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For Crystal Palace`s broadcast frequencies see its Channel Allocation Guides for

before and after the DSO. These also include the same information for most of the other major transmitters receivable within the coverage area of Crystal Palace, i.e. Sandy, Sudbury, Bluebell Hill, Dover, Tunbridge Wells, Heathfield, Reigate, Midhurst, Guildford, Rowridge, Hannington, Oxford and Hemel Hempstead. This data can be of great use in determining possible causes of co-channel interference and/or alternative transmitters to try if Crystal Palace fails to give an adequate signal, the importance of “Line Of Sight”. Note

how most of the broadcast channels from the various transmitters “Dovetail” together but it has not been possible to eliminate potential co-channel problems. The Channel Allocation Guides can also be invaluable if you are trying to find a spare channel for a modulated

output (e.g. for a Sky box or CCTV system) to be added to your TV setup/distribution system without suffering from co-channel.

Ofcom report there are slight restrictions from East round to South on all six digital MUXES.

DSO is due to occur in April 2012 and unsurprisingly it has been confirmed by Ofcom that Crystal Palace will stay an A group at DSO.

Crystal Palace is transmiting a pre switchover low power HDTV MUX (on CH31 at 10kW)

from December 2009. Due to co-channel interference issues its radiation pattern will be

restricted so just because you can get all six standard digital MUXES, this does not mean

you`ll necessarily get the temporary low power pre switchover HD MUX. You will obviously need a new Freeview HD set top box, and these are due on the market from Spring 2010.

There are two interleaved spectrum channels allocated to Crystal Palace, CH29 and CH42.

It will be noted that CH 29 is within the previously announced Post DSO group but CH42 is

not. However the latter frequency will have co channel issues with at least three other

transmitters so its power and radiation pattern will be severely restricted. See the Ofcom

document showing the proposed transmission pattern for this particular interleaved

frequency, it`s on page 19 of 24. I`m not an expert on interpreting these but as far as I can

tell only those to the East and the NNW would stand any chance of getting it ! Under these

circumstances, together with the fact it will be out of band for the great majority of the

aerials within its coverage area, one wonders who would actually pay much for it ! Those

who want the option of it should fit the Log 40 or the XB16A if in a poor spot. Group A

aerials fitted after the mid 1990s (when the group was extended from CH34 up to CH37)

may well receive CH42 in strong signal areas. The above Ofcom document also shows the

proposed transmission pattern for the CH29 interleaved frequency P18 of 24), and it is far

more omni directional.

The channel planners were able to fit all the Digital / Freeview MUXES (transmitted at 20kW) within the A group along with the analogue stations so an aerial change may well not be necessary. Furthermore those in poor reception areas, who may require an

upgrade, can take advantage of the superior performance of an A group aerial over a wideband. In fact such is the widebands inferiority at the bottom of the band that there is

no such thing as a “High Gain” wideband aerial for the A group frequencies and nobody should ever fit a “high gain” wideband on an A group transmitter, e.g Crystal Palace.

If the site is in a poor spot an A group aerial should be used. On the other hand if the signal is strong (or medium) then by definition it doesn`t need a “high gain” antenna anyway !  Under these circumstances a Log Periodic should be fitted instead.

See Crystal Palace transmitter`s graph and the wrong aerial for Crystal Palace.

For Crystal Palace we recommend the DM log for strong signal areas, the Log 40 for medium signal areas, the Yagi18A for outside installs in poor signal areas,

the XB10A for loft installations in poor signal areas, and the XB16A for those with the

most marginal signals. Unless you have a massive loft we`d normally recommend the XB10A over the XB16A for a loft install due the smaller size of the former aerial

The dimensions and test performance of the aerials can be found on the relevant tables.

See this customer Aerial Report.

These are the wrong aerials for Crystal Palace (or any other A group transmitter).    

(see Crystal Palace graph)

Both these aerials were spotted in Purley On Thames, just West of Reading, and they`re

both on Crystal Palace transmitter which is about 40 miles away. The thing is, they`re the

wrong aerials for Crystal Palace, or any A group transmitter come to that.

I`m not familiar with the signal strength in this location (though the one on the left was on

a bleedin` high pole....) but whether it`s a strong or weak area the installer has still fitted

the wrong aerial.

