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Hello, BITXs!!

I'm sorry but the modification by Allison doesn't work in my dual band
BITX (15 and 20meters). It makes great white noise in the receiver.
Without the modification the noise is little and the band sound is
good. After the modification the white noise is loud and the band
sound is muffled.

I test also to add another coil to the ring diodes mixer. But this
modification don't make diference aparently. The band sound and
sensibility remain unchanged.

I am working in an dual conversion BITX, after the "disaster" of 32MHz
FI due to the bidirectional amplifier feedback configuration I work in
a dual conversion. First FI 32MHz, second FI 10MHz. The mixers are
identical ring diodes based, the oscilator is 12MHz cheap and easy to
source. I want to mantain the bidirectional architecture. I will use a
bidirectional amplifier made up of dual gate mosfets and resonating
coils for 32MHz.

I will post the result of works and schematic. I will like to make VHF
with this configuration.

Greetings
I got my all band ticket!!
EA7ARX, ex EB7HPM/EC7ALV

Hello,

Turning the moddulator around should not negatively impact
operation. My proto(20M) and testing the second (6m) show
the revised is prefered for many reasons.

The high noise suggests several things. You may have RF getting
into the audio amplifier or one or more stages are oscillating
when they should not.

As to 6 meters, I've done enough building of transceivers for that
band that dual conversion is viable with care. The reason I say with
care is that more stages and more oscillators require good shielding
more undesired signals are likely. Also more stages means more gain
and that increses the possibility of unwanted oscillation.

I am working on 6M and to date I have the entire audio, and IF section
working and tested. I will use doubly balanced mixer (mixer with two
transformers). Local oscillator will use PLL of my design. Another
approach for those not wishing to build PLL is to take a crystal osc
such as 35mhz and mix that with VFO of 5mhz to get 40mhz at good
stability. In any case after 4 prior VHF radios the local osciallator
system must be shielded and well filtered to keep undesired signals
away from the rest of the reciever.

Basic lineup for the 6m radio is 9.6mhz IF and filter (have those
crystals). Q1 and Q13 transistors are 2n3866 (good VHF device)
and the power amplifier chain willl not use IRF fet. I plan to use
a VHF power transistors 2SC1970 and 2SC1971.

Allison
KB1GMX