Appendix 6

Available filters types

The list below gives brief details of some commercial filters (mostly designed to combat CB interference).

The names and addresses of some manufacturers of filters are given on page 23. Others, no less reputable filters and manufacturers undoubtedly exist.

Mains filter

Type 57A
Rated 1 1/2 Amps. Bandwidth 150 KHz to 25 MHz.

High pass filters

Type 72A
Turnover Frequency 470 MHz.
Attenuation 100 dB at 200 Mhz, 60 dB at
350 MHz.
Insertion loss 470 to 860 MHz not greater than
3 dB.

Wolsey Elect
Type CB 100
Attentuation 100 dB below 30 Mhz

Waters & Stanton
Type HP4A
Attenuation 50 dB at 27 MHz, 60 dB at 54 Mhz.
Braid attenuation 16 dB at 27 Mhz.

Braid breakers

Type 64/lA and 64/2A
Frequency range lA = 3 to 40 Mhz
        2A = 40 to 220 Mhz

Braid attenuation nominally of the order of 10 dB or better in the respective frequency ranges.

Type 74A
Insertion loss 4 dB from 30 to 50 MHz 3 dB from 100 to 860 MHz.
Braid attenuation over these ranges nominally of the order of 10 dB.or better.

Combined high pass/ braid breakers

Eldee Technology
High pass attenuation 65 dB at 27 MHz.
Braid attenuation 25 dB at 27 MHz.

Labgear
LPT223
High pass attenuation 60 dB at 27 MHz.
Braid attenuation 25 dB at 27 MHz.

Labgear
JH 11
High pass attenuation 70 dB at 27 MHz.
Braid attenuation 25 dB at 27 MHz.

A range of small tubular filters matching types 72A, 74A and 64/1A, 64/2A are made by AKD together with a combined high pass broadband braid and notch braid.

Band-stop filters

Type 68A
Attenuation in the frequency range 71 to 88 MHz
(low band PMR) 50 to 60 dB.
Insertion loss approx 3 dB.

Type 67A
Dual, tunable band-stop covering the two frequency ranges 70 to 90 MHz and 130 to 170 MHz.
Attenuation of the order of 35 dB over the tunlng ranges.
Insertion loss approx 3 dB.

Type 69B
Frequency range 130 to 165 MHz.
Attenuation 50 to 60 dB.
Insertion loss approx 3 dB

Tunable notch

Type 73A
Notch attenuation approx 25 dB tunable over the range 400 to 850 MHz.
Insertion loss approx 3 dB.

Toroidal Choke Components

EMC Datacare Type D918 Clamp-on choke kit of 'split' construction ferrite rings. Impedance of not less than 5 ohms per turn between 1 and 100 MHz.

Filter Manufacturers

Labgear Cablevision LTD

Address: AbbeyWalk Cambridge, CBl 2RQ
Tel: 0223 66521

Wolsey Elect

Address: Gellihirion Trading Estate, Tretorest, Mid Glamorgan. South Wales, CF37 5SX
Tel: 0443 853111

Waters & Stanton

Address: Warren House. 18-20 Main Road. Hockley Essex, SS5 4QS
Tel: 0702-206835/204965

Eldee Technology

Address; 22 Oulton Street, Lowestoft, Suffolk, WR32 3BB
Tel: 0502 68106

Belling and Lee

Address; 540 Great Cambridge Road, Enfield, Middlesex, ENl 3RY
Tel; 01-363 5393

Cetronic GB LTD

Address; 1 Goodmayes Road, Goodmayes, Ilford, Essex 1G3 9UQ
Tel: 01-5992392

Rasmi Electronics LTD

Address; Quaking House, 61 Third Street, Stanley, Co Durham, DH9 7HE
Tel: 0207 232159

Panorama Antennas LTD

Address; 73 Wadham Road, London, SWl5 2L5
Tel: 01-8705192