If it`s a strong or medium reception area he should have fitted a Log Periodic aerial,

but if it`s a weak reception area an A group aerial should have been used instead.

I estimate that over the Crystal Palace frequencies the aerial on the left would average

about 1.5 dB more than a DM Log and the one on the right about 2.0 dB more.

But if you`re short of signal a Yagi18A would give about 4.7 dB more, and an XB16A

about 6.7 dB more. We had a customer who was shielded from Crystal Palace transmitter by the Arsenal football stadium. He originally had a DAT75 but his pictures were very poor,

so he swapped to an XB16A and reported that whilst his signal wasn`t perfect it was much better, “we can actually watch TV now” was his exact comment !    QED #1

Don`t get me wrong, I`m not saying these wideband aerials aren`t working for the particular

installations, but the fact is that on Crystal Palace the performance difference between one of these huge aerials and a decent Contract 10A would be minimal. The Contract would be about a tenth of the price and have much less wind loading as well !  We don`t actually recommend Contract aerials but our Log40 would perform just as well (over the A group frequencies) as any wideband Tri Boom antenna, yet have much less wind loading, still be

a wideband and have all the advantages that a Log Periodic aerial offers. QED #2

In my opinion if any installer tries to sell you this type of antenna for Crystal Palace

(or any other A group transmitter) you can quote me that he’s fitting the wrong antenna.

Although I think Tri Booms are over rated (particularly for frequencies at the bottom of the band) it`s possibly a little unfair to pick on them because all of the comments in this article apply (to a large extent) for any wideband Yagi type aerial, whether X Beam or not.

But all Tri Booms are wideband so at least I can be sure what I`ve photographed !   

See this customer Aerial Report.

Those situated to the North or NW of Crystal Palace may find that during certain weather condition they can suffer from co-channel interference as their aerials are pointing towards the continent.

Crystal Palace is situated 6 miles South of The Tower Of London, though it was built rather more recently than the latter, in 1950. The tower is 222m high (see How High is High ? )

and in some ways looks similar to the Eiffel tower in Paris, although the French structure

is taller at 318m. I have often wondered why the owners of Crystal Palace don`t learn from their Parisian counterparts and build a public viewing platform. I`m sure they would recoup the investment many times over, after all it`s far higher than “The London Eye” ! In this day and age there`s bound to be some Health & Safety B******s ruling to stop it though.

The site gets its name from the original Crystal Palace which was built for the Great Exhibition (of 1851) and moved to this site in 1854, unfortunately it was tragically destroyed by fire in 1936. Also located near the tower is the National Sports Centre of 1964. For years this housed London`s only 50m swimming pool (until a second one opened in Ealing) but it also has various sports halls plus the the well known athletics track.

In the old 405 line VHF days the transmitter only broadcast the BBC and a second similar design (152m in height) was constructed in 1962 for ITV * at Croydon. When UHF started transmission in the 60`s (1964 from Crystal Palace) the distinction between BBC and ITV broadcasting sites was discontinued and everything was transmitted from Crystal Palace.

In fact in 1985 when the VHF signals were finally switched off it seemed Croydon`s days as a TV transmitter were over. However this was not quite the end of the story because when Channel 5 began broadcasting in 1997 Croydon was given the job of transmitting it (also at 1000kW) to the London area. Although Crystal Palace does not transmit analogue C5 the vast majority of those receiving their signals from it will still pick up C5 perfectly well because it`s within group and Croydon is only 1 mile away to the SSW !

That said, the word is that analogue C5 is severely attenuated to the S/SE, possibly to

avoid co-channel with Tunbridge Wells C5, plus the continental TXs ?

In any event Digital C5 (on MUX 3) is broadcast from Crystal Palace.

* This double transmitter scenario was also used for Sutton Coldfield / Lichfield,

Emley Moor / Holme Moss and Pontop Pike / Burnhope amongst others.

External links

Crystal Palace Transmitter page at The Big Tower

Crystal Palace Transmitter page on Wikipedia

Crystal Palace transmitter`s channels in relation to the TV band and the gain of the aerials we recommend for it. DM Log    Log40    Yagi18A    XB10A     XB16A

Also see other relevant A group curves.