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Scanner & SW Listener

8 February 2024

Proprietor;- Mr A.J. Nailer HNC BA G4CFY 

12 WEATHERBURY WAY, DORCHESTER, DORSET, DT1 2EF, ENGLAND

Phone UK 01305 262250 International 0044 1305 262250

Please email or phone for a quote or for a Paypal money request or for bank details. Payment can be by direct bank transfer or by credit/debit card or via Paypal to g4cfy@spectrumcomms.co.uk  together with a note stating product required. Purchase of several items is likely to make a saving on postage. You can also obtain products by using my Ebay shop https://ebay.co.uk/str/Spectrum-Comms and pay via Paypal.

Orders & quote & technical requests to  g4cfy@talktalk.net

Understanding Radio Book 1 is a re-write of the Technical for the Terrified Book 1 published by Practical Wireless and compiled from 27 articles of that name previously published in PW Magazine between February 2005 and October 2008. The first chapter is a short revision for everyone who has not used algebra since leaving secondary or grammar school.  It should also be useful to youngsters still at school and trying to get to grips with it.  The articles have been reworked into chapters so there is now a natural progression of information through the book.  All the circuits have been redone and a lot of wasted space and unnecessary comments removed.  It runs to 112 pages, which is 10 less than the T4T Book 1 but there is a lot more in it.  The writing style is aimed to be easy to read and should be of great value to readers of all technical levels.   Subjects include; Algebra; Resistors & Ohm's Law; Diodes and Rectification; Transistors - FETs & Valves; Transistor biasing; Amplifier Classes of Operation; Reactance & Resonance; Parallel Tuned Circuits; Bandpass Coupled Pairs; Small Signal Bipolar RF/IF Amplifiers; Small signal FET & Mosfet RF/IF Amplifiers; Oscillators; Mixers; Decibels; Modulation Modes; TRF & Superhet; Filtering in HF & VHF Receivers; Modes & Demodulation; Choosing RF - IF & LO; Phase Locked Loop; PLL in CB & 10M rigs; Antennas & Feeders.  

Understanding Radio Book 2 is a re-write of Technical for the Terrified Book 2 including all the articles 28-49 published in PW between October 2008 and April 2013 plus article 51 published in August 2013.  The articles have been condensed into chapters and unnecessary duplication of information has been trimmed back and then the subjects further expanded.  It runs to 114 pages and the subjects include Passive components, old and new; Equivalent circuits; Variable Frequency Oscillators; Crystal Controlled Oscillators; Feedback & Amplifier Stability; Singly Balanced Mixers; Analogue Low Pass Filters; Laying out Printed Circuit Boards; Measurements and Test Jigs; Receiving 100kHz - 30Mhz; Superhet Receivers; AGC of RF & IF Stages; Superhet with Tuneable IF; Coax & Twin Feeder; SWR/PWR Meters & the Noise Bridge; Aerial Impedance - Bandwidth & Gain; Aerials for Receive & Transmit; ATU's for Receive & Transmit.

To buy either books on its own including postage pay £18.00 to my personal Paypal account antony.nailer@talktalk.net or through Spectrum, or by direct transfer to my bank.

To buy both books together pat £30.00 to my personal Paypal account antony.nailer@talktalk.net or through spectrum, or direct transfer to my bank.

The VHF and UHF bands are dominated in the UK by broadcast FM radio in the range 88-108MHz and by broadcast TV from 550MHz up to about 900MHz.  Any preamp that is wideband enough to include wither of these broadcast bands is likely to overload and then not be able to amplify the low power communications in the range 110-400MHz.  The preamp includes quite sharp high pass and low pass filters with a passband as shown in the screen shot.  The top of the screen is +20dB and the vertical scale is 10dB steps.  The horizontal scale is 100MHz steps. Gain is 0dB at 500MHz falling to more than -25dB to 1000MHz.  Passband gain is 18dB +/-1dB.The mains version is housed in an unpainted diecast box 120x95x34mm with BNC sockets and a 1 metre mains lead and plug. A 0.6m BNC-BNC lead is included.

