[Lowfer] Re: New antenna

[Ed Phillips]

Alberto di Bene wrote:
> 
> Ed Phillips wrote:
> 
> >
> >         Wonder if anyone has experimented with using some of the power VMOS or
> > IRC Hexfets?  Many years ago Bill Oxner (?) from Siliconix gave a talk
> > at Hughes in which he recommended their VMOS for really wide
> > dynamic-range applications.  Used POWER devices as RF amplifiers and
> > active mixers.
> 
> Yes,
>    I made a test using a small power VMOS, the VN10KM, 12V at 40mA with an
> heathsink. Being it a Mos-Enhancement device, where no current flows unless
> you give it some polarization, you have to change a little the circuit.
> It works well, maybe a bit better than the U310, I didn't perform
> any formal measurement, only subjective listening.
> A small bit of intermodulation is still present, though not very pronounced.
> Probably, should I not be able to get hold of the CP-666, this will be the device
> I will use for my antenna.
> 
> 73  Alberto  I2PHD

	I was thinking of the VN10KM in particular, but suspect that some of
the higher-power RF MOS devices would be better.  I haven't been able to
find the characteristics of the CP-666 anywhere, but assume that at the
bias point guys have used it behaves as a perfect square-law device,
with resultant absence of intermod.

	A number of years ago I built a very wide dynamic range IF amplifier
for some radar experiments, and was able to reduce the front-end
intermod through use of transformer coupled negative feedback to the
source of the input stage, but don't remember the details any more. 
(That was about 25 years ago.)  

	There's a lot of literature on "ultra-linear" RF amplifiers being
published these days in such throw away magazines as RF Design  and
Microwave Journal, but haven't been paying much attention to it.  Will
keep any future articles of interest and report on them.

Ed