Posted by
Vic Dively on
Feb 12, 2005; 8:08pm
URL: http://elecraft.85.s1.nabble.com/40M-band-pass-filter-alignment-very-little-signal-getting-through-tp374565.html
Well, I finished up the assembly Part 2, and everything seems to be going
perfect except for the very last step - the 40M bandpass filter
alignment. All of the checks were in the expected range, except for U6
pin 8, which was 36.8 ohms instead of greater than 100 ohms. Everything
else works perfect. I think the receiver itself is working perfectly,
because I am able to hear several stations with no antenna connected at
all; when I try that with my FT 817 and my Argonaut 509, I couldn't pick
up anything without an antenna attached. On the other hand, with my
antenna attached, I'm picking up lots of stuff with either the FT-817 or
the Argonaut, and almost nothing additional, when attached to the K2. I
assume the receiver for 40M is supposed to be fully functional at this
stage. However, I seem to be having very severe attenuation between the
antenna input and the receiver itself. So while the receiver seems to be
nearly "deaf" I think the problem is in the path from the antenna jack to
the receiver, not the receiver proper.
Unfortunately, just before performing the 40M band pass filter
adjustment, my Pug started choking on something, so I jumped up to see,
and naturally the headphone cord was wrapped around my leg so I yanked
the K2 off the table onto the floor... I could kick myself! I redid the
checks, and it all seems to be the same, so I don't think I broke
anything new, I suspect my problem is something that already existed.
L34 seemed to perform as expected, a very mild peak, near the top of the
can... the L1/L2 peaking seemed to work, I could definitely make the
signal come and go, with the antenna attached.... there is a very mild
improvement when the antenna is attached, but as I noted, the signal is
quite severely degraded, compared to attaching the antenna to one of my
other two qrp radios...
I did check my toroids for continuity from the pads, not touching the
lead wire, to be sure that the wires had good connections to the solder,
so....its now on to the signal tracing, a new experience for me. If the
answer is obvious to anyone, let me know! Thanks.
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