Incorporating G2DYM Aerials & Garex Electronics

Quality English products hand-crafted to order













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 re-written T4T Book 1 as Understanding Radio Book 1 is now available, see below.  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 of 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.  

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 2017 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.  


4001 FM 4m Transceiver

Morse Keyed Oscillator 5 Band 100W TX LPF
HF Switched Preamp 1.8-30MHz VHF Transmit Amplifiers, 25/50/100W
QRP TX Attenuator 5W HF Wideband Linear Amplifier
QRP TX SPC ATU Speech Processor
VHF Station Preamps - Switched PSK31 Interface
VHF Masthead Preamps - Switched Portland VFO

4001 FM 4m TRANSCEIVER   70.2500 to 70.4875MHz in 20 channels in 12.5kHz steps. Originally AKD, then GAREX, now Spectrum. This rig is really easy to use, not menu driven and in the event of failure is easy to repair.  The default channel at switch-on 70.450MHz. Now upgraded to give excellent audio quality on receive and transmit.  RF output 25W or 5W presetable and switchable. Sensitivity better than 0.25uV for 20dB SINAD.  Audio output 500mW rms. Supply requirement 13.5V DC 4A on high TX, 1.5A on low TX, 130mA on RX.  This product is now being custom built to a high quality standard rather than down to the cheapest price. Type 4001S 195.00 UK, 203.00 EU,  including tracked carriage & insurance.


4001 small.jpg 



Supplied either as a kit of parts to build the board shown in the picture as well as a drilled and labelled box, and all associated hardware, or ready built.  It is a stand alone Morse practice oscillator or digitally keyed Morse code generator that can be fed through the microphone socket of an SSB transceiver.

The boxed kit includes 3.5mm jack sockets for Morse key, and for logic input (+5V gives a tone) from a computer, and an output to drive an extension speaker, a SPST toggle switch, volume control, LED and holder, internal loudspeaker, PP3 battery holder and the necessary nuts and screws.  The kit even includes various coloured hookup wire and four stick on feet.  The battery shown in the pictures is NOT included.

PCB & Hardware kit 34.00.  Ready Built 48.00.  Prices include carriage by Hermes.



Through handling power 150W. Fail safe operation, straight through path when switched off.  1.8-30MHz in 4 bands, with highly selective tuneable filters, reduces overload from strong broadcast stations.  Gain 10dB at band edges and 25dB mid band, adjustable down to 20dB.  12/13.5V DC operation at 20mA.  SO239 in/out connectors. Two-part stove enamelled box 150x100x75mm.  Weight 410gms.   Box kit 72.50 UK, 82.00 EU, 86.050 World.  Ready built 123.00 UK, 129.00 EU, 133.00 World, including tracking & insurance.

HF Switched Preamp small.jpg


QRP TX ATTENUATOR, RF SWITCHED. This allows a rig running 5W output to achieve QRP output levels of 500mW, 250mW, 100mW, and 50mW, using just three switches.  Straight through path when off.  

Box kit 49.50 UK, 56.50 EU, 60.50 World. Built 70.50 UK, 80.00 EU, 84.00 World. Including tracking and insurance.


The QRP TX SPC Aerial Tuning Unit is based on the Series Parallel Capacitor ATU configuration used for transmit matchers which prevents the circuit becoming a high pass filter with certain choices of tuning capacitors and inductances.

It will work with long or short random wire aerials or with aerials fed with coax cable.  In this version the inductances are wound on toroids to provide high Q, small space, and low unwanted coupling.  Power handling will be limited by a 100V rating of the polyvaricon capacitors and the impedance of the antenna being matched.  By definition QRP means up to 10W SSB in the UK.

With a random wire antenna presenting a high impedance at the required frequency the voltage when matched can be quite high and that is the limiting factor for this and all TX ATU's.  Indeed for really high powered transmission the variable capacitors are wide airspaced with flashover ratings in excess of 2kV.

When matching to a low impedance antenna only a small amount of inductance is required to achieve the match.  Conversely with an antenna a bit short for a quarterwave (or resonant at a higher frequency than required) more inductance and less capacitance is required.



The ATU is provided with a single wire yellow terminal post for random wire aerials and with a single wire black terminal post for a connection to ground. Also an SO239 coax socket for a coax downlead.   Output to the transceiver is via another SO239 coax socket. 

Price 85.00 including Hermes carriage.



For 2, or 4, or 6  metres. 100W through rated on transmit. RF & DC switched 0-20dB panel adjustable gain. 2m, 4m, & 6m types use BF964 with noise figure under 1.5dB. 10m type uses BFR84, with noise figure under 3dB. Over-voltage and reverse voltage protected.   Protected against transients and EMP at input and output ports. PCB size 68 x 46 x 28mm. Purpose made box 76 x 70 x 38mm. Fitted with SO239 connectors. DC supply 13.5V 80mA. Types RP2S, RP4S, RP6S, & RP10S. PCB Kit 24.00 UK, 30.00 EU, 30.50 World. PCB & hardware kit 55.00 UK, 61.00 EU, 63.50 World. Ready built 79.50 UK, 87.00 EU, 89.75 World. Tracking & insurance included.

