Tuesday, 12 September 2017

We donated £100 to Cancer Research UK From our Summer Raffle

Thanks so much for all your support we have now made the donation of £100 to Cancer research UK

Thursday, 7 September 2017

Simple 70cm Fox Hunt Reciever

After building the Simple transmitter I decided to use the companion reciever module to the FS1000a emitter used previously, again the concept was to keep everything simple and easy for children to construct (under supervision).

The reviever is contructed around the MX-RM-5V module which operates on the 433.92Mhz ISM band. Again using parts from the junk drawer I came up with this simple circuit.

The circuit runs from a 6v battery pack (4x AA Cells) and utilises both audio output via headphones and visual feedback from an LED. The main component is a BC547 NPN transistor, however pretty much any NPN transistor could be used. Output from the transistor provides just enough current to drive the headphones without the need for an audio amplifier but a simple single IC solution like the LM368 could be utilised. Now I must note the 433.92Mhz ISM band can become extremely congested and this will reflect on the receiver, however as we plan to use it in a large country park it should not be much of an issue.

I originally wanted to build a simple 70cm Yagi from a tape measure, however decided the sharp edges were not child friendly so I came up with the idea of using copper self-adhesive tape on a pre-constructed frame. The frame is built from 15mm pine and contains a director, driven and reflector element. The design shown below used pre-cut pieces that can be sandwiched to produce the yagi frame.
Each element is 400mm long, the inital spacing is not important however the 100mm and 80mm spacings between the director, driven and reflector elements is important. The overall length of the frame is also users choice but should be long enough to accomodate the pcb/battery and handle.

Copper tape is then stuck on to each element for the total length, this can then be cut to 'tune' the antenna. The middle 'driven' element needs to be cut in the middle to isolate the two halfs of the element and can then be soldered directly to connect the reciever. The follow lengths are what worked best for me, but feel free to play with them;

Director:   306mm
Driven:     312mm 
Reflector: 360mm

I used a cheap plastic lunchbox to house the electronics and co-axially mounted the battery pack, this doubles in purpose as the unit lacks a power switch. The clear plastic of the box also negated the need to externally mount the LED.

If anyone has attempted to build this project or improved on it I would love to hear about it!

Simple 70cm Fox Hunt Transmitter

While discussing with a few friendly hams about the coming summer we came up with the idea of running a fox hunt for the kids, so I set about looking at how we could do this.
Ultimately we needed a transmitter and receiver that could be easily constructed and operated by children. Fortunately I came across these cheap UHF transmitter / receiver pairs whilst browsing Amazon..
The pair labeled XY-FST-RX / MK-RM-TX can be had for only a few pounds and are available in the 315Mhz, 418Mhz, 433Mhz and 915Mhz frequency bands, so out of interest I purchased a few of the 433Mhz (70cm) varients. The modules operate with AM on 433.92Mhz ISM band which is fortuently license exempt (power limit!) in the UK and are designed for basic data transmission (The band is popular for car remote locking, wireless doorbells, etc). The emitter has 3 pins (Vcc, Data, Gnd) and a pad located in the top right for an antenna, however I have seen the same module with four pins (Vcc, Data, Gnd, Ant). Likewise the reciever follows a similar layout and has four pins (Vcc, Data0, Data1, Gnd) however upon inspection the two data pins are actually bridged. 
After breadboarding the emitter and manually pulsing the data pin whilst monitoring with the HT it became clear that oscillating the pin with an MCU could be a viable method of producing a crude CW signal. I eventually came up with this circuit using parts from my junk drawer and an Arduino Nano MCU.
 The circuit is very simple, with power being provided from a 9v PP3 battery and the datasource being provided by a PWM digital pin on the arduino. I added the LED for visual feedback. Those looking to reduce costs could probably use an ATiny MCU or PIC instead. The circuit was built onto a scrap piece of copper veroboard, without any antenna. I wrote a simple sketch to test my thoery, by interpreting morse: 0 - pause, 1 - dit and 2 - dah to control the timing of the pulses.
//msg = FOX HUNT M3RKV
int msg[]={0,1,1,2,1,0,2,2,2,0,2,1,1,2,0,0,1,1,1,1,0,1,1,2,0,2,1,0,2,0,0,0,2,2,0,1,1,1,2,2,0,1,2,1,0,2,1,2,0,1,1,1,2,0,0,0};
int i;
int t;
void setup() {
  // Setup Pin 3 (PWM) as output
 pinMode(3, OUTPUT);

void loop() {

 for(i=0; i < (sizeof(msg)/sizeof(int)); i++){
  if(msg[i] == 0){t=800;}                   //Pause
  if(msg[i] == 1){tone(3,1200,100);t=400;}  //Dit
  if(msg[i] == 2){tone(3,1200,300);t=600;}  //Dah (3x dit)

