This is the homepage of Lars Thunberg in Sollentuna, Sweden. Amateur radio callsign SM0TGU e-mail lars(at)larsthunberg.se For information about my satellites and amateur radio activity please see this page where most of the info are in english. Also see all the posts about amateur radio or use the web page search .
With an antenna RX splitter I did some fast compare between a simple RTL-SDR v3 SDR dongle and my IC-705 on 21 MHz and 14 MHz FT8. The RTL-SDR v3 is not original designed to run on HF, but with HF Quadrature mode it is possible to use it on HF.
And I was very surprised that this very cheap SDR could decode a lot of the stations that the far more expensive IC-705 did. The spectrum was cleaner from the IC-705 and more stations was decoded, but the results from the SDR was impressive because it is such a cheap and simple device.
PSKReporter map compare – 15 minutes RX on 14 MHz.
14 MHz
WSJT-X window. Cleaner spectrum from the IC-705.
WSJT-X screendump
Logbook from PSKReporter.
PSKReporter
Signals in dB from WSJT-X. The yellow reports are from the same station. I could notices some difference and RTL-SDR via SDR Console would often give higher dB values, but I have no idea why.
Some test with the internal LNA (P.AMP) of the IC-9700 and external LNA. What combinations will give the best SNR? Note that all tests are done without any type of professional equipment – only by looking at the waterfall and listening with my ears.
I have used my VHF and UHF yagis and external LNAs Mini-2 and Mini-70 mounted just below the antennas. I have aprox. 16 meters of high quality LMR-400 cables between the IC-9700 and antennas/LNAs.
VHF – beacon SK1VHF at 144.447 MHz
Without internal P.AMP and external LNA
Not possible to hear beacon
With only internal P.AMP
Possible to hear beacon
With both internal P.AMP and external LNA
Better SNR but needed to reduce RFGain to get good SNR
With only external LNA
Best SNR! No need to reduce RFGain.
Note on VHF: The difference between using both internal P.AMP + external LNA and only external LNA is not huge, but is clearly audible.
UHF – beacon SK1UHF at 432.405 MHz
Without internal P.AMP and external LNA
Not possible to hear beacon
With only internal P.AMP
Possible to hear beacon
With both internal P.AMP and external LNA
Better SNR but needed to reduce RFGain to get good SNR
With only external LNA
Best SNR! No need to reduce RFGain.
Note on UHF: Almost the same result as VHF, but the external LNA gives better result and SNR compared to VHF.
Summary:
If you do not have an external LNA it is mandatory to use the internal P.AMP on the IC-9700 for very weak signals. If you have a good external LNA mounted close to the antenna it is best to turn off the internal P.AMP to get best SNR.
LNB a part of the SatRover, feed with normal 75 ohms TV cable coax
60 cm dish from Triax (TD64) branded as Canal Digital
IC-705 as TRX
10 dB attenuator and a number of meters of Hyperflex 5 coax cable to make the output on 2.4 GHz at the Helix to aprox 100 mW (legal power limit in Sweden)
The SatRover combined 2.4 GHz TX Helix and LNB for 10 GHz RXFirst test of fixed installationRear connections of the SatRover SatRover and the IC-705Frequency stability test with an web SDR receiver for full duplex and FT8. Very good!
