I built some kits from QRPme a few years ago, all based on tuna cans. I’ve never managed a QSO using the transmitter so a couple of weeks ago I got the kits out of storage.
I tried for a QSO last week but I discovered that my receiver was receiving a couple of kHz lower than my TX was transmitting; not good!
I negotiated some SOTA time for this evening so thought I would use something different in the way of a rig. I took my tuna tin RX to work with me today and I changed an inductor in the oscillator circuit to bring the receive frequency up a bit. I hit the nail on the head, I am now able to zero beat the TX in the middle of the tuning pot’s range. I am now able to choose whichever side of zero beat that has least QRM.
I took the entire tuna can radio system with me tonight and set it up on Rombalds Moor, G/NP-028. 20m seemed to be in pretty good shape but I found it extremely difficult to score QSO’s.
First in the log and the first ever contact with my ‘SUPER Tuna ]’ was with OM1AX followed a little later by HA5LV. Both contacts were dificult, I was suffering with broadcast interference and QRM was reported by the other stations. I was stuck on one frequency I’m afraid, I really should try to get some crystals for 20m that aren’t on 14.060 MHz, that frequency is too busy.
The tuna RX (Sudden Storm) is a version of the ‘Sudden’ receiver by George Dobbs, G3RJV, it is basically just a 602 mixer chip followed by a 386 amplifier chip - extremely simple.
I was very pleased to actually make a contact with the system and it made the activation a bit different!
After the tuna can fun, I fired up my SW-20+ which is a rig that I intended to use for SOTA until the MTR kit came along and made the SW-20+ redundant. I thought that I’d get quite a few contacts on the SW but it was hard work to find chasers. I managed 6 QSO’s in 40 minutes before it was time to head home.
Picture of tuna can system here (phone camera)-
73, Colin, M0CGH
Later edit -
SUPER Tuna ] transmitter puts out about 200mW on 20m. Different bands available by using plug-in band modules. My rig has the PicoKeyer add on board fitted so I can use a paddle key.
The ‘SUPER Tuna ]’ has now been replaced by the ‘SUPER Tuna ]+’ which adds a VFO and increased power output to around 2 watts.