Ready Built only, £61.00 UK, £71.50 EU, £77.50 World. Including insured and tracked carriage.

                                   110-400MHz PREAMP 12V

This version  is powered from an external 12V supply.  It uses the same board amplifier boards as the mains version but is now supplied in an unpainted diecast box, which looks more rugged and is a little cheaper than the painted version shown in the picture.  It is supplied with a 0.6m RG58 BNC-BNC lead.

Ready for external 12V and built in plain diecast box £41.20 UK, £49.50 EU, £53.30 World.

Ready built in black diecast box, £45.50 UK, £53.50 EU, £57.30 World.  Includes tracked carriage. 

HF TUNEABLE PREAMPLIFIER

1.8 - 30MHz.  Configured in 4 bands, Band A 1.8-3.8MHz, Band B 3.8-7.6MHz, Band C 7.5-15.0MHz, & Band D 15.0-30.0MHz..  Band A gain is 10dB at 1.8MHz rising smoothly to level off at 16dB at 3.5MH to 3.8MHz. Band B gain is 10dB at 3.8MHz rising smoothly to 16dB at 6.6 to 7.6MHz.  Band C gain is 11dB at 7.5MHz rising smoothly to 16dB at 13.5MHz to 15MHz. Band D gain is 7dB at 15MHz rising quite steeply to 15dB at 21 to 30MHz.  Gain adjustable down to -20dB.  Runs from external 12 or 13.5VDC at 20mA via a 2.1mm DC connector. input and output RF sockets are SO239. Two-part stove enameled box 150x100x75mm.  Weight 410gms. 

Ready built £102.00 UK, £112.00 EU, £118.00 World.  

REGENERATIVE RECEIVER

REGENERATIVE RECEIVER (G3RJV-G4CFY).  This is my development of the circuit described by George Dobbs G3RJV in April 2013 PW.  It comprises an FET infinite impedance detector and a conduction controlled Q multiplier or oscillator to enhance AM reception or receive and decode SSB signals.  It also includes an IC audio amplifier to drive a loudspeaker.   Version A 1.8-3.8MHz uses 45u0H coil.            Version B 3.5-7.5MHz uses 11u0L coil.              Version C 7.0-15.0MHz uses 2u6L coil.             Version D 11.0-23.0MHz uses 1u2L coil.

PCB kit and pots & polyvaricon £24.50 UK,  £27.50 EU, £28.30 World.  Conversion kit to 4 Band Receiver £14.50 UK, £16.50 EU, £17.25 World.

Knobs and phono socket NOT included.

RX L-type AERIAL TUNING UNIT

For short random wire end fed aerials.  Gives improved signal strength and lower receiver noise from 200kHz to at least 21MHz depending on wire length.  Diecast box 114x64x55mm. Fitted with terminals for aerial and earth inputs, and phono or BNC or SO239 coax output.  Includes a switch for tuner or bypass.  State required output connector when ordering.  Ready Built £43.00 UK, £51.00 EU, £54.80 World.  

RX SPC AERIAL TUNING UNIT

For all types of antenna, except short random wires.  It has an SO239 socket for coax inputs and a binding post for direct random long and short wires.  It works from 1MHz to 32MHz and will tune high and low input impedances and provide a low impedance output via an SO239 socket to the receiver.  Housed in a two part stove enameled aluminium case 150x100x75.  Price £65.00 UK, £75.50 EU, £81.50 World.  Including tracking & insurance.

CLARA 2 DIRECT CONVERSION RECEIVER  

Single band design, can be configured to work on 160m, or 80m, or 40m, or 30m, or 20m.  High stability Hartley VFO.  12/13.5V DC operation.  Box kit £68.00 UK, £77.00 EU, £79.00 World. Box built £94.50 UK, £103.00 EU, £105.00 World. Includes tracking and insurance.

VFO board inside the box

Buffer board outside the box