This is the post excerpt.
Okay if anyone has been by here, its obvious I have no clue yet what I am doing. I have a bunch of projects to document, and some projects to mend, and ideas for more projects. If I spend to much time here — well then that is less time for the projects. Here I am at my main operating position, with my K2 that gets the most use. Other rigs are nearby and will be shown one of these days.
The fascination in seeing how far our signal can go is part of the ham radio experience. WSPR is a way to do it with low power and little effort from the operator.
I discovered and built the Ultimate 3S from QRP Labs. I obtained the full combination including a multi-band switched relay board for its low pass filters, GPS and enclosure. Not too many days later the main kit arrived from the far east, and the enclosure not too many days afterwards.
The main board includes the microcontroller and a BS170 power amplifier, and not much else. A daughter board is a synthesizer that can operate from LF to VHF. A single low pass filter plugs into the main board. The kit can be used in this fashion, or the relay board can be added to permit easy band selection – and even setting the unit to transmit in sequence on multiple bands.
Connected to my WM-2 power meter – the U3S is outputting 300 mW on the lower bands, around 200 mW on 30 and 20 meters, and 100 mW on 10 meters. How far can this thing reach? Europe is routinely reached before dusk on 30 meters, and around dusk and after on 40 meters. One morning it reached Australia on 30 meters – and this is in mid-summer! It should do even better in the fall and winter. My judgment is that this is enough power for WSPR where one has a reasonably effective antenna (here I am using verticals on 80 to 30 meters). More power results in more QRM to other users of the spectrum and seems unnecessary. I may consider an amplifier for 160 meters knowing the inefficiency of my short vertical.
Few issues in the build – the modular construction with boards that plug together works nicely. Conquering the instructions to use the device – well more careful reading is required than my initial readings. I needed just a little help from the QRP Labs Reflector https://groups.io/g/QRPLabs — including getting some needed tips from other messages there. I may post some tips in a follow-up entry someday here. Once programmed, easy to select the operating band(s).
On the GPS – very cool. Without it, the time must be manually synchronized to within +/- about 1 second of the world’s atomic clocks. It can be done …. but plug in the GPS -and each time it is powered it takes just a minute or two to set the clock. The GPS module is made to use remote from the U3S case – mine sits on desktop near a downstairs window – it works wonderfully. Cool to see your latitude and longitude, along with the time, displayed when the GPS synchronizes the U3S. The white raised object on the board is the patch antenna to receive GPS – the electronics are on the lower surface (along with 3 LED indicators I mounted on the wrong side – no worry I can see their flash – and the U3S display itself tells me when the GPS is locked on.
This view also shows the construction – the LCD in the front, above this the main board (a single toroid can be seen which is the transformer at the output of the PA. The synthesizer is to the left and a low pass filter (this one is 30m) on the right. Finally the relay board with 4 of the 5 LPF filter slots occupied. The two push buttons are for commanding the U3S. At the other end the DB9 is to interface with the GPS, and the DC power connector (5 volts) and BNC RF output. The well-crafted case has space for expansion.
That old receiver I had used many years ago as a novice needed some air time with a transmitter again !
Several parallel thoughts came together for this venture. There was the interest to quickly build something home brew. My original ham band receiver sits here not used in a QSO in 4 decades. This board I once constructed to mate a QRP rig with a receiver into a QSK-worthy combination has been sitting unused. Then there was the interest in building a transmitter with a HEXFET final. Finally, a strange interest in using crystals again to perform oscillation.
The parts had long been gathered, and I ran across a recent design by N5IB that he describes as a tuna tin transmitter line-up followed by a HEXFET stage. I started the build Manhattan style, but before I was done some ugly-construction technique mounting the parts direct on the ground plane got into the mix. I confess I am less about form than function – if I can follow the circuit arrangement. Lacking the same HEXFET, I found the IRF-510 requires a different bias arrangement with more DC bias on the base. Except for the IRF510 PA all the circuit details come from the N5IB schematic, and the PA details are based upon the NB6M mini-boots amplifier.
A few notes about the receiver. It was purchased by my dad for my first ham station in 1976. No markings by the builder of this HR20 Heathkit but it dates from around 1960, a SSB receiver intended for mobile or home use. I made my early QSOs with it before leaving for college, then it has sat with intermittent use since then. Possibly it has the original tubes. Very stable receiver that features a 3 kHz wide crystal filter – no worry a CALF audio filter (subject for a future post) turns it into an effective CW receiver.
A unique board called the Magic Box designed by K8IQY and kitted by 4 State QRP was used to integrate the Tx and Rx. I had thought this board could integrate ANY solid state QRP transmitter with any receiver. Everything was plugged together – 3 coax cables and 4 audio cables between the gear. Nada. Troubleshooting inside the magic box — a hot part was discovered — a IRF-510 used for keying the transmitter. Long story short – the Magic Box presumes minimal current flow on the keying line. The Tuna Tin exciter has the 13.8 volt supply direct on the key – ouch. Fortunately a PNP keying circuit, a la the K7ZOI Ugly Weekender Tx came to mind – the solution was at hand. A few parts landed to further ruin the Manhattan appearance – but succeeded in making the rig.
In the picture above the HR20 is the prominent Heathkit item in the lower left with the illuminated dial. The Magic Box circuit board sits in the clear box with the cables attached to its front panel. To its right in the black box – with only a red push button featured for spotting the transmit frequency in the receiver – is the home brew transmitter. Those are crystals of various kinds sitting on top of the transmitter. Still lacking any crystal sockets the transmitter uses a pair of alligator clips to engage the crystal. The CALF audio filter sits on top of the HW8 (not used in this episode).
Tried to use the rig before and during the Zombie Sprint. I could not raise anyone. The next day – magic – the ions were arranged to allow 2 nice arm-chair copy QSOs with neighboring states – both getting RST 579 and enjoying some nice CW from the HR20 again.
More to come on adding a second band to the home brew transmitter ….
Its been on my to do list for a while to begin an on-line discussion of my radio building and operating adventures. Its fall so some projects on the bench, in thought for the future, and about time to install the short Beverage antenna across the yard. The gear here is a mix of commercial, kit, vintage and home brew items. Much to catch up on as I will try to document some recent projects also.