Incorporating G2DYM Aerials & Garex Electronics

Quality English products hand-crafted to order











AMATEUR - 15 November 2017

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 to place an order by credit/debit card or for a Paypal money request. Purchase of several items is likely to make a saving on postage.

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

Technical queries to  tony@spectrumcomms.co.uk 



BREAKING NEWS  In the Editorial in November issue PW the Editor has stated that I am unable to submit articles for the forseeable 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.  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, maybe it is time to stop.


T4T Books I & II small.jpg  Book 1 includes the first 27 articles of Technical for the Terrified, of which I am the author published in PW between February 2005 and August 2009 and have been compiled into a 124 page book of the same name. The writing style is aimed to be easy to read and should be of great value to readers of all technical levels.  Subjects include; a little maths, inductors & capacitors, DC circuits, transistor biasing, decibels, amplifiers, diodes & rectification, the superhet, SSB & CW, FM & AM, bandwidth, Q, antennas & feeders, band-pass circuits, RF/IF amplifiers, phase locked loops, HF transceivers, filtering in receivers, mixers, FET RF amplifiers.  Price is 12.00 plus 3.50 P&P.

 Book 2 now available at 12 plus 3.50 P&P.  Buy both books and pay only a single 3.50 P&P.  Book 2 reproduces the next 23 articles from PW up to June 2013 and deals with components, equivalent circuits, crystal oscillators, amplifier stability, analogue low pass filters, transmitting ATU's, the superhet receiver, feeder cables and transmission lines, antenna gain and bandwidth, measuring RF power and SWR, measuring AC & DC voltage - inductance - capacitance - frequency & Q, circuit analysis, broadcast and television interference, singly balanced mixers, laying out PCB's, antenna advice for the listener, antenna tuning and the noise bridge, more on antennas and feeders, receiving 100kHz to 30MHz, homebrew receivers for the HF amateur bands, and circuit matching.  Just so much in it. 

Contents - In number and alphabetical order

5W Broadband HF Linear Mixer - Osc for 4 metres Speech Processor
7MHz DSB QRP TX Portland VFO Transverters
7MHz DSB RX Poundbury 70MHz Front-end Toneburst, Piptone, & Kaytone
4001 FM 4m Transceiver Poundbury SSB TX & RX IF VHF Masthead Preamps - Switched
CTCSS module PSK31 Interface VHF Station Preamps - Switched
HF Tuneable Preamp Switched QRP TX Attenuator VHF Transmit Amplifiers, 25/50/100W

4001 FM 4m TRANSCEIVER 70.2500 to 70.4875MHz in 20 channels in 12.5kHz steps. Originally AKD, then GAREX, now Spectrum. Really easy to use, not menu driven.  Default channel at switch-on 70.450MHz. Now upgraded to give excellent audio quality on receive and transmit.  RF output 5W or 25W 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.

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UPGRADE KITS FOR 2001, 4001, 6001

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.

Noise Squelch, to give a quite background and excellent weak signal reception, upgrade kit 20.00 excluding P&P.

HF TUNEABLE PREAMP - SWITCHED,   through handling power 100W. Fail safe operation, straight through path when switched off.  2-32MHz 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.

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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.


STATION PREAMPS RF Switched, 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.

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MASTHEAD RECEIVE PREAMPS SWITCHED    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.

MASTHEAD RECEIVE PREAMPS SWITCHED    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.

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TRANSVERTERS 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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TRANSMIT AMPLIFIER (20/25W) For use with 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.

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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.

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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.

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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 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. 

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MIXER - OSCILLATOR, 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.

POUNDBURY (2) 9/10.7MHZ 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

6-POLE CRYSTAL SSB FILTER. 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.

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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.

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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.

CTCSS Module.  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.

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.

PIPTONE 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.

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

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