Re: Bitx multiband

kilocycles <kilocycles@...>
 

The SSB would be inverted for the Local Oscillator (VFO + Pre-mix
Oscillator)injection frequencies of 12.5 and 16 MHz, since they are
higher than the IF and the mixer must select the difference frequency
in both of those cases to get the IF frequency. 20 meters would not be
inverted since the VFO is used directly and the frequency is lower
than the IF. Since you will have two BFO/carrier oscillators
available, one for LSB and one for SSB, it will not be a problem.

The Local Oscillator outputs will need to each go through bandpass
filters (12.5 and 16 MHz, with the center frequency of each being the
center of the SSB range of the band), preferably triple-tuned, before
the signal is sent to the mixer.
73,
Ted KX4OM

--- In BITX20@..., "ea4dsy" <ea4dsy@y...> wrote:

As I am interested on a Bitx working on 80, 40, and maybe 20 meters,
I am thinking on a Heterodine VFO and of course for the Bitx the band
switching as descrived on: http://www.phonestack.com/farhan/xcvr1.html
I am thinking of a heterodyne VFO using a oscilator from 5-5.3 more or
less, connected to the pin 1 of a NE602 acting as a mixer-oscillator
and a multy quartz crystal switched by diodes connected on pin6 of
NE602, at the output of the NE602 (pin5)there is a band pass filter
switched by diodes and finally a simple transistor as an emiter
follower amplifier.
The relation of the mix regarding that my IF value is 9Mhz is:
80meters: 7.5Mhz crystal+5Mhz Vfo=12.5
40meters: 11Mhz quartz crystal+5Mhz VFO=16 Mhz
20meters direct 5-5.5 VFO.
I think the VFO readout tunes directly on all three bands, and the SSB
is inverted but this is not a problem switching the carrier BFO
crystals.
Does it look right?

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