NOTE: All Channel Frequencies below are in Mhz. Below you will find details of the 405 and 625 line systems as used in the UK and Eire.

405 LINE CHANNELS: BAND1. BBC Transmissions.

CH1: Vision Carrier: 45.00 Mhz. Sound Carrier: 41.50 Mhz.

CH2: Vision Carrier: 51.75 Mhz. Sound Carrier: 48.25 Mhz.

CH3: Vision Carrier: 56.75 Mhz. Sound Carrier: 53.25 Mhz.

CH4: Vision Carrier: 61.75 Mhz. Sound Carrier: 58.25 Mhz.

CH5: Vision Carrier: 66.75 Mhz. Sound Carrier: 63.25 Mhz.

405 LINE CHANNELS: BAND 3. ITV Transmissions.

CH6: Vision Carrier: 179.75 Mhz. Sound Carrier: 176.25 Mhz.

CH7: Vision Carrier: 184.75 Mhz. Sound Carrier: 181.25 Mhz.

CH8: Vision Carrier: 189.75 Mhz. Sound Carrier. 186.25 Mhz.

CH9: Vision Carrier: 194.75 Mhz. Sound Carrier: 191.25 Mhz.

C10: Vision Carrier: 199.75 Mhz. Sound Carrier: 196.25 Mhz.

C11: Vision Carrier: 204.75 Mhz. Sound Carrier: 201.25 Mhz.

C12: Vision Carrier: 209.95 Mhz. Sound Carrier: 206.25 Mhz.

C13: Vision Carrier: 214.75 Mhz. Sound Carrier: 211.25 Mhz.


Standard Vision IF: 34.65 Mhz.

Standard Sound IF: 38.15 Mhz.

Note that the Vision and Sound Carriers are reversed when mixed from RF to IF.

Some sets may have a built in VHF Radio: IF is usually 10.7 Mhz.

Frame Rate: 50Hz. Line Frequency: 10.125 Khz.

Vision Modulation: AM, Vestigial Sideband. Positive Going Modulation. i.e Mod Depth INCREASES with brightness.

Sync Pulse Amplitude rises from 0% Mod to 30% Mod.

Blanking Level: 30% Mod.

Black Level: 35% Mod.

Peak White: 100% Mod.

Picture Signal Rises from 35% to 100% Mod.

Highest Video Frequency: 3 Mhz.

Sound Modulation: AM.

As this site is concerned with practical old TV restoration and repair, the very interesting issue of experimental 405 Line colour transmission has been left for another day.


Rather than list all the channels 21 to 68, There is a simple formula for working out the frequencies of the carriers. It is:

Vision Carrier = 8N + 303.25 Mhz, where N is the channel Number.

Sound Carrier = Vision Carrier + 6 Mhz. Level is 10dB down on Vision.

Colour Subcarrier = Vision Carrier + 4.43 Mhz. This is 17dB down on Vision.

There are 47 UHF channels, 21 to 68. Some sets also use Ch69! I'm not listing every single one!!!!


Standard Vision IF: 39.5 Mhz.

Standard Sound IF: 33.5 Mhz.

Note that Vision and Sound Carriers are reversed when mixed from RF to IF.

Frame Rate: 50Hz. Line Frequency: 15.625 Mhz.

In order to find the Colour Subcarrier at IF, look 4.43 Mhz BELOW the Vision IF. i.e. in the above example, It would be at 39.5 - 4.43 Mhz, i.e. 35.07 Mhz.

4.43 Mhz is however a commonly used approximation. The exact gap between Vision Carrier and Colour Subcarrier is 4.43361875 Mhz. This exact frequency was chosen to minimise visual effects on Monochrome receivers. Look under Theory!

VISION MODULATION: AM Vestigial Sideband. 4.43 Mhz subcarrier amplitude modulated onto Vision Carrier. Negative Going modulation.

Modulation Depths at 625 Line UHF: Due to the use of Intercarrier Sound, vision modulation does not drop below 18-20% at Peak White. Mod levels are... Peak White: 20% Mod, Black and Blanking Level: 77%, Sync Pulses extend from 77% to 100% Modulation.

SOUND MODULATION: FM. I have chosen to ignore such modern gimmicks as Nicam in this site as we are concerned with proper TV sets!!!


In order to keep the bandwidth of the transmitted TV channel within its channel allocation, Vestigial Sideband is used. This means that the carrier, all of ONE sideband and lower frequency part of the other is transmitted. For example, on a 625 line PAL system in the UK, only the 'first' 1.5 Mhz of the lower sideband is transmitted. The carrier and Upper Sideband remain complete. All the necessary picture imformation is transmitted, but the IF response of the receiver must have a suitable response curve to accommodate this.

In order to complicate matters further, many VCRs , TV Games, Cable TV set tops and Sattelite Receivers transmit Full AM. (Cheap...!) This is why I strongly reccommend that the setting up of a TV set, should it prove necessary, be conducted with a suitable signal generator or using a BBC off air transmission! A domestic video does not make a precision signal source.