Update

Update 22 August 2010

New supplies of dual gate mosfets have arrived.  We are now able to offer 3SK45, 3N201, 40673, and BF964 devices.  A new table is included in the Components page giving technical details and prices.  Also BF256B is being stocked in preference to the BF256A.  A table showing the technical details of this and the J309 is also included in the components page.

Update 24 June 2010

The Portland VFO has been updated to include a preset to set upper edge of the tuning range.  This exceedingly stable VFO meets the requirements for the Intermediate Licence VFO project.  See further information on the Amateur page.

Update 21 May 2010

A new 90uH coil has been added to the Spectrum 10mm coil series, and the tables about the coils in the Components page of this site gives updated details on all coils.

Update 26 March 2010

TECHNICAL FOR THE TERRIFIED The first 27 articles of this series from PW have been reprinted into a book, which is now in stock.  A really good textbook for the theory of radio and invaluable for those wishing to progress to intermediate licence and beyond, or for those just wishing to revise or learn more about radio.  £15.50 including P&P.

NEW Triband Active Receive Preselector for 80,40, & 20m. Tuneable on 80m, fixed tuned on 40 and 20m. Can be configured for maximum gains of 16dB on 80m, 23dB on 40 and 20m, or 11dB on 80m 17dB on 40, and 18dB on 20m. Complete kit comprises amplifier and switch PCB's and components, 2 pole 3 way switch, polyvaricon, and 10K log gain pot. £20.50 inc P&P.

Update 20 February 2010

The Upwey AM/LSB Top Band Receiver project as featured in January and March 2010 Practical Wireless is now completed.  Details of kits and parts available to purchase can be found in the Amateur page.

Update 27 November 2009

The Poundbury Receiver project reached its concluding part in the November 2009 PW.  Since then there has been a further change to the AGC circuitry for better gain control and S meter scale.  Details of the product and price are to be found on the Amateur or the DiDB & PW web pages.

Update 5 October 2009

Sales of the new ICOM dedicated transverters are now almost as common as the standard general purpose versions. Users of the IC735 have found problems with PTT holding on with connection via the ACC2 port.  When the cable wiring is changed to use the SEND phono socket the problem is cured.

Update 20 July 2009

Development work has also been undertaken on 14MHz traps for the half size G4CFY Trapped Dipole.  A nice solution has been found for the windings of the traps, and the effects of the dielectric constant of the potting material taken into consideration.  The inductance of the traps has been measured, and the value of resonating capaitance calculated.  These figures have been used to calculated the exact lengths of outer wires for resonance on 7.1MHz.  The dipole now measures 53 feet 4 inches, insulator to insulator.

Update 6 June 2009

Coils the equivalent to TOKO 3335R are now in stock. Other 10mm coils are in the process of procurement to establish a new range of coils made specially for Spectrum.  These will include the following values, 0.4uH, 1.2uH, 2.6uH 5.2uH, 11uH, 23uH, & 45uh.  Taps will be provided to suit aerial input and Hartley oscillator use.  Eventually it is hoped to include duplicates in each value with taps to suit interstage use.

The new high power rated twin feeder is meeting the approval of all who have had samples and who have purchased it.  This feeder supplied with G4CFY trapped dipoles is performing well and receiveing acclamation.  Those who have purchased it for for their own dipoles are really impressed with its construction and performance.

Update 26 April 2009

New low impedance twin feeder, now in stock.  24/0.2 cores individually polyethylene sleeved with an overall sheath of polyethylene. 2kW rated with an SWR less than 2:1.  Loss only 0.04dB/m at 10MHz.  75p/metre plus carriage at cost, or £70 for 100 metre drum including P&P.

Supplies of TOKO coils are now drying up, with the exception of one company with stock at high prices.  TOKO stopped production of the 10K and 10E series over a year ago.  I have now found a company in the far east able to manufacture equivalent parts and initial supplies of the popular 3335R type is now on order.

