Some K2 observations and questions

[N2PD]

Just finished building and aligning sn 05834.  Have a couple of questions:
1 - Preamp...I wonder if anyone else has noticed a very noisy K2
preamp...with no antenna or just dummy load connected, when I turn on
the preamp there is a marked increase in noise output.. Is this normal
or do I have a problem?

2 - I aligned the filters with spectrogram....is there any way of
getting the bfo set so that the received signal is the same pitch on all
4 filters? and, does the pitch change when switching filters affect the
transmit frequency?

Thanks for any input
Paul
N2PD
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[Ron D'Eau Claire-2]

It's normal to hear a substantial increase in background noise when the
preamp is turned on, even when no antenna is connected to the K2. The K2 has
more than enough over all gain for normal operation without the preamp,
which is why it has an on/off switch. The preamp is only needed when using a
very poor antenna or in the higher bands (e.g. 10 meters) when QRN levels
are quite low.

Even though the preamp noise is readily apparent when you turn it on with no
antenna, its noise level is well below what you'll normally find on the HF
bands. So even if you choose to use it on the lower bands, you won't hear
the noise. The band noise level will completely swamp the internal noise
generated by the preamp.

Of course, using the preamp when it isn't needed reduces the dynamic range
of the K2's receiver by about 20 dB, but the dynamic range of the K2 is good
enough that the loss will very seldom be noticed unless it's being operated
very close to other transmitters.

The basic "rule of thumb" about using a preamp with any receiver applies to
the K2: if you hear an increase in background noise when you connect your
antenna with the preamp turned off and using your narrowest I.F. bandwidth,
the preamp will not allow you to hear weak signals any better. Indeed, since
strong-signal overload often sounds just like increased background QRN, you
may actually cause weak signals to be lost. The same applies when deciding
when to use the Attenuator. Using it helps prevent the possibility of
overload and it will not hamper weak-signal performance one bit as long as
you hear an increase in background noise when connecting your antenna when
using the narrowest I.F. filter.

Ron AC7AC



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Paul Del Negro
Sent: Friday, November 24, 2006 6:39 AM
To: [hidden email]
Subject: [Elecraft] Some K2 observations and questions


Just finished building and aligning sn 05834.  Have a couple of questions: 1
- Preamp...I wonder if anyone else has noticed a very noisy K2
preamp...with no antenna or just dummy load connected, when I turn on
the preamp there is a marked increase in noise output.. Is this normal
or do I have a problem?

2 - I aligned the filters with spectrogram....is there any way of
getting the bfo set so that the received signal is the same pitch on all
4 filters? and, does the pitch change when switching filters affect the
transmit frequency?

Thanks for any input
Paul
N2PD
_______________________________________________
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Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

_______________________________________________
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Post to: [hidden email]
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 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com