Re: experience with Sunil VU3SUA's enclosures #ubitx

Dave New

I just completed the basic build last night, and i have some observations:

1) I was slow to realize that in spite of the pictures, that the main board must fit OVER the front panel PCB, so that you can mount the LCD display up close to the front panel.  This became an issue for me because I put vertical male pins on the ends of the front panel PCB, which meant that there was insufficient clearance.

So, if you want to put male pins on the front panel PCB, you should use the right-angle ones (and then the mic connector will be a tight fit against the chassis mount four-pin mic connector, but I was able to just make it work).

I ordered a Dupont kit of male pins, female sockets and housings from Amazon and a suitable crimp tool:

The crimp tool works fine, but I spoiled a few female sockets before I got the hang of it.

If you are crimping female sockets on the ends of the original wires that come from the Relimate sockets on the ubbitx (trim them to 8 inches first, then you can use the extra for other wiring, see below), then it seems the wire gauge is about 22, but the crimp die in the center of the tool that is marked for 22 ga is too large and won't crimp the wire properly.  I ended up using the crimp position for the smallest wire size, and it worked fine.

It is also important to insert the female socket in the tool first (I found that by clicking the tool 3 clicks it closed the jaws just enough to make it easy for me guide the socket into the tool), then push the female socket in far enough so that the box that encloses the male pin is completely outside the dies on the back side of the tool.

Then lightly pressing the handles to keep everything in place, insert the stripped wire into the back of the female socket, and crimp.

The wire should be stripped only about an 1/8" of an inch, and the insulation should be inserted into the back of the female socket such that the bare wire bundle is crimped with the smaller crimps, and the insulation is held by the larger diameter crimp at the back end of the female socket.  If you strip off to much insulation, you will either fail to get the insulation into the back crimp, or you will force wire into the female socket area, and that will interfere with the male pin when it is inserted.  If you've done everything correctly, tugging on the wire shouldn't make it come out, it will seat correctly on a male pin, and you should not have to resort to soldering anything.

Soldering crimp joints is a BAD idea, not only because the clearance in the female connector bodies is very close, but the solder that wicks into the wire bundle will stiffen the wires past the crimp, and create a stress point that will eventually break the wire if subjected to vibration and movement.

So I ended up using Dupont housings/connectors on the Audio, Digital (both 8 pin), Mic (three pin), Volume (three pin), encoder (4 pin) and speaker connectors (2 pin).  When you cut the ubitx supplied analog and digital wire bundles to the recommended 8 inches, you end up with enough left over that you can make all the other front panel connections with using the left over wire.  You can even select the appropriate colors, as documented in the wiring instructions on the hfsignals site.

2) I completely missed that there was a small PCB board included for the encoder switch.  I ended up tack-soldering the ends of the four-wire bundle coming from the front panel PCB to the actual switch pins.  It works fine, but I plan to re-do that using the supplied PCB at some point.

3) I somehow got the wiring backward on the volume control (hi end vs. low end), and was "surprised" by a VERY loud noise when I first powered it up.  If you mount the control with the soldering tabs on top so you are viewing them directly when looking down at the rig with the top off, then the correct colors from left-to-right (with the front panel closest to you) is yellow, orange, green (given the wiring colors shown in the wiring section on the hfsignals site).

3) The power supply wiring was an issue, due to the power on/off push-push switch.

It is NOT meant for soldering, as the tabs are practically impossible to solder to (don't know the material, but it does NOT accept solder), and the body melts in an instant.  The tabs are meant to be used with push-on tab crimp connectors (I found suitable ones at the local auto store in the electrical section).

I still wanted to use the PCB board, so I ended up inserting the power switch tabs through the board, pushing the auto tab crimp connectors on, and then tack-soldering the crimp connectors to the board.  Ugly, but effective.

Before I figured that out, though, I had partially melted and loosened one of the power switch tabs, so at the moment, I'm plugging/unplugging the DC power cable, rather than exercising the switch.  I intend to find a better switch that can actually be soldered to, or failing that, going back to the original volume control with integral switch that was supplied with the ubitx.

The rest of the power PCB board wiring went OK.  I put a three pin header and connector on the end of the board going to the ubitx supply wiring.  I ended up originally using a right angle male header, but discovered that interferes with the mounting bracket (and likely the board when installed) for the digital interface PCB.  So I ended up bending the pins up from the board at a 45 degree angle.  Ugly, but effective.

Check the actual wiring of the DC power plug.  The diagram supplied with the enclosure kit shows using a pin for ground that I found was a no-connect.  The other unused pin turned out to be ground (the sleeve on the DC plug).  Double-check your wiring in this area with a VOM to ensure that 1) You have continuity where you expect it from power supply to ubitx board, and 2) You haven't inadvertently reversed anything or shorted anything out.  Don't forget the chassis ground to the solder tab that comes with the SO-239 socket.

3) I used the supplied antenna 2 pin connector and wiring that was supplied with the ubitx, but it was not possible to keep it only 2 inches long in this enclosure.  It's more like 4+ inches.  I plant to revisit this with a short piece of RG-174, instead, to lessen any possible pickup of birdies, which so far seem to be minimal.

4) I haven't done any of the digital interface for the back panel, yet, nor the front panel RX/TX LED.

I wanted to get the basic radio done for the Detroit Make Faire, which is this weekend.  We have three clubs doing a joint showing of amateur radio as the ultimate DIY hobby.  We plan to have three stations running, one SSB, one CW/digital (FT8?) and one QRP, with a rotating set of QRP homebrew rigs to show.  We will use the special event callsign N8M (for Maker Faire) again this year.  We are listed in the Julyl QST in the special event station listing (the last one).  Give us a call and get a nice QSL card with Detroit Make Faire images on it.

Initial checkout of the rig went fine, aside from discovering I had reversed the wiring on the volume control which was easily corrected.  I haven't touched any of the calibration (for one thing some of it requires using PTT to complete, and I haven't wired a mic up, yet), but it seems that everything is pretty spot on from the 'factory'.

The displayed frequency on my unit seems about 100-150 Hz high, but the BFO seemed properly centered in the passband, and I was able to get 5 watts out on 40 meters on CW.  I'm still trying to figure out if it makes any difference if I'm in USB or LSB mode when operating CW.  In either case, it seems that the CW signal is not exactly where I would expect it (listening on my calibrated Elecraft K3s), so I'm unsure if I might have to use RIT to transceive correctly on CW.

If I have any time tonight while I'm packing everything up for the Maker Faire, I'll see if I can come up with a quick interface for the mic.  I have an Elecraft condenser KX2 mic, but it has a four-pin plug on it (it has up and down buttons on the mic), so I'd need to adapt the wiring somehow.  I also have a K3 electret hand mic, which has a round 8-pin connector on it.  Maybe that will be easier to adapt?  I almost never use that mic on my K3s, preferring to use my Heil headset, instead.

I hope all this helps those that are trying to use Sunil's enclosure kit.


-- Dave, N8SBE

-------- Original Message --------
Subject: Re: [BITX20] experience with Sunil VU3SUA's enclosures #ubitx
From: "Eddie Esserman" <ee@...>
Date: Thu, July 26, 2018 7:58 pm

Thanks, Sherman, that's a good idea, and will at least help ID some of where the parts go.  Sunil is great, and when he has a break, he said he plans a manual.  It did come with four pages and a packing list.  The package is quite impressive and a great value.

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