Re: Tell me your favorite uBitx mods

Diver Martin <diver.martin@...>

So, this is roughly what I'm thinking for the layout thus far.  Here's what you're seeing thus far:  uBitx is underneath the PCB on .5" standoffs (Supplied with the uBitx kit).  The uBitx itself is 1/4" away from the bottom** of the case.  PCB mounts on top.  Upper left:  Power input, 2x (one for 8V+, other for 12V or PA power, default is to just use the 8V+ line, a relay can change the PA power).   Going counter-clockwise, 5V regulator (I'm going to move that to the lower side of the PCB and use the .1" header from the raduino instead, so that +5V doesn't cross under the RF path), BNC RF output, DSP audio output, Teensy 3.2 control module (Due to higher power MCU w/ dsp capability), Key jack, PTT jack.  There's plenty of room for an AGC mod, the raduino header, and the audio connector.  Right side, the vendor I use for PCB's has options of 15cm x 20cm, so I made use of the extra space on the right to create a 'front panel' pcb.  So Mic and headphones on the front (blue comment layer circles show where the audio jacks would pop out), and one would break off the additional PCB that contains a variable pot for audio gain, encoder (reused from uBitx kit), some pushbuttons (for whatever function you want), and then the HD44780 display shipped with the raduino.  Two headers so that it can be mounted upside down or however you wish. 

**(or top of case) I did this because some people might want the display on the right side of the unit, others on the left, and this can be easily achieved by simply flipping the entire thing upside down in the enclosure.  I'm not sure if the HD44780 can be flipped upside down (I can't see why not), but just in case, footprints are free, would be up to the user to decide where it gets soldered in.  There's a 595 shift register for the display as well.  One thing not shown yet are the connections for right angle .1" headers that would connect the front panel to the main board, easy enough to add later, just haven't done it yet.  

Going back along the top, SWR Bridge components, and the lions share of space for the tuner, and a cutout notch for the uBitx heatsinks.

As you can see, plenty of room on the system for mods.  Just... harder to get front panel space :)

So, full list of features:
AGC(Pending design, feedback is good! - include S-meter)
Fast MCU w/ USB back panel access [cat control]
Dual power supplies for TX pwr
DSP audio output
Keying interface
Pushbuttons for the front panel
SWR Bridge
Linear control (Pending, Just a cheap reed relay hooked up to the PTT line basically)

I haven't even thought too much about how much it'd cost to make,  Probably a significant amount :)  I'm putting single-unit costs in my components in the schematic, so that I can take a guess at just the raw BoM cost eventually, but all in due time.

On Mon, Jan 1, 2018 at 5:03 PM, Diver Martin <diver.martin@...> wrote:
So looking at the schematic, it's basically an IF amp (MC1350P, which is obsolete/harder to get, though I have gotten them from Jameco before) with a dual gate mosfet as the attenuation stage.  The rest is just a separate amplifier (Q504-509) and a detector diode (D502) feeding that gate.

What I would ultimately want to do I think is provide one input, and one out on the add-on PCB that I'm doing, and maybe cut at Q30 on the uBitx to get the RF input.  To do the mod, one would cut the trace as indicated, and then solder in some 30ga wire that goes up to the motherboard, which provides the modification.  I'm thinking Q30 is probably the best place to put the AGC, as after the 12Mhz narrow filter, there is no other amplifier, so I'm kinda limited to the 12kHz bandwidth filter to do the AGC I think.

On Mon, Jan 1, 2018 at 2:29 AM, Dave Bottom <ars.kd6az@...> wrote:

The Heathkit SB-104/A/HW-104 has an uderly simple AGC system that works so well it was easily the easiest rig to just sit and read the mail.  Round tables with so many different strength signals and it was so pleasant to listen to.  Just a dual insulated gate FET ahead of the IF Gain and there are 8 transistors in the AGC Amplifier, Fast/Slow AGC and S-Meter output.

Schematic attached of SB-104A.


I actually had a couple of pre-amps for a hi fi project, but used for this Kit 98, works, but there are simpler circuits.

Dave WI6R

On Mon, Jan 1, 2018 at 1:27 AM, Diver Martin <diver.martin@...> wrote:

I agree with many of your points, very specifically, the AGC.  I tried listening in with my uBitx once I got the case wired up, and then promptly had my ears blown off by a nearby static pop or something.  I haven't listened to it since, and won't until I get some form of AGC, hopefully RF-derived... I am very touchy about my hearing, as it's sensitive and you only get one set of years (I wore earplugs all new years this year... hope yours was quieter).  I need to figure out the proper AGC scheme that is best, it should be reasonably easy to do.

