Speed control units (particularly ones that work off back-emf sensing) tend to be poor at producing low speeds. Brushless motors are a classic example.

PWM controllers can do slow speeds - that's what railway modellers use for shunting - but the motor drive tends to be jerky (which the railway modellers like because it breaks track adhesion)

For radar you want a slow but smooth rotation. For that, gears are the obvious answer, since they suppress jerkiness...

just had a hunt around on the web

http://www.amazon.co.uk/6-24V-Small-Motor-Speed-Control/dp/B00ENE03MO


£4:26 including the motor

rather than a gearbox which will be noisy since its engineering is basic why not just use a direct drive small motor and control its speed electronically?

http://freecircuitdiagram.com/2009/01/02/small-dc-motor-speed-controller/

a simple design which should solve your problem

I have just finished making the radar for 12th scale mersey lifeboat using a geared motor from GIZMOSZONE.COM they supply a large range of miniture motors of all different speeds and sizes and are very quiet hope this helps

HI trillium I got one on the way give it a try it can't be any noisy than the servo I've got in there. Thanks for the heads up.

HI dodgyGeezer just had a look got one on the way will try it out, thanks for your help.

I have one of these ebay motors and think it's noisy. Mine is fastened on the underside of the deck which possibly amplifies it.

One of these any good? 6v, 30RPM thumbnail size...

http://www.ebay.co.uk/itm/SS-30-RPM-DC-6V-2-5KG-Micro-Gear-Box-Speed-Reducing-Motor-/321769328212?tfrom=231579573434&tpos=top&ttype=price&talgo=undefined