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Focus on VHF and Above 14 October 2018
Audio version here
In today’s tutorial we are going to talk a little about Digital Voice.
What is digital voice?
What it essentially is you have two sound cards in your PC. Your microphone or PC headset is connected to the one and your radio to the other one. Your voice is digitized by software that controls the sound card where your microphone is connected. This digitized audio is compressed and packaged and then sent to the radio via the second sound card for transmission over a normal analogue voice channel.
From the FREEDV website “There are several reports of the new FreeDV 700D mode outperforming SSB at low SNRs. At high SNRs FreeDV 1600 sounds like FM, with no annoying analog HF radio noise.”
But this is used on HF!
Yes, but think about all the DMR systems like D-STAR, DMR, P-25, C4FM (Yaesu System Fusion), and NXDN. All these systems use the AMBE vocoder to encode and decode digital voice. The only difference between all the systems is the packaging of the digital audio stream and that is all that prevents these systems from talking to each other. All these systems operate on VHF and UHF.
On the internet is information on FreeDV 2400A where Brady O’Brien, KC9TPA, has been working hard on two new FreeDV modes for VHF/UHF radio. To the existing Codec 2 1300 bit/s mode, he has added framing/sync logic and our high performance 4FSK modem. This mode is designed to be “readability 5” at -132dBm, which is 10dB beyond the point where analog FM and 1st generation DV systems stop working.
On the SARL Digital forum are guys already discussing playing around with FreeDV on FM. There are also some hams here in Pretoria who play with DMR who are also very good with digital voice codecs.
When you start playing in this space you are entering the world of Software Defined Radio. This is a whole new and exciting ball game.
Gone is analogue radio as we know it today.
Let us now look at some news about the VHF and Above bands...
The early part of this past week has been fantastic along the West Coast.
The following report provided by Charles ZS1CF:
Monday 8 October 2018 certainly was NOT a blue Monday along the West Coast, it was actually a SUPER Monday regarding VHF tropo ducting propagation at its best!
At 06h00 in the morning, Charles, ZS1CF, in Langebaan heard Pieter, ZS3PV/M calling while driving from Kleinzee to Koingnaas for work. It was the second time me made contact while Pieter was mobile and again it was on 145.500 simplex, a distance of 367km. The signal from Pieter varied from a S4 to a S1, and we could communicate until he arrived at Koingaas. Later Andre, V51B, from Oranjemund also called, and we had a 3 way conversation. Andre was received in Langebaan with a S7 signal over a distance of 526km. Well done in the mobile Pieter, seems it is becoming a regular thing!
The best was still to come though!!
The West Coast Radio Group has a net every Monday evening at 19h30 on 145.500 MHZ. As the net progressed, a total of 12 stations eventually called in which is now a record for the group. As time progressed, the signals from the long distance stations also improved significantly.
Andre’s signal from Oranjemund was s9+40db, while Cobus’s signal from Port Nolloth was s9+60db! Considering the distances involved and hearing such good signals is actually mind-blowing and is quite something to experience.Click here for video link1 Videolink 2
Congratulations to Marais, ZS1NOS and Dawid, ZS1DK, both from Langebaan, for their very first QSO’s over long distances. Both made contact with Cobus, ZS3CVB, in Port Nolloth (440 km) and Dawid also managed a contact with V51B in Oranjemund (526 km). What a pleasure it was to hear the excitement in their voices. Gents, your achievements are something to cherish for a very long time, well done!
Tienie, ZS1HO, in Vredenburg and Chris, ZS1FC, in Jacobsbaai also made contact with Andre in Oranjemund.
Following is a list of the 12 stations that called in:-
ZS1HO(Vredenburg), ZS1NOS(Langebaan), ZS1DK(Langebaan), ZS1CF(Langebaan), ZS1FC(Jacobsbaai), ZS1NAZ(Goodwood), ZS1ROD(Duynefontein), ZR1JOJ(Goodwood) ZS1HZ(Goodwood), ZS3PV(Kleinzee), ZS3CVB(Port Nolloth) and V51B(Oranjemund).
All contacts were made with vertically polarized antennas.
Thank you to all for a SUPER Monday evening along the West Coast.
On the SARL Forum, Paul, ZS6NK also reported some good contacts on 6m EME:
03 Oct C21GJ
04 Oct ZA5Z
04 Oct KB7Q
Peter, ZS2ABF posted on the SARL Forum that he had to remove the morse program that he was using on his smartphone and will in future only be on SSB voice.
Carl ZS6CBQ has requested that we have a quick discussion during the VHF Workshop at the NARC regarding the VHF contest, prior to submitting changes to the Contest Manager for inclusion in the Blue Book which contains all the SARL contest rules.
The registrations for the VHF Workshop are growing. Thank you to all the folk who have already registered.
Have you booked for the VHF and Above Workshop on 20 October 2018?Goto http://amsatsa.org.za/, download and complete the registration form and send it to admin@amsatsa.org.za along with your proof of payment. Closing date for registration is Monday 15 October 2018.
Well that is all the VHF and Above news for this week.
Please send your news snippets and information about activities on VHF and Above including information for the tutorial to vhfnews@sarl.org.za.
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