** Latest WVARS Project ***

WVARS Winter 2021/22 Project

RF Signal Generator


At the club in November 2021, we started to build our winter construction project, an handheld RF Signal Generator.  Most of us completed the build in the 2 hours we were at the club, and all worked which is always great to see.  Help was also on hand at our meeting on Monday 17th January 2022 to get the remaining kits finished off and tested.


Welland Valley Amateur Radio Society Winter 2021/22 Construction Project - RF Signal Generator.


(1) What is it?


An RF signal generator that produces a signal from 10kHz to at least 200MHz.

The power output can range from 10mW to a few uW making it suitable for many purposes from

a temporary Local Oscillator to a receiver test signal. It's intended to be a useful bit of test equipment in the shack.

The signal is normally non-modulated CW.

Included is the ability to send a short CW modulated message of 32 characters. This message can be 

edited into the source and is non-volatile and repeating, so the unit becomes a CW beacon.


Control of the functions is by a rotary encoder and two push buttons. There is a 4 X 16 character OLED 

display. RF output is by 3 SMA connectors.


The power source is a PP3 type 9V battery.


IMG_1428.JPG

This is a picture of the prototype.


(2) How easy is it to build ?


The unit has been designed to be easy to put together. Everything mounts on a single PCB.

There are no Surface Mount components to solder. It's all Thru Hole apart from the SMA connectors.

They solder to the top end of the PCB. There are some fairly small parts, but nothing too bad.


PCB Front.JPG

This is the PCB, and yes they really are this colour.

This drops straight into a 60 X 100mm plastic box.

The box has pre-cut holes for the connectors, and the lid of the box is pre-cut for the

display and the controls. The code is pre-installed on the 28 pin IC, so it all should just work.


I reckon it should be a relaxing 2 hour build. No need to rush.


(3) What does it cost


The complete kit costs £12. This includes everything apart from a PP3 type (MN1604) battery.


(4) What tools do I need to build it


Essential:-

Small soldering iron and suitable solder

Small cross head screwdriver

Small flat end screwdriver

Pair of small wire cutters

Useful to have:-

Tweezers/Small pliers

Good light source and suitable extension cable

Multimeter for testing


Tim (G8JFX)


DVB-T SDR

Receiver Setup

For Windows XP

Several WVARS member have recently dug deep into their pockets and bought one of the small DVB-T receivers these dongles are originally sold to allow you to watch Digital TV on your PC/Laptop etc.  However when used in conjunction with the correct driver and SDR software it will allow you to receive all modes from about 24MHz to 1800MHz. Please Note: The information below is to help those with Windows XP get their DVB-T Dongle working as one or two club members have had problems compared to those who use Windows 7 where the default install seems to work.






OK Here goes.........

Part 1.  Install the Windows XP Driver.
  1. Plug your Dongle into a USB Port (Always use the same USB Port when using the dongle).
  2. Ignore all of the Windows prompts to install the drivers, just keep clicking cancel each time.
  3. Once Windows has given up trying to prompt you into installing drivers you are ready to download and install the Windows XP version of ZADIG.
  4. Download the Windows XP driver by double clicking here: >>  zadig_xp <<  
  5. The file is zipped so will need extracting to your Desktop etc....
  6. Once it is extracted remember where you have saved it for example your Desktop.
  7.  You should now have a file called "zadig_xp.exe"
  8. Install the driver by double clicking on the new file "zadig_xp.exe"
  9. You should then get a pop up window as the install starts and “Bulk-In, Interface (Interface 0)” should be displayed. 
  10. If not then use the down arrow to the right near the edit button to select the drop down menu.  Then select “Bulk-In, Interface (Interface 0)”.
  11. Then click “Install Driver”.
  12. You should see the driver installing and finally a pop up window saying “The driver has installed successfully”.
  13. Click on Close.
  14. That completes the installation of the driver.
Part .  Install SDR software.
  1. Download the sdrsharp software from by clicking here >> sdrsharp >>
  2. Save the file on your PC, for example on your Desktop.
  3. Again as the file is Zipped, so you need to extract it for example on your Desktop.
  4. Once extracted Double click on the “sdr-install” folder to open the folder.
  5. Double click on the install.bat file to install SdrSharpe.
  6. Click on Run.
  7. A black MS-Dos type box will appear and you will see the files being installed.
  8. Once installed you will find a new directory called “sdrsharp”.
  9. Open that directory and delete the file “zadig.exe” as that is the newer Windows 7 driver and as you are using Windows XP you don’t need that driver.
  10. To run the software double click on the file “SDRSharp.exe” that has an icon like a Blue Headless Flamenco!!!!
  11. Once the software has started you need to select the Dongle.
  12. Just to the right of the Play button on the top left, you should see a box with “Other (Sound card)” displayed.
  13. Click the down arrow to the right of the box and select “RTL-SDR / USB”.
  14. Then click the “Play” button.
  15. Click on "Configure" and look towards the bottom for the RF Gain slider, slide it fully to the right (49.6dB) for maximum sensitivity.
  16. As a test select 102.3MHz and select WFM and you should hear Harborough FM.
  17. Or try GB3CF the Leicester 2m Repeater on 145.600MHz NFM or the Echolink Node on 430.0125MHz NFM.
 That should get you up and running. 

