The BITX20 discussion group is a community of people with like interests
and experiences. Some are casual users of the equipment, and most are
licensed ham radio operators who have technical talents as evidenced by
their passing the ham radio exams. The uBITX, and BITXxx, before uBITX
were designed for the Ham radio community. Most of the members of this
discussion group are here to discuss mods, operating, and camaraderie.
As of today there are 7871 members of the group, most of which are
satisfied with their uBITX, BITX40, or earlier BITX20 units. BITX units
have evolved over time, usually involving on-line discussions and suggestions.
The people on this group are willing to help with problems, but that requires
working with these helpers. If one just powers up a new uBITX and starts
pushing buttons without understanding what it might do, then problems may
occur. If you look at the block diagram, and then at the schematic, you will
see that the uBITX is not a simple circuit. It is the result of several years of
design, testing, re-design, and more testing by those with experience in
uBITX boards are "factory tested" before they are shipped. It is unlikely
that a defective uBITX board was overlooked and shipped without testing.
The tests performed at HFSignals have been listed earlier on this group.
The tests performed could be listed again but probably would not mean
much unless the owner takes the effort to understand how the radio works.
Now, some "remote guessing" at what might be the problem.
- Others have suggested that the BFO adjustment could be off.
That is the most likely problem...and could have been reset by
yourself when initially trying to operate the rig. We do need
you to perform the BFO alignment procedures before we go
further. To do this you need to understand the concepts of
"zero-beat" and "offset". Picture the IF filter as an open door
that allows only passband frequency signals to go through.
Unless the incoming signal mixing with the tuning oscillator
is heterodyned to inside the filter passband, you will not be
receiving the desired signals. Once the desired signal is
passing through the IF filter, it is again heterodyned to audio
by mixing that signal with the BFO.
On transmit this process is reversed with audio plus BFO
(balanced for Suppressed Carrier DSB generation) and
presented to the IF filter which slices off the sideband that
falls outside the filter passband. Note that if your BFO is
misaligned so that both sideband fall inside the filter
passband, you will be transmitting both sidebands, or what
is known as Suppressed Carrier AM.
- The next but unlikely possibility is that one of the balanced
demodulator diodes was installed backwards at the factory.
We can test for that if you are willing, but first we need to
know that the BFO is adjusted properly. Without that any
tests might be counter-productive.
- Highly unlikely is that the IF transformer feeding the detector
has been mis-wired or mis-connected at the factory. This
would have been caught at testing time, but we will not rule
it out as a last resort.
- Least possible possibility is that your crystal filter is not filtering
properly. That would have been caught during factory testing.
And, please remember that the members of this group who volunteer
their time to help you with your uBITX are not employees of HFSignals
and do not get paid for their time. The BITX phenomena started as
an idea on an aircraft flight between New York and India. It was initially
built by individuals from junkbox parts. Then one ham started offering
bags of parts (no PCB) for building your own BITX transceiver. And,
the rest is history. Group support is rather unique among manufacturing
of technical products, but is not unheard of. It has worked well for the
uBITX and for the group.
Yes, a long email, but it may help to understand the idea of Group support
and of the uBITX itself.