testing the signal chain

Connecting the front-end mixer to the bi-directional IF amplifier/
filter to the product detector. Using two bench signal generators,
one for the VFO the other for the BFO, i could tune in local HAMs on
20 m with a simple wire antenna.

More to come....

product detector

Here is it, the completed product detector

front end mixer

Here is the front-end mixer module. Inside this module you will find
a double balanced mixer with a 14.25 Mc, 500 Kc BW front-end filter,
a 4 MHc 1 MHz BW IF filter, and a 3 dB LO PI attenuator.

68 dB bi-directional IF Gain stage and SSB filter using 4 MHz CPU crystals

After testing all of my 4 MHz CPU crystals i followed the procedures
in the 2010 ARRL handbook to design a 2 KHz bandwidth SSB filter.

I incorporated this filter into a bi-directional IF sub-system that i
designed using AD8009 current feedback op-amps (with 1 GHz GBP) and a
Motorola MC1350P IF amplifier, which provides 40 dB of gain and a
very nice analog attenuation for AGC.

Bi-directionality is achieved by the use of two dual pole two-way
relays. Some shielding had to be installed to eliminate a low-level
oscillation. As it is built no oscillation occurs in this stage.

Shown in the photos you can see the inside of the IF AMP built into a
Bud die-cast aluminum enclosure with an RF gasket. You also see the
IF amp connected to two DBM mixers, where, i used a pair of signal
generators as the VFO and the BFO respectively. In this
configuration i was able to tune in a local ham station using a wire
across the ceiling connected to the RF port of the front-end mixer.

building an SSB transceiver from scratch, step 1: testing surplus CPU crystals

A SSB filter crystal filter can be built out of surplus CPU crystals,
according to the 2010 ARRL handbook. I have found large volume of 4
MHz CPU crystals and have characterized all of these in order to
design my SSB filter. I use a spectrum analyzer, frequency counter,
and a phase-locked signal generator to characterize the series,
parallel resonances and the series resistance. I use an LCR meter to
find the parallel capacitance.

I will use these old crystals to design a suitable 2 KHz SSB filter.

Stay tuned for the results....

Design your own vacuum tube audio amplifier.

Ever wonder how you could design your own vacuum tube audio amplifier?

Read this briefing to see how it is done.

http://glcharvat.com/website%20pdfs/MIT_Haystack_Lunch_Talk_2_3_10.pdf