EMRFD Message Archive 449

Message Date From Subject
449 2007-02-07 11:29:44 ter753 i q vfo
Ed, very nice design!. I am going to build it very soon. thanks for
posting it. best 73, terry lynch
450 2007-02-07 19:09:02 topossibilities Re: i q vfo
I did a PCB layout for the I-Q VFO and added the the etching pattern
in the files section.


Foil side shown.

While I don't have a parts overlay many of you will be able to figure
it out or just use the digital half. I recall that there were a couple
of jumpers required.

Nice features of the Johnson ring counter is that the I-Q symmetry is
as good as you can get and it's broadband (e.g. intra and inter band).
I've been told that without the 100 ohm resistors, there is 17 dBm of

In reply to Bill's (AB1AV) question regarding the purpose of U1, while
a Johnson ring counter only requires (2) flip flops, I did this for a
reason but I can't remember why (built this 10 years ago). Think it
had something to do with making it bullet proof the first time.

The purpose of the (2) 100K resistors was to bias the flip flops mid
way between the on / off states so that a low level signal would
provide toggle.