u/Bicurico

Cobra aquática no Algarve

Viva.

Quando eu era miúdo, nos anos 70 e 80 passava as férias de verão no interior do Algarve. Era costume as pessoas, incluindo a minha avó, ter hortas que regavam no verão com água de barragem. As "barragens" eram na realidade uns lagos artificiais com uns 20m de diâmetro e 1-2m de profundidade.

Por vezes tinham peixes (asgãs, não sei como se escreve, eram a novidade na altura). Outras barragens tinham rãs. Como miúdo passava as tardes junto à barragem a apanhar as rãs ou a fazer canais de água.

Nessas barragens era frequente ter cobras aquáticas (pelo menos estavam sempre na água). A barragem da minha avó tinha sempre umas 3. Eram amarelas com listas castanhas. A cabeça era arredondada e as listas perfeitas. Cheguei a apanhar uma vez uma para um balde e na brincadeira meti na pia do burro. Eram inofensivas.

Tenho certeza disto e guardei o aspeto delas em memória. Eram muito comuns, qualquer barragem tinha 2-3. Apanhavam sol à superfície da água. Eram bonitas e quem gosta de aquariofilia já viu os peixe-"cobra" Kuli: a coloração é mais ou menos esta.

Mas nunca fui capaz de encontrar qualquer referência destas cobras na internet.

Gostaria de ouvir testemunhos de quem saiba do que estou a escrever e, claro, o nome desta cobra. Não tenho dúvidas das minhas memórias de infância, mas acho estranho não encontrar nenhuma fotografia dessas cobras.

Obrigado.

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u/Bicurico — 4 days ago

Free Interactive Spectrum Analyser Training Course (RBW/VBW, Waterfall, Heterodyne vs FFT, Front-End Protection)

I’ve been developing a free HTML-based training course focused on practical spectrum analysis fundamentals, mainly aimed at onboarding junior broadcast/RF engineers, SDR users and technically curious HAMs.

The course is fully interactive and browser-based (no installation required). It includes animated simulations for concepts that are often difficult to explain statically.

Topics covered include:

  • Time domain vs frequency domain
  • dB, dBm, dBW, attenuation
  • Frequency span and zero span
  • RBW and VBW (interactive sliders)
  • Live / average / min / max traces
  • Waterfall / spectrogram interpretation
  • Heterodyne spectrum analysers
  • FFT spectrum analysis
  • Front-end overload and measurement pitfalls
  • DC blockers and external attenuation
  • Reading analyser specifications correctly

Some parts are animated, for example:

  • RBW changing the effective IF filter width
  • Sweep-time tradeoffs
  • Heterodyne downconversion with swept LO
  • Waterfall behaviour with drifting or burst signals

The goal was to make something more visual and intuitive than traditional PDF slides or textbooks.

There’s also:

  • final exam
  • printable certificate
  • fully offline HTML format

Would appreciate feedback from RF engineers, SDR users, HAMs or anyone teaching spectrum analysis concepts.

https://vma-broadcast.com/training/

reddit.com
u/Bicurico — 4 days ago
▲ 21 r/broadcastengineering+1 crossposts

I built a free interactive DVB/Broadcast engineering training site

Over the past months, I have been building a free interactive DVB / Broadcast engineering training platform as part of my VMA Broadcast side project.

The idea was to make some of the more abstract broadcast concepts easier to visualize interactively instead of using only static diagrams or PowerPoint slides.

So far I have been adding animated/simulated pages for topics such as:

  • MPEG Transport Streams
  • PSI/SI
  • DVB-S vs DVB-S2
  • QPSK / 8PSK / APSK
  • IQ signals
  • Viterbi / FEC
  • MER / BER
  • DVB-S2 framing
  • RF spectrum behaviour
  • satellite IF conversion
  • etc.

Most of this was motivated by trying to explain DVB concepts more intuitively to junior engineers and students.

It is not a commercial training platform or polished corporate product — just an independent engineering project built alongside the DVB/IPTV tools I develop for VMA Broadcast.

Feedback from broadcast/RF engineers is very welcome, especially ideas for additional simulations or concepts that are usually difficult to teach.

https://vma-broadcast.com/training/

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u/Bicurico — 5 days ago