Is the minima still alive ?
Tryed to make 2 and the 2 failed to work.
Pedro Almeida
CS8ABY
NRA: PN063
Em 25/07/2016 15:37, "Mark Smith" <dmarc-noreply@xxxxxxxxxxxxx> escreveu:
Thank you Ben for that. I looked at the schematics and understand them.
I've been a ham since 1991, but am just getting into RF electronics and
circuit design. Schematics like that one make it so much easier to
understand what's going on. Thank you!
One question, that's not specific to your design. I've never understood
the benefit of more than two conversions, one IF. Why does the HF1 convert
to 45MHz, loosely filter with LC, then convert again to 10MHz and filter
with crystals? How is that better than converting to 45MHz, filtering with
crystals, then converting directly to base band?
There are also a couple more amp stages in there, but those are probably
just to make up for losses in the filters and conversions, and could be
added anyway without the extra conversion.
To be clear: I'm not saying you're wrong, I'm totally ignorant and asking
for education. :-)
Thanks!
-Mark
On Jul 25, 2016, at 7:23 AM, Ben Aupperlee <beninturkye@xxxxxxxxx> wrote:
Hello Mark,
There is now an HF1, with a high first IF of 45 MHz and even a newer
version where i am working on with an if of 60 MHz, with better filters.
Regards Ben (in Turkije)
-------- Origineel bericht --------
Van:"Mark Smith (Redacted sender "smittyhalibut" for DMARC)"
Verzonden:Mon, 25 Jul 2016 17:15:29 +0300
Aan:minima@xxxxxxxxxxxxx
Onderwerp:[minima] Re: for minima project
Forgive my ignorance. "The old minima project?" Is there a "new minima
project?"
This is the one I've been working off of:
http://www.phonestack.com/farhan/minima.html
Is there something else I should be looking at too, or instead?
-Mark
On Jul 25, 2016, at 5:33 AM, allison <ajp166@xxxxxxxxxxx> wrote:
On 7/25/16 4:19 AM, Computer Burgas wrote:
In old minima project, after series of tests I found that Si570 has too
many harmonics and frequency counter reported me them rather than the
fundamental frequency, which means that the mixer and quartz filter
probably being down work properly.
SI570 and the 5331 all provide a square wave output which is rich in
harmonics. The frequency counter may be
such that it has higher sensitivity at harmonic frequencies or your not
coupled adequately.
Also the cost of Si570 in ebay is 2-3 times higher than , for example -
AD9851. Moreover BFO also realized unstable frequency. I decided to work
towards replacing VFO and BFO with the 2 pcs of AD9851 DDS generators. So
with this I will get freq accuracy and easy programmability of LSB and USB
in BFO and VFO.
From cost perspective ok. However you need a micro to set it and DDS have
spurs. Minimally the DDS will require gain to drive the DBM adequately.
Old minima project will still require better filters and more of them to
avoid out of band unwanted signals.
Allison
