design) with 28V running about 55W on 40m and 37W at 10M and after 6 years of wrong antenna and all sorts of usual havoc its still running with the same pair. 

Granted, the RD16HHF1 is 10x more expensive. 
So folks using the IRF510 might tend to be more "experimental" and blow one occasionally.

Yes, heat transfer from die to tab on the IRF510 is not ideal.
So if working it hard, be sure to give it an adequate heatsink.
Likewise the RD16HHF1 has a lower Vds max, so don't run it from supplies much over 12v. 

Jerry, KE7ER

On Sat, Apr 28, 2018 at 09:08 pm, K9HZ wrote:

Well, data shows that the RD16HHF1 does have a lower “kill rate” than the IRF510.  In fact, the RD16 device can run at higher power and still survive usual SWR problems (short, open, etc).  I don’t think it has anything to do with voltage spikes, as the maximum voltage of the IRF510 is about double the RD16 device limits.  I have not studied the dies thoroughly, but I think it has to do with heat removal and the way the junctions are manufactured.


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