- June 2002 -- Rev C of the SOP Kit ships. Please review the following notes, as they will definitely help in assembly and tune-up of the SOP receiver.1) The version of the kit latest pcb (rev C) and the manual that came with it should also say Rev C on the front cover. The schematic is labeled 'rev C' and parts layout diagram is also labeled 'rev C' on the sheet ... but we forgot to change the lettering on the board itself. The Photo tour will still show the rev B board, as we didn't re-do that whole big manual for the rev C update. Rev C changes accommodated the proper pinout/layout of the FET transistors.
2) We overlooked putting R29 in the parts list, so it wasn't initially ordered or kitted in the SOP parts bag. We'll get a 27K resistor to you if you don't have one in your junk box.3) You should install R12 and C18. They provide a wide band termination to the mixer output.
4) C35 (100pF) should also be installed for 40m operation, but it seems we left this off the parts list. (There was a note to this effect on the rev B schematic but it mysteriously went away in this latest rev.) This will tune the output of your Input RF Amp for 40m and give you some good signal coming through. It'll therefore allow you to tune T2 for a peak in signal at 7MHz. We'll send a 100pF cap for this if needed.
5) RFC-2 is only need for 80m operation, in case you wanted to put the SOP on that band. (RFC-1 designator is not used in the project, in case you were looking for it.)
6) C20 should be peaked for max signal with the LO wire jumpered over to the input, as described in the manual. That adjustment, and the one for T2 are fairly critical for good front end operation.7) The audio output might be a little soft (i.e., low level) with some mono headphones). Builders might want to try experimenting with different headphones for better/different audio quality.
8) Some homebrewers have found it difficult to get all specified winding on T2 using the #26 wire supplied in the kit. Using #28 (or even #30) magnet wire will help.
9) N2CX wrote fabulous article in QHB #7 "SOP App Notes", wherein he described how to put the SOP on different bands and the specific component selection for that. Hope you have that issue handy - it's a great reference.
July 2000 -- Rev B of the SOP Kit ships. Please study the following notes only apply to Rev B of the kit.
1) Jumper for LO frequency selection" -- For 40m LO frequency selection, it is necessary to connect the "B" jumper pads 1 and 3 (located next to L1). The manual incorrectly states pads 1 and 2 on page 16. (Thanks to Richard Fisher, KI6SN for catching this subtle typo in the manual. If the jumper is placed as directed in the manual (pads 1-2), then only 3.58MHz LO signal will get to the buffer and mixer, yielding a nice 80m signal for your 40m stock SOP!)
2) " Bypass Filter Mod for T2" -- One of the SOP builders found that front end RF sensitivity could be vastly improved in some cases by adding an R/C filter to the V+ supply to T2. A 47-ohm resistor can be added in series with the V+ supply to the T2 primary by carefully slicing that trace on the bottom of the board at the V+ pad of T2 primary and putting a 47-ohm resistor from it to the thin V+ trace coming over to the transformer. Then, a .01uF capacitor is soldered from that T3 lead to the adjacent ground plane.
3) A ground trace is missing on the emitter of transistor Q4 and you need to make a very simple fix in order for this audio amp to work. Locate the 3 pads of Q4 on the bottom of the board (seen also in the diagram on page 15 of the manual as the 3 vertical pads closest to C10), and solder a small piece of scrap wire from the lowest of the three pads to the adjacent ground plane. This fix will enable the Q4 amplifier to work and pass the low-level audio signal from the mixer on to the low pass filter. (Thanks to Bob Confrey WA1EDJ and the NOGA QRP Club guys for their great assist in working through the board issues!)
4) We've discovered a mix-up we had in the parts-stuffing effort for the kits. The bags were stuffed according to a parts list that was for an earlier version of the schematic ... the schematic changed but the parts going into the kits didn't. The Parts List on the website is corrected, and everyone will be sent the missing components during the week of 7/10. We apologize for this mix-up. Summary of the parts corrections:
a) 6 capacitors are included in the kit but are actually not used:
C14 = 47pF; C8,15,27 = .01uF; and C11, 20 = 0.1uF.
You should use one of these 0.1uF caps in the C27 position, and just add the others to your junk box.
Note that the 0.1uF C15 is still used on the board.
b) 3 resistors are included in the kit but are actually not used:
R5 = 4.7 ohms; and R11,13 = 10K
You should just add these extra resistors to your junk box.
Note that the 220-ohm R11 is still used on the board.
c) The following 7 missing resistors will be sent to everyone:
100K = R10, 17, 18, 20, 21
27K = R29
4.7K = R13
d) #26 magnet wire was sent with kit, instead of #28 wire, making it
difficult to get all 36 turns onto T3. A length of #28 wire will be
sent to all customers
e) C35, across the IF transformer (T2) in the RF Amp section, was
omitted from the text and Parts List. The value of C35 required
to resonate on 40m with the T2 primary is 100pF.
This cap will be sent to all customers.
5) R10 (100K) omitted from Parts List. Website version now corrected.
6) Errata Sheet shipped with initial group of 200 kits. Contained updated Parts List, Schematic and Parts Layout. (Each of these items are corrected on this website.)