Well,
Following on from my last post, I've been making some more bits and bobs to go with the SSB exciter:
http://g0mgx.blogspot.co.uk/2014/06/history-repeating.html
I've made the Triple Balanced Mixer:
As is becoming an apparent recurring theme, my isolation between the different ports isn't measuring as good as the author, however I can measure LO-RF and LO-IF isolation of about 40dB and more like 50dB of RF-IF isolation; which isn't at all bad.
The mixer uses 5 bifilar wound inductors, each of 12 turns on a FT37-43 and two well matched sets of diodes.
I have then added the post mixer amplifier and constructed the first of many band pass filters. This one is for 40M or 7.0 - 7.2 MHz.
Information on the filters is here:
http://homepage.tinet.ie/~ei9gq/bpf.html
which includes a link to a spreadsheet credited to John Charlton G3VRF which is an excellent calculator tool.
When I first built this filter is was too low in frequency (the yellow trace below) so I reduced the inductors by one turn each to get the purple trace. The markers are at 7.0MHz and 7.2MHz:
So the filter, at least, is now looking rather good.
I've had another good look at the exciter from last time but still I can't see why my output level is so much lower than the authors; will have to look again tomorrow!
Good, egh?
Following on from my last post, I've been making some more bits and bobs to go with the SSB exciter:
http://g0mgx.blogspot.co.uk/2014/06/history-repeating.html
I've made the Triple Balanced Mixer:
As is becoming an apparent recurring theme, my isolation between the different ports isn't measuring as good as the author, however I can measure LO-RF and LO-IF isolation of about 40dB and more like 50dB of RF-IF isolation; which isn't at all bad.
The mixer uses 5 bifilar wound inductors, each of 12 turns on a FT37-43 and two well matched sets of diodes.
I have then added the post mixer amplifier and constructed the first of many band pass filters. This one is for 40M or 7.0 - 7.2 MHz.
Information on the filters is here:
http://homepage.tinet.ie/~ei9gq/bpf.html
which includes a link to a spreadsheet credited to John Charlton G3VRF which is an excellent calculator tool.
When I first built this filter is was too low in frequency (the yellow trace below) so I reduced the inductors by one turn each to get the purple trace. The markers are at 7.0MHz and 7.2MHz:
So the filter, at least, is now looking rather good.
I've had another good look at the exciter from last time but still I can't see why my output level is so much lower than the authors; will have to look again tomorrow!
Good, egh?
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