Hi!
?
Arv is quite right. Here we also took a similar route. First was the need for a cheap common PSU so we selected a portable BW TV transformer sec abt 20V AC unloaded around 1.25amp. Unreg DC goes to IRF.
?
Later I realised that 2N3866 is 24V device so I gave it unreg DC too on collector thru a simple choke on the binocular cores abt 9-10turns. Emitter resistor 10ohms, base to gnd 2k2 and base to 12V TX for bias 10-12K. The collector director?drives the gate via a 0.1 cap?of IRF530. Current drawn is abt 1amp now and power more than 12W.
?
Incidently the Mousefet series of TX also drive the power fets in similar manner.
?
Rest of the ckt is powered thru reg 13.6VDC by a LM317 as evident from my linear board layout. This scheme of 3866 on unreg DC also reduces some load on 317.
?
BTW I have stacked 2-3 nos of tap washer for LPF, the number of turns for required inductance is less and more manageable.
?
73
?
Rahul VU3WJM
?
?
Arv Evans wrote:
Chris
My BITX40 uses 24 volts on the IRF510 for a power output of 11 watts.? It
required the addition of separate sheilding, 2 ferrite beads on the gate
lead, and a paracitic suppressor (2 ohm 2 watt carbon resistor wound with 4
turns of #16 AWG) between drain and output filter to tame it.
If you have a variable power supply, try bringing the voltage up slowly once
you have it working properly with 12 volts.? I did not do this the first time
and it cooked an IRF510!?????? 8-(
My IRF510 is mounted on the heat sink for a computer CPU.? The original CPU
fan is mounted on the other side of the heat sink and turns on with the PTT
controlled voltage for the IRF510.? I bolted the IRF510 directly to the heat
sink, which is mounted to the chassis via 1/2 inch (1.3 cm) nylon
standoffs.?
The fan housing is plastic so this isolates it from RF on the heat sink.
Next step might be to replace the IRF510 with push-pull IRF510s or IRF630s and
a 48 volt supply!
Arv K7HKL
_._
On Wednesday 20 July 2005 03:17 am, vdberghak wrote:
>? Hi all,
>? did anyone tried to put higher voltage on the IRF stage?
>? If so, I am interrested about the results like:
>? - stability,
>? - increase of output power.
>? If the output power is not much higher and other problems will show up,
>? I will not try it...
>? Thanks,
>? Chris.
>
>
>
>
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