As far as I can tell, the diodes are OK but I have doubts about the input capacitor values. I think they should be the same value to avoid LF phase differential at the mixer.
Bear in mind you should NOT get any output until audio is fed in. The potentiometers are there to null any residual carrier. Also bear in mind that it is designed for very narrow frequency use with only (probably) 170Hz difference in input audio tones. It is DSB, not USB as can be seen in the spectrograph. If you want SSB you have to filter out one of the sidebands.
Brian.
Any of those phasing SSB approaches are such complicate to build and to tune (phase AND amplitude), that barely worth to spend time on them.
A diode DSB (double side band) modulator followed by a cheap ladder crystal filter would work with decent performances right from the start, with a minimum of tuning. And the SSB signal will be steady whatever hoarse voice you have or how loud you speak into the microphone.
Making a 4 pole crystal filter, which gives at least 40dB side band suppression, its easy and really cheap. Use trim capacitors (and trim resistors for in/out resistance) to tune the filter. You need only a good receiver to listen the SSB signal. Most probably the tuning doesn't take more than few minutes.
The main rule to get a good SSB ladder crystal filter, when you don't have adequate test equipment to measure it (e.g. VNA), is to choose crystals with frequency lower than about 5MHz (3.57MHz, 4.000MHz, 4.43MHz, 5MHz, etc). Those crystals, even they are from different manufacturers, they have pretty close characteristics, which is a requirement for ladder filters.
Indeed, is that easy to make a decent ladder crystal filter for SSB without having fancy test equipment. For CW filters is even easier.
On the net are tons of schematics, papers how to do it, or online calculators.
http://www.giangrandi.ch/electronics/crystalfilters/xtalladder.html
http://www.changpuak.ch/electronics/Quartz_Crystal_Filter_Designer_2.php
http://pages.suddenlink.net/wa5bdu/crystal_slide_show.pdf
6MHz crystals already enter in a different category for crystal qualification. If you don't have proper test equipment to measure the filter, stay on crystals below 5MHz. But if you have a lot of them, doesn't cost you anything to try 6MHz also.
For a 4 crystal filter, use trim capacitors for those 3 shunt caps in the middle and 5k trim resistors for in/out resistors.
http://www.abcelectronique.com/annuaire/montages/cache/3251/laddermodel.gif
In this way you can tune the filter whatever crystals you use. When is done, measure their value, and replace with fixed value components.
Of course. This is exactly what I meant..
Generally using equal value capacitors is not working always for ladder filters using more than 3 crystals. Using 4 crystals, make at least the middle cap variable for proper tuning (especially for side band rejection).
For 6 MHz crystals, and depending by the target bandwidth and terminating resistances, I would go for capacitors between 50pF and 100pF. As I said you have to use trim caps to adjust for proper tuning.
To get inp/out symmetry, usually the 1st and the 3rd caps have the same value, when the middle cap has a bit different value.
Have to remember that, lower the caps value, wider will be the bandwidth of the filter.
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