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Sprat Magazine Information

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".

If you are wondering if the latest Sprat has been posted then look up and select "Club News"

SPRAT is a quarterly magazine which 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.


Sprat Index.

Download the entire index (up to Sprat 190) in Excel format. This includes the Spring SPRAT 2022.

Bill K7WXWThe index is maintained by Bill K7WXW (shown left). If you use the index and appreciate his work, why not drop him an email.





Advertise in Sprat

For queries about advertising in Sprat, please contact the Treasurer Graham G3MFJ.

Writing for Sprat.

It would help the Sprat Editor (G1TEX) greatly if you would submit articles using this MS Word template.

SPRAT authors and readers should be aware of the nature of the publication; it is a means for G-QRP Club members to exchange ideas and/or report on their experiences.

To quote our founder; “One of the great joys of my amateur radio life is editing SPRAT. Perhaps editing is too strong a word because the preparation of each issue is not very stringent and what I do is compile rather than edit. The most I can claim for the radio construction articles in SPRAT is that each of them worked at least once for the author. Some might think this a rather careless approach to a technical (perhaps semi-technical?) publication. However, it does throw up some wonderful stuff. This in turn encourages discussion and debate amongst members.”
- The Reverend George Dobbs, G3RJV, Practical Wireless, May 2015, p30.

George may no longer be editing SPRAT but we have not changed this approach. So, please be aware that we do not peer review articles prior to publication and publication does not mean the Club in any way endorses the content. To be 100% clear, we do not test circuits or carry out detailed checks on information prior to publication.

The Club does not therefore assume any liability for the information and opinions provided in SPRAT, - or through any associated material on our website.

SPRAT readers must carry out their own checks before following any information shared via SPRAT or posted on the Club website.

Any work you do is solely at your own risk. Where you have any doubt over your own competence, you must seek advice from a competent person.
Any questions about the accuracy, or safety of the content should be directed to the authors, whose details are normally included with their articles.

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 ERRATA (and notes)

Sprat 190

The article by John G0UCP. A small error crept in to the circuit diagram of the 1950s style TX on page 10. Anode and grid pin numbers on V1A were transposed. The grid pin should be 3 and the anode pin 2. All the other pins are correctly labelled.

Sprat 188

The article about providing mains power to an outdoor shed in SPRAT 188 raised a few concerns from members. Our chairman Steve G0FUW addresses those concerns in this document.

Sprat 186

Page 5. It’s been pointed out that the schematic has a 2N3189 Fet.
(Just below where it says “4+25+4 turns onT68-2 Toroid”).

This should really show as “2N3819”.

Page 21. A Simple VFO Kevin Wheatley, M0KHZ

Kevin's long link to the Kicad video is a little hard to type so here it is - and he also has a video showing the construction and operation of his excellent VFO in action. [The one featured in Sprat 186].

Sprat 185

A Tunable whip antenna mount: On page 26 we missed including Gareth GM7WFT's email address. It is gareth@edwardsfamily.org.uk

‘Master-Robert’ by Alain F4IET
Alain has kindly provided a full circuit diagram of his project.

Sprat 183

On the cover contents we showed an alternative for a 40763 but the article wasn't included. You can download it from here.

Sprat 180

In this issue, Tony G3PTD and Tony G4WIF introduce a digital attenuator.
Additional information and the arduino sketches are here.

Sprat 179.

In this issue Phil G3SES wrote about a precision current source. We managed to print the wrong schematic diagram which is available here. Our apologies - especially to Phil.

Sprat 176

In this issue Pete N6QW introduced the first part of of an inovative design for an SSB transceiver. Pete produces his boards by milling them on a rather nifty CNC milling machine. There are more affordable ways of manually milling but some people may be more comfortable etching - and this is where Nick G8INE helps out. He has designed his own PCB's and has made Pete's project. He offers the gerber files which most design software will accept.

Page 9 Schematic was unclear. It can be downloaded here.

Page 20 Schematic was unclear. It can be downloaded here.

Sprat 175

When you get it you might find that the content of page 38 & 39 is reversed. Now that you know this, it is easy to read Chris Page's Member News column - just read page 39 and then 38.
I will not be sending out replacement copies.

The circuit diagrams on pages 5 and page 8 came out a bit tiny. Please select the above links to download a better copy.

On page 17 Doriano IW1PAG describes a simple constant current charger and a mistake crept into the redrawing of his circuit (on page 18). Here is the corrected version

Sprat 172

Sierra Band Modules Article corrections

On page 11 Graham G3MFJ mentions the new club sales item of the TDA2822 audio chip. The datasheet is here and there is some advice how to use it here.

On page 18 Peter G4UMB describes some plug in filters and we neglected to include the details in the article as printed. Here they are.

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 http://iza.gandi.ws/ 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".

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. https://www.cosycave.co.uk/product.php?id_product=323

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 http://iza.gandi.ws/ 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.

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

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

Sprat 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. 

Sprat 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)

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

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.

Article Reprints.

Years ago the club offered this member 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.