[TowerTalk] Radio's/tunnels

[K7GCO@aol.com]

The reason for the use of lossy coax with slots was to spread radiation full 
length of the coax run--not heat.  Cheap RG8 with semi open mesh will do 
about the same.  The actual resistive loss of this coax is just slightly less 
than full mesh shield.  80% of the attenuation of coax is in the shield if it 
is full.  This is why increasing the size of the center conductor in polly 
foam reduced the loss of RG8 .2 db/100' at 30 Mz.  The reduced loss of using 
a foam dielectric doesn't start to be an advantage until above 30 MHz.  k7gco

In a message dated 05.05.00 00:19:54 Pacific Daylight Time, 
conatore@teleport.com writes:

<< The reason for the question is simple - to determine if there is a special
 "value" or reason for using this "special" lossy coax over simply stringing 
RG58.
 I suspect there is, and I suspect it has to do with losing the energy to 
heat vs.
 radiating it. Maybe there is a hole in this line of thought? (I am not an RF
 engineer, just an interested party with enough knowledge to be dangerous).
 
 Is there a reason to know this? Apparently there is for someone. Do I really
 care? No, but it is an interesting topic. We spend so much energy and time 
trying
 to reduce losses in our transmission lines, yet here is a case when having an
 appropriately lossy system is useful. I think it is interesting. The reason 
I say
 "appropriately lossy" is again to illustrate that it MAY make sense to have 
this
 special line over simply using cheap stuff in certain applications.
 
 That is my whole point. It is worth no more or no less than the point that 
lossy
 coax may do the job.
 
 73,
 Mike
 K7NT
 
 K7GCO@aol.com wrote:
 
 > In a message dated 04.05.00 12:48:26 Pacific Daylight Time,
 > mconatore@fredmeyer.com writes:
 >
 > <<
 >  But with cheap coax, you have a lot more loss in heat rather than 
radiation,
 >  don't you?
 >   >>
 > If heat is a problem the power levels used are excessive.  I have no idea
 > what the heat loss vs radiation loss ratio is.  Is there a need to know 
this?
 >  I'm not sure the reason for the question? k7gco
  >>

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