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Photos by Dan Glover Page last updated: 2012-04-18

April 2012 - DSO and other changes

On a recent trip through the area I glanced up at the top of Balfron Tower and thought "something looks different".

After a bit of research it was time to make a proper visit.

There are three things of interest:
- new transmit antenna
- the significance of the SHF dish
- additional receive antennas on Alexandra Palace

At DSO Poplar has reverted to a conventional relay of Crystal Palace: the SHF link and alternative feed via Alexandra Palace are no longer in use.

Although there are communications antennas on the roof of the service tower, the relay is on the south west corner of the main roof.

The bow ties have been replaced by a pair of dipoles, still with a log facing Crystal Palace below. The SHF dish alongside forms part of one attempt to resolve the difficulties in obtaining a clean analogue feed.

To the left are two yagis which were subsequently added to obtain an alternative feed from Alexandra Palace.

From this angle the sun was reflecting from the new metalwork. The question is: why replace the bow ties?
[Ed] They were replaced in December 2011 as the bow ties were found to be in poor condition when preparatory DSO work was being done.

The dish is part of an SHF link via one of the Canary Wharf buildings. It was added some time after 2001 due to the impact of additional development on direct reception of Crystal Palace.

We understand that the SHF link is no longer in use since it is possible to receive an adequate DTT feed directly from Crystal Palace

These look to be horizontally polarised - but that's right as Alexandra Palace is a HP relay.

The yagis were added, initially on an "emergency basis", to allow an alternative feed due to failure of the SHF link. A planning application in 2005 comments that changes at Alexandra Palace meant all four services could have a reserve feed.

The use of two 18-element yagis does, however, suggest a certain degree of difficulty in obtaining an adequate signal, perhaps CCI was an issue?

The planning application says the two yagis are mounted on the same pole.

The building residents apparently use Crystal Palace...perhaps the COM multiplexes are an attraction?

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