The All-band HF Amateur Radio Transceiver: Just waiting to be modified
Accessories for your uBITx
Olivier has connected his uBitx to a homebrew converter (using an NE612) (see schematic attached) and PA0RDT’s mini whip just to see what he could find on the VLF bands.
R N Harp needed a regulated power supply to run his µBitx and a couple of arduino kits, but he didnt feel like shelling out hard cash for a $100+ power supply unit.
Instead, he modified an ATX power supply from a dead PC. He gets 3v, 5v, and 12 volts. Additional parts were already on hand. He also salvaged a bunch of other parts from the dead pc, including a few toroids from another power supply.
A number of constructors have eyed up adding an afterburner to their µBITx. The usual cautions apply: make sure your µBITx has clean output with earlier v3 and v4 boards having been upgraded to remove harmonics and spurs, before even considering adding a power amplifier.
There are a range of cheap Chinese and Russian kits available to give you between 40w and 70w output. However, these may be better avoided, since you can build a WA2EBY power amplifier without a lot of effort. This is a very solid design, and well proven.
Some list members suggested it may be hard to source boards for this amplifier design. However, take a look at:
http://www.golddredgervideo.com/kc0wox/wa2ebyamp/ (pointer to availability of boards) and
http://diycrap.blogspot.com/2016/06/wa2eby-irf510-amplifier.html and
http://kit-projects.com/AMP.en-us.htm
Allison KB1GMX commented:
Its a good design and allows for getting good performance at higher frequencies. Mine with a little effort does 37W on 10M (1.8W drive) and with the same drive at 40M about 55W. 80 and 20 are about 50. Never though to try 15 or 17m but I’d expect about 44w. The 1.8W is because I use an attenuator at the amp input as most of my HB radios do 4W which is excessive power or the amp. FYI I run it at 28V.
It is a good amp. Mine is now 13 years old and still running the same set of IRF510s. I did use a large heatsink (4×8″ with 1″ fins and the base thickness was .300″). Some call it overkill, but with no fan running and with a brick on the key for 10 minutes, the amp doesn’t fail.
At least one of the “70W DIY AMP” I’ve seen did produce that much power for about 1 minute into a dummy load before it blew up. Failure was likely due to self oscillation or overheating of the supplied heatsink. The heatsink was maybe pentium II vintage with mounting points for
a fan and not at all large or having many fins.
https://amateurradiokits.in/product/hf-linear-amp-40-watts/
MVS Sarma also points out that Sunil VU3SUA sells a set of black masked PCBs for the WA2EBY amplifier.
Jack W8TEE, a keen µBITx experimenter shows off his new creation. A dummy load with a screen and microprocessor. What the?
Good for up to 70W for 10 seconds; QRP levels ’til the cows come home.
Cost: About $20.
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.
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!”.
Jim W0EB, TSW Project Coordinator, has announced he has just got the boards and all the kit parts for this little adapter that allows the DC input for your µBITx (or any other kit or homebrew rig) to be protected.
The board allows connections for optional Reverse Polarity (series Schottky diode), a switch on the volume control (or separate power switch) and the switched DC output to whatever item is being powered. This is achieved t through a small PC board using MOLEX or MOLEX Style male/female connectors. Everything can be plugged in and unplugged for ease of troubleshooting without having to solder or unsolder wires from the rig’s terminals.
TSW is making either the bare board or a full kit of parts available. The picture shows everything that’s included in the kit.
Full details are on the TSW website
The manual for the SwitchedPowerAdapter is available in PDF form so you can see what it’s all about.
Kees K5BCQ found this design by Milt Cram, W8NUE. He has adequately tested the design and came up with an excellent “slope and intercept” calibration procedure which should further improve accuracy…
Hans G0UPL who operates QRP-Labs has released his 10W HF Linear Power Amplifier. This kit comfortably produces 10W from a 12V supply. It is a compact design with huge heatsink included, which will not overheat even on continuous 100% duty-cycle operation. The amp provides 26dB gain with +/- 1dB gain flatness from 2 to 30MHz.
This 10W HF Linear Power Amplifier kit has no Surface Mount Components (SMD) to solder. There are a number of small transformers to be wound, and assembly requires care and patience.
The push-pull driver stage uses two BS170 transistors in the amplifier design used in the SoftRock transmitter stage. The final uses two IRF510 transistors in push-pull. Yes, this humble low-cost MOSFET really is capable of excellent performance all the way up to 10m band and beyond! Short lead-lengths and PCB layout are extremely important, they are the key to success.
Features:
As Hans advises on the BITX20 I/O Groups list:
I am not suggesting that this amplifier will solve all problems and without wishing to be offensive, the “garbage in, garbage out” rule always applies – in particular, if you feed it a signal containing spurs, harmonics, or other problems… then you will get the same thing at the other end, just amplified 26dB. It also still applies that all stages leading up to the final amplifier must have flat gain. If the pre-drivers cannot provide a big enough signal then you won’t get full power output.
But, it could be useful or interesting, in the BITX context, to look at the details of this amplifier kit and see the short lead lengths, symmetric PCB and extensively “stitched” groundplanes.
For further information see the product on Hans website.
Tom WB6B wanted to build a new filter for use with the uBITX (to overcome harmonics on his output). However, he didn’t want to build a filter that would be strictly tied to the uBITX.
So he built a standalone Low Pass Filter box that works as an add on filter for the uBITX as well as becoming a general purpose piece of Ham equipment he can use over and over for other needs.
It uses an arduino to measure the frequency you’re transmitting on and select any individual or combination of filters you like. The proposed design uses a set of filters and a relay switch board; such as to ones by QRP Labs. But, the Sketch code should be easy enough to modify for whatever you like.
The controller can show the selected filter with LEDs. Alternatively it can be configured to use an LCD display, which will display the transmit frequency as well.
Tom’s unit is still under construction, but he has built and tested a prototype with a signal generator.
He is releasing the preliminary design now because it is complete enough for people to try out on their own filter designs. It makes using outboard filters really easy, and he thinks people will like it.
Tom welcomes feedback on improvements people make while building their own “Auto Filters” with the controller.
The code for the controller is here: https://github.com/mountaintom/TX_Auto_Filter