Update 18 June 2013

Now having worked on another Lafayette Telsat 805B I have at last found the solution to the pulsing problem evident mostly when on USB or LSB.  The cure takes about one and a half hours to sort out, so for a rig previously properly aligned it will cost £36 plus return carriage by Interlink of £14.50.  For a rig in needs of a full alignment the cost is £60 plus return carriage of £14.50.

Update 29 May 2013

Feedback from customers regarding the G6LBQ 9 band filter and the G4CFY improved values kit reveal excessive insertion losses on some bands.  This was caused by the coupling capacitors being either too large or too small. This was due to the assumption of perfect coupling between primary and secondary of the transformers.  Each of the filters has now been constructed and tested and new coils substituted where necessary to achieve better loaded Q and then coupling capacitors adjusted for best compromise between bandwidth and insertion loss.  The re-developed filter component kits of parts can be found on the Component pages of this web-site.

Update 20 January 2013

Some Spectrum product prices were set in the late 1990's, others were updated as recent as 2004, which is 9 years ago.  Since then there has been massive increases in postal charges, as well as VAT increase to 20%, an increase in cost of diecast boxes by up to 100%, and an increase of 40% in the price of VHF power output transistors. All Spectrum products which will continue in production have been recalculated.  We will now endeavour to maintain the new prices as many years as possible.  Hopefully the next threatened increase in postage prices by Royal Mail in April will not force further increases.

Update 17 June 2012

NEW STOCK Replacements for TOKO MC120 types 100112 and 100076. Spectrum coils SC112 70nH, and SC076 220nH.  See Components page for details.

Upgrade kit for audio quality on RX and TX of 2001, 4001, 6001, & 7003 rigs, together with improvement to IF amplifier stage £10.  This kit plus new narrower IF filters £14. Channel spacing upgrade with CTCSS for 2m and 6m rigs £20.  Noise squelch kit £20.

Update 8 December 2011

The AKD/Garex 4001 FM transceiver typically exhibits a bit of audio distortion.  Having now worked on the rig I found that the first filter was not properly matched so the passband was distorted.  By changing the coil driving it and a resistor following it there is now no audio distortion for deviations from zero to 4.5kHz.  Also I have successfully added a noise squelch to the rig so that any signal rises from a quiet background and there is no longer gunshot noises typical of FM rigs when the squelch breaks or going from TX to RX.  An upgrade kit type NS1000F to add the noise squelch and correct the front end filter matching is available at a cost of £20.00 including P&P.   

Update 10 November 2011

The GAREX HPFS filter has been critically examined and the circuit and PC layout have been changed to produce a dramatic improvement in performance.  The passband ripple has been reduced, the cut-off point is now sharper and the stopband is better than -60dB DC to 200MHz. It is now designated as HPF-450.

The GAREX HPF2 which was a 3 element high pass T has been converted into a bandpass filter by the addition of a 3 element low pass filter.  It will now be more effective in reducing engine management noise interfering with car radios and will now reduce interference to domestic VHF FM reception.  It is now designated BPF-100.

A new filter has also been designed using 5 element high and low pass Chebychev filters with a much narrower passband around the VHF FM broadcast band.  The skirts are sharper and the lower stopband is now better than -60dB DC to 20MHz and -50dB at 30MHz and even -26dB at 50MHz.  The upper stopband is about -26dB at 144MHz and drops to beyond -60dB at 300MHz.  It then returns with considerable ripple up to 1000MHz but not exceeding -40dB.  This will be designated BPF-101. Final production PCB and case are not yet finalised. 

Update 19 October 2011

On 14th October 2011 an agreement was signed with Peter Longhurst for Spectrum Communications to purchase Garex Electronics with effect from 30 November 2011.   Peter now aged 74 has decided he no longer wishes to be tied to the manufacture of the proprietary products and wishes to enjoy his retirement.  Production will continue of the 4001 & 6001 FM transceivers, the Blackline TV and Broadcast FM interference filters, the receive preamplifiers, portable passive and active wire aerials, flexi-whips and rigid monoband & dual band VHF whips, and the high quality magmount.

The first 27 articles of Technical for the Terrified of which I am the author were published in Practical Wireless between February 2005 and August 2009 and have been compiled into a 124 page spiral bound 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.  It is intended to extend the knowledge of radio and to assist students of the Intermediate and Advanced Radio Amateur courses.  Price is £12.00 plus £3.50 P&P.

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