Posts by IS0GRB

    DIY's third Helix antenna was tested tonight and can work in SSB mode.And make QSO with PA1EW and PA3FYM.PA3FYM gives the signal report of s58.Receive using websdr, websdr currently has many delays and pauses.Also used IS0GRB websdr page, almost the same effect...Can anyone give more options for websdr?

    Hello BG0AUB, i added the audio buffering size setting in my WebSDR.
    The default of the websdr is 250ms, now you can reduce it to 125ms (useful for data communications) or increase up to 2 seconds if you have internet problems or high jitter and/or interruptions


    Roberto IS0GRB

    Good morning, after exactly one month of various tests and optimizations, thanks also to the availability and expertise of Oscar DJ0MY, Gustavo PR8KW and the author of the VARASAT modem Jose EA5HVK, we arrived at an efficient and high-performance system that allows you to receive and send emails at high speed if the license issued by EA5HVK is used.

    Unfortunately, without the license the speeds are low and we asked to Jose if it was possible to slightly increase the speed in the free version, to guarantee a ham radio free system worthy of the name.

    The server after 1 month of testing is now definitive and always operational on 10489635.

    The latest version of the VARASAT modem is 3.1.2.

    Thanks to all those who have tried the system, we will try to improve again


    Roberto IS0GRB

    Hello Oscar and thank you for this important report

    After various changes made by jose EA5HVK, today has released the VARA SAT 3.0.8, which integrates a function to follow the frequency drift faster

    Also, with all our tests, the author of the RMS Trimode Winlink server, just released a new version that solve a bug that did not immediately close the connection if the server reached the session timeout.

    I made a video during a connection with Gustavo PR8KW and with the help of Jose this bug has been solved.


    Roberto IS0GRB

    This evening Jose EA5HVK has released the version 3.0.5 of the VARA SAT modem.

    This version, at our request, integrates the Calibration function, very useful via satellite and for those without GPS.

    In the Calibration menu the client transmits a signal to the server, normally controlled by GPS, or to another client controlled or not by GPS, which reply with its signal and the shift detected by the client who launched the test.

    It is therefore possible to know your own AFC value detected by the correspondent and center the VFO, so as to reset the AFC to 0 (zero) without the aid of a WebSDR and therefore of internet connection.


    Roberto IS0GRB


    This is a test from my server:

    This evening, after other changes and adaptations, another great test with Oscar DJ0MY.

    He sent an email with an attachment of 100kB in 10 minutes with a constant speed of 2000bps.

    I made a video, that unfortunately has no audio because was selected the audio virtual cable interface.

    We can consider it a record through the QO-100 satellite in SSB.

    Link of the video:…7TZNMNZI/view?usp=sharing

    We have also reported some bugs to the author of the VARA modem, which will soon be resolved in the next software releases.


    Roberto IS0GRB

    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:

    - Install always the last version of the Winlink Express program:

    - 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 ( 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


    Roberto IS0GRB