Topband: OT - Bonding Radials at Intersections

[donovanf at erols.com]

Hi Jeff, 


Micro arcing can be excited by just a few volts of RF. While micro arcing 
probably is n't a fire risk, micro arcing radiates low level phase noise 
on transmitted signals. This is can cause a serious interference 
problem to nearby receivers such as neighboring hams or co-located 
receivers such an in-band receiver in a contest station. 


I personally experienced these problems with megawatt transmitters. 
In one instance, a massive radial system for a one mile long of array of 
HF phased verticals had to be completely replaced because it generated an 
elevated noise floor that degraded the performance of the HF over the 
horizon radar. In another case a poorly engineered, badly installed and 
inadequately maintained radial system for a 500 kw VLF system caused 
severe television interference to neighbors that forced premature site closure. 


73 
Frank 
W3LPL 

----- Original Message -----

From: "Jeff Blaine" <KeepWalking188 at ac0c.com> 
To: topband at contesting.com 
Sent: Saturday, November 7, 2020 5:43:25 AM 
Subject: Re: Topband: OT - Bonding Radials at Intersections 

I of course defer to Frank's expertise here. But after thinking about 
this for a couple of hours, I'm trying to wrap my head around this arc 
risk concept as well. It's interesting and I toss this comment out 
because my two sets of 4sq don't have a single cross-bonded wire 
anywhere - all the ground structure is ground mounted, with overlapping 
wires literally all over the place. And despite that, the do seem to 
work more or less OK, as far as I can tell. 

I guess my thinking is list this... All those radial wires are laying 
out on the ground. So they are at least connected at some point, at a 
DC level, assuming your talking about something conventional like a 4SQ. 

Of course, we are talking about AC here, so I will agree that maybe the 
conditions could exist where - with just the right configuration between 
the two radials - that some larger than expected voltage differential 
may be present. Given how low Q a 4SQ is, how current is split between 
multiple elements, my gut feeling is that the excitation voltages are 
pretty mild even if you have your 1500W source right there at the 4SQ 
input. 

And on top of that, the wires are laying on the ground, right? The 
radials are in more or less intimate contact with the ground, so I would 
expect there to exist leakage resistance between adjacent conductors (if 
they are bare). And if they are perfectly insulated, this being AC, 
that means there is going to be some amount of cap coupling between 
adjacent wires and to the ground. With all of that R&C spread out all 
over the field, I would certainly think this conspires to work against 
the probability that any two optimally aligned individual crossing 
conductors would provide a condition sufficient to support an arc, and 
that if so, it would survive long enough to cause a fire. 

It's very very very dry here in the summer and again in the winter. So 
fire risk is something we keep a real close eye on. Then again, out here 
in the Midwest some of us do a lot of IL-advised things because they 
seem to work and of course because laziness is a BIG part of the 
calculation. ha ha. Maybe we have been taking a walk on the wild side 
without realizing it. Hope not because I sure don't want to go try to 
rectify this poor decision 3 years post installation! Say it ain't so! 

73/jeff/ac0c 
alpha-charlie-zero-charlie 
www.ac0c.com 


On 11/6/20 10:59 PM, donovanf at erols.com wrote: 
> Always beware of any communication that begins "with all due respect" 
> 
> ----- Original Message ----- 
> 
> From: "Wes" <wes_n7ws at triconet.org> 
> To: topband at contesting.com 
> Sent: Saturday, November 7, 2020 4:49:23 AM 
> Subject: Re: Topband: OT - Bonding Radials at Intersections 
> 
> With all due respect, I must ask, how many megawatts are you guys running? 
> 
> Wes N7WS 
> 
> 
> On 11/6/2020 3:26 PM, donovanf at erols.com wrote: 
>> Hi Carl, 
>> 
>> 
>> If the insulation breaks down they will arc, potentially causing a fire 
>> 
>> 
>> 73 
>> Frank 
>> W3LPL 
>> 
>> On 11/6/2020 4:27 PM, Richard (Rick) Karlquist wrote: 
>>> On 11/6/2020 1:10 PM, Carl Clawson wrote: 
>>>> Frank, 
>>>> 
>>>> “Must” is a strong word. What goes wrong if you cross them? 
>>>> 
>>>> 73, Carl WS7L 
>>>> 
>>> Also, if insulated wires are used for radials that cross 
>>> over each other, is that to be treated differently than bare 
>>> metal wires that cross over each other and touch 
>>> so as to have electrical connectivity? 
>>> 
>>> Does it matter if cross over radials are soldered at the 
>>> crossovers, so as to prevent parasitic "diodes". 
>>> 
>>> For whatever weird reason, the price of insulated wire is 
>>> nearly always lower than the equivalent bare wire. And 
>>> Romex sells for less than the equivalent individual wires. 
>>> 
>>> Rick N6RK 
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