 //Pause between Messages

As you can see I  used the tone() function to produce the signal required, where the first parameter is the Pin used, the second is the frequency and the third the duration in mS. I will come back here at soon to revisit the code and improve it but for the purpose of testing it does suffice.
Sure enough, tuning my HT to 433.920Mhz allowed be to hear the crude signal being produced and even without an antenna I was able to move around the house and outside without complete loss of the signal, however even when placed directly next to the emitter the AF signal was not strong enough to break through the squelch on my HT dispite it being on the lowest possible setting. 
The enclosure is a standard project box and provides enough space for the battery, PCB and antenna. The antenna is a simple J-Pole designed for 70cm and made from 18SWG enameled copper wire. Moving forwards it would probably be a good idea to terminate with an N-Type connector so that multiple antenna configuration can be used.

Sunday, 3 September 2017

Virtual Build a thon 2 / 70 Diplexer surface mount kit video

Presented by Bob M6FLT / KG7VZD (above)



Here is the board as constructed by Chris G0JPS (above)

Here is the board as constructed by Matthew M0ZKK (above)

Andrew DL1UGH doing the live build

Meanwhile in Florida Kevin KK4YEL is battling a storm of his own...You can hear the rain and thunder from his shack....

Maurice G4YHE

Michael G0POT joined us and kept the questions and the banter going 


Thursday, 31 August 2017

CRC Summer Raffle draw

1: Retevis RT-82 Ryan Ballard

2: Retevis robot walkie talkie set Leigh Preece

3: Amsat-UK membership Bob Conduit

4: m0tgn morse tutor David Jolly

5: DX40 RX Allan Gallop

6: pixie 40 meter CW D P Wickes

7: international Antennas book Martin Harvey

8: stealth antennas book Alex Champkin

GB8SSD qsl infront of Space Shuttle Discovery Thanks to Smithsonian Air and Space!

Wednesday, 30 August 2017

Land Mobile magazine publishes article on Project Thomas watch

GB8SSD Space Shuttle Discovery Maiden Space Flight 33 years ago Today

Chertsey Radio Club continues to celebrate the 33rd anniversary of the maiden space flight of Space Shuttle Discovery with SES GB8SSD

Discovery's Maiden Voyage
Space Shuttle Discovery soars away from Launch Pad 39A at the Kennedy Space Center, beginning its maiden voyage and a storied spaceflight career that spanned more than 26 years. The on-time liftoff occurred at 8:42 A.M. EDT.

NASA’s Space Shuttle Discovery (Orbital Vehicle-103) took off for the first time on August 30, 1984, beginning what would become 27 years of reliable service.

In its nearly three decades of use, Discovery successfully completed 39 missions, the first of which was putting three communication satellites into orbit

This maiden voyage came more than two months later than planned. It was delayed from its originally scheduled launch date after experiencing the Space Shuttle program's first launch abort at T-6 seconds on June 26, 1984.

Discovery includes among its many credits the launch of the Hubble Space Telescope, John Glenn’s second flight (when he was 77 years old), and both research and International Space Station assembly missions.

Discovery’s last launch was in February 2011, before it was retired in March 2011. It was the first operational NASA shuttle to be retired, followed by Endeavour and Atlantis.

Discovery celebrated its retirement with an April 2012 victory lap where it piggy backed on a modified Boeing 747 to the Smithsonian's National Air and Space Museum in Washington, DC, on its way to be put permanent display. 

STS-41D, Discovery's first launch & landing (8-30-84)

ABC News Coverage of the STS-41-D Launch

1984 Space Shuttle Highlights NASA STS-41-B, STS-41-C, STS-41-D, STS-41-G, STS-51-A

Wednesday, 23 August 2017

Emergency call via GB3WR - M6MGE & G6ASK

May Day May Day !!

Image result for champion

Chertsey Radio club contacted Mike to congratulate him on professional handling of the call / situation and let him know he did an amazing professional job. A credit to himself and the hobby.

Mike M6MGE unexpectedly had to handle a 999 (equiv 911) emergency call from John G6ASK via the repeater GB3WR 

The YouTube description reads: 

Wasn't expecting this, So got a little tongue tied!

UPDATE: Michaela (May) Has made a full recovery and continues to enjoy her holiday in Exmouth.

Tuesday, 22 August 2017

ISS cross band repeater active over UK 15:30 **We have contact**

Today we were lucky enough to send voice message via the International space station and talk to other ham radio operators around the world.

Signal was sent up on 437.050 and relayed back by the space station on 145.800

Happy to report I was able to work 2M0SQL, G0ABI, G7SVR (Isle of wight) and F4DXV

Audio from Peter 2M0SQL here

My audio linked below:

ISS repeater active over UK 13:57

Peter 2M0SQL recording here

My recording below

ISS FM repeater active over UK 12:17

ISS was 145.800 downlink and 437.050 uplink again today.

In the above you can clearly hear 2M0SQL Peter working his magic.