SPECTRUM COMMUNICATIONS

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AMATEUR & LISTENER BOXED PRODUCTS   

14 November 2023

Proprietor;- Antony Nailer HNC BA G4CFY. 

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

Phone UK 01305 262250 International 0044 1305 262250. Email: g4cfy@talktalk.net

 You can pay by card or to g4cfy@talktalk.net via Paypal, or direct to my bank Santander, Spectrum Communications, sort code 09-01-29, account 67273308. For multiple quantities or multiple items, please email for a quote or for a Paypal money request.  You can also obtain many of my products from my Ebay shop https://ebay.co.uk/str/Spectrum-Comms

The 50W and 100W amplifiers are back in production using the BLW60 devices.

 

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 first print run was early June. It 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 an individual book will cost £18.00 including P&P.

To buy both books will cost £32.20 including P&P.

 

CONTENTS 

RX L-TYPE ATU 110-400MHz Scanner Preamp 13.5V
RX SPC ATU 110-400MHz Scanner Preamp Mains
QRP TX SPC ATU Masthead Preamps RF Switched, 2m, 4m, 6m, 13.5V
HF Tuneable Preamp 1.8-30MHz 13.5V Masthead Preamp Receive 137MHz 13.5V
HF Switched Preamp 1.8-30MHz 13.5V Transverters from 10m to 2m, or 4m, or 6m 13.5V
Station Preamps RF Switched, 2m, 4m, 6m, 13.5V Transmit Amplifiers 50W & 100W, 4m & 6m

 

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 £54.30 UK, £64.00 EU, £71.60 World including tracked carriage.  

RX ATU tiny.jpg

 

RX SPC ATU small.jpg

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 £71.00 UK, £80.75 EU, £88.35 World.  Including tracking & 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 is limited by the 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.


When matching to a low impedance antenna only a small amount of inductance is required to achieve the match.  Conversely an antenna that is too short to be a quarterwave at a certain frequency, 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.

Ready Built £85.85 UK, £95.55 EU, £103.15 World. Prices include tracked carriage.

 
QRP TX SPC ANTENNA TUNING UNIT

 

 

 

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..  Bands 1.8-15MHz flat gain of 16dB. Band D starts at 12dB at 15MHz rising steadily to 16dB at 18MHz thereafter flat to 30MHz.  Gain adjustable down to -20dB.  Runs from an 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 £97.30 UK, £17.00 EU, £114.60 World. Including tracked carriage.

 

http://www.spectrumcomms.co.uk/HF Switched Preamp small.jpg

HF SWITCHED PREAMP 1.8-30MHz

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 16dB adjustable down to –20dB.  12/13.5V DC operation at 20mA.  SO239 in/out connectors. Two-part stove enameled box 150x100x75mm.  Weight 410gms.   

Ready built £114.30 UK, £124.00 EU, £131.60 World. Tracking & insurance included.

 

RP-S front small.jpg

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. 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. Ready built £82.60 UK including tracking carriage.

 

110-400MHz SCANNER PREAMP - MAINS

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 also included.

Ready Built only, £66.25 UK, £75.85 EU, £83.45 World. Including tracked carriage.

110-400MHz SCANNER 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 built for external 12V in plain diecast box £42.70 UK, £52.40 EU, £60.00 World.

 

 

MASTHEAD PREAMP WEATHER SATELLITE, 137MHz

This is a receive-only preamp with 16dB gain and 1.5dB noise figure to improve the signal to noise ratio of a weather satellite system.   The masthead unit has a fitting plate bolted to its rear with tabs protrudin top and bottom.  It is provided with two releasable tie wraps that will fit round a 2" (5cm) diamter support mast. It has a 6ft (1.5m) tail of coax with a PL259 for connection to the WX antenna.  Both the masthead a station box are fitted with SO239 connectors for the coax downlead.  There is another SO239 socket on the Station box to connect it to the receivber antenna socket. The station box is also supplied with a 3ft (1m) black-red twin lead to cvonnect to a linear 13.5V bench supply.

Price ready built, £80.20 UK, £89.90 EU, £97.50 World, including tracked carriage.

 

MASTHEAD PREAMPS, RF SWITCHED, 150W Rated

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. Supplied with masthead fitting plate and releasable tie-wraps. Types RP2SM, RP4SM, & RP6SM. Ready Built £96.40 UK, £106.10 EU, £113.70 World, including tracking.  

MASTHEAD PREAMPS, RF SWITCHED 400W Rated

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.  Ready built £71.20 UK, £80.90 EU, £88.50 World, including tracking.  

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

Masthead Preamp.jpg

 

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 of the transceiver to minimum and use a single connection to the transverter from the rig antenna socket.  

This is a new version with 3-terminal regulated oscillator supply and a crystal oven to make if suitable for very narrow band digital work. Add 2 or 4 or 6 metres to a rig with 10 metres. 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. The RF sensing of the transverter will work at drive levels from 5W down to 100mW.  Below that drive level, hard switching is required. 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.

Coming soon a 60MHz version, 5m.

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 0-15dB gain and NF less than 1.5dB.   PCB size 150 x 93 x 18mm. Box size 200x160x77mm. Types TRC2-10TL, TRC4-10TL, and TRC6-10TL. Coming soon TRC5-10TL.  Ready built £323.00 UK £329.25 EU, £345.50 World. Prices include tracking carriage. 

 
TRANSMIT AMPLIFIERS

TRANSMIT AMPLIFIER (50W)

Single stage switched class AB linear amplifier suitable for CW, SSB, FM, RTTY, and PACKET. 4m and 6m versions typically 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 171x121x55mm with a heatsink 150x99x32mm on top. Fitted with SO239 connectors and comes with 1 metre of 42.0.2 red/black DC cable. Types TA50W4M, & TA50W6M.

Ready built £146.00 UK, £153.30 EU, £160.30 World.  Price include tracking.

 

 TA100W4M small.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. Type TA100W4M.

Ready built only £233.50 UK, £239.75 EU, £247.00 World, including tracked carriage.

 

UPGRADE KITS FOR 2001, 4001, 6001 AKD/GAREX TRANSCEIVERS

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. £28.20 including P&P.

4001 replacement PIC to change to 12.5kHz channel spacing. Supplied with replacement reference crystal and handbook with new frequency listing.  £12.00 including P&P.

6001 PIC module to change to 10kHz channel spacing and add CTCSS. Supplied with handbook with new frequency listing.  £25.70 including 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.  £17.10 including P&P.

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