Another addition to my uBITX project is a variable audio bandpass filter that I built from a constructional article by Eric GW8LJJ (Practical Wireless, May 2018).
The uBITX is a wonderful all band transceiver, but it has no filtering like the popular DNR, DNF and DBF filters that are found in commercial transceivers. To get around this a simple audio low pass and high pass filter connected in the audio output would make a big difference in reducing noise and separating CW stations on the bands. This design uses a very effective variable ‘brick wall filter’ The low pass filter is very sharp which is variable between 200Hz – 4Mhz.
On the back is a power socket, audio input / audio output and speaker connections. At the front is power, high pass filter and low pass filter controls.
Results with the uBITX are excellent, I can now filter out most of the background noise and separate stations, particularly CW stations, easily and effectively by adjusting the brick wall LPF. The HPF is less effective, but this only works between 40Hz – 200Hz, which is designed to filter out hums and other low frequency noise.
I decided to build the filter in an external box so that I can use it with other receivers, but this could easily be integrated into a uBITX itself.
I am really enjoying this renovation bug! I have already renovated two of my favourite receivers from the past, the HRO receiver and R1155 receiver. Both are working well and I am quite proud to have these old classics back to life again. My next project takes me back to 1971 when I bought a Hallicrafters SX24 receiver to replace my old R109A receiver. The Hallicrafters covered 1.8 – 30Mhz, my first all receiver. I kept this receiver until 1980 when I gave it away to a friend. I had moved on to buying a Yaesu FT101E at that time.
The Hallicrafters SX24 receiver in my shack in 1978
The Hallicrafters SX24 was a great receiver at the time and I always regretted getting rid of it. I wondered if I could get hold of one these again and renovate it like the one that I had before. Unfortunately, SX24 receivers are few and far between, I never see them on eBay apart from some in America. When I mentioned on Facebook that I was after getting hold of a Hallicrafters receiver, I was offered a Hallicrafters S20R receiver that needed some TLC and renovation. As the S20R is very similar to the SX24 apart from the S Meter and crystal filter and the circuit is virtually the same, I took the challenge.
The Hallicrafters S20R receiver before renovation.
The S20R receiver is working, but needs a lot of work, particularly changing all the capacitors and resistors underneath, this is something that I did with the SX24 many years ago, so I am quite familiar with the circuit and workings of this receiver. The dials on the S20R are very yellow with age and the Perspex windows are warped. All the switches are original and made from wood and need replacing. The chassis is mucky with some rust, but just needs a good cleaning with wire wool or emery cloth. The speaker is original and the cone has been repaired a few times, but it still works after 80 years!
The Hallicrafters S20R stripped down.
I remember spending a lot of time under the chassis of the SX24, I almost know by heart what all the trimmers do in the RF unit, alignment was fairly straight forward. I also remember that the mains transformer burned up one Sunday afternoon and had to be replaced. There were no fuses fitted then, with the S20R I will make sure that fuses are fitted.
I started to replace the components step by step. First replacing the smoothing capacitors and then moving on to different sections of the circuit. I tested the receiver after replacing each section so that I had not made any mistakes.
Underside and above after renovation. The old bulbs have been replaced with banks of LEDs, this makes the dials much brighter than the bulbs.
The case needed some TLC, I managed to mix some enamel model paint to match the colour of the case and touch up the scratches and parts where the paint had worn away. I used T-Cut Turtle Wax to renovate the colour and gloss of the paintwork without removing the decals on the front panel. I also made a decision to change the colour scheme of the Hallicrafters S20R to look like my SX24 by painting the main dial and speaker grill black. I also added a black fabric speaker fret on the front of the speaker. I replaced the dial windows with acetate that I designed on the computer to be identical to the originals. Unfortunately, apart from cleaning I could not do very much with the discoloured yellow dials, but they look much better with the clear acetate windows. I will add the aluminium side trims later, these will be painted black to match the rest of the case.
The renovated Hallicrafters S20R receiver with an external S Meter fitted. This looks and feels very much like my old Hallicrafters SX24 receiver!
The uBITX is an all band HF Transceiver kit made in India. It will produce about 12 watts output on the lower bands and drops off a bit on the higher bands.
I bought the uBITX Transceiver kit back in May, but until now I have not had time to build it up. I also bought a ready made case for the transceiver to make it easier build without having to find a suitable enclosure and drill all the holes.
The main board comes already built up and tested. It comes with a digital display and all controlled by an Arduino (called a Raduino) this can be updated by changing the firmware. Updating the firmware is quite straightforward once you have found the latest software. There is an immense amount of information on the internet about the uBITX, so before building I started my learning curve by finding the relevant information. I then saved links to it all the important things on my computer.
A word of warning…don’t be put off by the amount of information out there as a becomes very confusing and turns into a jungle. Just take one step at a time!
I started by building the small PCB that comes with the case, this houses the front panel sockets. (PTT Mic, Phones and Key) It is important that you follow the instructions as you have to add a 4.7k resistor on the board to make it work. I decided to solder in the connecting leads as this seemed the easiest method.
