Re: uBITX Questions

Ashhar Farhan
 

I gave those a value of 0, to indicate that those capacitors are not needed. 
That said, i havent found time to update the circuit, essentially, the new version uses four LPFs instead of two, a 45 mhz crystal filter in place of the LC band pass filter. I has posted the new schematic a few months ago. I cant seem to locate it now.
There was a problem with the LC band pass filter, the 14 and 10 mhz signals are just 2 mhz from the 12 mhz IF. When operating in these bands, the tx output was looping back into the second mixer, creating weird spurs. One way to avoid it is to separate out the PA board from the rest. the other way, which i have adopted, is to use a narrower crystal filter. These filters are easily available for less than a dollar as 45m15a or 45m15b. They are commly used in cordless phones and vhf or uhf handies.
- f


On 5 Oct 2017 5:44 am, "Dexter N Muir" <dexy@...> wrote:
I'm not going to regurgitate the whole of this thread here, Jerry, but will offer this: I reply online, and refrain from the tedium of cut-and-paste for context. I haven't tried it here, but on Facebook I can highlight the material I respond to and it's auto-included. That's easy if I reply to the emailed Digest in the mailer, but less immediate so the less preferred option. And as before, those few seconds' consideration can avoid 'foot-in-mouth' disease. Besides, your reaction triggers my 'follow it to resolution' response (life imitating art, check "The Good Doctor") so this has become more than an 'aside' and should be elsewhere than this forum.

73 de ZL2DEX

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