Down the line, but a quick note:  Panel space is the biggest premium I'm dealing with. The display alone takes up 3.2" of front panel space.  Either one has to create a mezzanine board to 'stack' buttons/encoders/etc vertically, or you start going to the back panel, the side panels, etc.

1) Already covered above
2) Already in my schematic (I use a BY-1)
3) Already in my schematic
4) S-meter would have to be derived from the AGC, but I see no reason it couldn't be.  I've added in an analog pin.
4b) I have one 'undefined' front panel button.  I'd like to have more if possible... I might add in an extra MCP23S17 to expand my IO's...  (I'm nearly full on the leonardo)
5) Not sure how to implement this one, but if you've got a rough schematic to point me to of your modifications, I can probably include it.  Depends on how the wires would need to go to the PCB below, or if it's something that can just be put inline with the microphone.  Could do a microphone amplifier I suppose...  This is probably the lowest priority out of the things listed for me.
6) It's easy enough to pipe the TX line out to a relay.  I'll consider it based on panel space.
7) Yep, already in the schematic.  For now I'll probably stick to linear / non-phase detector method, but it probably wouldn't be hard to modify for a phase detector.  Just would need to focus on how to do it on the cheap instead of using an AD8307 or 8302 (Which are like $10-25 at digikey).

On Mon, Jan 1, 2018 at 1:15 AM, Dave Bottom <ars.kd6az@...> wrote:
Hi Martin,

 A Second Story is a neat idea that could eliminate wiring with a suitable case that can take advantage of PCB mounted connectors.
Here's my wish list...

1) Well the top of my list is a really effective AGC.  This is what separates a really great rig from a really good rig.
The basic MicroBITX so reminds me of my SBE SB-33 (1966 - mobile rig) it is the audio derived AGC. 
Back in the day Collins S-Line had great (but complex) AGC that worked(s) great, but..
Nearly every Heathkit SSB rig back in the day had great AGC whether it was a tube HW-12 or a solid state HW-104.
Check out the HW-104 AGC system...

2) Solid CW Keying and for a paddle

3) USB interface to rear panel -  One big reason for this kit is to become proficient working with software.

4) Well if those are done an S-Meter is nice.

Nice to have:
4) Momentary button to toggle between VFO A and VFO B.  If you work split this is really necessary (Yes, I chase DX on QRP)

5) Mic Pre-Amp and Mic Gain -  I added this tonight with the PCB temporarily stuck on the rear panel (all my jacks are on the rear panel out of the way of knobs. 
It helps a little so I don't feel like I have to climb in the Mic, however a Speech Compressor might be more worthwhile.  Being able to use typical Electret Condenser Mics (e.g. ICOM radios) it needs more gain and an adjustment even if a PCB mounted internally accessible set and forget pot.

6) Keying interface for a Linear.  Band data and keying - This baby will drive an RF-KIT 2K+ LDMOS linear to legal limit. (when life is too short for QRP)

When you have nothing better to do:
7) VSWR Bridge with Display for forward/reflected power.  The tuner gets a lot simpler and an external tuner may not need power (manual tuner).

Oh, wait, didn't you do that one already?  LOL

Dave WI6R

On Sun, Dec 31, 2017 at 6:29 PM, Diver Martin <diver.martin@...> wrote:
Hello all,

As I'm doing a motherboard mod, I'm looking to incorporate a bunch of mods into one PCB.  Right now, what I've got going are the following:

* A tuner + SWR Bridge (phase detector maybe?)
* A spot for an RTL-SDR (blogV3) dongle
* AGC Modifications
* Integrating LCD and headphone/mic/BNC/Power/etc jacks into the PCB

Other things I've thought about, space depending:

*Adding in footprints for a chinese AD9850 DDS module for one of the clock signals

I would like to hear the top mods you've done, and what you'd love to see integrated into a motherboard PCB that fits on top of the uBitx.  Battery charger?  Battery adapter? I dunno, bring it on!  If you have a favorite AGC mod, please tell me about it, and make some suggestions as well.  This is not promising to be a cheap kit, and full of SMT, but something I might make available.

Happy new year,

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

73 Dave WI6R

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

73 Dave WI6R

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

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