This cache is hidden close to the TTR NDB. You will be able to see this to SSE as two towers with a wire between them. The TTR NDB is aligned with the direction of runway 12 at Hobart Airport and is 12nm (about 22km) from the runway threshold. Generally, aircraft arriving into Hobart, especially in bad weather, will overfly this NAVAID to ensure that they are flying a direct course to the runway.
Please Note:
There are limited places to park near to GZ - please park sensibly and be careful on and around the road and railway line near to GZ. There is no need to cross any fences or interfere with anything with warning signs advising you not to touch.
NDB Information:
A non-directional (radio) beacon (NDB) is a radio transmitter at a known location, used as an aviation or navigational aid. As the name implies, the signal transmitted does not include inherent directional information, in contrast to other navigational aids such as low frequency radio range, VHF omnidirectional range (VOR) and TACAN. NDB signals follow the curvature of the Earth, so they can be received at much greater distances at lower altitudes, a major advantage over VOR. However, NDB signals are also affected more by atmospheric conditions, mountainous terrain, coastal refraction and electrical storms, particularly at long range.
NDBs used for aviation are standardised by ICAO (International Civil Aviation Organisation) Annex 10 which specifies that NDBs be operated on a frequency between 190 kHz and 1750 kHz, although most NDBs operate between 190 kHz and 535 kHz. Each NDB is identified by a one, two, or three-letter Morse code callsign.
For TTR NDB the transmission is “— — •—•”, morse code for “TTR”. The frequency that the NDB transmits on is 374 kHz - you may be able to receive this signal using your AM radio.
Further information about NDBs, including how they work, and how aircraft navigate using the VOR can be found on Wikipedia here: http://en.wikipedia.org/wiki/Non-directional_beacon
Common Adverse Effects
Navigation using an ADF to track NDBs is subject to several common effects:
- Night effect: radio waves reflected back by the ionosphere can cause signal strength fluctuations 30 to 60 nautical miles (54 to 108 km) from the transmitter, especially just before sunrise and just after sunset (more common on frequencies above 350 kHz)
- Terrain effect: high terrain like mountains and cliffs can reflect radio waves, giving erroneous readings; magnetic deposits can also cause erroneous readings
- Electrical effect: electrical storms, and sometimes also electrical interference (from a ground-based source or from a source within the aircraft) can cause the ADF needle to deflect towards the electrical source
- Shoreline effect / Coastal refraction: low-frequency radio waves will refract or bend near a shoreline, especially if they are close to parallel to it
- Bank effect: when the aircraft is banked, the needle reading will be offset
While pilots study these effects during initial training, trying to compensate for them in flight is very difficult; instead, pilots generally simply choose a heading that seems to average out any fluctuations.