I spent about 3 hours today verifying that the 20/30m TXPA is functioning. It is.. at 13.0v it put out about 1050 mW, about what was expected. I suppose I should have taken a picture of the Wattmeter, but I did it out in the shack in my detached garage, the 20m band was starting to die with sunset, so it wasn't worth heating it and attempting QSOs. IT WAS COLD out there. Oh well.. Next weekend.
When I tried setting up everything outside the first time I couldn't hook my other set of amplified speakers up, nor my Bencher because the slot was, again, too small to put certain 1/8" stereo connectors through to the connectors on the PCB... even when it was mounted flush with the proper screws (which again were BLACK ones I added.. :O) ).
I, quite frankly, am tired of that. I want to be able to use any molded 1/8" stereo connector and the very fine gold connector on my Bencher paddles. So I decided to do it. I got out the metal nibbler again, a file and a Sharpie. It turned out okay.. and now I have no issues with any of the connectors I use.
I widened up the slot one nibble on each side, but the side that meets with the PCB is the one that needs to be wider. I'm recommending that everyone do this or you will have to be very picky about the type of 1/8" stereo jack you use with the SDR-Cube.
I then verified the rig worked on TX, listened around on 20m on a good antenna. It works well, but I still think there could be more gain on the line output of the CODEC (i.e. an Op-Amp following it, since I have to turn up all of my amplified speakers up pretty high) and in my low noise environment, I think more AF gain into the CODEC also. I think maybe another Op-Amp stage with maybe 10-20 dB of gain, but configured as another 0-8 KHz LPF would work. I experimented with more RF gain but if I do that I get significantly more "blow by" of SWL stations.
Anyway.. I will only briefly comment on the mounting of the X-LPF. You all know by now what I think of things that are not screwed down, and the X-LPF attaches with solder. Also the instructions say to solder it to the connector and then use the connector tab to solder to a landing on the PCB. This only works, however, with the supplied connector if you cut off the Teflon spacer (cut it nearly flush with the connector edge). Then it will reach the landing. You have to be careful not to short the body of the BNC against one of the filter caps, though when you do it.
Also, on my Cube (which probably has a slightly longer stand off set on the sr63ng than came with George's kits on the "real" Softrock 6.3's), I had to flip around the heat sink on the plug in to be able to get it on and off of the sr63ng because of the awkward placement of the X-LPF-- which is in the way.
Here is a picture of it. It's ready for a 20m QRP CW QSO right now. I'm going to try to also wire up a MIC and a PSK-31 connection to the Cube in the next few evenings.
It all seems to work nominally now. Not horrible for a project of this scope.
Overall.. I like the rig. If I had it to do again I probably would have only bought the boards and not the case, and neither cable kit (I bought both). But the case is cute, and it will make for a GREAT demo at the local ham club meeting..
But it really doesn't fit together that well. For a Ten-Tec case, I am rather disappointed by the lack of a "D" punch on the BNC and the hack job on the DB-15. Greenlee makes punches for both that could have been done by hand if anything else. The plug-in philosophy of the Softrock 6.3 has been discontinued by Tony Parks, and for good reason. The cabling and the plug ins will require maintenance because they will come loose. I gave some suggestions on how I partially mitigated this.. but I can't fix everything that is floating loose in this case.
Putting the boards out flat would have been better. I am not the slightest bit surprised that the first working cube was a board only kit because many hours of fiddling, mistakes, rework, swearing would have been avoided by me if I'd not have built it into the cute little case.
If you want a little CW and PSK QRP rig that is the size of an oversized Rubik's Cube.. then it's worth all of the effort to put it into the cube case. This, admittedly is Midnight Design Solutions normal customer base, and I can not fault him for "cubifying" the rig. The QRP crowd loves this sort of thing, and for their little portable uses it is an excellent fit.
But for those of us who want to use it for a building block for something bigger the mechanics of the cube enclosure will get in the way.
I think the CODEC needed an op-amp on both Input and output.. I don't like almost anything about the I/O board (including no op-amps for the CODEC!).. I may redesign this card in the future.
The software is excellent.. the latency is controlled better than any SDR I've ever used, and the audio is super clean. You'll be proud to put this on the air. CW is pleasant with the rig, and will get better with some software tweaks (like being able to reverse the paddles they are set up for a lefty by default!)
AGC would make the rig unstoppable but that may happen with software in the future.
I'd like to potentially try undersampling a HF RX with a filter on a IF. More gain could be used and the blow by issues will go away. I think the Softrock IF is a weakness for this rig, but still it works remarkably well overall. With only an 8 KHz IF bandwidth, a "roofing filter" at an IF and then undersampling probably would work much better with this design.
I think I know what I am going to do to multiband this rig while leaving it into the Cube package.. which is different than my initial ideas.
I'm going to build a 20 mW output broadband (not filtered) PA plug in. That will go out the DB-15. On my PA will be a 5W Class-A RD16HHF amp running into the AN762 with filters controlled by a microcontroller. Then I'll try to come up with an all band RX-AMP at the same time in the 'Cube and then the Cube will be a 20 mW (unfiltered) receiver/exciter. The filter and band switching on TX will happen in the other box. On RX, a multiband RX-AMP arrangement will do the band filtering.
The problem with putting 5-10W in that little 16 sq. in box is dissipating 10-30W of heat in it. Not worth messing with IMHO. 20-50 mW out driving a 5W driver makes much more sense.
As for the Microcontroller.. I did a little preliminary work on the ATMega644 (or 644P I've not decided if I need the second UART or not yet) board that will go into the 100W amp:
The green board already has the contrast pot (it works) on it and the power to the LCD. I need to use a different pin out than on past AVR projects because I want to leave the analog inputs alone instead of using them for the LCD. So I haven't wired up the data lines or ported my LCD driver code over to that processor board yet. Should be fairly trivial to do.
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