[TowerTalk] Pneumatic Mast

[Ian White, G3SEK]

K7LXC wrote:
>
>In a message dated 08/30/2000 7:22:25 PM Pacific Daylight Time, 
>w7ni@teleport.com writes:
>
>> You might consider contacting your local TV Station with a portable video 
>> link in a news truck.  They typically use a pneumatic mast for their link 
>antenna 
>> and  I think the go about 30 feet or so.  You might find out where they get 
>> theirs from.
>
>    These things are used in their ENG (electronic news gathering) vehicles 
>are they are REALLY expensive. $10-15K wouldn't surprise me.
>

They are available as military surplus in Britain, but they have lots of
disadvantages for long-term use - mainly that you need to maintain
permanent air pressure in the mast to keep out water. If you lock up the
sections and turn off the compressor, the seals relax and let rainwater
run down into the inside. After a few months, it can easily collect a
gallon or two in there. The water corrodes the inside, and in a cold
climate the water will freeze and split the tubing. Maintenance is a pig
of a job, with lots of little corroded screws and delicate feather-edge
air seals. 

Pneumatic masts are fine for ENG use where the mast is up for relatively
short times, and only has to last as long as the vehicle. For permanent
use... maybe not.

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.com/g3sek

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