Topband: intersecting ground radials

[ZR]

While Im not in a high lightning area we do get some beauties plus Im on top 
of an exposed hill. The #18 insulated and stranded used on the old Beverages 
was fine when removed after 20 years and reused as were the same type that 
were relocated for raised radials. It was all part of a pair of 5000' reels 
I picked up at a hamfest in the late 80's for cheap since scrap was at the 
bottom and radial material wasnt popular yet. Finding large reels at any 
price these days at a hamfest is slim to none.

Carl
KM1H

 ----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>
To: "Bob Kupps" <n6bk at yahoo.com>; "topband" <topband at contesting.com>
Sent: Tuesday, September 18, 2012 7:59 AM
Subject: Re: Topband: intersecting ground radials


>> Hi I would like to place monopoles for 160 and 80m bands 30m apart 
>> causing their ground radials to intersect. The radials are #20 bare 
>> copperweld (since I happen to have 4000m) that would be laid out on top 
>> of the soil before turf was placed on top. These antennas would be used 
>> for transmitting only and never at the same time. Is it necessary to 
>> solder the intersecting wires together where they cross for any reason 
>> like they recommend for phased arrays? Naturally I hope not...>>>>
>
> They either should be soldered together, or well separated. The last thing 
> any of us want is a poor connection. A poor connection can make RF noise 
> or rectify and mix signals, and a close spaced connection can arc and make 
> a heat source that literally can cause wires to blow apart in lightning 
> hits.
>
> I hope you are not in an area of severe lightning if you are going to use 
> #20. While I get away with #16 without any issues at all in repeated 
> direct lighting hits, I would not risk  #20. Maybe if you had many radials 
> #20 would work, but otherwise there is some danger you could reach the 
> fusing current limit.
>
> Fusing current of #20 is 58 amperes, which is half of #16 and one quarter 
> of #12 AWG copper. I use a minimum of 30 long radials of number 16 and 
> have no problems with lighning melting wires **IF** they are not laying on 
> other conductors with poor connections.
>
> I left a piece of guy strand laying on the ground below a tower, where it 
> crossed both a large heliax cable and a wide copper flashing. After a 
> strike or two I found it had melted the wide flashing and blown a hole 
> through the heliax jacket. I sure learened a lesson on "close but not 
> bonded" conductors!
>
> My arc welders don't melt the very thin welding wire except at the arc 
> point. :-) My experience is this carries over to unintentional arcs.
>
> 73 Tom
> _______________________________________________
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