On Wed, 21 Feb 2007 13:57:39 +0100, MAc
wrote:

Did anybody use MAR as a HF(1.8-28MHz) (not VHF) preamplifire?

What about results?
Any usable links or advices?

The problem seems to be that they have a lot gain (especially MAR-8
with a huge gain below 100 MHz), not so spectacular output intercept
point, thus the input intercept point is quite low, which can cause
problems, if a broadband antenna signal is fed into it.

Even if you have sufficiently selectivity in front of the MAR, you
have to watch out for leakage capacitances around the filter, since
the amplifier has gain well into the VHF and UHF bands.

I once tried to use a MAR as a preamplifier for the 29 MHz satellite
band with a filter in front of it that I hastily, but since I have a
few FM-BC stations (100-200 W each) and VHF and UHF TV transmitters (a
few kW each) at 1-2 km distance, I got quite a lot of intermodulation
products from these on the 29 MHz.

So even if you are making a filter for HF, you still would have to be
careful about stray capacitances in the coils and stray inductances in
the capacitors, in order to keep the strong VHF/UHF signals out of the
MAR input :-).

Paul OH3LWR