Are any µBITx constructors planning to be in Dayton for the 2019 Hamvention? If so, this is your chance to meet the designer of the µBITx, Ashhar Farhan VU2ESE.
It is suggest that you meet him over dinner and coffee on the Thursday 16 May. Meet up outside the Holiday Inn at 7 pm.
Ashhar is bringing with him a new project that combines an SNA and SWR meter and another one that is ‘something about a raspberry’.
Hans Summers G0UPL of QRP Labs fame will also be at Dayton Hamvention. Hans says, “I will be arriving late Tuesday night. Staying in the Holiday Inn. Will look forward to catching up with you and any other BITXers or QRP Labbers!FYI I will also have with me stock of most of QRP Labs product line, which will be available at vendors’ evening on Thursday, and throughout the hamvention on Friday/Saturday/Sunday at the QRP Labs booth 6612.”
Jack W8TEE, a keen µBITx builder and co-designer of the JackAl board, is giving a presentation at FDIM (in advance of Dayton Hamvention) this year on his new Morse Tutor project. He will no doubt publish his arduino code and schematic after the talk on 16th May 2019.
He has, however, given us his Bill of Materials so that those wanted to get a jump on ordering parts could do so.
Dan MW0UZO has an interesting story to tell about building a µBITx on his website.
And a matching speaker to go with it.
Daniel Conklin says “I guess I’ve had enough fun with this radio and now it’s time to move on.”
He is selling his UBITX v3 which is built into an Apache case. It might inspire others to build their rigs into these clamshell like cases.
There is space for the mic and a battery pack to sit when the case is closed. The mic and PTT switch are mounted in an old BaoFeng mic housing and it works well.
Finding a case for your µBITx is easy … finding a good case is more tricky. Many use one of the many µBITx cases sold by Sunil. Others have their own favourites
Two new suggestions from Jack KZ5A are worthy of a second look.
The Cheval case illustrated below can be obtained in both steel and aluminium versions (we would strongly recommend the aluminium version). This case will have to be imported from Thailand. It is also available on eBay. It is a very nice looking enclosure, reminiscent of Heathkit enclosures from the 1970s.
The Circuit Specialists aluminium instrument enclosure is a not quite as good looking enclosure, but at a very good price ($US21 excl shipping).
Mike ZL1AXG purchased several aluminium cases from aliexpress.com that are intended to house stereo amplifiers. This particular model (Breeze 2207) is 228mm x 70mm x 215mm. A good size for incorporating a few additional circuit boards alongside the µBITx main board. These cases are precision made and look really nice. They can be acquired for around US$15 each (plus shipping – that will be more than the cost of the enclosure). Mike has yet to transplant his µBITx into the new case.
Derek G4VWI has used a sub-miniature MIL spec rotary switch to switch between common, off/slow/fast as per the ND6T wiring diagram for the Kit Projects board.
A screened pre-made wiring loom helps ensure the exposed sections are kept nice and short. Derek suggests choosing good quality connecting wire and pre-soldering the pads before tacking on the leads for best results. He believes that this is by far the easiest AGC board design to fit.
Pop VU2POP has added a LiPo battery inside his µBITx case as illustrated above. He says “I installed a homebrew 3S2P li-ion battery pack into my ubitx cabinet. I had planned my cabinet for the right space & fit. Now I can carry my ubitx for outdoor action!”.
This must be the best calibration guide yet from Steve N3SB. Thanks to MVS Sarma for bringing it to our attention.
Ashhar Farhan VU2ESE observes that ALC is just one way of controlling output power from a linear amplifier stage and that an easier approach is to do it in software.
This needs software that can control the ‘mic volume’. You could set the value differently for each band. There is another pay-off with software mic gain, it can make a major difference to the transmit IMD. At voice peaks, the tx linear chain compresses. The gain is not constant between low and high levels of modulation. This is the cause of in-channel IMD. Now, if we have a look up table that amplifies the peaks more than the lows, we can ‘correct’ the gain back to being linear. This simple concept goes by the name of ‘pre-distortion’ in the SDR world.