Mono Link Transmitter.  48.425, 48.475, 48.525, 52.875 or 52.925MHz,  0-1W presettable output, synthesized circuit in 25KHz steps. Deviation + - 25KHz.  Audio bandwidth 50Hz to 15KHz with pre-emphasis. Built in mono compressor and peak limiter.  Built-in output power monitor. Two part painted aluminium case. With 1/4" audio input jack, ON/OFF power switch and LED, out of lock LED. SO239 RF socket, BNC RF sampler socket, BNC AF monitor socket, DC input connector, and fuse holder on rear panel.  Supplied with 1 metre DC power lead.  £330.00.  Power supply 13.5V 2.5A  £20.00.  Optional, XLR female connector and balanced line transformer input £21.00.

Transmit Amplifier 10W, to suit frequencies as transmitter. Single stage amplifier typically requires only 500mW to produce 10W output. Harmonic attenuation to better than -60dB below the carrier at full output. Large diecast box with extruded heatsink that runs at about 40 C in continuous operation, ON/OFF toggle switch and LED on front. SO239 input and output sockets, 1metre twin DC input lead on rear. In-line fuse holder. £100.00.  Power supply 13.5V 5A £35.00.  Optional, Patch lead for transmitter to amplifier £2.50.

Mono Link Receiver, 48.425, 48.475, 48.525, 52.875 or 52.925MHz,  single channel crystal controlled circuit, sensitivity typically 1uV for 20dB SINAD. FM deviation + - 25KHz gives line level AF output. Includes audio amplifier and monitor loudspeaker. Two piece stove enamelled aluminium box with 1/4" audio output jack, volume/on/off, squelch, power LED and signal meter on front.  DC input connector, loudspeaker, and SO239 antenna socket on rear. £280.00.  Power supply 12V 500mA £10.00.  Optional, XLR male and balanced line output £5.00.

Stereo Link Receiver, 48.3, or 52.75MHz, crystal controlled single channel circuit, sensitivity typically 4uV for 20dB SINAD. FM deviation + - 100KHz gives line level AF output.  Includes audio amplifier and monitor loudspeaker.   Two piece stove enamelled aluminium box with 1/4" audio output jack, volume/on/off, squelch, power LED and signal meter on front. 1/4" stereo jack for decoded outputs or a BNC for multiplex output, DC input socket, loudspeaker, and SO239 antenna socket on rear. £340.00.  Power supply 12V 500mA £10.00.

Normal delivery 3-4 working weeks.  Emergency service 7-10 working days add £75 to transmitters & to receivers and £40 to amplifiers, please send for a quote or pro forma invoice. 

Mono 1W Link Transmitter,  2U x 150mm rack case with integral power supply. 48.425, 48.475, 48.525, 52.875 or 52.925MHz, 0-1W presettable output, synthesized circuit on 25KHz steps. Deviation + - 25KHz.  Audio bandwidth 50Hz to 15KHz with pre-emphasis. Front mounted ON/OFF toggle switch and LED indicator, out of lock LED indicator, SWR/PWR switch, SWR cal control, SWR/PWR panel meter. Rear mounted IEC filtered connector for mains input, XLR 3 pin female connector for audio input with balanced line transformer, BNC AF monitor socket, fuse holder, and SO239 connector for RF output, BNC RF monitor socket. IEC mains cable. 1W version £465.00. 10W version £575.00. 

Stereo 1W & 10W Link Transmitter, 2U x 250mm rack case as Mono version above plus a compressor and stereo encoder with an additional XLR socket and line transformer. 48.300 or 52.75MHz.  Average desk levels from -6dB to +14dB are gain adjusted by the compressor to 0dB average signal. Deviation + - 100KHz. The stereo encoder produces a near perfect sinewave pilot tone with the third harmonic at 57KHz 50dB below the pilot tone level.  This means it can be successfully used with RDS encoders.  The separation of left and right channels within the multiplex signal is typically 50dB (300:1). 1W version £595.00. 10W version £695.00. 

