[time-nuts] Lightning arrestors for GPSDO antenna

Mike Seguin n1jez at burlingtontelecom.net
Fri Oct 17 08:33:53 EDT 2014

A peak inside a PolyPhaser 095-0927T-A unit....



On 10/17/2014 2:18 AM, John C. Westmoreland, P.E. wrote:
> Hello Dave,
> I think we had a similar question recently - and I have been told the
> PolyPhaser products are gas tubes - I haven't opened one up yet.
> TESSCO sells these online - you can find them here:
> https://www.tessco.com/products/displayProducts.do?groupId=90143&subgroupId=91046
> Regards,
> John W.
> On Thu, Oct 16, 2014 at 10:23 PM, ed breya <eb at telight.com> wrote:
>> Of all device types, I think gas tubes are the best for this sort of
>> application - very low C, and high surge current rating. I'm picturing the
>> kind that are used in power supplies and such for limiting line transients
>> - about 1 cm dia and length with axial leads. I don't know what kind are
>> used in "lightning arrestors," if they are the same or scaled up in size.
>> Whether you make it able to take a direct hit depends on how big of a hit,
>> your budget, and the environment of the antenna and lines. If it's the
>> tallest thing in a huge field in a lightning-prone area, then it could be a
>> big issue, but I don't think most people have that situation.
>> You may want to look at the US National Electrical Code (NEC) for ideas -
>> I believe that subject is covered there. The main thing there would be
>> safety against injuries and fire, even if the equipment is destroyed.
>> I think what you would want is kind of a pi network - the lowest impedance
>> path to ground at the antenna zone that can be practically realized, then a
>> high common-mode impedance (or even fusible) line to carry the signal to
>> the building, then another low impedance path to ground at the building.
>> This means that in my opinion, you should not put the feedline in metal
>> conduit unless it's essential for protection - or underground, which should
>> improve the grounding. You want the antenna zone to absorb the brunt of any
>> discharge, then use the higher line Zcm to hopefully give some degree of
>> isolation from there to the building.
>> Ed
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.


Mike, N1JEZ
"A closed mouth gathers no feet"

More information about the time-nuts mailing list