Next, I mounted the PCB to the front panel and screwed the main board into the case. There is another small PCB (again, this came with the case) that fits on the rear panel. This is for extra Jack connections, USB and Digital.
Finally, I wired up the supply, switch and fuse. An SO239 connector provides the aerial.
After completing the building I tested the receiver which works very well on all bands. I did need to set up the BFO frequency to make sure that USB and LSB sounded correct. This is explained in the instructions. The receiver is very sensitive and quiet as it does not need an RF Amp stage.
To test the transmitter, I used a dummy load and measured the output. I was getting 12 watts on 40m and 80m with a CW output, on 15m and 10m the output had dropped to about 5 watts. When I used SSB I found that the audio was a little low for my voice with the CB type microphone that I was using. There is no gain control on the board, so I built a small microphone amplifier with a gain control. This solved the problem.
The uBITX works fine at it’s basic level, now its time to start adding on to the basic uBITX. The first involves updating the firmware to make the transverter more user friendly, it gives more functions on the display. The firmware is supplied by KD8CEC and instructions are provided on his website http://www.hamskey.com.
One major problem with the uBITX is the lack of AGC. As there is no RF Stage it is difficult to add a normal AGC circuit. After doing some more research I found several circuits that had been tried with the UBITX, most of them audio derived AGC. I found a nice simple circuit by VK3YE that was quite novel, it samples the audio input from the volume control and drives an LED. The light from the LED is used to operate an LDR (Light Dependent Resistor) which is strapped across the volume control. It is very simple, but very effective. The sensitivity of the AGC can be adjusted. I built a printed circuit board for the circuit and can switch the AGC in and out by having a push / pull switch on the volume control.
Now we have the AGC working I next looked at the S Meter. There is provision for an S Meter on the display, but first you have to build a small circuit and update the Firmware. Again, I found a simple, but effective add-on circuit. You can find all the details here: http://www.hamskey.com/2018/06/creating-simple-s-meter-sensor-for.html
Finally, I added a very simple RF sensor to drive an LED on the front panel.
The uBITX with added S Meter circuit (black tape) AGC circuit, Mic Amp and RF sensor (bottom right)
I am really impressed with this little transceiver, it forms the basis of something much bigger by adding a NEXTION Display and a linear amplifier to give more output on the HF bands. The uBITX can also be CAT Controlled and ideal for use with FT8 and other digital modes.
Latest News on the uBITX project:
My next step with the project was to add a Nextion Display. I ordered a 2.8″ Enhanced Nextion Display from ebay, which is a genuine English version. It cost a bit more than the Chinese version, and came from a UK supplier. I was a little bit apprehensive about starting this modification as it involves updating the firmware again as well as adding the software for the Nextion itself. However, this turned out to be quite easy once you get your head around downloading the latest versions of the software. You need a micro SD card for the Nextion Software, which you plug into the card holder. There is only 4 simple connections to replace the original LCD display. I followed the instructions carefully and switched on the uBITX.
Wow! What an improvement…the uBITX is starting to look more like an Icom 7300!
This is definitely a ‘must do’ modification for the uBITX, the touch screen is easy to use and it is great to have a full colour screen. All the instructions needed for the modification can be found here: http://www.hamskey.com/2018/06/ubitx-with-nextion-lcd-cec-firmware.html
My Autumn project this year has been the renovation of an old HRO receiver that I picked up on ebay. This is another receiver that I have always wanted to have. Many years ago when I was still at school I was given one, along with power supply and coils. I carried it home with my friend on the bus all the way from Bury. I never got to use the receiver because I gave it to my friend as he didn’t have a receiver of his own.
Now I have one of my own with a full set of coils to renovate and have pride of place in my shack.
The HRO and coils were in a poor state having been stored for many years, covered in rust and full of dead spiders! However, the inside and underneath was untouched and in its original state. Ideal for a renovation project.
I didn’t even think about powering up this baby yet, first some cosmetic work was needed, it needed a good cleaning and some of the rust removed. I removed the case and front panel and set about cleaning with a wire brush and metal polish. Taking the covers off the valves were quite tricky as they are a tight fit and it is tempting to twist the cover which would also twist the class on the valve causing the glass to separate from the base. This had already happened with one valve in the past.
After a good clean I decided to paint the chassis and cover up the rust patches. I have lots of small tins of Humbrol model paint that I use for model making and realised that the HRO chassis colour is actually Pru-Blue and I have that colour. Painting needed a lot of patience with a small paint brush, but the results are amazing, I am very pleased with the results.
The next step involves a rebuild under the chassis by replacing all the wax capacitors and old resistors. I managed to get all the capacitors (10n and 100n, 650v) on ebay and got all the 2 watt resistors from Modern Radio in Bolton. Identifying all the components was fairly straightforward from the original HRO manual, to make things easier I took photos of the underside of the chassis and labelled all the components. Rebuilding was an enjoyable experience, I had to call on my soldering skills to change all the components while keeping everything neat.
