[TowerTalk] Receiving HF? (long question)

[Dick Flanagan]

>What is a good noise antenna?

The idea behind a noise antenna is that you want it to hear the undesirable
noise, but =not= the desirable signal.  The noise cancelling circuit then
attempts to remove what it hears on the noise antenna from what is heard on
the main antenna.

In the case of local computer-hash or power line static, this isn't very
difficult to do.  A small piece of wire in the shack or outside in the
bushes usually works just fine.  If you make the noise antenna too large,
however, you risk it receiving the desired signal, too, and then the noise
cancelling circuit begins to work against you.  That is why noise
cancelling circuits advertise they work against local noise only, not
atmospheric noise.

You will find that most noise cancelling circuits introduce about 3 db
signal loss, but when you figure they will probably allow you to hear a
signal that was totally obscured before, the loss usually isn't significant.

I have an ANC-4 and it makes 160 a comfortably usable band when the local
hash is particularly high.

73, Dick

--
Dick Flanagan W6OLD CFII Minden, Nevada
Visit http://wadg.greatbasin.net/siera/



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