GB3SM Staffordshire Moorlands.
GB3SM, Received Interference from Pager Transmitter.
To summarise the various events that have taken place between the 6th to 15th July, regards the received paging interference to the GB3SM (and later discovered GB3CB) 70cm Repeater receivers.
1) July 6th, first effects of the Paging Interference were heard.
2) Weekend of the 10th and 11th of July, the source of the interfering paging signal was located by Paul 2E1EUB and Phil G4SCY, as the New Queen Elizabeth Hospital Birmingham.
3) Whilst the paging transmitter was confirmed to be transmitting on it's correctly allocated frequency, it was also and at the same time transmitting on several unauthorised frequencies.
4) At no time was the Hospital in any way to blame, the problem and fault was entirely down to the company that supplied and installed the Paging Equipment.
5) During the early stages of investigation it was discovered that the Birmingham UHF Repeater GB3CB was also experiencing a receiver problem of desense, but at that stage the keeper was unaware of the true cause of the said problem.
6) It was positively confirmed that both GB3SM and GB3CB's receive problems were being caused from the same source, the out of specification 50 watt ERP paging transmitter.
7) I made contact with a helpful PMR company in Birmingham City Centre, conveniently located only one mile from the Queen Elizabeth Hospital it was now possible to supply a detailed report of the badly polluted UHF Radio Spectrum in and around the general area of Birmingham, whilst acting upon events here in Stoke-on-Trent.
8) Keeping in constant touch with both the Paging Equipment Company and Ofcom in London, the situation turned critical when other polluted frequencies were discovered.
9) Ofcom Field Ops were notified of the problem and a case number was raised to officially investigate the situation.
10) I notified the paging equipment company of Ofcom's post-haste intervention and they immediately dispatched an engineer to site.
11) The Spurious emissions were removed, but replaced with Wide Band White Noise.
12) The paging company sent more engineers to site and a Bandpass Filter was fitted along with other remedial work to rectify the problem.
All in all the problem was first noticed on the 6th July and corrected on the 15th July and time will tell if it stays that way, but should it reoccur then all the required ground work is now in place.
Whilst we will never know exactly just how many other users of the UHF Radio Spectrum were also affected by the rouge transmitter, I do suspect it may well have been several dozen and with the close proximity of Birmingham International Airport, the consequences could have been very serious indeed.
73,
Geoff, G8DZJ.