SEN issue 1119 - 30 July 2007

Table of Contents

  1. Rubber Storage
  2. Airtek Radio DT

Rubber storage Stolen From: [freeflightml@yahoo]

From: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Sunday, July 29, 2007 6:22 PM
Subject: [freeflightml]

Hi Gang,

I'm interested in hearing how the experts store their rubber motors, anywhere from one week to a full season! I have had a motor break winding it the first time, and some after 6-8 times. Is this something we have to live with using tanII and super sport? I store my motors in a brown paper bag, which is placed in a zip loc baggie.

Any hints? Thanks, Frank

Posted by: "Homer Smith"

Sun Jul 29, 2007 11:51 pm (PST)

I am no expert, just lots of experience.

My rubber is stored in a ziplock freezer bag in the freezer. I have had rubber last a long time, like 7 years.

If you wind more that 70% or 80% you will get a lot of breaks after a wind or two. Check the motor for nicks and holes before using.


Posted by: "Tapio Linkosalo"

Mon Jul 30, 2007 12:48 am (PST)

I store my rubber in their original cardboard boxes, in cool room
temperature, but away from light. More recently after a move into a house
with a cellar I have moved the rubber there. The ready-made motors are in
their zip bags, in a larger bag, in the same cellar.

The oldest 10lb box that still has some rubber left is from 1998. I made
and tested a few motors of that box this spring, and the energy return on
the motors is still on the same level as ever.

So I see no point in freezing the rubber. Besides, and active wakefield
flier has a few tens of pounds of rubber anyway, so it would take a
freezer of its own.


Airtek Radio DT (RDT) System for Free Flight Models

July, 2007
Basic System Specs
- Radio Frequency: 902 – 928 MHz IMS license free band. Each system is preset to a
unique channel within this band and also is programmed with a unique digital code.
- Range: 5 km or more line of sight typical, but varies with installation and conditions.
- Response time: up to 1 second delay from transmitter activation to DT.
- Compatible with most Black or Red Magic timers.

Receiver Details
- Size: 12 x 24 x 2mm board plus 3 pin connector and 80mm wire antenna.
- Weight: 1 gram.
- Power: 3.3 to 8V, 2mA average current, 17mA peak taken from host timer.
- Interface: 3 pin male connector 2.54mm spacing; ground, power, and output signal.
Adaptor cable needed to connect to host timer.
- Signal format: normally high impedance, active low pulse when valid transmission
received. Host timer provides pull-up resistor to positive supply for logic compatibility.

Transmitter Details
Transmitter comes with built in rechargeable LiPo battery.
- Transmitter size: 80 x 40 x 15mm, 30 grams, 80mm flexible antenna.
- Battery life: 500 DTs for fully charged LiPo.
- On/Off switch arms the system and DT button triggers continuous transmissions as long
as it is held down.

The receiver must be connected to the Magic timer with a 3 wire adaptor cable very
similar to 3 wire servo connectors. The receiver can be placed anywhere inside the
model but the antenna should be entirely exposed outside the model for best range.
Check that the ground wire of the connector lines up with the black ground mark on the
receiver. The connector must be plugged in the right direction for the system to work,
but no harm will be done if it is connected backwards. For Stamov F1A models which
have the RDT connector built into the top of the nose pod, the receiver can be made with
the 3 pin connector mounted at a right angle to the board so that it will plug directly in.

When the transmitter is turned on the LED will flash three times indicating that it is
armed and ready to transmit. The DT transmission occurs when the DT button is pushed.
This button should be held down until the model DTs which may require about a second
of time, or several seconds if the model is far away. The LED blinks rapidly during
transmission, each flash corresponding to a full transmission of the code. The receiver is
in a low power mode most of the time to save the model battery, but wakes up and listens
for the transmit signal about once a second which is the reason for the occasional one
second delay. After the successful DT the power switch should be turned off. Note that
when testing the system on the bench it may not work when the transmitter is held right
next to the receiver because the powerful transmitter will overload the receiver. Moving
the transmitter a few feet away will solve this.

Charging the LiPo Transmitter battery
Although the battery may contain enough charge to last for a year of flying it is good
practice to keep it close to fully charged. Typically this might mean charging every
month or two depending on the usage, but if not used it can sit for a year or two and still
work. A simple, inexpensive Airtek charger can be used which, being a slow charger,
should be left on for about 24 hours or more, or any charger for LiPo batteries can be
used with a compatible connector as long as it is set for very small cells of about
150mAh. Never use any charger designed for Nicad or other batteries. The 3 pin battery
charging connector is configured for positive on the center pin and negative on the outer

Price Details
Item Price
RDT Transmitter with internal LiPo battery (normal configuration) $175
RDT Receiver $125
(specify normal 3 pin connector or Stamov external F1A style)
Charger for LiPo battery $15
(board only, requires 6 to 12V power adaptor with 5.5mm plug)
Power adaptor for above charger $15
(120vac “wall wart” for US plugs)

Shipping charges added where needed.
Ken Bauer
2306 Turquoise Circle
Chino Hills, CA 91709
This email address is being protected from spambots. You need JavaScript enabled to view it.

Roger Morrell