Cable Antenna
In case the range of your radio is increasingly going down and a problem on the radio itself or the cable to the antenna can be excluded, a problem of the build in antenna in the vertical tail is probable the reason. This can occur because of the age and the influence of moisture in combination with the landing impulse. The antenna - mostly made from aluminum and steel - cannot emit the high frequent energy from the radio anymore. In turn, this can destroy the power stage of the radio.
As a simple test the resistance of the antenna can be measures by removing the antenna cable from the radio (attention: switch it off before!) between the core and the outer contact. Your should measure an infinite resistance. If this is the case and the range of the radio is anyway not good, the short installation of another radio in your glider with following range check - only on ground - for flight you need a admission. Does this test work, your radio is broken - if not, the antenna or the cable is broken.
In this case a repair is complicated, because the antenna in glued in the vertical tail and cannot changed therefore. As a solution a so called cable antenna can be used: this antenna consists mainly of an BNC coaxial cable (50 Ohm, the same which is used for the cabling from the radio to the antenna), which is modified on the free end by pushing back the outer meshwork on a defined length. Because of the small dimensions and the small weight such an antenna can build in in nearly every glider.
The installation can be done in the undercut of the yaw ruder inside the vertical tail. This mounting has in all cases to be checked by an inspector, because if the antenna gets of the yaw rudder can be blocked. Further on a new barycenter weighting is needed. A instruction to build this type antenna can be found here (Thanks to Bernhard), on the same place a acquisition is possible, if a do-it-yourself construction is not possible.
Annotation: do never operate your radio without connected antenna! The energy created by sending a transmission will destroy the power stage in your radio.
Wave Blocker
If your radio produces a whistle voice during sending in the receiving station and a defect directly on the radio can be excluded (e.g. by changing the radio), beneath a problem with your antenna so called jacket waves can be possibly the reason. This jacket waves produced directly at the antenna if the antenna cannot emit the complete high frequent power of the radio (the radio guys call this a standing-wave ratio unequal one) and therefore a part of the energy travels back on the jacket of the antenna cable back to the radio.
A blockage of the jacket waves and therefore a disappear of the wizzle noise can be done by a wave blocker. In the picture shown on the right two typical styles of waves blockers can be found: the torus made from ferrite wrapped with antenna cable is called balun. The thickened cable left from the balun is made with ferrite torus put on the cable with the same effect. Ideally the wave blocker has to be mounted directly on the antenna, which is in case of a glider mostly not possible because inaccessibility.
In this case the mounting performed as far as possible away from the radio, e.g. behind the seat. Because of the size a balun can normally not used - collapsible ferrites are easier to use. They are divided in their symmetry plane and can be easily installed by pressing them on the antenna cable. You can find them often on the cable from the computer to the monitor.
The ferrite can be purchased at online electronic stores. Keep in mind to buy ferrites for the frequency range from 0-200 MHz. The number of ferrites needed has to be determined during a test and can go up to 10 pices.
If you have questions to this topic please send a mail to WebMaster@GliderDesignParts.de .
PTT-Switch
The PTT-switches shown for the pilot stick are very reliable. You can get at by the typical electronic-stores online with the description "vandalism-secure".