The layout and wiring of the HRO receiver is easy to follow and everything is done logically. A pleasure to work on!
At the same time I also worked on the plug in coil units. They need stripping right down and cleaning, some were in a poor state. After cleaning the coil units the paint work needed some renovating. At first I was going to re-paint the fronts of the units, but I found an easy way, I used a cheap permanent marker pen. This really worked well! The graphs on the front of the coil units needed a bit of TLC, they were originally covered by Perspex, but had all perished. As I removed the metal frames I had to be careful not to disturb the paper graphs. Some were stuck to the metalwork, so I had to carefully peel them off without ripping them. I managed to find copies of the graphs on the internet, so I printed off the bandspread graphs to put in the second metal frames.
The coil units came in the original HRO wooden storage rack, after cleaning I painted it black with matt spray paint.
Now the moment of truth…will it work?
I had not built a power supply yet, but I already had a Codar AT5 power supply that I built previously which should be fine to power up the HRO.
At switch-on the filaments glowed nicely and after warm up a loud hum started to appear from the speaker, but nothing else. This is where I had to call my fault finding skills.
I managed to trace the fault down to the 6B7 Detector/AGC/Audio Valve. After a hunt on eBay I found a new valve cheap and ordered it. When it arrived I changed the valve and switched on.
All the controls were working fine, but there was a problem with the S Meter. To solve that problem I found an old article in Short Wave Magazine which suggested a modification. I carried this out and the S Meter worked fine. The original S meter had a horrible yellow face and the numbers had worn off, so I made a new one.
Finally, it was time paint the case and front panel then build a power supply for the HRO. I needed a suitable Mains Transformer, Smoothing Choke and Smoothing Capacitor. First of all I measured the current being drawn from the AT5 power supply, this was about 50ma. So I searched on ebay to find something suitable. I managed to get all the components at a reasonable price. I also needed a case for the PSU. On a visit to the rally at Rochdale I found an old CB PSU which was an ideal size. I stripped it down, gave it a coat of black paint and began building the HRO PSU into the case.
This has been a wonderful project, I now have a fully working HRO Receiver and set of coils that has pride of place in my shack!
A very useful addition for the HRO is a frequency counter. The HRO frequency readout on the dial together with the coil graphs are somewhat inaccurate. An external digital readout would be ideal. Frequency counters complete with IF offsets can be found very cheap from China on e Bay. I sent for a nice large, blue 60Mhz counter and mounted it into a project box.
Received a nice award certificate today to celebrate receiving SSTV signals from the International Space Station on 29th October 2018. Managed to receive two images on the same pass at 10.28am using my colinear and Yaesu FT857D on 145.800Mhz.
Here are the two images received using MMSSTV Software to decode.
Just completed building a G7FEK antenna. Seems to work fine after a little bit of tweeking of the two counterpoise / radials.(Used 65ft and 33ft) Now have good SWR on both 80m and 40m without a tuner. I am now comparing signals on 80m and 40m with the random Longwire that I already have up. Listening on 80m and 40m tonight with the G7FEK. First contact with FT8 on 80m was TF3GB in Iceland (was only just detectable on the Longwire) Went on 40m and was amazed at the number of stations across the Atlantic in both North and South America. Have not managed to work any yet because I am only running low power at the moment. Switching between the G7FEK and Longwire I can’t even detect any stations Trans-Atlantic stations. It’s working well.
I have now added a loading coil for 160m Topband and it is working well. I built the loading coil of 30 turns on 4 inch pipe with taps so that I could find the best setting for low SWR. The SWR peaks at 1.9Mhz with 16 turns. I have found that the G7FEK works best for local groundwave contacts on 160m, gives about 2 S points more on receive when compared to my existing longwire. The longwire seems better with more distant stations. Not sure about DX stations yet.
Yesterday afternoon I listened to an interesting conversation about Morse on the Bolton Wireless Club Network Radio.
It made me think about how I learned Morse Code. I was taught by George (Geo) G3ZQS back in 1970. He produced some tutorial ‘tapes’ that you could learn to read the morse alphabet from scratch. George’s method was to group letters together, the first ones that I learned were A, W and J (di dah, di dah dah, di dah dah dah)
The tape would introduce the letters, then send them mixed up so that you could recognise them. After that you move to the set of letters in this case N, D, B
(dah dit, dah di dit, dah di di dit)
Again on the tape, learn the letters then listen to them mixed up.
The next step was to try to receive both groups of letters together before learning the next group (Which I think was E, I, S and H)
George always emphasised that we listen to the rhythm and not the dots and dashes. Some letters you can remember from the rhythm like Q (dah, dah, di, dah God Save the Queen) and F (di, di dah dit Filling Station)
I found this method very effective (for me) You just take your time and if you want to, try to practice sending the letters that you have learned.
Sadly George is now silent key, but he founded FISTS which promotes the use of CW throughout the world.
I have been trying to trace one of his tapes, but without success. It would be great to get hold of a copy to maybe produce a digital version.
Many of these tapes were in circulation around the Bolton and Blackburn areas back in the 1970’s.