RP-S front small.jpg



100W through rated on transmit for 2 or 4 or 6 metres. RF & DC switched and DC fed via the coax. Gain 20dB, NF less than 1.5dB. Supplied with a DC/RF Station Box with SO239 connectors for the shack. Heavy duty waterproof plastic box fitted with SO239 connector for feed coax and 1 metre of coax for connection to the antenna. Box size 82x80x50mm. Types RP2SM, RP4SM, & RP6SM. PCB & hardware kit 57.50 UK, 65.75 EU, 68.50 World.  Ready Built 80.00 UK, 87.50 EU, 90.25 World, including tracking.  Masthead fitting kit 8.00 extra.


400W through rated on transmit for 2 or 4 or 6 metres.  RF switched. Supplied via separate wire DC feed.   Gain 20dB, NF less than 1.5dB.  Protected against reverse and over voltage and against EMC transients at input and output. Heavy duty waterproof box fitted with SO239 connector for feed line and 1 metre of coax to connect to antenna feed point. Box size 82 x 80 x 50mm. Types RP2SH, RP4SH, & RP6SH.  PCB & hardware kit 49.25 UK, 55.25 EU, 57.75 World.  Ready built 69.00 UK 76.50 EU, 79.25 World, including tracking.  Masthead fitting kit 8.00 extra.

Picture opposite is the RP2SH type with external 13.5V supply.

Masthead Preamp.jpg


Early commercial transceivers often had a transverter facility with a low level output from the transmit driver stage and a means of disabling the power output stage.  This meant there were two connections for an outboard transverter, one from the low power transmit port, the other for receive via the main antenna socket.  Some of the top of the range rigs still have this facility but most modern rigs do not have any transverter facility at all.  To use them with a transverter simply reduce the power to minimum and use a single connection to the transverter from the rig antenna socket.  The RF sensing of the transverter will work at drive levels from 5W down to 100mW.  Below that drive level, hard switching is required.

Add 2 or 4 or 6 metres to a rig with 10 metres,  or 4 or 6 metres to a 2 metre rig.  The transverter main board contains an attenuator in the transmit path and can be configured for 1-500mW or 0.5-5W drive levels and gives 300mW output. Class AB linear operation gives all mode use.   The standard product includes a linear amplifier giving panel adjustable output 5 to 20W on 2m, or 5 to 25W on 4 or 6m.  All spurious and harmonic outputs better than 45dB below carrier.  Capable of withstanding long periods of transmit into bad SWR.  Receive side has panel adjustable gain 0-20dB gain and NF less than 1.5dB.   PCB size 150 x 93 x 18mm.     Box size 200x160x77mm. Suffix s is used for single IF drive arrangement, suffix d is used for dual IF drive version, the suffix L is for integral linear.

TRC2-10s, 4-10s, 6-10s 10m 0.5-5W Single
TRC2-10d, 4-10d, 6-10d 10m 1-100mW Dual
TRC4-2s, 6-2s 2m 0.5-5W Single
PCB Kit 69.50 UK, 76.50 EU, 77.50 World.  PCB built 99.00 UK, 105.00 EU, 106.00 World.  Box kit 110.50 UK, 119.25 EU, 125.25 World.  Ready Built 173.00 UK, 179.00 EU, 185.00 World. Prices including tracking & insurance.  
TRC2-10sL, 4-10sL, 6-10sL 10m 0.5-5W Single
TRC2-10dL, 4-10dL, 6-10dL 10m 1-100mw Dual
TRC4-2sL, 6-2sL 2m 0.5-5W Single
PCB kits 173.00 UK, 177.50 EU, 180.25 World. PCB's built 213.50 UK, 218.25 EU, 221.00 World.  Box kit 215.00 UK, 222.00 EU, 228.00 World.     Ready built 283.50 UK 290.00 EU, 296.00 World. Prices include tracking & insurance. 

Repeater shift for 2m output versions, add 8.50 to PCB kit or Box kit, 15 to PCB built or Boxed built.

ICOM COMPATIBLE TRANSVERTERS  A version of transverter specially dedicated to certain ICOM rigs, complete with 60cm long cables, ready to plug-and-play.  It is known to be suitable for the IC756Pro, 756Pro2, 756Pro3, 775, 781, 7600, & 7800, and any other rig not mentioned which requires just one TVTR IN/OUT RF lead plus a 7 pin DIN plug with a switching signal on pin 6.  Types TRC2-10L/IC1, TRC4-10L/IC1, & TRC6-10L/IC1.  Box kit 216.50 UK, 223.25 EU 229.25 World.  Ready built 289.50 UK, 296.00 EU, 302.00 World.

NOTE:  The following ICOM rigs are NOT plug and play compatible, but can be used with a standard transverter: 77, 78, 703, 706, 707, 718, 725, 726, 728, 729, 736, 737a, 738, 746, 746Pro, 756, 7000, 7400.

