Communications projects
Investigation into interference of wind farms and large structures on domestic television and microwave communications.
RF surveys pre- and post windfarm construction
Wideband transceiver with 65MS/s sampler for specialised military application
Switched mode power supplies / systems for ECLIPS (extended capability lithium ion power source) for military man pack radios
Mobile phone battery life investigation for Advertising Standards Authority
VCSEL laser diode driver, DDS and microwave synthesiser and receiver for an optical test set
Investigation of integration of GPS /GIS systems into UHF radios for Egyptian Ministry of Interior, Cairo, 2002
TV Surveying at Cefn Croes windfarm (65 MW) in Wales
Reported interference of the windfarm was investigated in the area and TV interference monitored and recorded.
In the case of Cefn Croes, the interference was not due to the site. However, in areas
within 500m of the turbines, blade-induced multipath and brightness modulation were severe.
The effects on actual transmission have been recorded as an AVI file. Note however, that in some cases,
domestic television interference has allegedly been reported out to 20 km
from a site.
198 kHz off-air standard
Using the 198 kHz BBC Radio 4 signal transmitted from Droitwich, this circuit was intended for lab use as a frequency standard. The Analog Devices PLL
with extremely narrow loop bandwidth was used to phase lock a 1 MHz crystal oscillator. The Radio 4 program is also phase modulated
with a low bit rate time code signal. The device worked well but suffered from mains transients continually knocking the PLL out of lock, which could not
be overcome, so the project was scrapped. The antenna was a high Q screened loop.
13.56 MHz RFID antenna prototype and production unit
ISO 14443 RFID communications interceptor receiver, prototype and production
Intelligent power supply and controller
(Metalwork designed by JWD and manufactured by Datum Products Ltd, Horsham, Sussex,
for a production run of 18 units)
25 Watt, 900 kHz power amplifier for experimental magnetic driver
(Power device by Semelab, UK)
Covert ISO14443 card reader/grabber
Designed to fit in a suitcase/large brief case, this 100 Watt high power reader and active cancellation gradiometer
energises contactless cards at up to 1.2m. Under certain conditions, the card to reader communications can be intercepted and decoded over similar distances.
Wrapping the contactless card in baking foil detunes and de-Q's the resonant system, preventing
fraudulent activation of the card. Cards can also be destroyed at shorter ranges.
Part of the reader circuit and 13.56 MHz high power transmit matching network
Contact details:
JWD Ltd
Telephone/Fax: +44 (0)1403 261251, Mob: 07973 173808
email:
julian @ jwdltd.demon.co.uk