Latest SSTV Images (auto updates!)

Posted on by

The Slow Scan TV images below will update every 30 seconds if I’m running the reciever for them. You never know what you might see so is kinda cool to see them appear in real time. I’m showing the last 20 images which have been decoded, usually from either 20m or 40m bands.

Slow-scan television (SSTV) is a picture transmission method, used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color.

A literal term for SSTV is narrowband television. Analog broadcast television requires at least 6 MHz wide channels, because it transmits 25 or 30 picture frames per second (in the NTSC, PAL or SECAM color systems), but SSTV usually only takes up to a maximum of 3 kHz of bandwidth. It is a much slower method of still picture transmission, usually taking from about eight seconds to a couple of minutes, depending on the mode used, to transmit one image frame.

Since SSTV systems operate on voice frequencies, amateurs use it on shortwave (also known as HF by amateur radio operators), VHF and UHF radio.

Read More »

Yaesu WiFi TX and Voltage Sensor for Home Assistant

Posted on by

A simple and quick project for detecting when a Yaesu transciever is transmitting and feed that status to Home Assistant to then perform actions. This can be used to, for example, automate killing the power if the radio gets stuck TX’ing when using automated digital modes software such as WSJT-X remotely. It can also measure the supply voltage, which is always useful information to know, especially when operating remotely.

Read More »

Calculating performance of outdoor wireless network links

Posted on by

This article contains information on how to calculate the operating margin of a wireless 802.11 network using a known distance between the two points.

fresnel

I wrote this quite a while ago and although the throughput of wireless links has dramatically increased the basic theory still applies. Of course we now have 5GHz available, which is very useful for this application. You should be able to substitute ‘f’ for 5000MHz and the maths will still work.

You can now get a 150mbps PTP link over 15km using equipment that costs £160 for both ends – that’s the entire cost of the system (minus a couple of poles and brackets). Crazy value for money when you think about it. The Ubiquiti NSM5 NanoStation is one such example. The Ubiquiti product range is pretty impressive to say the least. The NSM5 seen below is the big brother of the LOCOM5, which at £125 can still do 10km at the same rate and are around half the size.

nsm5-kit

 

If you are considering an outdoor wireless link, give this article a read so you understand how high above objects you need to mount your shiny new kit!

Read More »

JSON Parsing Nagios Script

Posted on by

Parsing JSON in Bash is never usually the best idea but sometimes it may be necessary or preferred. Here’s a nice easy script which uses the ‘jq’ command to perform JSON parsing in Bash.

imgres

Let’s imagine you have the following JSON which is outputted by a stats gathering process:

{"web_rate":1,"db_rate":2,"php_rate":2}

Parsing that in Bash by writing some regex’s etc is perfecting possible but there’s an infinitely easier way. Welcome to ‘jq’. Let’s see it in action.

Read More »