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Possibly one of the mixer diodes is in backwards.
The original BITX20 had a very sensitive receiver, which allowed
spurious signals to be heard if there was no RF input and if the
volume was turned up way too high.
What is your MDS (Minimum Discernable Signal) in microvolts?
MDS should be in the 0.2 to 0.4 microvolt range.
If you do not have capability to insert a clean 0.2 to 1.5 microvolt
signal then ignore that test.
Like all superhet receivers the BFO frequency needs to be adjusted
to between 10 and 12 db down the side of the crystal filter passband.
Setting it above the filter passband will give you LSB and setting it
below the filter passband will give you USB reception. Setting the
BFO within the filter passband will give you DSB reception. If you
set the BFO too far outside the filter passband your received audio
will be distorted. where you adjust the BFO relative to the filter
passband will affect the amount of highs or lows in your received
signal, and in your transmitted signal.
On Sun, Jul 5, 2020 at 11:37 AM dries breughe <driesbreughe@...> wrote:
i built the bitx20 original version in 2012 but it functioned very badly