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Sprat Magazine

[If you have landed on this page looking for how to renew your membership, look to the left where there is a menu option "Membership Renewals".
If you are looking to join, then look up to the menu item where is says "Join GQRP".]

SPRAT is a quarterly magazine, edited by George G3RJV. SPRAT contains many circuits, technical hints and ideas for QRP construction projects, together with club news, contest and award information and other items of interest to QRP operators. SPRAT is an exclusive QRP journal and contains much practical information in each issue.

Writing for Sprat. It would help George G3RJV greatly if you would submit articles using this MS Word template.

If members are interested to find out which is the current issue and if the next issue is due soon then bookmark the news page for the latest updates.


Sprat 169

On page 23 the diagram for the G0KJK receiver does have a resistor missing (220k from c to b on the LM386 driver transistor). Here is the revised drawing.
There is also a diagram missing after the article for the SLA charger (on page 18). Here it is.

Sprat 168

In SPRAT 168, on page 32 we were unable to show the colour version of G3YVF's trap construction. That drawing is available here.
Colin G3VTT would be grateful for any feedback if you try it.

Also, on page 8 we omitted to include the circuit diagram for Bill G4KIH's Antenna Changeover Relay. This can be viewed here.

All the above are included in this document which you can print and tuck into your magazine.

Sprat 164

A real tuning knob for SDR radio - G4WIF
Here is a video of it working
(you may be prompted to log in - but closing that window allows you to watch the video).

Sprat 163

In SPRAT 163, Member news, there is a typo for the webpage where you can download all the relevant information for an ILER-40 Buildathon in 4 sessions. The URL is and the English version is down the page.

Datamodes using the RTL2832U Dongle

I regret that this article didn't get written before Sprat hit the streets and probably won't appear for a few weeks more. Time has gotten away from me.

For now I will document some "hints" which will probably suffice for many. Usually, we decode data signals from an external soundcard device such as the excellent SignaLink which takes its input from a traditional receiver.

Using software on our computer such as "FLDigi" we take the external soundcard output (usually USB) as the input to this software.

With the "RTL Dongle", we somehow need to get the output from the SDR software (such as SDR Sharp), back into our computer. Of course, we are already using the existing soundcard for SDR Sharp output to our speakers, and theoretically we could take that output and feed it into a 2nd soundcard if we had one.

This method allows us to use just the one sound card.

It would be useful if we could feed the SDR Sharp output back into a different kind of soundcard - a "Virtual soundcard", which we can then tell FLDigi to take as its input. What we need is a Virtual Audio Cable.
There are some that you can buy, and some that are free. This is one of the better free ones.

Here is the screen shot for SDR Sharp which shows how to switch output from the speakers to the virtual cable.

Here is the screen shot for FLDigi which shows how to switch input to the virtual cable.

Sprat 162

In this Sprat, Ken Marshall G4IIB brings us a "primer for Software Defined Radio (SDR) using the RTL2832U R820T Dongle". Later in the magazine Tony G4WIF shows how the conversion allowed the dongle to be used as a simple spectrum analyser.
Here are the extra notes and photos promised in Tony's article. Ken has provided a text file with all the hyperlinks contained in his article. Ken has also written an article "Getting your RTL2832 Dongle to work under Linux. The Easy Way".

New GQRP member Brian Steadman GW8FSN has provided a heads up on an upgraded dongle offered by a company called "Cosycave" in StHelier. They offer upgraded dongles with an R820T2 tuner (better LNA) an upgraded and stable crystal oscillator, a reinforced antenna socket and a modified PCB with solder pads for the the Q channel (pins 4&5) to connect the toroid to for a price of £10.30 inc P&P. It just goes to show how fast SDR is moving.

Sprat 162

In the Spring 2015 Sprat in Member news, there is a typo on the webpage where you can download all the relevant information for an ILER-40 Buildathon in 4 sessions.The URL is and the English version is down the page. jon, ea2sn.

Sprat 160

An archive of SM6LKM's "MJB" software, (reference [2] in the M0XPD article "Speaking in Whispers") can be downloaded from here. Contact Paul Darlington M0XPD with any questions you might have.

The WSPR Frequency Calibration Tool sketch is here. Contact John Roberts G8FDJ with any questions you might have.

Simple DDS VFO - VK5TM. Resources page here.

Sprat 159 - Centre page.

Here is a copy of the circuit diagram that had a section repeated.

A few members have reported pages 6 & 39 incomplete and those are downloadable from here. The other possible incomplete pages are about the Rishworth Convention and there is a left hand menu entry for that on this site, and an advertisment which need not be reproduced.


Notice of printing error - Sprat 156:

Unfortunately, there was a snafu at the printers, and the diagrams which should be full page have got split up and mixed in with the annual renewal insert. The only people that will be affected by the split standing order page will be new members, and those who need to correct their Standing Order due to a missing membership number (and there are quite a few of those still). The diagrams will be repeated correctly in the next Sprat, but not the Standing Order form as it will be too late by then for members to use. If you need a copy of a diagram please click here and here (these are PDF files). You can also download the standing order form.

