The second Kiwisdr at the remote location has been under-utilised, so a re-purposing was considered. The plan was to purchase a 50 – 28 MHz transverter with minimal complications (as transmission was not required) and interface it with the KiwiSDR.
A search on Ebay.co.uk uncovered a circuit board from a source in Ukraine. At a total price with postage of less than £20 it was good value, and arrived from Ukraine in just over one week.
Connecting up was simple – Pins 1 and 2 to the KiwiSDR antenna input, 7 and 8 to the 6m antenna and 5 and 6 to to the 12V supply.
To use the transverter, the KiwiSDR ‘Frequency Scale Offset (kHz)’ box in the config page of the administrator settings must be completed with the correct offset, in this case 50000-28000 kHz = 22000 kHz. Also, the ‘Max receiver frequency’ dialog was changed from 30 to 32 MHz to allow tuning from 50 to 54 MHz.
Initial testing began with WSPR transmissions from the home location to determine frequency accuracy and stability, and the sensitivity of the new combination.
The test transmission was conducted at a power setting of 0% on the transmitter. An estimation of the power would be 1W or less, over a 50 Km path. The WSPR signal was decoded and the drift was well within limits. The stability and sensitivity are up to standard.
The frequency accuracy is almost there, but not quite. The receiver is tuning about 500 Hz low. So, in the above example, after the WSPR decoder is started the frequency in the bottom right dialog needed to be changed from 50293.00 to 20292.50 to correctly position the signal. That being said, for most purposes being 500 Hz out in frequency will not make much difference. As the transverter is stable – and turning trimmers on the board may affect that – the first approach is to see if the KiwiSDR software will allow greater granularity on the frequency offset to correct it that way, which is work in progress.
With the caveat of that small amount of unfinished business, the implementation of the transverter/KiwiSDR project was a low cost and quick operation which has produced something which will be useful to observe 6m band activity as conditions improve.