The John Welsh Collection

Introduction
Introduction

A Short History Of Radio
Earliest Times
Late 19th Early 20th Century
Early Last Century
Did Marconi really hear those Transatlantic signals?
The Tuned Spark Transmitter
The Coming of the Diode
The Triode, the start of modern electronics

Historic Electronics
Tesla Etcetera (Part 1)
Tesla Etcetera (Part 2)
Tesla Etcetera (Part 3)
Tesla Etcetera (Part 4)
The Thermionic Diode
The Triode Valve
The Klystron
The Klystron – Addendum
The Magnetron
The Magnetron Addendum

Principles
Analogies of Electricity Part 1
Analogies of Electricity Part 2
Scale: Some Numbers
A Crystal Set
The Electron
Wire Baluns (Part 1)
Wire Baluns (Part 2
Transmitter Impedance
The ‘Q’ of a Tuned Circuit
The Phase Locked Loop
The dbs
Units Of Measurement
Lead Acid Batteries
The Microphone
Thoughts on the Magnetic Field in a Toroid

Componants
The Transistor
The Semiconductor Diode
Capacitors (Part 1)
Capacitors (Part 2)
Resistors
Inductors
Ferriteless Toroids
The Thyristor

Aerials
Aerial Gain
The Dipole
Low Frequency Aerials
Shortend Dipole – pt1
Shortend Dipole – pt2
Low Frequency Aerials
Off Centre Fed Aerials
Aerials for Circular Polorisation
Loading Of Aerials
Traps In Aerials
Wave Polorisation (Part 1)
Wave Polorisation (Part 2)
Aerials and their Q
Monopoles and Earth Image
Radiation From A Wire

Feeders
Aerial Feeders
Coax – Does Size Matter?
Coax Calculations
Coax Impedance – Power
Coax Impedance – Loss
Skin Effect
Standing Waves (Part 1)
Standing Waves (Part 2)
Transmission Lines

Earth
Earth Image
The Measurement Of Earth Resisitance
The Importance Of A Good Earth At Low Frequencies
Monopoles and Earth Image

Operating
Are You Getting Out? The Sniffer Box
The Evolution Of Morse Code In Radio Science
Slow Morse (Part 1)
QRSS – Noise (Part 2)
Back To QRSS – (Part 3)
Q Codes

Other
Atmospheric Attenuation
Impedance Of Free Space (Part 1)
Impedance Of Free Space (Part 2)
Impedance Of Free Space (Part 3)
Impedance Of Free Space (Part 4)

CW Class

I have recently started airing some CW training classes on a Tuesday evening. We have a number of club members who seem keen to learn the code, so we have taken to using the 2m Slow Morse Frequency (145.250). Sessions start at 8pm if you wish to join us. Below are recordings taken off air ... Read more

DDRC Rally

This is a reminder that the Radio Rally at Stockwell Park, Luton, is coming up on Sunday, 18th May 2025, with official event times from 9:00 AM to 4:00 PM. Our club will have a stall featuring a range of club gear and other equipment for sale. If you plan to offer personal items for ... Read more

The Secret Genius

Have you ever wondered about the origins of the smart doorbell? Although a modern phenomenon, it has a history dating back over 100 years. During the latest series of The Secret Genius of Modern Life, Hannah Fry explores its early origins with a device created by Leon Theremin. During the episode radio amateur Neil, G4DBN, ... Read more

Why not help run GB0IARU

Reminder – GB0IARU, this week’s scheduleI will be in the cabin as follows:-9th 12:00 – 18:0010th 14:00 – 20:0011th 12:00 – 18:00 All are welcome – foundation/intermediate operators may operate under supervision of the station manager – in this case – me.Modes will be CW/FT8 and possibly SSB.73 – John – G4KZD

DDRC Rally

Dear Club Members,   This is a reminder that the Radio Rally at Stockwell Park, Luton, is coming up on Sunday, 18th May 2025, with official event times from 9:00 AM to 4:00 PM.   Our club will have a stall featuring a range of club gear and other equipment for sale. If you plan to offer ... Read more

Special Event news

The Royal Air Force Amateur Radio Society, also known as RAFARS, will be holding its popular Airfields On The Air special event activity from the 1st of April. RAF Stations will be activated primarily during the 5th and 6th of April, as well as the 12th and 13th of April. More information can be found via ... Read more

Mills on the air (MOTA)

Taking place on Saturday 10th & Sunday 11th May 2025, this years Mills On The Air. The event itself is not run as a contest. The aim is to bring together amateur radio operators and clubs to promote the hobby, whilst helping preserve some of the wonderful heritage of our Windmills and Watermills. However we ... Read more

Maritime Radio Day

Maritime Radio Day 2025 starts at 1200UTC on the 14th of April and finishes at 2200UTC on the 15th of April. The annual event takes place to commemorate the almost 100 years of wireless telegraphy service for seafarers, which ended in the UK with the closure of Portishead Radio on the 30th of April 2000. ... Read more

Clubs On The Air

Amateur Radio Clubs On The Air has launched a new activity for radio amateurs to promote their club, have some fun and collect points for an award. All bands and modes may be used including SSB, CW, FM, RTTY, FT8, FT4 and other digital modes. This is an ongoing award, and contacts may be claimed ... Read more

Operating from the Caribbean

A new article has been added to this website produced by Peter G4HSO. This gives details of his operation and lessons learnt while he was operating from Martinique in the Caribbean. The article can be found HERE! (open this article by clicking on the headline to activate the link to take you there!) https://www.verulam-arc.org.uk/operating-from-martinique-in-the-caribbean/
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