[Elecraft] Alignment question

Sun Jul 13 17:12:03 2003

It's not a "dumb" question at all, George.

Aligning for "maximum noise" will NOT help you hear weak signals any =
better.
The K2 has plenty of gain to rattle your eardrums on either speaker or
phones unless you are trying to use the speaker in a very noisy =
environment.
In that case the cure is more AUDIO gain, NOT more RF gain, since more =
RF
gain simply compromises the performance of the receiver.

On the HF bands, atmospheric noise determines how weak of a signal you =
can
hear. Narrower bandwidths help, down to the bandwidth of the signal you =
are
receiving, by cutting out excess noise coming through to improve the
signal-to-noise ratio. So on SSB, about 2.2 kHz or so is the best
compromise. That's why the stock K2 filters are about that wide. On CW,
basically the narrower the bandwidth the better for pulling in a weak =
signal
since the fastest-keyed CW signal you are going to encounter is still =
going
to be less than 100 Hz wide.

Adding more RF signal input by tweaking the input filters, turning on =
the
Preamplifier, or doing anything else is not going to help. It will =
increase
the band noise as much as it increases the signal level, and you gain
nothing. If you increase the input signals too much, you can cause =
overload
of the receiver, producing even more internally-generated noise that =
will
actually make the signal harder to hear, not easier.=20

The K2 is a VERY robust receiver design with great dynamic range - the
ability to handle very strong signals near the frequency of the desired
signal without causing interference. Even so, pumping enough RF into the
front end can overwhelm it. That's why the K2 has an ATTENUATOR as well =
as a
Preamplifier. On the lower frequency bands where there's lots of =
atmospheric
noise, it's a good idea to run with the attenuator on - especially if =
there
are any "locals" with strong signals on the band.=20

On rare occasions or when you have a very low-gain antenna you may need =
some
RF amplification up on the higher frequencies - 10 meters and, if the =
bands
are VERY quiet or you have a very poor antenna perhaps as low as 14 MHz.
That's why the K2 includes a Preamplifier. Using it to make more "noise" =
on
the other bands does nothing to help you hear weak signals and can =
actually
get in the way.

There's a very simple and very accurate test to tell if you need more RF
gain. Switch to your narrowest bandwidth, make sure your ATU is adjusted =
for
the band in use and tune to a frequency where there are no signals =
present.
Turn up the gain so you hear the "band noise" in the speaker or phones. =
Then
disconnect your antenna from the K2. If you hear the noise drop in =
volume,
you have plenty of RF gain. Adding the preamplifier, tweaking the BPF
settings, etc., won't do a thing to help you hear a weak signal. Your
ability to "hear" is limited entirely by the atmospheric noise coming in
with the signals, not by the gain in the K2.=20

Ron AC7AC
K2 # 1289

-----Original Message-----
From: [email protected] =
[mailto:[email protected]]
On Behalf Of gwlillie
Sent: Sunday, July 13, 2003 6:13 AM
To: [email protected]
Subject: [Elecraft] Alignment question

Here is a dumb question. Is it best to align the rec. for max signal or =
max
power?  With the band pass filters the book says it will be the same. I =
just
wonder if there is a happy medium.

George  N8GW