WLW (Was An O/T but interesting Topic)

Thu Mar 3 14:13:04 CST 2016

Second attempt

Begin forwarded message:

> From: David Crosthwait <david at dcvideo.com>
> Date: March 3, 2016 8:57:44 AM PST
> To: Quad List <quadlist at quadvideotapegroup.com>
> Subject: Re: [QuadList] An O/T but interesting Topic
> 
> Peter,
> 
> High-powered transmitter RF makes for interesting reading, particularly in the case of WLW in the 1930's. 500 KW on medium wave , 700 khz.
> 
> http://www.ominous-valve.com/wlw.html
> 
> "Needless to say, W8XO's late-night tests went on for months. This wasn't your mom's hot plate. When Ohio's famous lightning hit the tower, RF would simply sustain any resulting arcs, at the air gap or anywhere else, until the carrier was interrupted. There were folk tales, probably accurate, of talking rain gutters, sparking fences, singing water pipes, and nearby street lights dimming on modulation peaks."
> 
> Best Regards,
> 
> David
> 
> 
> 
> On Mar 2, 2016, at 10:28 AM, Peter Ford via QuadList wrote:
> 
>> 
>> 
>> From: Peter Ford <pford at windowslive.com>
>> Subject: An O/T but interesting Topic
>> Date: March 2, 2016 10:27:51 AM PST
>> To: <quadlist at quadvideotapegroup.com>
>> 
>> 
>> Thanks for you replies David, Johan and Ted.
>> 
>> First I have a correction.  The combined RF power output into the mast is currently 250 KW.
>> 
>> At the petrol pump we are advised not to use mobile communications devices - This is UHF at less than 2 Watts.
>> 
>> An Induction cooktop boils water very quickly - EVLF at about 1 KW - but minimal spacing between the pot and the induction coil.
>> 
>> MF AM Radio is between these.  We have 250,000 KW at 0.5 Km from the metal film cans/shelves.  So will there be any heating effect and is there a risk of RF arcing?
>> 
>> Peter
>> 
>> 
>> 
>> 
>> 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
>> 
>> 
>> On Mar 1, 2016, at 1:03 PM, Johan Glas via QuadList wrote:
>> 
>> 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
>> 
>> 
>> 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?
>> 
>> Ted
>> 
>> 
>> 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?
>> 
>> 
>> 
>> 
>> 
>> ______________________________________________
>> Please trim posts to relevant info when replying.
>> 
>> Change subject to reflect thread direction. Thanks.
>> _______________________________________________
>> 
>> Send QuadList list posts to QuadList at quadvideotapegroup.com
>> Your subscribe, unsubscribe and digest options are here:
>> http://mail.quadvideotapegroup.com/mailman/listinfo/quadlist_quadvideotapegroup.com
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://quadvideotapegroup.com/pipermail/quadlist_quadvideotapegroup.com/attachments/20160303/242d4293/attachment-0003.html>