Incorporating G2DYM Aerials & Garex Electronics

Quality English products hand-crafted to order












7 December 2019

Proprietors;- Mr A.J. Nailer HNC BA G4CFY, Mrs J.R. Nailer. 


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@talktalk.net 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 with the name spectrumcomms and pay via Paypal.

Orders & quote requests to  jean@spectrumcomms.co.uk

Technical queries to  g4cfy@talktalk.net 


NEWS UPDATE. The first article of the Radio Design & Construction series about a hybrid valve/transistor 20 & 80m AM/USB/LSB receiver is now ready for purchase at a cost of 2.50 direct to my bank or 2.85 to my Paypal email address antony.nailer@talktalk.net  The first article of the Understanding Radio series about Op Amps is still available at a cost of 2.00 to my bank or 2.35 to my Paypal account.  In the future I also intend to rework the last 20 something articles of Technical for the Terrified into a book called Understanding Radio Book 3.  

MY RETIREMENT AS AUTHOR FOR PW.  In the Editorial in November 2017 issue PW the Editor stated that I am unable to submit articles for the foreseeable future.  This is not true!  I am quite capable of submitting articles for Doing it By Design and for Technical for the Terrified BUT the Publisher for the new owner is unwilling to even discuss a requested small increase in my remuneration nor the shared copyright agreement and arrangement I had with the previous owners.  

I had not contemplated a retirement BUT having done this every month, with the exception of just two or three issues, since 2004, consuming on average in excess of 1/10 of my time I was always on the go.  

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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 Loops, PLL in CB & 10M rigs, Antennas & Feeders.  Price 15.50 to my personal Paypal account antony.nailer@talktalk.net or through Spectrum, or by direct transfer to my bank.

 I have now started compiling Understanding Radio Book 2.  


Intermediate Licence VFO Piptone PT1000S
TX 100W 5 Band Low Pass Filter Kaytone KT2000
5W Broadband HF Linear Portland VFO
RX Front-end Filters, 5 & 10 band 7MHz DSB QRP TX
SSB Detector & CIO 9 or 10.7MHz 7MHz DSB RX
SSB Detector & CIO 455kHz CTCSS Encoder 
SSB IF Filter 6-Pole, 9 or 10.7MHz  Audio 500mW Amplifier



SUPER SUDDEN RECEIVER As featured in the latest issue of SPRAT Magazine from the GQRP Club.

PCB (on its own) with a circuit diagram that matches the PCB layout 7.50 including P&P.

Complete kit of parts with circuit diagram that matches the PCB layout, and includes the special pulse transformer, 30 including carriage.




Here is a simple stable variable frequency oscillator suitable for the qualification of the UK Amateur Intermediate Licence.  It is a Colpitts Oscillator with the output taken from a link winding on the oscillator coil and fed through an FET buffer.   The output is low impedance and typically has the second harmonic 40dB down, which produces a sinewave on an oscilloscope screen that looks perfect. The PCB kit and tuning potentiometer 16.50 UK, 18.50 EU, 19.25 World.


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Five relay switched 5-element Elliptic Low Pass filters for use in conjunction with wideband HF linear amplifiers. The standard board has the classic bands 80, 40, 20, 15, & 10m.  160, 60, 30, 17, & 12 are also possible. Two boards can be paralleled to give a 10 band facility. The relays are high sensitivity requiring only around 15mA each for activation from a 13.5V switching voltage.  There is insignificant passband loss for each filter and ultimate attenuation 'As' is specified at either -30dB or -40dB in excess of 3 times the cutoff frequency.   A notch just below the 2nd harmonic is typically 20dB further down than at As.

PCB Kit with pre-wound toroids 76.00 UK, 81.50, 83.00 World.  PCB Built 86.50 UK, 92.50 EU, 94.00 World.  




Push-pull transistor HF linear covering the range 1.8-29.7MHz with full out for input levels between 37 and 97mW drive.  Harmonics typically are 2nd -42dB, 3rd -18dB, 4th -49dB and 5th -29dB.  This amplifier needs to be used together with a double Pi type low pass filter, details of which are supplied with the kit.

Full kit of parts with drilled heatsink. With pre-wound toroids 45.00 UK, 50.50 EU, 51.50 World.  Ready built and tested 50.50 UK, 56.00 EU, 57.50 World.  Tracking included.  The prices do NOT include the low pass filters.



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Triple bandpass coupled receive filters.  DC diode switched with 5 bands to a board.  Kit 5A 80/40/20,15, & 10m.  Kit 5B 160/60,30/17/& 12m.  Insertion loss below 5dB on all bands. Switching DC resistance 1k Ohms, draws 8mA from 8V or 12mA from 12V.  Two boards can be interconnected for 10-way band switching.  board size 92 x 84 x 15mm.  

One PCB 5-band kit of parts 40.00 UK, 45.50 EU, 47.50 World. Single PCB built 54.50 UK, 60.00 EU, 62.50 World.  

Two PCB 10-band kit of parts, 77.50 UK, 83.50 EU, 85.00 World. Two PCB built 106.50 UK 112.50 EU, 114.00 World. Prices include tracking.


