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Pete
There are more simple ways to get on 500. Simple dds or
sig gen at freq of interest if sine wave just sq it by using a couple of
diodes
then a driver chip tc4426 use one side and straight into
the FET PA then an inductor and a couple of capacitors, an old lopt transformer
for matching roughly from 6 ohms to 50 ohms. I built one in a couple of hours
away back and it gave good service until I modified a decca unit.
Mine was a QRO rig using a big fet at 60 volts to get the
required 10w erp
You do not need push pull class D to complicate
matters.
mal/g3kev
----- Original Message -----
Sent: Thursday, June 28, 2012 6:41
PM
Subject: Re: LF: Re: RE: 472 kHz PA
running at 12 VDC
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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