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[liberationtech] digital to analog: Syria radio help needed

Bernard Tyers - ei8fdb ei8fdb at ei8fdb.org
Mon Feb 4 08:07:02 PST 2013


The approach taken would be: self contained IP->FM transmitter box that can be detected without any danger to people setting it up. 

If there was access to technology I would suggest a multiple of low cost computing devices (raspberry pi/etc) receiving IP audio stream, connected to a reasonably low powered FM transmitter. These nodes can be found and destroyed but cost is low and safety is maintained (as much as possible).

Caveat: These are quick ideas off the top of my head. There are probably better ways, but technically these would be possible. Security may be compromised. Some [BIG] assumptions are made.

Not knowing the availability of radio transmitter hardware within the area, my suggestions would be:

Option 1: 

* The IP based streaming input will be available within Syria? If some censorship is being carried out, have the audio stream available on a "standard" IP port, 80 (web server) for example. If so use the IP streaming audio as input for the FM transmitter. I would not think encryption of the IP stream would make sense (and would possibly raise flags/get it blocked)

* Coupling (connecting electrically) the actual radio transmitter via a point-to-point (possibly multiple points) microwave link to the antenna installation. This will give some basic protection -instead of coupling the antenna installation via co-ax cable to the radio transmitter which give away the location of the radio straight-away.

* Allow the system to be controlled remotely, if necessary: although that would give the possibility of   some surveillance. A more secure way would be to leave it as a self contained system that dies when/if its discovered.

Ultimately the audio will need to be available to broadcast FM transmitters on the 85Mhz - 108MHz range.

Ultimately the transmitter would be found, if any signal interception is being carried out.


Option 2:

* The IP stream is sourced from outside the country,and is coupled to an FM transmitter outside the country. The FM signal is broadcast with a directional antenna, over the border into Syria.
* Again, depending on the availability of FM radio hardware, a repeater/relay installation receives this -> original radio station broadcasts on 88.5MHz for example, the repeater  receives it and retransmits it on 101.0MHz

This could be chained a number of times hiding, for a short time, the each FM retransmission point. Eventually it would be found as "somewhere across the Syrian border", and whatever happens happens.

Ultimately the audio will need to be available to broadcast FM transmitters on the 85Mhz - 108MHz range.

Ultimately the transmitter would be found, if any signal interception is being carried out.


I hope these ideas can give some help. Please verify the assumptions made, at least discuss with a broadcast engineer if possible.

Bernard


On 4 Feb 2013, at 15:17, Stefan Geens wrote:

> A Syrian whom I trust and who I've helped with security-related issues before needs some help that I am not qualified to answer, so perhaps somebody on this list knows what to do or where to turn for expert help. I don't want to suggest anything to him that gets (even more) people killed...
> 
> He writes: 
> ========
> I am working now on a radio for Syria that needs to cover Homs governorate, since people there don't have internet or electricity, the only way to reach them is by radio.
> We are working to establish a FM radio station that covers Homs governorate and all Syria later on, it will be based on an online radio that is streaming from outside Syria and we are looking for the best solution to stream on the ground in Homs. We are looking for the best solution to transmit the digital signal into analogue one.
> The point is if we want to use a normal transmitter on the ground it will be known for the regime warplanes and it will be destroyed after few minutes.
> So, what are our options and the details of the best solutions (using inside or outside Syria base)?
> ======
> 
> Thanks for any help you may have. I'll forward it to him.
> 
> Stefan
> 
> --
> stefan.geens at gmail.com
> @stefangeens @ogleearth @dliberation
> +46 73 504 5261
> Skype: stefan.geens
> PGP: 0x54ABD155F7CE9B68
> 
> --
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--------------------------------------
Bernard / bluboxthief / ei8fdb

IO91XM / www.ei8fdb.org

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