SSB DETECTOR & CIO 9 or 10.7MHz. The board includes two carrier insertion oscillators (CIO) connected at the transistor collectors like Siamese twins.  This allows each to be selected by switching the base bias to the transistors.  This avoids the usual pulling effect of one oscillator tuning on the other.

The SSB signal is demodulated using an FET product detector with an audio transformer in the drain circuit to select the audio and completely remove any residual 9 or 10.7MHz IF or carrier signal.   Choose 9MHz or 10.7MHz.

PCB Kit 21.50 UK, 23.50 EU, 24.50 World.  PCB Built 29.50 UK, 35.50 EU, 36.00 World.

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SSB DETECTOR & CIO 455kHz.  The board includes two carrier insertion oscillators (CIO) connected at the transistor collectors like Siamese twins.  This allows each to be selected by switching the base bias to the transistors.  This avoids the usual pulling effect of one oscillator tuning on the other.

The SSB signal is demodulated using an FET product detector with an audio transformer in the drain circuit to select the audio and completely remove any residual 455kHz IF or carrier signal.

PCB Kit 17.00 UK, 19.00 EU, 20.00 World.  PCB Built 21.50 UK, 23.50 EU, 24.50 World.


6-POLE CRYSTAL SSB FILTER. Ladder filters using 6 crystals for 9MHz or 10.7MHz. Bandwidth at -6dB 2300HZ .  Bandwidth at -60dB 6000Hz.  Shape factor 2.6:1. Insertion loss 2dB.  Termination 560 Ohms and less than 5pF.  PCB size 60 x 27 x 15mm.  Choose 9MHz or 10.7MHz.

PCB Kit with wound toroids 18.50 UK, 20.50 EU, 21.50 World. PCB built 21.50 UK, 23.50 EU, 24.50 World. 

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PIPTONE. An end of message tone for 250mS for weak signal SSB use. The unit provides 50mV across a 600 ohm microphone. The tone and amplitude are presetable. A relay is included for receive and PTT switching. PCB size 44x25x17mm. 

Type PT1000S. PCB Kit 9.00 UK, 11.00 EU, 12.00 World. PCB Built 12.50 UK, 14.50 EU, 15.50 World. Prices include carriage.


KAYTONE. A name coined by Spectrum, this unit is the successor to the original Kaytone sold in 1979. End of message Morse K particularly useful for weak signal situations. Adjustable pitch, speed, and level. A relay is included for TX and RX switching making it suitable for all rigs. PCB size 58 x 39 x 15mm.   

Type KT2000. PCB Kit 14.50 UK, 16.50 EU, 17.50 World.  PCB Built 21.50 UK, 23.50 EU, 24.50 World. EU & World tracking 5.50 extra.

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PORTLAND VFO. A rock stable FET VFO for 6.995 - 7.205MHz for a direct conversion for the extended 40metre band, or 5.0-5.5MHz for 20m and 80m rigs with a 9MHz IF.  Now includes upper band edge adjustment.  The Buffer (2A), mounted on the rear of the box, delivers 1.6V p-p into 50 Ohm with second harmonic 40dB down.  

Drilled Box and PCB kit with potentiometer and feedthroughs 33.50 UK, 40.00 EU, 41.50 World. Ready built 45.50 UK, 51.00 EU, 52.50 World. Prices include tracking.  State required frequency when ordering. 



A 250mW double sideband transmitter comprising microphone amplifier, diode ring modulator driver and output stage. Works in conjunction with a Portland VFO and can be combined with the 7MHz DSB receiver to form a transceiver. The PCB kit of parts including a TO5 heatsink, a 10k log mic gain pot and wound toroids. Price 33.00 UK, 37.00 EU, 37.50 World. PCB built plus log pot 41.00 UK, 45.00 EU, 45.50 World. Including carriage.


A double sideband direct conversion receiver requiring just the addition of a Portland VFO local oscillator.   Works in conjunction with the 7MHz DSB QRP Transmitter and Portland VFO.   PCB and kit of parts including volume control.  Price 28.00 UK, 33.60 EU, 34.10 World.  PCB built plus 40.00 UK, 43.65 EU, 44.15 World. Including carriage.


 Designed originally by Ken Ginn G8NDL, then modified and a new PCB layout by Spectrum.  Produces all nine CTCSS tones that can be selected by a link or using a 9 way rotary switch. The unit is triggered by the microphone PTT and in turn provides a PTT output to the rig via an opto-isolator. The module includes a trimpot to set the tone level output to accommodate different microphone impedances.  PCB size 67x55x10mm.  PCB kit 18.00 UK, 19.50 EU, 20.50 World.  PCB built & tested 25.00 UK, 27.00 EU, 28.00 World.  Including P&P.

500mW AUDIO AMPLIFIER. A handy audio output stage using a TBA820M with a gain up to 48dB, 0.5W into a 8 Ohm load, low quiescent current, and low noise.  Article in PW March 2006. PCB Kit 9.00.