HI, Mark

Hope this finds you well, and a very Happy New Year to you. I saw you pop up with your command car discussion and wanted to ask your opinion on something.

One of many items on my "Goxhill items that need better understanding" has to do with radios. We know from a list of airfield call / code words that Goxhill's codes were "Midmorn Point to Point" and "Heatwave VHF / DF".

I've reread the Air Ministry's AP 3024 having to do with various communications bands and their range and use in the RAF (and USAAF), and I've cobbled together the statement below that I hope is both concise and accurate, but I'm not enough of a radio guy to have confidence in that.

Would you please look at this and tell me if it seems reasonably accurate?

5. Radio Call signs list “Goxhill MIDMORN Point to Point, HEATWAVE VHF-DF” What are these distinctions? Is one for telegraphy and the other telephony? Morse vs. VHS? When “Midmorn” and when “Heatwave” and for what purposes with what equipment. Suggestion is that “Midmorn” is all voice traffic and “Heatwave” is Direction Finding only for lost aircraft(?)

The British used the designations “R/T” (Radio Telephony) and W/T (Wireless Telegraphy) for communications in the air. R/T is a voice transmission, and W/T is a keyed Morse transmission. W/T had the disadvantage of being cumbersome to use but was normally capable of far longer ranges for dealing with aircraft. Additionally, there were three frequency bands available, Medium Frequency or MF (range up to 300 miles but dramatically lower over higher terrain), High Frequency or HF (range of 5-20 miles on R/T and 300-800 miles on W/T), and Very High Frequency or VHF (range of 90-150 miles) on R/T only.

The Air Ministry’s AP 3024 “Flying Control In The Royal Air Force”(Their ATC “Bible”) stipulates that four frequencies of VHF were typically available for “World Guard” a channel available to any aircraft that might be unable to otherwise communicate, “Group Guard” – a common use channel for any and all aircraft of the same Group as the airfield in question, “Sector Operational Control” – a common channel for all aircraft in the same RAF sector, and “Flying Control” – the channel used by a specific airfield for local control of that airfield.

Since HF had shorter range, it was best for communications by hundreds of airfields with their own aircraft to avoid frequency congestion.

It may be that Goxhill’s code MIDMORN might have been used on MF and HF, with HEATWAVE being used for VHF and DF (Direction Finding).

Many thanks!

Mike Potter