[BC] Tube transmitter do better in lightning

[Stan Tacker]

I would add a "me to" on proper grounding.  I've seen installations with
point to point grounding and lightening tends to chew up solid state
equipment.  But, convert the site to a single point ground and the
lightening damage is minimized.  

I've started driving in ground rods at each tower, putting a toroid on the
transmission line (at the tower end, between the transmitter and the ATU)
and another at the transmitter/phasor).  Then inside the transmitter
building, all grounds run to a central point.  Knock on wood, lightening
damage has gone way down.

Stan
-----Original Message-----
From: broadcast-bounces at radiolists.net
[mailto:broadcast-bounces at radiolists.net] On Behalf Of Mike McCarthy
Sent: Saturday, August 05, 2006 8:03 PM
To: broadcast at radiolists.net
Subject: [BC] Tube transmitter do better in lightning

Seems the ground at this station wasn't very good.  I've got several 
SX series boxes and all have survived direct strikes to the towers 
many times...knock on wood.

I think if the insurance company really wanted to get to the bottom 
of the problem, they would have brought in their own consultant to 
assess the site and ground system.

MM

At 03:15 PM 8/5/2006 -0400, Harveyesmith at aol.com wrote
>Re "head examination" for keeping tube type transmitters in service past
>their prime...
>
>
>I sort of agree with you, but there are exceptions.  I experienced one...
>
>A brand new Harris SX-1 on lightning hill in Limon, Colorado.
>
>Over the 1st 5 years of service, the total cost of keeping that box on line
>after lightning hits was over $40,000 parts and labor.
>
>much of this was paid for by insurance, and yes, they wanted to replace
>entire cards with new Harris design, no local repair, -keep the 
>scrap cards locally
>for future use- but the ownership was still miffed by the lightning caused
>losses of air time and revenue
>
>the SX-1 transmitter (running at the allocated 250 W daytime) was replaced
>with a Gates BC-250 tube type running 810's (industrial heating and
diathermy
>still MFG. tubes)
>
>Which then ran successfully without out further lightning outages for 4
>years, till the station went dark.
>
>Lets' face the obvious.... (the same truth that exists for continental
>electronics in their 1 MW medium wave and short wave transmitters) 
>also holds for am
>stations worldwide... tubes can take lightning, transistors cannot.
>
>Yes, continental still makes vacuum tube high power transmitters for the
>obvious reason   -lightning survival-  they will tell you this at the NAB
and
>proudly so.
>
>
>And guess what is saving the HDTV industry...  the one tube solution for 55
>kW output (the klystrode) with an estimated 40k hours of service per
tube...
>it seems there is no fighting success and proven durability.
>
>Sort of like the automotive industry trying to convert to plastic piston
>engines, just does not seem to be working.
>
>73's
>
>Harvey E. Smith



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