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 _______________________________________________ Elecraft mailing list 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
Paul, N2PD
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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 _______________________________________________ Elecraft mailing list 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 _______________________________________________ Elecraft mailing list 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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