Datong RF Clipper Archive
This page is dedicated to one of the most useful bits of radio gear you’re likely to find skulking at the back of a rally junk table. My friend Michael (M0APC) picked this RF Clipper up for me at a junk sale for £4 not knowing whether it would be working or not. There was almost nothing on the web but after a bit of working out how to connect it up I got it working and it’s not at all bad. I came across Mark’s website (G4FPH) displaying his Clipper and it was just where a Clipper deserves to be, right on top of your rig!
See the DATONG CLIPPER ARCHIVE – manuals and other useful info (with thanks to Mark). If you have any Datong RF Clipper or ASP information, I would be glad to receive it or a link and I’ll put it on this page.
The pictures below show the ‘blue’ box RF Clipper to the left and the ‘black’ box Auto Speech Processor to the right.
I did a mod to power it externally from 13.5V rather than using the internal 9v battery, however this proved to be a very bad move. Despite ferrite rings, capacitors across the audio i/o connections and shielded cables it sucked RF straight in and caused nasty feedback! I reverted to the internal 9v battery and it works fine, drawing 5.8mA. To remind me to switch it off I added a 12v LED (with built in resistor) across the power-rails (total current drawn at 9v is now around 10mA).
Some time later, Tony G0DLX advised me to try feeding external power to audio equipment from a separate power supply to remove the feedback problems. So I revisited the Datong equipment and other than adding some ferrite beads on the power line, that was all I needed to do to get it working without the feedback!
Settings I use are Output at between level 5 and 10 depending on the mic and Input level between 3 and 7. Mark G4FPH kindly sent me the manual and useful advice which revised the way I perceived the equipment. He explained that the Clipper is rather more clever than I imagined…
The Datong RFC takes in microphone level audio; makes SSB at around 60 kHz with it; clips and demodulates the SSB envelope back to audio; filters it and sends it out as audio. The reason it goes to all this trouble is to maximise the effectiveness of the clipping (make the signal sound as loud as possible) as observed at the remote receiver, consistent with minimising distortion on the transmitted signal. Units that operate purely at audio frequencies cannot clip as aggressively (and thereby achieve the same level of perceived loudness improvement) as, in trying, they would distort the signal too much.
The ‘output’ control on the Datong is effectively in series with the mic. gain on your TX – the purpose of the both of them is to make sure that the TX can be fully modulated, but no more. The degree of clipping is set by the ‘input’ control on the Datong. Once you have set the output control to be correct, you should only really twiddle the input control according to how much ‘punch’ you want your signal to have. I tend to leave my Datong switched in all the time and adjust the clipping according to conditions.
Datong FL-2 and FL-3 Audio Filters
There’s very little difference between the FL-2 and FL-3 filters; they both provide excellent variable, multi-pole and notch filtering with the FL-3 having an auto-notch facility. I picked up my FL-3 in 2005 and was immediately very pleased with its performance. I tend to leave it in circuit all the time although I’m not so keen on the auto-notch facility. The auto-notch works reasonably well but it gives a slight ‘sweeping’ sound which I don’t like and I prefer to use the manual notch if that’s needed.
With thanks to Mark Hill (G4FPH)for donations of material.
Nick (G4IRX)’s Datong archive site – now extremely comprehensive and well worth visiting
Datong RFC (Blue Box) manual
Datong RFC (Blue Box) Alignment manual
Datong RFC (Blue Box) simplified circuit
Datong ASP (Black Box) picture
Datong ASP (Black Box) Operations manual
Datong FL2 Audio Filter manual
G3SEK No-splatter info
Last updated: 26th August 2007