Hello Pete,
I assume that the more exotic parts are the power FET (IRFZ48N) and the driver IC (ICL7667).
The IRFZ48N is a 55V / 64A / 0.014 Ohm device. For a first try you could replace it by far more common IRF460 that is 100V / 28A
/ 0.06 Ohm.
A bit of reverse engineering: Stefan states 50W output at 80% efficiency = 62.5W input = 5.2A at 12V.
So with a 28A device you are on the safe side.
The larger Ron (0.06 Ohm vs 0.014 Ohm) will (in theory) reduce the efficiency. But 5.2A in 0.014 Ohm is only about 0.4W loss (for a IRFZ48N). For a IRF460 it
is 5.2A in 0.06 Ohm = 1.6W loss.
So the losses (12.5W) are probably more due to the non perfect switching than due to the Ron of the FETs.
An alternative for the ICL7667 is a TC4426 or a homebrew driver (see
http://www.pa3bca.nl/images/stories/500KHz/500khz_transverter_full.gif).
73, Rik ON7YD - OR7T
Hi Stefan
I like this and would like to make to make it. I so far have tracked down most bits but as usual the
Unobtainium of so many construction projects that fall at the last hurdle unless they are Kits........ no chance of that I suppose?
There will be those who tell me its easy to get the bits but unless you work for a company that uses this stuff it can not be slipped through the "Purchasing" it becomes a positive stop!!
Like the Litz I just put that in one of our big outfits with min orders and it said it had over one hundred thousand
Litz and promptly
collapsed. But they have one of the
toroids (T1) wow and its not a min order either double wow!
Litz can be fabricated from 0.125 Cu/En?
Hmm it's plaited ?
Wima caps are available from
Maplin haven't checked in depth but they usually are.
I like the idea of using a DDS or
Transceiver as a master osc source div. by four.
Generally I buy my power
FETs by the hand full off E-bay they may not be ideal but are cheap!! 50P (eer 60Ec) (Never mind the quality but feel the width... principle) and the drivers TC range
for slightly more.
I'll keep searching for a bit but if anyone has a kitting list (UK source) may be they could publish it?
And thanks Stefan nothing under the Sun is "New" but in context it is new and worth while thanks!
73 es GL Pete M0FMT IO91UX
Hi MF,
Late at night, i made draw the schematic. Here it is:
https://dl.dropbox.com/u/19882028/MF/100W%20475kHz%20PA.png (picture of prototype
https://dl.dropbox.com/u/19882028/MF/DK7FC%20472%20kHz%20PA%2015W%2B100W.JPG)
Most of the parts are not critical.
The ferrite cores are the blue EPCOS types, N30 material. Details are in the image. But you may use a FT140-77 alternatively and double the primary and secondary number of turns.
There are many alternatives, also to the FETs. Instead of the
IRZF48N you may try a
IRF1405. This one has a lower on-resistance but a higher input capacity. Maybe it works even better, i didn't try to many parts. Switching times are not critical. So you need to find a compromise between low on resistance and input capacity while the
Drain-Source voltage should be 55V for a 12V supply.
Instead of RF litz wire (i use this one:
http://www.reichelt.de/index.html?ACTION=""> ) you can also use 1mm diam. enamel. Cu wire or better 5x0.4mm or what you have. It just affects the efficiency, more or less.
The overall dimensions of this prototype are 15cm x 10cm x 3cm, so it is quite compact and since it runs from a 12V battery you can use it for /p tests. Also you can of course use more than 2 power steps by using a
multi step switch and more taps.
A DDS signal generator with rectangular wave form or a sine signal coming from a HF TX may be used. The waveform doesn't matter as long as the peak input voltage exceeds 5
Vp.
73, Stefan/DK7FC
PS: Yes, it is nothing new and someone has done it before!
Am 28.06.2012 11:46, schrieb M0FMT:
Hi again Stefan
The Litz is too, only by the Km or 10Kg reel.......... :@((
Do you create your own I have 0.125 solid C/E guess that could be stranded up to make a
synth?
73 es GL Pete M0FMT IO91 UX
Hi Stefan
Just over £5 a pop!
Just over £6 a pop!
But what is the “Unobtainium” ferrite?
…… ;0)
Chees Pete FMT
Hello Stephan ,
Me too
73 , Jean-Pierre F1AFJ
Le 28/06/2012 10:36, M0FMT a écrit :
Hi Stephan
Me Too
73 es GL Pete M0FMT IO91UX
like
----- Original Message -----
Sent: Thursday, June 28, 2012 6:35 AM
Subject: LF: RE: 472 kHz PA running at 12 VDC
If someone is interested i may convert the circuit from my mind into a schematic as a png file.
Always interested ;-)
73, Rik ON7YD - OR7T
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