Incorporating G2DYM Aerials & Garex Electronics

Quality English products hand-crafted to order













15 November 2018

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.

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 issue PW the Editor has 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.  

The Editor has further threatened that he will find other authors for my series and may not then be in a position to accept submissions from me.  Considering the attitude taken by the Publisher and the Editor I will not be unhappy to retire as a PW author.  As I have received no communication from the Publisher or Editor since early September it is clear they are no longer interested in my contributions.   

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.  

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 15.33 to my personal Paypal account antony.nailer@talktalk.net or through Spectrum, 14.50 by direct transfer to my bank.

 Now to make a start on re-writing T4T Book 2 into Understanding Radio Book 2.  


Intermediate Licence VFO 7MHz DSB QRP TX
5 Band 100W Low Pass Filter 7MHz DSB RX
Poundbury SSB Exciter 5W Broadband HF Linear
Poundbury 70MHz Front-end PSK31 Interface
Mixer - Osc for 4 metres CTCSS Encoder 
Portland VFO Upgrade kits for 2001, 4001, 6001, & 7003
6-Pole SSB IF Filter Piptone PT1000S
  Kaytone KT2000


Intermediate Licence VFO Project.

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 together with the tuning potentiometer is priced at 13.50 including tracked and insured carriage by Hermes within the UK.




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 64.00 UK, 69.00 World.  PCB Built 78.00 UK, 86.00 World.  Box Kit 95.00 UK, 102.50 World.  Box Built 126.50 UK, 132.50 World.



POUNDBURY SSB EXCITER.  The POUNDBURY (2) board is a 9 or 10.7MHZ SSB Generator and Receive IF. A traditional SSB generator incorporating a speech processor.  Carrier suppression typically in excess of 50dB. The board now connects directly to an external SSB filter which has a termination impedance of around 560 ohms and a few picofarads. Other termination impedances can be accommodated by the change of a single resistor. The circuit has provision for USB and LSB carrier crystals which are DC switched. Receive section uses Fet and Mosfet IF amplifiers and a singly balanced diode product detector and discrete audio derived AGC. Includes 1W audio amplifier. The crystal filter and carrier crystals are not included in the PCB kit.  PCB Kit 70.25. PCB built 100.00.  Optional extras, SSB filter 18.50. Carrier Crystals 3.00 each. Mic gain 4K7 log pot, Volume 100K log pot, 1.75 each.  Signal meter 9.00.  8 ohm Loudspeaker 2.00.  P&P on optional extras 3.50.

POUNDBURY 70MHz FRONT END.  A receive preamp and mixer together with a transmit mixer and three amplifier stages to give 250mW output on 4 metres.  Works in conjunction with the Poundbury Generator & Receive IF, the Portland VFO, and the Mixer-VFO board to give a complete 4metre transceiver.  Can also work with the TA4S4 amplifier to give 25W output.   PCB & Parts kit including 2 panel pots 50.00.  PCB built 69.75.

MIXER - OSCILLATOR for 4m, a module for use in conjunction with the Portland VFO to produce a very stable local oscillator signal for a 4 metre receiver or transmitter with a 9MHz or 10.7MHz IF. Uses either a 51.4MHz crystal for a 10.7MHz IF, and a 53.1MHz crystal for a 9MHz IF. Comprises an overtone oscillator, a 4 quadrant multiplier mixer, a filter and buffer amplifier. PCB kit including choice of crystal 26.00 UK, 26.00 EU, 27.00 world. Ready built 36.50 UK, 40.50 EU, 41.00 world.


VFO inside small.jpg

PORTLAND VFO, a rock stable FET VFO for 6.995 - 7.205MHz for a direct conversion for the extended 40metre band, or 7.900 - 8.400MHz for use as part of a mixer VFO system as local oscillator on 70.000 - 70.500MHz band, or 5.0-5.5MHz for 20m and 80m rigs with a 9MHz IF.  Now includes upper band edge adjustment, and meets the requirement for the Intermediate Licence VFO project.  The Buffer (2A), mounted on the rear of the box, delivers 1.6V p-p into 50 Ohm with second harmonic 40dB down. Kit of 2 PCB's and parts 18.25 UK, 18.25 EU, 19.25 World.  Drilled Box and PCB kit with potentiometer and feedthroughs 35.00 UK, 39.50 EU, 40.50 World. Ready built 46.00 UK, 50.50 EU, 51.50 World. Prices include tracking.  State required frequency when ordering. 


6 crystal ladder filters for 9MHz and 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.  Kit of parts 17.00 UK, 19.00 EU, 20.00 World.  PCB built 21.50 UK, 23.50 EU, 24.50 World. Including carriage.

7MHz DSB QRP TRANSMITTER.  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.

7MHz DSB RECEIVER.  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, 28.00 UK, 33.60 EU, 34.10 World.  PCB built plus 40.00 UK, 43.65 EU, 44.15 World. Including carriage.

5W BROADBAND HF LINEAR AMPLIFIER   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. Without wound toroids 36.00 UK, 41.65 EU, 44.15 World.  With pre-wound toroids 43.00 UK, 48.65 EU, 51.15 World.  Ready built and tested 51.00 UK, 56.65 EU, 59.15 World.  Tracking included.  Prices do NOT include the low pass filters.



This is designed as an interface between a computer sound card and a transceiver.  PCB kit 20.00 UK, 21.50 EU, 22.50 world.  Box kit with cables and jack plugs 39.50 UK, 45.00 EU, 47.50 World.  Ready built 54.00 UK, 59.50 EU, 62.00 World.  Includes tracking.


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.

UPGRADE KITS FOR 2001, 4001, 6001,7001

2001 PIC module to change to 12.5kHz channel spacing and add CTCSS. Supplied with replacement reference crystal, LED in-between channel indicator and handbook with new frequency listing. 22.50 excluding P&P.

4001 replacement PIC to change to 12.5kHz channel spacing. Supplied with replacement reference crystal and handbook with new frequency listing. 8.50 excluding P&P.

6001 PIC module to change to 10kHz channel spacing and add CTCSS. Supplied with handbook with new frequency listing. 20 excluding P&P.

Upgrade kit for 2m, 4m, and 6m versions for improved IF amplifier, better RX filter matching and improved transmit audio. Supplied with replacement IF filters 10M07 and LTW455HT and complete circuit diagram & board component layout 14 excluding P&P.

7003 upgrade to receive IF amplifier and transmit modulator section is pending post design work but is likely to be similar to the kit above except that the 21.4MHz first IF filter will not be changed.

AUTO TONEBURST A stable RC oscillator to provide a 500mS burst of 1750Hz audio for repeater access. The board has option for 7-10V or 10-16V operation. PCB size 29 x 27 x 15mm. Type AT1750. PCB Kit 7.00 UK, 9.00 EU, 10.00 World. PCB Built 10.00 UK 12.00 EU, 13.00 World. Including carriage.


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, 10.50 EU, 11.50 World. PCB Built 13.25 UK, 14.75 EU, 16.00 World. Prices include carriage.


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 14.25 UK, 16.25 EU, 17.25 World.  PCB Built 21.25 UK, 23.25 EU, 24.25 World. EU & World tracking 5.50 extra.