 

Club Construction Project

M0UKD's 9:1 Un-Un Balun

Many thanks to M0UKD for the design.  See his website http://www.m0ukd.com for more information.

These are usually called a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance long wire (~450 ohm), down to a 50 ohm unbalanced coaxial input. I have heard them called an UnUn which seems more appropriate. I almost bought one of these for around £30, but then decided to make one. The toroid is a T130-2 Iron Powder core, with 3 x 9 turns of 18SWG enammeled copper wire, and the connections can be seen below.



Construction Project 2008/2009

RX/TX Computer Interface.

(Originally by Rahul Srivastava, VU3WJM)

 

These days it's very easy to dig deep into your pocket and pull out £100 and buy an off the shelf black box type interface to use on the "DIGI MODES".  However it's much more rewarding to build your own for a few pounds.

This interface can be used on one of the many DIGI Modes such as PSK31, MFSK16, MT16, Hellschriber, SSTV, RTTY, AMTOR, PACTOR, PACKET, CW, Echolink and EQSO. Not forgetting the later WINDRM or FDMDV Digital Audio over analogue radio modes.

The original design by VU3WJM can be found on the following webpage http://www.hamradioindia.org/circuits/digivu.php

Step 1.  Making the PCB.

Equipment Required

  1. Photosensitive PCB (Positive) material 60mm x 80mm.

  2. Transparency of the PCB overlay track.

  3. UV Light box.

  4. Laser Printer.

  5. Ferric Chloride Hexahydrate Granules.

  6. Universal Developer.

  7. Container for developing the PCB.

  8. Container for etching the PCB.

  9. 0.5Lt Water.

  10. PCB Drill.

  11. Eye protection goggles.

  12. Latex protective gloves.

Photosensitive PCB

 

Universal Developer

Ferric Chloride Granules

 

 

Transparency of the PCB Overlay

Right Click image above and "Save As"

When printed the two holes shown below

should be 70mm between centres

(Check as different printers vary)

 

  1. Download the PCB overlay.

  2. Print the overlay image of the PCB tracks onto a transparency sheet of the type used on overhead projectors.  You will get much better results using a laser printer. Also print in monochrome and not greyscale or colour.  When you look at the black tracks they should be solid black in colour.

  3. Place the Overlay in the Light box and then place the Photosensitive PCB on top of the Transparency.

  4. Expose to UV light (Time depends on UV light source).

  5. Remove the Photosensitive PCB from the light box and you should see a fait outline of the tracks on the PCB.

  6. Dissolve the universal developer powder in warm water (50°C).  Use 25g of universal developer powder to 1/2 litre of water.  Allow to cool down to about 22°C before use.

  7. Pour your developer solution into a suitable container and placing the UV exposed PCB into the dissolved developer solution.

  8. Gently rock the container to create a small waves in the solution.  You should see the tracks starting to appear.  Leave in the developer and keep rocking the container gently until all of the tracks appear clear.

  9. Remove the developed PCB and rinse under running water.

  10. Dissolve the Ferric Chloride Granules in warm water (50°C) in a suitable container.

  11. Allow the dissolved Ferric Chloride solution to cool to about 22°C before use.

  12. Place the developed PCB into the Ferric Chloride solution and again gently rock the container from side to side, it can take between 10 to 20 minutes for the etching process to complete. 

  13. Once the PCB has been etched and you can clearly see the tracks of the PCB, remove it from the solution and rinse the board off under a running tap.

  14. Use a small PCB drill to drill the component mounting holes.

Homebrew PCB

 

Components Required

Component
Description
QYT
PCB1
PCB 
1
D1 & D2
1N4148 Diode
2
R1
3k3 ohm 1/4 watt Resistor
1
R2 & R3
1k5 ohm 1/4 watt Resistor
2
R4
100 ohm 1/4 watt Resistor
1
R5 & R6
33 ohm 1/4 watt Resistor
2
OP1
Opto Isolator  IC
1
SK1
6 pin DIL Socket
1
T1
600:600 Audio Transformer
1
VR1
500 ohm potentiometer
1
C3
1 uf 63v Electrolytic Capacitor
1
C1, C2 & C4
0.01uf Ceramic Capacitor
3

Step 2.  Soldering components to the PCB.

 

The PCB below shows where all of the components should be installed.  The component layout is very straight forward.  Just take care to install the electrolytic capacitor the correct way around and also the two 1N4148 diodes

 

Your board should look something like this below.....

Here is the circuit diagram