tag:blogger.com,1999:blog-7590176649168185428.post2913890114960797065..comments2024-03-29T07:34:28.586-04:00Comments on SolderSmoke Daily News: Doug Demaw and Vlad PolyakovBill Mearahttp://www.blogger.com/profile/07662500663603350847noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-7590176649168185428.post-69678762946926431302011-07-21T10:52:50.291-04:002011-07-21T10:52:50.291-04:00Hello Bill,
Thanks for the question.
The question ...Hello Bill,<br />Thanks for the question.<br />The question ”why?” Is always the most difficult question. I first answered another question. Are L2 and C1 really tuned to 7 MHz? For 7 MHz C1 must be adjusted to 54 pF. For 3.5 MHz C1 should be 216 pF. Further C2 must be adjusted to 7 pF to tune the oscillator to 7 MHz. (C2+100pF=107pF)<br />So L2 and C1 tune for 7MHz and also the oscillator is tuned to 7 MHz.<br /><br />In this chapter Doug wrote about DC receivers, in which the oscillator runs on the receive frequency.<br />So I think that Doug choose the <b>most simple mixer</b>. <br />Both in terms of number of parts and to avoid a more complex bifilair transformer or extra potentiometer for balance. It's not the best mixer but.... As Doug wrote: This Polyakov mixer does not match the performance of a balanced mixer. Page 112.<br /><br />I used such a simple balanced mixer in my HDC14 Transceiver, which is doing great, with just 1 potentiometer more. Please look at the handwritten schematic on my website.<br />http://a29.veron.nl/pa1b-02.htm#rx<br /><br />So I think, Doug kept it simple.<br /><br />73, Bert PA1BBert, PA1Bhttps://www.blogger.com/profile/14064917598289627232noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-1278422459821901382011-07-20T23:40:09.571-04:002011-07-20T23:40:09.571-04:00I don't know why Doug did it that way but that...I don't know why Doug did it that way but that circuit would make a great little test receiver for bench work. <br /><br />Make the VFO band-switching (or use a DDS), a MBT for the front-end selectivity, add some audio bandpass filtering and a speaker amplifier, voila, you'd have a "Vlad The Inhaler"!<br /><br />73.......Steve Smith WB6TNLSteve "Snort Rosin" Smith WB6TNLhttps://www.blogger.com/profile/01570621886789949035noreply@blogger.com