Re: [Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread David Rowe
Hello Samuel, I just wondering best way to get really sensitive comms, so a 5W HT could go for miles and miles. The Wenet project shows what can be done with careful engineering of the modem, e.g. sending HD images at 100 kbit/s @ 50mW over 100km: http://www.rowetel.com/?p=5344 The key

Re: [Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread Bruce Perens
The analog FM modulator/demodulator is going to be your main limit. Of course, we don't have off-the-shelf handheld SDRs yet. On Sat, Dec 2, 2017 at 1:27 PM, Samuel Hunt wrote: > Hi Adrian, > > > > This I understand, but then to double the air rate would then lead to a >

Re: [Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread Samuel Hunt
Hi Adrian, This I understand, but then to double the air rate would then lead to a net reduction in sensitivity due to the wider bandwidth. What I trying to establish is if the coding gain from increasing the error correction would be more than the sensitivity loss for widening the bandwidth.

Re: [Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread Adrian Musceac
Hi, Channel coding will improve performance, depending on the type of code used. For example, in QRadioLink I use a rate 1/2 convolutional code, which leads to twice the symbol rate. This gives me an improvement of 3 dB over no code/half symbol rate mode. LDPC and puncturing would improve it even

Re: [Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread Nino Carrillo
Hi Sam, I’ll take a stab at your baud question. Seems to me that lower symbol rate equates to more energy per symbol, and therefore higher probability of receiving said symbol at the distant station. At the same received power level, a system with a lower symbol rate will be more successful

[Freetel-codec2] Ultra-reliable sensitive comms

2017-12-02 Thread Samuel Hunt
I am hoping there will be some people on this list far more experienced than me to be able to advise on this! Am playing with VHF voice, etc, and I am thinking what is the best way to get ultra-reliable (super-sensitive) performance on a VHF modem. I am thinking for VHF, based on a radio

Re: [Freetel-codec2] Data Modem

2017-12-02 Thread Jeroen Vreeken
On 12/02/2017 09:28 AM, Jacob Falzon wrote: > Hi there Jereon, > > thanks, you're right about the function! Thanks! > > What do you mean that the functions would work on any other system > exactly? > The compilation of the modes is conditional, for SM1000 (M4 cortex actually) they are not