On Feb 19, 1:38*am, wrote:
I recently acquired one of these cheap 2m handhelds from China, an
FDC-150 I think. It's great for the price (£30) apart from a problem
with QRM.

I use the radio with a 3 element beam from SOTA activations from hill
tops. It varies from location to location, but I often get strong
intermodulation effects (caused by pagers I think). I suspect the
radio, being wide band 136-174MHz, has insufficient filtering to
reject these strong signals.

The intermod is a real problem, as I am often unable to hear stations,
or only get half of what they are saying before they are wiped out. I
was wondering about building a 2m bandpass filter like the one athttp://www.arrl.org/tis/info/pdf/0005054.pdf

Does this look like a good bet?
Also any ideas where I can get the semi-rigid coax (UT-141 or RG-402)
in the UK?

This kinda agrees with what Steve posted...

First, if you want to build it, there's no reason you have to use semi-
rigid. It should work fine with any reasonably low loss coax if you
adjust for velocity factor variations from the design-specified coax.

But...if you have a way to tune an LC filter, you can make a more
compact filter using coils and either explicit capacitors or the
distributed capacitance as in a helical resonator. Using RG-59 size
coax at 150MHz, you'll get resonators with an unloaded Q about 100 --
and it takes a piece of line about 40 cm long to do it. You can get
well over twice the unloaded Q from a coil only about 6mm diameter and
6mm long. Higher unloaded Q allows you to build sharper filters and/
or filters with lower insertion loss. Coaxial stub filters make
sense--a lot of sense--at GHz and higher frequencies, but unless you
want to use really large diameter resonators for something like a
repeater duplexer that requires seriously high Qu, you're probably
better off with an LC filter at 150MHz. If you don't have access to
equipment to tune up a home-brew filter, use of a pre-tuned filter
like the helical resonator Steve suggested is a good idea.

Cheers,
Tom