Thanks for the good info dear Allison,
?
Yes, in the meantime I discovered MOSFET IRF's are not most favourable candidates for a 6 m PA. The 2SC Japanes transistors are more common and most likely much easier to use.
?
About the synthesizer circuitry, in the past I have used a divider 4059 in combination with a 4046.
?
If after the VFO a hi-speed divider (e.g. 74F74 or U256) is used you can go up to the GHz range and have a rockstable vfo.
?
Disadvantage; 4059 might be diffictult to obtain and is rather expensive. Maybe someting with a couple of 4017 's (1...9 dividers) can be done.
?
73 de Ron
PA2RF
?
ajparent1 wrote:
--- In BITX20@..., "Ron" wrote:
> Hi fellow BITX-homebrewer,
> Yesterday I was browsing through some old "Electrons" (Dutch Ham
> magazine) and found an interesting article in which it was told that
> our famous MOSFET IRF-family (in particular IRF510 and IRF540) could
> work on 50 MHz ! I am surprised by this. The article did not show
> fixed designs, so maybe it is just wishfull thinking...
> According to the article, achievable power levels should less lower
> than at, let's say 7 MHz ( 2 Watts versus 12 Watts RF).
> Anybody experience in this field ?
To drive the input of the mosfet at 6M you will have to use very
different networks so the input capacitance can be absorbed into the
network.? Same would have to be done for output.? Major redesign
of the "linear
module" is the result.? I've tried the IRF510 and
friends and they can generate fair power at 6m but they are hard to
drive and not as stable.? Devices like the 2SC1307, 2sc799, 2sc1970
and 2sc1971 are easier to use and fairly common (found in 27,mhz
US CB radios). Power out with those can be as high as 10W.
> However, with an IF of 10MHz, VFO freq of 40MHz might be too high to
> get a (simple) rock-stable VFO.
The easiest way to get a 40mhz VFO is to take a 4mhz VFO and mix it
with a 36mhz crystal and filter the result to 40mhz.? then you get the
stability of 4mhz VFO and the required high frequency.
I'm doing it with whats called a sampling tracking PLL.?? Simpler
than a full digital PLL and somewhat less trouble with spurs and
sidebands. Tuning between the digital steps is by varying the VXO
used in the down conversion osc.? It allows me to use older PLL
chips that have /n counter that
only count to 255 or maybe 512.
Allison
KB1GMX
Yahoo! Mail
Stay connected, organized, and protected.
