[AMRadio] gas tube protection of front end


John Lyles jtml at losalamos.com
Mon Mar 2 13:18:20 EST 2009


Ne2 or Ne51 or whatever you have in it, are good for protecting hollow state front ends. As they ionize between 50 and 90 volts, they will conduct static buildup before it builds enough to open a coil in the front end. Although i have never heard of that happening either. Commercial receivers sometimes use more expensive devices like Claire makes, with a narrow specification for breakdown voltage. The capacitance of a neon bulb, before it ionizes, is low. For solid state RX, however, neons might not have low enough breakdown to protect fets, varactors, etc. You cannot simply put an MOV or transorb across a HF circuit as it will have a lot of capacitance. Sometimes back to back diodes are applied. Spark gaps and gas tubes still rule. 
John 
K5PRO

> Message: 1
> Date: Mon, 2 Mar 2009 00:57:58 +0000 (UTC)
> From: w0ng at comcast.net
> Subject: [AMRadio] Receiver Antenna Input Question
> To: boatanchors at mailman.qth.net, amradio at mailman.qth.net,
> 	national at mailman.qth.net
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> 	<1524953191.2309561235955478082.JavaMail.root at sz0147a.emeryville.ca.mail.comcast.net>
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> Would appreciate some advice here. I have a National NC-303 receiver that I'm restoring. I had a 75A-2 once that had a neon lamp (NE-2 ???) across the antenna input connection to supposedly act as a surge supressor for lightning, strong static charges?and strong rf energy from nearby transmitters. Is this a good idea? Does this really work? Is there a better device than a neon bulb? Appreciate any opinions, etc. 73, Bill, w0ng 



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