New WSPR receiver from RemoteQTH

RemoteQTH is a small company in the Czech Republic and they have just announced the release of a new receiver for WSPR. 

It can be used from 0.1 to 28 MHz and is described as follows..."The openWSPR receiver is a stand-alone HF receiver for WSPR. Just connect an antenna, internet and a DC power supply and you're ready to go! With this tiny receiver you can decode and relay WSPR messages to WSPRnet.org. 

Since the entire project is open source, receivers can be easily reprogrammed to receive signals other than WSPR. The nanoPi board inside runs Raspbian OS and several user programs, which are automated by custom scripts, making the receiver completely maintenance-free."

It is selling for €125 which at first glance sounds expensive but I guess one of the main features of this WSPR receiver is that it doesn't require an external PC or computer to run. All of the decoding is done inside the unit. All you need to do is connect the various cables, configure it, connect an Ethernet cable and it uploads the spots to WSPRnet.

Looking at the size of the box relative to the SMA or Ethernet connector then it's really small and just a few cms across.

Future products... They are also developing a separate transmitter module.

They have no information on this in terms of power output but 200 milliwatts seems to be the norm.

It's also interesting to see that they are developing a series of band pass filters...

I think these will be attractive to users of other WSPR products as well as all you need are the connecting SMA patch leads.... no construction, soldering or winding of torroids. 

The photo above shows the surface mount components inside the filter.

Nearly all of these low power WSPR transmitters have a square wave output and require some sort of filter to remove the higher harmonics. This is usually done with a low-pass filter rather than a bandpass filter which tends to have slightly more loss.

Where bandpass filters shine is with the receiver module as they keep all of the potentially large signals on the lower bands out of the front end of the receiver. I think these standalone filter modules may be of interest to anyone with a SDR receiver and who want to concentrate on one band.

Link... More info on the RemoteQTH website

Disclaimer: Just to clarify, no-one paid for this post or sent any product to me for review. These are new products that I think people will be interested in.

Addendum: Since putting up this post, someone hs asked about whether the receiver can hop between bands? Does it run WSJT-X? And what is the performance of the receiver?

I looked at the files section of the site and found a circuit diagram. The receiver schematic shows the input RF going straight into an IC without any preceding RF stage amplification. This might be ok on the bands on the lower bands like 40m or 80m but is it going to be sensitive enough on bands like 10m / 28 MHz?

The input has a single LC parallel circuit which suggests that it is intended for single band use. If these components are left out then an external band pass filter is required for each band.

Evolution of modern Direct RF radio receivers

 

I recently came across a 15-minute video presentation from Analog Devices about cutting edge radio receivers and I have embedded it at the end of the post. I think anyone with an interest in RF technology will find it of interest.

The image above shows the evolution of receivers.

A) We have the Superhet receiver which was the stable design for many decades. In amateur radio transceivers, there were usually two IF (intermediate frequency) stages... one often around 8-9 MHz and the second one at 455 kHz. Anyone who has a radio from say the 1980's or 1990's will probably have this design. Functional but complex and expensive.

B) We have the more modern Zero IF or No IF design. A digital local oscillator generates two local oscillator signals with one 90 degrees out of phase relative to the other one. These are fed to two mixers which then generates an I and Q signal which are at baseband. These signals are then converted into a digital signal by two ADC's (Analogue to Digital Convertors). There is no IF stage. Many modern receivers use this design.

C) The most recent development is to directly sample the RF signal with no mixers at all. Essentially the signal comes into a RF filter, then a low noise amplifier and then it goes to the ADC where it get's converted into a digital stream.

This images above is a screenshot from the video presentation and it shows the modern generation of Direct RF receivers going up to 18 GHz! I still find it amazing that an IC can sample RF signals in the tens of MHz range let along going all the way to 18 GHz.

Needless to say, all of this cutting else stuff is expensive and is aimed at commercial and military users but it shows the direction of travel. In time, the technology will trickle down and will appear in lower cost products.

Video... The main part of the video is from 3:10 to 7:30 if you want to skip ahead. The second half of the video after 7:30 is about the most recent Analog Devices product.