Update 17 July 2007

Sometime ago I was encouraged to look at the 4 Metre website as my transverters were mentioned there.  I found a poor statement and the photograph of the inside of an old Spectrum transverter.  Otherwise there was really good editorial about an OZ unit, also the Meon, RN Electronics, Mutek, and even Microwave Modules.  So I sent a picture and details of the current transverter with an equally good write up.  Having just looked at the site again, I find there is one paragraph which doesn't do the unit justice, and a picture of the two boards from my transverter.  It is quite clear that the owners of the site are giving a poor presentation of my transverter in favour of the OZ Unit, that being the only competition.  Consequently I have added a page to my website to promote my Four Metre Equipment.

The Link Receiver and Transmitter have now been post designed in accordance with the the requirements of ETSI EN 300 454-2 Part 2 Harmonized standard under article 3.2 of the R&TTE Directive.  The RSL Transmitter is currently being built and tested in accordance with ETS 300 447.   Account has also been taken of the facilities required of RSL transmitters in the OFCOM Engineering Code sections 2 & 4, and also the OFCOM RSL information document Section 9 Appendix II Technical Conditions.

The foregoing approach means that both Link and RSL transmitters will have the same construction format and again are offered in economy and rack mount versions.  Orders are now being taken for Link systems for delivery at the end of March.

G2DYM Update  The design equations show that the coax traps having a higher L to C ratio than used in the W3DZZ design need to be used with an inner wire length of 33 feet and an outer wire length of 19 feet 7 inches.  Some 2 feet shorter overall than as sold by G2DYM. Customers who have tried these lengths found that correct resonance occurred on both 80 and 40 metres.

Update 5 November 2006

On 30th October 2006 Spectrum Communications acquired G2DYM Aerials.  That business has run for exactly 30 years selling Trap Dipoles mainly to the Amateur Radio fraternity.  Richard Benham-Holman G2DYM the previous owner had just had his 84th birthday and due to failing eyesight was unable to continue running the business. 

Together with manufacturing materials, tools, and moulds, we received a quantity of made up aerial wires for both full size and half size trap dipoles, and a quantity of 7MHz traps ready for potting.   Since receiving the stock we have been busy cataloguing it and going over all aspect of manufacture of the traps.  Also delving into my radio books and learning the theory of trap dipoles, and researching different types of potting compounds.

Stangely enough, during my employment with the ministry of Defence at Portland Dorset I spent 6 months in the Coils and Filters Section involved in potting transducers with epoxy resin.  That experience made me conscious that different types of potting compound and filler have wide ranging effects on the coils being potted. 

DiBD & PW Projects

You may have noticed that my site now includes a new linked page DiBD & PW Projects to accompany the successful by-monthly Doing it By Design Series which has been running since March 2004.  This linked page also includes any stand alone projects which have also been published by me in the last two years.  These include the Whitcombe 4m converter, a Two Tone Tester, the Mellstock 4m 1W AM Transmitter, and the companion Mellstock 4m AM Receiver.  Now also the Portland VFO & Buffer.  The May issue of PW featured a Mixer - VFO unit to work in conjunction with a Portland VFO to create a local oscillator for a 4 metre receiver or transmitter with a 9 or 10.7MHz IF. 

Radio Remote Control Unit

Designed for use with track and field events requiring starting and stopping lights or indicators to be activated remotely from the command or control centre, to remove the need for extended cable connections. The system comprises encoder and decoder units which can be wired to suit most transceivers by plugging into the microphone socket at the transmit end and into the earphone or extension speaker socket at the receive end.  The encoder box is fitted with green and red large push buttons with large matching colour LED indicators.  The decoder unit has large green and red LEDs and an output to drive an external relay.  Both units run from 13.5V DC supplies and draw less than 50mA each.   Ready built and fitted with traditional jack or microphone connectors the complete package costs £160.   There may be additional charge for special connections to the radio equipment.

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