Picture of pre-digital VDF indicator
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Picture of pre-digital VDF indicator
I'm trying, so far unsuccessfully, to find a photo of a pre-digital VDF screen. The earliest I can find look like this:
I have a memory of earlier equipment that I saw c1980 with a milky green screen and a little alive green thing in the middle that spiked in the direction of the return, the screen being surrounded by a compass ring with bearing to and from that could be aligned to either magnetic or true north to give QDM/QDR/QTE etc.
Is this a false memory? If not, does anyone have a photo of said screen?
I have a memory of earlier equipment that I saw c1980 with a milky green screen and a little alive green thing in the middle that spiked in the direction of the return, the screen being surrounded by a compass ring with bearing to and from that could be aligned to either magnetic or true north to give QDM/QDR/QTE etc.
Is this a false memory? If not, does anyone have a photo of said screen?
The military CADF (Commutated Antenna Direction Finder )display had the green trace. It could be selected for VHF and UHF frequencies. As far as I recall, civil VDF only ones had an orange trace.
The picture you show appears to be a Furneaux display which at Farnborough, replaced CADF in about 1978 and could still show VHF or UHF bearings.
You could select either QDM or QDR but I don't recall being able to select deg true instead of mag.
When it was flight checked after installation, FCU were still at Wyton and the Argosy (dates it doesn't it) was still reporting Class 'A' bearings as it descended overhead Wyton down to quite low level.
The picture you show appears to be a Furneaux display which at Farnborough, replaced CADF in about 1978 and could still show VHF or UHF bearings.
You could select either QDM or QDR but I don't recall being able to select deg true instead of mag.
When it was flight checked after installation, FCU were still at Wyton and the Argosy (dates it doesn't it) was still reporting Class 'A' bearings as it descended overhead Wyton down to quite low level.
Last edited by chevvron; 29th Nov 2017 at 15:10.
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We've only recently dispensed with our Echo 235 analogue VDF (The Search aerial is still standing). PM me an email and I'll send you a pic. Unfortunately it was not switched on at the time so you will have to imagine the trace.
When I did my PPL course at Cambridge in '71, they still had a D/F with a large needle which normally parked itself at north and slowly swung round when someone transmitted so you were briefed if you want a QDM, make a longish transmission.
I think Dunsfold also had one of these when I visited in '74.
I think Dunsfold also had one of these when I visited in '74.
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Thread Starter
Join Date: May 1999
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That might be the one I saw, it was at Church Fenton in early 1980. Scratchy uniforms had gone by then, though. It's a learning objective in the ATPL theory exams, to describe the operation of ATC VDF equipment in 'general terms'. I now have a wealth of VDF equipment examples, thank you all.
