Just checked a 7 page pdf Svenn Martinsen did on Radio London's frequencies I helped him with:

Chris Elliot's Wonderful Radio London Story: "Philip Birch said he had taken expert advice and was reasonably satisfied that 1125 was a clear channel although he expressed concerns about a 10kw Belgian station on an adjacent channel....it might be worth having a couple of reserve wavelengths up our sleeves. I am therefore having two more checked." He said they'd need two more crystals but they weren't expensive. On 21st August 64 he ordered crystals for 1125, 1040 and 1020.

The Belgian station was located in Brussels and operating on its assigned frequency of 1124. There was 10kw station in Barcelona and a 20kw station in Leningrad on the same channel. 1040 and 1020 were not European assigned channels, 1043 had a 240kw East German station on it, 1016 a 300kw West German station.

Benelux DX Club has logs of them on 1125, 1127 and 1129 from December 14th 64 to May 4th 65. All would result in heterodynes when the Belgian station or others were able to be received at a listeners location.

First report of them on 1133 is June 6th 65. 5kw Spanish station on the same frequency plus Zagreb 135kw and 4 other Yugoslavian stations, 50kw, 20kw and two 2kw. Frequency was allocated to Yugoslavia in the 1948 frequency agreement. They complained to the European Broadcasting Union and the UK Foreign Office about interference to them from Big L. I found in North Yorkshire, as it's dark earlier in Yugoslavia thus giving skywave from the reflection point, I was getting interference from them from late afternoon in the late autumn and winter.

Radio 270 first logged on 1115 June 9th 66, Radio London June 6th though both might have been on there a few days earlier. Radio 270 increased power from 2.5kw to 10kw June 15th. When on 1115 Radio London had a second harmonic on 2230 causing problems to marine traffic on/near that channel.

Radio London logged on 1137.5 June 20th, 1139 June 21st from then on split frequency 1137.5, some logs say 1137 hence the heterodyne. AFN Bremerhaven was on 1142. At some point they reduced power at night to reduce the interference in Yugoslavia. Stayed there until they closed down.

They did a test with the 10kw reserve transmitter on 1079 on December 5th. 150kw BBC Home Service transmitter on 1088

When Radio London was on 1115 my Dad told me that in a phone call they had told Radio 270 that they would "jam them off the air". His friend 270 director Tony Rylands would have told him that, would think Wilf Proudfoot was his source. Heated conversation between the two stations. Calmer heads prevailed. I did report that to the Benelux DX Club for their next monthly bulletin, don't think my Dad knew.

Radio London engineer Dave Hawkins in Chris Elliot's book: "We were always looking for a better frequency, we used to do that by using an Eddystone communications receiver at night when our own station was off the air but there simply wasn't one. Caroline in the early days had grabbed by far the better frequency." Goes on to say that they had a better more appropriate mast system.