Tag: signal

WSPR – weak signal propagation reporter

What is it?

I could go into lengthy detail but I won’t bore you just yet. Below I have quoted the Wikipedia entry that explains things in a nutshell better than I ever could. I will however give a few details of attempts I have made and equipment I use for carrying out this mode of communication. I am currently building a new radio for this mode that I will cover in a later post.

WSPRnet map

WSPR (pronounced “whisper”) is an acronym for Weak Signal Propagation Reporter. It is a protocol, implemented in a computer program, used for weak-signalradio communication between amateur radio operators. The protocol was designed, and a program written initially, by Joe Taylor, K1JT. The software code is now open source and is developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands. WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station’s callsign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with a signal-to-noise ratio as low as −28 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.

Wikipedia

What fascinates me most about this mode of communication is that in recent weeks it has gained a new audience as a result of a television documentary. This documentary was regarding the search for the missing Malaysian airways flight MH370 that vanished from radar screens on the 8th March 2014. An investigator tracking its disappearance has been cross referencing WSPR signals in the area that the aircraft was last reported and he has apparently plotted the route taken by monitoring these signals as they were reflected or distorted by the aircraft’s footprint in this area, well beyond the planned flight path.

Wspr on the 80 Mtr band
Wspr into Europe

My setup for testing propagation on a number of different bands is very portable as that’s normally the way I work when taking to the airwaves. I’m always moving around or working from different locations so it’s always good to be able to monitor conditions using a compact setup.

Wspr into Australia

I do also have an aerial system set up in my loft that cannot be seen, it’s kind of clandestine in that way it does not grab the unwanted attention of my neighbours. I specialise in low power communications and again this does not draw the attention of anyone living near by as disturbance and interference rarely occurs. The maximum power level I normally use is 10 watts, but more likely somewhere around the 5w QRP level. My WSPR setup operates between 200mW and 5mW of power. Extremely low power, there is probably more power in that sports watch sitting on your wrist than what I am transmitting.

My Portable setup

I have an inflatable aerial, yep that’s right inflatable! Perfect for mobile operation using QRP low power technology, It covers most of the high band frequencies and I mainly use it on the 20 Mtr band (14mhz) or the 40mtr band (7mhz) though other bands are also available. Fully inflated it stands about 6ft high and can be hung outside, inside or just perched in a corner somewhere.

Inflatable multiple HF band antenna

There is an antenna tuner , this is one I purchased from the States in a kit form and built myself. It’s called an Emtech ZM-2 Atu details can be found HERE

Emtech ZM-2 ATU

The actual transmitter sits in a small package not much bigger than a box of matches. This was purchased already built and is called a WSPRLITE classic. I am in the process of building a new transmitter and receiver combo that is also in a kit form, I don’t anticipate completing it any time soon as I just don’t have the time at the moment.

WSPR Lite transmitter

I have made a number of filters for the different bands (40mtr, 60mtr,80mtr and 160mtr) and these boards connect to the output of the transmitter to aid in obtaining a clean signal and to prevent deviation from the set frequency.

Band filters for WSPR operation

The power comes from a 3000 mAh 5v power bank. However the problem here is that the power draw from the WSPR unit is so small the power bank will some times close down, and for this reason I have had to build a small usb circuit that creates a minimal demand on the power bank keeping the power supply constant. With this power bank and the WSPR unit on its high setting I can easily get 16 hrs of continuous use. When I work on the lowest setting I can achieve 3 full days (72hrs) of use.

3000 mAh power bank
The circuit used to fool the power bank

And that’s about it, all this kit can fit in a small unobtrusive bag or box.

Operation

First and foremost the transmitter connects to a computer where you can access all the parameters of the unit and set it up how you want your operate, power, duration and frequency etc. The unit already has inbuilt filters for the 20mtr (14Mhz) band so you don’t need additional filters if that is your band of operation. Once the programming is done you can now set the system up in place as you want it. I sometimes use this from my loft to see just how well certain bands are working in certain directions at different times of the day.

The battery connects to the transmitter that in turn connects via the filter to the Antenna tuner unit. the antenna unit connects to the antenna.

Timing has to be precise when setting up, you set it to transmit at every 2 minute interval.

Once you are transmitting it’s worth leaving it be for about 30 minutes and then you can pop on to WSPRnet to check your signals. You can check what is being received and what strength of signal is getting through to your destination .

I use an app called WSPR watch that connects via the WSPRnet system so I can monitor my performance from absolutely anywhere just by using my mobile phone or iPad. How convenient is that? I can leave the unit unattended and monitor it remotely.

In summary the WSPR protocol uses a very weak signal to test atmospheric and solar cycle conditions to determine a viable route for a signal to reach a destination. if you were to listen in at the destination all you’d probably hear is white noise, however the decoding program is so accurate it can pick up a signal to noise ratio of as low as -28db.

Im leaving it there as I could ramble on for ages. If anyone for some strange reason wants to know more then please get in touch.

Bardic Lamp…A railway classic

The Bardic lamp was introduced into the British railway system by the Bardic company of Southampton sometime around 1962. Just about everyone who has worked on the railway since then in a trackside role was given one as a personal issue.

Fast forward to today and new plastic LED lamps are being issued, however they don’t have the appeal of the old lamps, they break easy and the lens colours are not true Red, Green and Amber that they should be. The old style Bardic lamp is still in use many of which are still being used today. I still have the original one issued to me back in 1992.

This post is going to cover a basic power conversion for these lamps that will hopefully result in them being used for many more years.

Bardic lamp
Ever ready AD28 battery
Two that I have recently converted at work

The fundamental issue with these lamps is that they use an old Mercury cadmium battery that accepts two pins that insert into the top of the cell. Even though these batteries used to be available for a reasonable amount of money, nowadays it is unethical to purchase these batteries due to their construction they have in theory been banned, so they are no longer manufactured. They can though still be purchased via the web at extremely inflated prices, however they can’t guarantee that they would still work – so you take your chances.

With this simple conversion we can extend the life of this unit and save it from being cast aside as waste. The conversion is very cheap, uses std “D” cell batteries and can be converted by anyone – even me. Kits to do this can be purchased for around £10 (GBP) on line, but this one should not cost more than £2 (GBP) even less if you have the parts as spares.

There are two ways of doing this conversion, the way the kit works is to use a couple of electrical “Choc bloc” adaptors to connect to the male pins of the AD28 connector (I’ve used that example on this page). The cheaper option is simply to have a 3 cell “D” type battery holder, cut the old AD28 connector off, solder the two wires together and use some heat shrink to cover the solder joints. Simple.

This really is a ten minute job that increases the lifespan by years.

Bardic lamp old AD28 connector
Bardic lamp conversion

The conversion is completed with the D cell battery holder being stuck to the base with some hot glue. I’ve also put some on the chocolate bloc connectors for some extra strength and protection from the damp.

We recycle these batteries at work with a company that we have connections with, I also take spent batteries to the local supermarket that also recycles. The old AD28 batteries go to a specialist company for recycling/disposal.

Pretty basic and I now have a constant supply of these coming into us from our locations throughout the East Midlands awaiting conversion. We now do the basic simple conversion with our own stock and I think we have the conversion cost down to about £1.80 GBP per unit. A very cost effective simple conversion that will keep a 50+ year old lamp going for a few more years.