Mono Link Receiver,  1U x 150mm rack case with integral power supply. 48.425, 48.475, 48.525, 52.875 or 52.925MHz, crystal controlled circuit  sensitivity typically 1uV for 20dB SINAD. Deviation + - 25KHz gives line level AF output.  Front mounted 1/4" audio output jack for headphones or loudspeaker, monitor volume, squelch, ON/OFF toggle switch, LED power indicator, and signal meter. Rear mounted 3 pin XLR male connector for balanced line output, SO239 connector for RF input, filtered IEC mains connector, and fuse holder. Single channel version £375.00.   Additional channels £15.00 each. 

Stereo Link Receiver, 1U x 150mm rack case as Mono version above plus a stereo decoder an additional XLR socket and two line transformers. 48.300 or 52.750MHz. With integral power supply, crystal controlled circuit, Sensitivity typically 3uV for 20dB SINAD. Deviation + - 100KHz gives line level left & right outputs. Separation of left and right channels at the decoded outputs is typically 34dB.  £435.00. 

NORMAL DELIVERY 20-25 working days, 4-5 calendar weeks.

EMERGENCY SERVICE 10-15 working days, 2-3 calendar weeks, add £100 to cost of the transmitter and the receiver.   Delivery by carrier, minimum £25.

141MHz Talkback Receiver, 1U x 150mm rack case with integral power supply. 141MHz NBFM single channel crystal controlled receiver for use on 12.5KHz channel spacing. Sensitivity typically 1.2uV for 20dB SINAD. FM deviation + - 3.5KHz gives line level AF output. Includes audio monitor amplifier.  Front mounted 1/4" audio output monitor jack for headphones or extension loudspeaker, monitor volume, squelch, ON/OFF toggle switch, LED power indicator, and signal meter. Rear mounted 3 pin XLR male connector with balanced line transformer for line level output.   SO239 connector for   RF input, filtered IEC mains connector, and fuse holder. £390.00

Normal Delivery 4-6 weeks.  Emergency delivery 2-3 weeks add £100. Delivery by Carrier, £25.

Link Antenna, The basic antenna for use with link receivers on short paths is the halfwave dipole.  This is constructed of seamless aluminium tube and cut for the centre of the band, either 48.45 or 52.9MHz taking into account the velocity factor of the elements.  It is available in two versions, one with a short boom for horizontal polarisation £20, the other with a long boom for vertical polarisation £25.00.

Link Antenna, the basic antenna for use with a link transmitter is the two element Yagi.  This is constructed of seamless aluminium tube and has been pre-assembled and the gamma match adjusted to give an SWR below 1.3 : 1 and dissassembled before despatch. The gain is about 3db relative to a dipole.  It is available in two versions, one with short boom for horizontal mounting £70, the other with extended boom for vertical polarisation £75.

Link Antenna, the largest antenna practical to use with a link system is the 3 element Yagi.  This is constructed of seamless aluminium tube and has been pre-assembled and the gamma match adjusted to give an SWR below 1.3 : 1 and dissassembled before despatch.  The gain is about 7dB relative to a dipole.   It is only available with a boom length of 2 metres and is intended to be used horizontally only.  The effects of mounting it vertically with the support pole between the elements ruins its tuning, gain, and radiation pattern and tuning. £100.

SWR Meter, to check the performance of the antenna and downlead. Many meters (regardless of price) are very inaccurate, and some don't work at all.  Each of these meters have been tested into a 1 : 1 and into a 2 : 1 load and modified if necessary to make the reading accurate within 5%.  The calibration will hold within 10% for 48, 52, and 100MHz.   £20.

SWR/Power Meter, calibrated the same as the SWR meter above but in this case the power scale will also be calibrated at 50MHz.  The power scale will be within 5% for 48 or 52MHz only and not suitable for 100MHz unless calibrated specifically for that band.     £25.

MINI 8 coax, 0.082dB/m loss at 50MHz                                         £1/m, £75/100m reel.

return to top

Spectrum Link Equipment development history

24 February 2007.  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.  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. 

5 October 2009. The first of the Economy Link transmitters in a two part painted box to match the Economy Receiver has now been produced, and obviously is more attractive than the unpainted diecast box version.  The price is as advertised and is the same for diecast or two part box versions.

