Cockpit SX Tutorials: Antenna Fixings

by Mike Shellim 28 August 2006

last updated 10 May 2010

Correcting poor balance when using short aerials

Poor balance is the bane of many first generation 2.4 GHz sets which were originally designed for much longer and heavier 35 MHz aerials. It can also be a problem if you use a short rubber ducky aerial on your 35 MHz tx. Fortunately, Geoff Gaunt has found a solution:

"I thought that some of you might find this useful: if you use the Cockpit SX with the short 'Rubber Ducky' aerial, the TX doesn't balance particularly well.

I took the risk and got one of the JR neck-strap adapters. The slot is the exact width for the SX attachment, and the base of the adapter just requires a little filing to flare it out to the radius of the attachment. It works a treat!"

JR neckstrap adapter mounted on SX attachment point

Swivel joint for normal 35 MHz antenna

Multiplex offer a swivel joint assembly (# 7 5129) which in theory at least allows the standard 35 MHz antenna to be tilted to any angle.

The base of the joint screws into the Tx in place of the regular antenna, and the antenna then screws into the angled section. Two set screws are used to set angle (allen keys are provided). The antenna can be removed at any time, while the swivel joint remains attached to the Tx.

Well that's the theory, sadly the practice did not live up to the promise. The knuckle joint would slip too easily and the whole assembly tended to unscrew itself. Not something I felt like persevering with but for the record here are some photos:


Components of swivel joint


Allen keys to lock pan and tilt angles


Ready to go

35 MHz stub antenna

In contrast, Multiplex's stub aerial (part no. #7 5126) makes an excellent alternative to the standard 35 MHz antenna for DLG or if you just like the convenience. I personally use it for DLG and slope soaring, and love it.

The only drawbacks are (a) the neckstrap adjustment point is optimised for the long aerial (but see above for a solution) and (b) there is some reduction in range (Multiplex provide only very rough guidelines about range).

If range is a concern, then I'd suggest using a receiver with a glitch counter like the Schulze 5.35 and 8.35, or some of the MPX IPD receivers. (Thinks... a real time field strength monitor mounted on the model with an RF downlink would be perfect!)

Finally, note that although the stub aerial for the 4000 may fit, it is not the same - stick with the right aerial for the job!


Cockpit SX with stub antenna fitted