This evening after the excellent results of email transfer with large attachments obtained with Gustavo PR8KW from Brazil with system without GPS and light drift in transmission up to 100Hz after about 10 minutes, another excellent result with Oscar DJ0MY with station equipped with GPS, that has transferred 10k of attached in 2 minutes and with a constant speed of 2000bps with the new 3.0.4 VARA SAT modem registered.
These are the screenshots reported from Oscar DJ0MY:
All these tests are of great importance and give the idea of how the system can work even with a simple configuration.
With the new modem VARA SAT 3.0.4 of Jose EA5HVK and with AFC of +/- 150Hz max, you can manage quite well also transverters drifts not equipped with GPS reference and this is very important, even if with a slight decrease of performance.
Today also Michael DG0OPK has tested the system even if with low speeds because the VARA SAT modem was not registered and therefore without enabling high speeds
-------------------------------------------------------------------------------------------------
After several tests these are the suggested configurations to achieve good connection results:
- Install always the last version of the modem VARA:
https://rosmodem.wordpress.com/2011/01/10/ros-2
- Install always the last version of the Winlink Express program:
https://downloads.winlink.org/User%20Programs
- Adjust the audio level of the analog receiver or the SDR so that the VU meter of the VARA SAT modem is in the first green segment after the initial yellow segment, around -30dB of signal, to avoid false decoding
- Adjust the receiver filter, if possible, to 2.8kHz or better to 3.1kHz, as with high speeds the VARA modem requires more bandwidth
- Equip the LNB and the converter / transverter with a GPS reference (not essential even if recommended)
- Before transmitting regulate, if internet connection is available, your own transmission frequency with a precise reference, for example a WebSDR, you can connect, for example, to my WebSDR (http://websdr.is0grb.it:8901) with GPS reference, set 10489635 USB, zoom in and send your VARA SAT modem in PTT from the Settings > Soundcard menu by pressing on the TUNE button.
Verify that the transmission frequency is exactly 10489636.500 (1500 Hz tone), otherwise adjust the VFO to center it.
This initial operation is very important and guarantees a secure connection for those who are not equipped with GPS, considering however a succession slip which the VARA SAT modem AFC can manage, but require internet connection and in places not covered this is not possible.
- If you use the Audio Virtual Cab driver, set the frequency of 44.100kHz and not above to the properties of the playback and recording device.
-It is absolutely important to request the registration key to Jose EA5HVK satellite tests in order to enable high speeds with the VARA SAT modem and contribute to the tests that Jose EA5HVK needs to further improve the performance of the VARA modem via QO-100.
-Avoid, if possible, to change the transmission frequency during a connection session, even if you notice the AFC vary, as the transfer performance decreases due to the failure of the 2 modems to synchronize.
The 2 modems automatically manage the AFC in RX and until the drift does not exceed 100Hz and ends in the yellow zone, leave the transmission frequency stopped
- Check the modulation level and avoid distorted modulations, possibly reduce the output power level of the transverter or the amplifier.
-------------------------------------------------------------------------------------------------
At the moment we have no news about the implementation of a new software version of the Winmor and Ardop modems by the Winlink developers, we are still waiting for news on the matter, so the only modem that can be used with the Winlink Epress program is the VARA SAT.
Thanks to everyone who until now has helped with the tests to make the system work and improve with their reports
73
Roberto IS0GRB