26 March 2010.  Experiments with stereo encoders and decoders coupled directly to each other have proved that channel separations as high as 52dB can be achieved.  A new version of the encoder has been produced including an elliptic low pass filter in the multiplex path to ensure the transmitted signal deviation is properly band limited.   Experiments will be undertaken in future to selectively match IF filters to achieve best left/right separation.

return to top

I am pleased that the British Antarctic Survey continue to buy my 1W transmitters for use on the Research Vessels and at Base Camps in Antartica.   The have found the economy versions reliable and sufficiently rugged that they have even used them as transmitters for audio from transducers in the ocean beneath the ice sheet.  Some of these units have been in continuous service since 1990.  The ones produced since the 2007 rework have included a very effective audio compressor. This is followed by a clipper, just in case anything gets past the compressor which might cause excessive deviation.

ECONOMY BROADCAST EQUIPMENT FOR 88-108MHz

Mono 1W Transmitter, 0-1W presettable output, synthesized covering 30 channels on 100KHz steps in a 3MHz portion of band II, typical versions 87-90, 102-105, & 105-108MHz. Audio bandwidth 50Hz to 15KHz with pre-emphasis. Built in mono compressor and peak limiter.  Output power meter. Two part painted aluminium case. With 1/4" audio input jack, ON/OFF power switch and LED, out of lock LED, PWR meter on the front. SO239 RF socket, BNC RF sampler socket, BNC AF monitor socket, DC input connector, and fuse holder on rear panel.  Supplied with 1 metre DC power lead.  £335.00.  Power supply 13.5V 2.5A  £20.00.  Optional, XLR female connector and balanced line transformer input £21.00.

Transmit Amplifier 25W, two stage amplifier tuned to cover a 3MHz portion of the band, typically requires only 400mW to produce 25W output and capable of running continuously at 32W output. Harmonic attenuation to better than -60dB below the carrier at full output. Diecast box with large extruded heatsink that runs at about 40 C in continuous operation, ON/OFF toggle switch and LED on front. SO239 input and output sockets, 1metre twin DC input lead and fuse holder on rear.  £120.00.     Power supply 13.5V 12A £70.00.    Patch lead (transmitter to amplifier). £2.50.

RACK-MOUNT BROADCAST EQUIPMENT FOR 88-108MHz

Mono 1W Transmitter, 2U x 150mm rack case with integral power supply. 0-1W presettable output, synthesized covering 30 channels on 100KHz steps in a 3MHz portion of band II, typical versions 87-90, 102-105, & 105-108MHz. Audio bandwidth 50Hz to 15KHz with pre-emphasis. Front mounted ON/OFF toggle switch and LED indicator, out of lock LED indicator, PWR panel meter. Rear mounted IEC filtered connector for mains input, XLR 3 pin female connector for audio input with balanced line transformer, BNC AF monitor socket, fuse holder, and SO239 connector for RF output, BNC RF monitor socket. IEC mains cable.   £470.00 

Mono 10W & 25W Transmitter, 2U x 250mm rack case with integral RF power amplifier and larger power supply, and fan cooling. Otherwise data as the 1W transmitter above.  10W version £580.00, 25W version £650.00. 

Stereo 1W Transmitter, 2U x 250mm rack case with transmitter as above plus a compressor and stereo encoder, additional XLR connector and balanced line transformer. Average desk levels from -6dB to +14dB are gain adjusted by the compressor to the same level as a 0dB average signal. £600.00. 

Stereo 10W & 25W Transmitters. 2U x 250mm rack case with integral RF power amplifier and large power supply, and fan cooling. Otherwise data as 1W stereo transmitter above. 10W version £700.00, 25W version £780.00. 

ANTENNAS, METERS & CABLE

Omnidirectional 'Slim Jim' Antenna, looks like a giant trombone on end, gives 1.5dB gain and together with an almost horizontal radiation pattern usually out-performs dipoles, folded dipoles, and colinears. 2.5metres overall height.           £50.00.   Mast to pole clamp to suit 2” mast.  £5.00.

SWR meter calibrated at 100MHz.                                                                         £20.00.

SWR/Power meter calibrated at 100MHz.                                                              £25.00.

Coax cable MINI 8, 0.126dB/m loss (measured)                          £1/m, £75/100m reel.

Normal delivery 15-20 working days, 3-4 calendar weeks.  Emergency Service 7-10 working days, 2 calendar weeks, add £75 to cost of transmitter and £40 to the amplifier.   Delivery by carrier, minimum £25.00.

return to top