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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.

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
_._

There are at least two or more designs using IRF510s in push
pull form. The power out was in the 30-45 watt range for two devices
running at 24V through 10M. This is reasonable for the class of
device. The real trick is as you go up in frequency (above 5mhz) you
need to pay attention to input and output matching. Failure to do so
will result in less power than expected. Also insure the driver is
both properly loaded and can deliver the required power.

Also testing these devices at RF find they exhibit poor IMD at 12V.
At 20-24V they perform much better.

Also to drive these properly the driver stage should easily be good
for 1watt. If any stage before the final amplifer or drivers cannot
deliver sufficient drive not only will power out suffer the signal
quality and bandwidth will be poor.

One of many articles using two IRF510:

home.cnham.com/pdf/amp/irf510/HF_use_FET_1.pdf

Allison
KB1GMX

--- In BITX20@..., Arv Evans <arvevans@e...> 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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Visit your group "BITX20" on the web.

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Allison

That URL for the MOSFET HF Amp is actually:



I wonder if anyone has ever tried a grounded-gate MOSFET linear...something
much like the grounded-grid valve type amps? I have no idea if it might
work, but it could be fun to try.

Arv K7HKL
_._

--- In BITX20@..., Arv Evans <arvevans@e...> wrote:

Allison

That URL for the MOSFET HF Amp is actually:

Good old crush and plaster ah, rather cut and paste. ;)
Oh well, you found it and dont forget there is information in
part 2.

I wonder if anyone has ever tried a grounded-gate MOSFET

linear...something

much like the grounded-grid valve type amps? I have no idea if it

might

work, but it could be fun to try.

Since you ask. I've done it on paper and it wasn't pretty. The source
impedence for power fets is very low and the gain is lower. It only
works for tube becuase of the low current and high voltages.

Actually pushpull with 4 devices really has a better shot.


Allison
KB1GMX

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.
>
>
>
>
>? YAHOO! GROUPS LINKS
>
>
> ?Visit your group "BITX20" on the web.
> ?
> ?To unsubscribe from this group, send an email to:
> ?BITX20-unsubscribe@...
> ?
> ?Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

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