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--- communication:nova1_radio_system [2006/09/25 19:01] – rocketboy
+++ communication:nova1_radio_system [2008/07/19 23:33] (current) – external edit 127.0.0.1
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-====== The NOVA1 Radio Data Downlink ======
+====== The NOVA1 Radio Data Downlink (by Steve Randall) ======
 The radio system used on NOVA1 was intended to be a test of what could be achieved using off-the-shelf  modules.  The system is essentially a standard 1200 baud packet radio TNC connected to a 10mW 434MHz licence exempt transmitter module - a small circuit is used to interface the two.  The antenna used was a coax dipole, which was directly connected to the transmitter output.
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 The TNC used is the TNX-X from Coastal Chipworks (see http://www.tnc-x.com/) - which is available as a kit or ready built.  The TNC-X weighs 45g and measures 63 x 96mm.
 ===== Transmitter =====
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 Ground-station Antenna – 7 element 434MHz “ZL”  yagi (11.5dbd).  A Narrow Band FM  receiver was used – feeding another TNC-X which was then used to feed a PC running a terminal emulation program.
-Accurate pointing of the antenna proved to be critical especially when the balloon was at distance.  In a subsequent flight the receive antenna was mounted on a camera tripod – which made the job of holding and pointing the antenna more pleasant.
+Accurate pointing of the antenna proved to be critical - especially when the balloon was at distance.  In a subsequent flight the receive antenna was mounted on a camera tripod – which made the job of holding and pointing the antenna more pleasant.
 {{:communication:tripod.jpg|:communication:tripod.jpg}}
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 ===== Improvements =====
-**Tune up signal** – A signal to allow manual peaking of the antenna direction.
+  * **Tune up signal** – A signal to allow manual peaking of the antenna direction.
+  *A **longer receive antenna** could be used – a antenna double the length of the existing antenna would not be unwieldy or present too much of a problem to align – this should provide an additional 3db of gain (40% in terms of distance)
+  *The addition of a **low noise pre amplifier** at the antenna output might improve the overall signal to noise ratio (depending upon the receiver)
-A **longer receive antenna** could be used – a antenna double the length of the existing antenna would not be unwieldy or present too much of a problem to align – this should provide an additional 3db of gain (40% in terms of distance)
+  *Slightly **wider transmit deviation** could be used and still remain within the narrow-band channel – this would improve the signal to noise ratio.
-The addition of a **low noise pre amplifier** at the antenna output might improve the overall signal to noise ratio (depending upon the receiver)
-Slightly **wider transmit deviation** could be used and still remain within the narrow-band channel – this would improve the signal to noise ratio.
+A combination of these improvements might at best double the overall communication distance to about 60Km.