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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 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.



TRANSMIT AMPLIFIER (20/25W) For Spectrum 0.5W Transverters. Two stage PTT switched class AB linear amplifiers for 2, or 4, or 6 metres giving a minimum of 20W out for the 2m version, and a maximum of 35W for the 6 metre version. Should not be run at more than 25W. Antenna relay with high speed TX/RX switching makes it suitable for all modes including data and RTTY and Packet. PCB size 125 x 57 x 28mm. Types TA2S4, TA4S4, TA6S4.   PCB kit 106.00 UK, 112.25 EU, 113.25 World.   PCB Built 121.00 UK, 124.50 EU, 125.50 World.  Prices include tracking.

TRANSMIT AMPLIFIER (25W) Single stage switched class AB linear amplifier suitable for CW, SSB, FM, RTTY, and PACKET. 4m and 6m versions 1W in gives 8W and 5W in gives 30W output. 2m version 1W drive gives 6W out and 5W drive gives 25W out. Switching circuit senses RF & DC and uses a monostable relay driver giving VERY FAST attack and a hold time of 250ms to 2s for SSB use. For data modes the hold function can be disabled. PCB size 102x72x25mm. Diecast box size 171x120x55mm. Fitted with SO239 connectors. Types TA2SA, TA4SA, & TA6SA. Box kit 88.00 UK, 97.00 EU, 101.00 World. Ready built 112.00 UK, 120.00 EU, 124.00 World. Prices include tracking.

TRANSMIT AMPLIFIER (50W) Single stage switched class AB linear amplifier suitable for CW, SSB, FM, RTTY, and PACKET. 4m and 6m versions 5W in 30W out, 7.5W in 50W out.  Switching circuit senses RF & DC and uses a monostable relay driver giving VERY FAST attack and a hold time of 250ms to 2s for SSB use. For data modes the hold function can be disabled. PCB size 102 x 72 x 55mm. Diecast box size 11x120x55mm with a heatsink on top 152x99x32mm. Fitted with SO239 connectors. Types TA2SB, TA4SB, & TA6SB. Box kit 102.50 Uk, 111.50 EU, 115.50 World.   Ready built 127.00 UK, 133.00 EU, 137.00 World.  Price include tracking.

TARP-SB medium.jpg

TRANSMIT AMPLIFIER 70MHz (100W) Single stage parallel pair of 50W devices in class AB for all modes, 20 to 22W SSB input gives 100W peak output when run on a PSU with 13.5V at a load current of 16A.  Rated for long periods on FM and Data at a continuous output of 50W.  Also can be used with AM with an output carrier power set to 25W and peak power of 100W.  RF sensed switching with fast attack and 500mS hang to avoid relay chatter when on SSB.  Unit includes a peak reading power meter that remains in operation whilst the unit is connected to the power supply even though the amplifier is not in operation.  Overall size 187x118x94mm.  Ready built only 240.00 UK, 247.50 EU, 255.00 World, including tracked carriage.

 TA100W4M small.jpg


TRANSMIT AMPLIFIER (25W) & PREAMP.  Linear amplifier and receive preamplifier together in one case with independent switching. Amplifier details as TA-SA above, together with 20/26dB gain preamp. Types TA/RP2SA, TA/RP4SA, TA/RP6SA. Box kit 125.00 UK, 131.00 EU, 137.00 World.  Ready built 159.00 UK, 164.75 EU, 170.75 World.  Prices include tracking and insurance.

TRANSMIT AMPLIFIER (50W) & PREAMP Linear amplifier and receive preamplifier together in one case with independent switching. Amplifier details as TA-SB above, together with 20/26dB gain preamp. Types TA/RP2SB, TA/RP4SB, TA/RP6SB.  Box kit 142.50 UK, 148.50 EU, 154.50 World. Ready built 181.50 UK, 187.25 EU, 193.25 World.  Prices include tracking and insurance.

TRANSMIT AMPLIFIER for 2, or 4, or 6metres. 250mW to 500mW input, 20w to 35W output, with RF & DC switching. Class AB operation gives clean output with intermod products 35dB down suitable for all modes CW, SSB, FM, & DATA. Designed as self contained amplifier as an add-on for 0.5W transverters such as MEON. Boxed size 127x102x38mm. Types TA2S2, TA4S2, & TA6S2. To be redesigned when time permits.

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.

SPEECH PROCESSOR to increase the sideband power and hence communications effectiveness of SSB and AM transmissions. The unit includes filtering which enhances the higher voice tones which carry most of the intelligibility. The peak to mean ratio of the transmission is improved by 10dB which has the same effect as increasing the transmit power by 10 times. It sounds nice too. Panel controls are included for clip level and output level. PCB size 82x45x17mm.    Type SP1000E. Box kit 48.00 UK, 55.00 EU, 59.00 World. Ready Built 66.00 UK, 75.25 EU, 79.25 World.  Prices include tracked carriage.

SP1000E 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. 

VFO inside small.jpg

VFO rear small.jpg

PSK31 INTERFACE, 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.

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