rad1o

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= Antennas

The board has a PCB antenna for the 2.5 GHz ISM Band, for stand alone operation on the Camp Area. **For other frequencies the use of an external antenna is highly recommended.**

== How to attach an external antenna

=== Temporary
To improve radio reception a little bit you can just press a thumb against the upper right corner and be a human antenna. 
The most simple real external antenna is a single-wire copper cable (others may also work). This can be pressed against an edge of the little black resistor on the top right corner.
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=== Soldering
<note important>**When soldering an antenna or SMA connector, a resistor (R315, 0 Ohm) must be turned 90 degrees or replaced with a bridge, connecting the RF line on the left to the SMA connector pads on the right**</note> (then the 0 Ohm resistor will be sitting on the R314 pads; R314 and R315 share the upper left pad). Use 2 soldering irons - so you can easily move the little resistor.

The SMA connector should be an edge-launch SMA connector for a PCB thickness of 1.6mm (see [[extension:rfkit|RF Kit]])

Resistor turned 90 degrees
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Alternative: Add bridge, remove resistor
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Using a soldered copper cable as antenna:
{{:rad1o_9.jpg?100|}}

Adding an SMA connector so that you can connect an external antenna for your specific needs.
{{:rad1o_12.jpg?100|}}


**WARNING: When soldering, don't connect the unpopulated large pads right below the antenna pads to the pads, this may result in blue smoke!** Best to check right after soldering, we did find a few cases of barely visible connection.

== Building an external antenna

Build your own dipole antenna with [[extension:d1pole|d1pole]]

German compendium about HAM-Radio-Antennas, very complete, with a lot of tipps and instructions for DIY-Antennas, Edition from 1968 (7th Edition). [[http://pi4oss.ham-radio.ch/hamsoft/Rothammel.pdf|Rothammel - Das Antennenbuch]] Current Edition is 13th, from 2012 ISBN 978-3-88692-065-5 
== Commerical antennas

HackRF recommends the [[https://greatscottgadgets.com/ant500/|ANT500]] antenna for beginners. Cheapest way to order in germany/fr/uk seems to be from [[https://www.passion-radio.com/gb/antennas/antenne-ant500-74.html|passion radio]] for 29€ (VAT not included!), shipping being about 2€. This shop also recommends the apparantly similar antenna [[https://uk.passion-radio.com/gb/sdr-antennas/srh789-sma-259.html|Diamond SRH789]].
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