Sprat CD version 3 - Issue 120. We managed to miss out page 20 when compiling the CD. You can download it from here.

Sprat 158 - Software and hardware resources to accompany m0xpd & n6qw's article "RF Generation for Superhets"

Sprat 156 - Software and hardware resources to accompany m0xpd's article "Occam's Microcontroller"

Sprat 132 - "RAMU" (Remote Aerial Matching Unit)

RAMU was conceived by Ian Keyser G3ROO as a system for matching aerials to their transmission lines at their feed points.
You can download the source code from here.

Sprat Index.

Download the entire index (up to Sprat 163) in Excel format. This includes the Summer SPRAT 2015.


Article Reprints.

Years ago the club offered this service but since the introduction of the regularly updated Sprat DVD there is no longer the need. The DVD is so reasonably priced - especially for members, that getting hold of that old article is no longer at all difficult. We ask that owners of the DVD respect the club copyright and do not pass on any DVD contents to others.
Here is a link
to help to order your own copy.


Here is a list of the currently available datasheets.

These documents are in Adobe Acrobat Format.

Laser Printer Transfer method of creating Printed Circuit Boards. Here in an article by Chuck Adams K7QO (printed in the Fall QRP Quarterly) the method is described with superb clarity. It is reproduced with the kind permission of the Amature Radio Club International president Ken Evans W4DU. Check out the ARCI webpages and consider treating yourself to a subscription.




Jesper OZ1XB has prepared an Excel spreadsheet for calculating transmission lines.
A Guide to Capacitors
by Paul NA5N. This is a fabulous document which will answer most of the questions you ever asked about capacitors. (1.6Mb)
A Short Guide to Harmonic Filters for QRP Transmitter Output by George G3RJV. (83kb)
The Resistive SWR Bridge - by Tony G4WIF & Ian G3ROO. (77kb)
Toko 10k Inductors for HF band use by George G3RJV. (37kb)
Quick and Easy Bandpass Filters for Receiver Input Tuning by George G3RJV._(36kb)
The "Direx" 40/20m DC Receiver by George G3RJV. (893kb)
The "SCD" complete Transceiver by George G3RJV. (71kb).
Installing the SPRAT CD by Tony G4WIF. This datasheet was created to assist with the installation of the CD from Funk Amateur containing all the issues of SPRAT from 1 to 100. (89kb).
Oscilloscopes by Paul NA5N (335k).
TAK893 Mixer by Paul NA5N (439k) - See SPRAT 108 page 24 for details.
S Units (54k) by Paul NA5N
A guide to Japanese / European Transistors by John G8SEQ
Club CW and SSB filters by Graham G3MFJ
Handymans Guide to Solar Acticity and HF Propagation
The Sprat Pixie File - collection of simple radios.
Making a Toroidal KANK - a replacement for those hard to get coils used in so many older Sprat projects.
Sprat CD version 1 - You have a new computer and no floppy drive in which to use the key disk. This document was kindly written by Ingo Meyer DK3RED.
GQRP Club toroid information by Graham G3MFJ
G8ATH / G0SIB crossed monopole antenna for HF / NVIS page 1 page 2
Toroid Inductance Chart - David Smith G4COE
TFM-2 mixers mentioned in the Summer 2013 Sprat.

Note: Your P.C. may be set up to open the pdf reader within your browser, and on some versions, there isn't a "save" option. An alternative is to right click on the link and choose "save target" and this will allow you to download the file.


Version 1 - Produced by a German radio club Funk Amateur. It has the blessing of GQRP but is a totally independent initiative.
All enquires (or even complaints) must go to Funk Amateur. The CD contains Issues 1 - 100 of SPRAT and is suitable for use with Windows 95/98 and Windows NT. It can be viewed using Adobe Acrobat Reader (which you have to provide). It arrives with a key (floppy) disc based on your callsign (which you provide with your order).

Version 2 was also produced by Funk Amateur and covered issues 1 - 109 but did not require a key floppy.

Version 3 is the first "in house" produced CD.

Version 4 is the first DVD because the information outgrew the capacity of a CD. It includes issues 1 to 148. For further information please see our club sales pages.


Check here (and the Index) for corrected article errors.

Issue 95 (Summer 1998) Urs Hadorn HB9ABO wrote a very interesting article on a PIC based Electronic Keyer, unfortunately, the circuit diagram on page 4 was a little indistinct. It can be downloaded from here. (68k)

Issue 98 page 5. There was a section missing from the circuit diagram. Download it here (92k).

Issue 107 (Summer 2001) The Epiphyte circuit diagrams were a little indistinct. They can be downloaded in these two PDF documents. Diagram A & Diagram B. My thanks to Derry VE7QK for his permission to put these on the web and for supplying the documents. 

Note: Your P.C. may be set up to open the pdf reader within your browser and on some versions, there isn't a "save" option. An alternative is to right click on the link and choose "save target" and this will allow you to download the file.

Issue 129 - "All Tubes" 80 CW QRP - HB9FAE. The circuit diagram didn't reproduce too well in Sprat so you can download it from here.