While the MOSFETs can output 1200 watts with four in parallel/push-pull, the
output transformer ratio will limit the practical output to between 800 and
1KW, using a 9:1 with a 50V power supply. The 9:1 optimal output is at 800
watts. Tokyo HyPower uses this design and they rate it for 1KW. I can also
get 1KW with my homebrew amp with (4) SD2933's, but prefer to run it closer to
800 watts to improve the IMD.
If you really want the full legal limit, you would be better to have two PA
modules and a combiner. Otherwise the output transformer design is going to
get real complicated. The other option is running higher voltage, which
complicates the selection of a power supply. 50 volt computer server switching
power supplies are low cost and easy to obtain.
I am happy with 800-1KW, but maybe someday I will try the combiner just for the
fun of it.
Don
K9AQ
---- Leigh Turner <invertech@frontierisp.net.au> wrote:
>
> Larry, the RF power MOSFETS to which I refer here are the VRF2933 devices
> from Microsemi. Sometimes one can find surplus and NOS ST Micro SD2933 FETS
> on eBay at low prices.
>
> 4 of these rugged 300 Watt rated devices in parallel/push-pull will yield a
> saturated output power of well over 1200 Watts. Six will comfortably yield
> over the US legal limit.
>
> 73
>
> Leigh
> VK5KLT
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Larry
> Sent: Wednesday, 11 September 2013 10:48 AM
> To: amps@contesting.com
> Subject: Re: [Amps] Future of RF AMPS
>
> On 10-Sep-13 5:51 PM, Leigh Turner wrote: using a readily available
> multiplicity (6 devices in parallel/push-pull) of cheap 50V MOSFETS sourced
> from the surplus market.
>
>
> Leigh,
>
> Exactly which cheap MOSFETS from what surplus market are you speaking of?
>
> Larry - W7IUV
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|