[QuadList] An O/T but interesting topic--nitrate film of all built on top of high-power AM antenna radials--Safe?

Tue Mar 1 15:15:48 CST 2016

When I was at college, I earned extra cash by babysitting the KDNT AM transmitter site from pre-sunrise sign-on till after sunrise when I changed antenna patterns and transmitter power. I had my First Phone and could use the cash, so I was game.

There was so much RF in the transmitter shack that I could not sit in the folding metal chair less my lower extremities would start burning.

In regard to nitrate, I don't think there would be enough energy in the RF field to cause an issue unless the material was right up next to the antenna. RF experts can chime in on the ratio of RF energy verses distance from the radiation source (it drops off quite rapidly).

Regards,

David Crosthwait
DC Video
Preservation Level Videotape Transfers and More!

david at dcvideo.com
http://dcvideo.com/
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On Mar 1, 2016, at 1:03 PM, Johan Glas via QuadList wrote:

> 
> 
> From: Johan Glas <trippedoverabox at gmail.com>
> Date: March 1, 2016 1:02:47 PM PST
> To: Quad List <quadlist at quadvideotapegroup.com>
> Subject: Re: [QuadList] An O/T but interesting topic--nitrate film of all built on top of high-power AM antenna radials--Safe?
> 
> 
> Nitrate is very dangerous burning, but try to start the fire, not easy. The danger here pointed out seems minor to zero to me.
> 
> Johan Glas, the Netherlands
> 
> Op 1 mrt. 2016 20:58 schreef "Ted Langdell via QuadList" <quadlist at quadvideotapegroup.com>:
> 
> 
> 
> ---------- Forwarded message ----------
> From: Ted Langdell <Ted at quadvideotapegroup.com>
> To: Peter Ford <pford at windowslive.com>
> Cc: "<quadlist at quadvideotapegroup.com>" <quadlist at quadvideotapegroup.com>
> Date: Tue, 1 Mar 2016 11:58:14 -0800
> Subject: Re: An O/T but interesting topic--nitrate film of all built on top of high-power AM antenna radials--Safe?
> Hi Peter,
> 
> Film cans as RF powered heaters.  Hmmm. 
> 
> There's at least one member of the group that might have a thought. I've forwarded this to him and he may reply either directly or through the group. 
> 
> Perhaps someone should be going into more than one of the vaults and doing some measurements with appropriate equipment?
> 
> If the building is concrete and made with any kind of wire mesh in the concrete, is it possibly acting as a Faraday cage?
> 
> Is there any plan to rebuild the taller antenna using the same antenna base, Et Cetera?
> 
> When you have a chance, please feel free to share any stories about your use of the AVR-1 and other machines.  
> 
> Pictures that add to the story and don't take the message above one megabyte total will pass through the Mail system without a problem.
> 
> Otherwise, I get a message that says I need to take a look and approve large files.
> 
> Thanks again for an interesting subject.
> 
> 
> 
> Ted
> 
> Ted Langdell
> Secretary, Quad Videotape Group
> Ted at quadvideotapegroup.com
> (530)301-2931
> 
> Dictated into and Sent from my iPhone, which is solely responsible for any weird stuff I didn't catch.
> 
> 
> On Mar 1, 2016, at 11:25 AM, Peter Ford <pford at windowslive.com> wrote:
> 
>> This is off topic, but members of the group may be able to help with advice as many of you have backgrounds in Radio and Television Broadcasting.
>>  
>> A Film and Tape Audio-Visual Archive (where I have previously carried out quad restoration work using an AVR1 - the connection?) is not permitted to store Videotape/Safety Film and Nitro-Cellulose (Nitrate) film in the same building.  Except for very small quantities undergoing restoration the bulk of the Nitrate Film collection had to be stored in disused ammunition bunkers in an isolated spot in the countryside.
>>  
>> About two years ago this Archive and the Government Archive combined their Nitrate Film Collections in a brand new purpose built climate controlled secure vault in a secret location.  Very commendable - but I have found the location and I see there may be a big problem.
>>  
>> About 40 Km from the city centre is an AM Radio Transmission site.  There are five transmitters with a combined output of about 150 KW.  They had two masts one 220 meters high and the other 137 meters.  However  recently the 220 meter mast was discovered to have a corrosion problem and was dropped with explosives.  It was this activity that drew my attention to the site.  To my surprise I  found the new Nitrate Film vault.  It had been built here over the top of the ground radials for the 220 meter mast and 0.5 km from the 137 meter mast.
>>  
>> Nitrate Film is extremely flammable....it has almost the same composition as Nitro-Glycerine a very hot burning explosive (5000 degrees C).  Having a large quantity of this stuff located in a very strong RF electromagnetic field is asking for trouble.  The films are in individual metal containers stacked 8 high on painted metal shelving.  My theory is each stack of 8 cans will be acting as an aerial and there will be a large RF potential difference between the bottom of the stacks and the shelving.  This is an ignition or detonation source only being suppressed by a thin layer of paint.  Because the transmitters run 24/7 if an arc starts it will not stop.
>>  
>> I spoke to the local council about the danger.  They assured me the vault has a 4 hour fire rating therefore complied with regulations.
>>  
>> Anyone agree with me this is a very dangerous situation?
> 
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