Re: RD16HHF1 power curve flattening...some

K9HZ <bill@...>

Nik... looks like you have most of it right.  Plenty of gain, now just need to make it stable.  You might go to 15 meters and set the drive pot to zero.  Its gotta be stable with no drive or it wont work.  The model simulations don't show oscillations but the modeling parameters are not perfect for those transistors.  Probably need a little work on the feedback circuit to stabilize the finals, then it will be ok.  Again this is really good work and you are very close to a really good PA solution. 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ


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Big Signal Ranch – K9ZC

Staunton, Illinois


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email:  bill@...


On Mar 11, 2018, at 6:54 PM, Nik VK4PLN <nickpullen@...> wrote:

Well, i have dont my mods and powered up. Results are mixed:
Here are the mods.
RD16 replace IRF510.
New output transformer 1:4 BN43-3321 with a 330pf cap on input.
feed back resistors. from 22ohm to 1 K ohm
piggy backed R87 and R88 with 220pf capacitor.
RV1 full drive.

So results.
80M - 20W + ( blew my 2 Amp fuse)
40M - 18W - Seems stable.
30M - 17W BUT I get BAD feedback/ oscillation by just going PPT with no voice. The watt meter goes up to 18W!
20M - 15W  -  Same feedback issue
15M -  Same feedback issue.
10M -  Same feedback issue.

I have been thinking ans looking at other RD16 schematics, in alot of cases they dont use the feedback on the finals?
Also could this issue be cuase in the driver stage?

THanks guys, I am in over my head here....

10M - Same feedback issue

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