[TenTec] Re. [Ten Tec] Grounds and balanced fed verticals

[Rick - DJ0IP / NJ0IP]

Steve you are absolutely correct.

As I said much earlier in this thread, Joel, W1ZR measured losses of the
various openwire antennas and HE EVEN DIPPED THEM IN MUD and measured it
again with the entire length covered in mud.
The losses did not go up, but the matchbox required a different setting.
That's all.

This whole thread has been kind of like people arguing the world is flat,
after Columbus sailed around it.
Yes, I know he didn't actually sail all the way around, but you guys get the
point.

If we return to the original question posed in this thread, the simple
answer is "YES".  End of thread.
;-)

There is nothing wrong with feeding an elevated groundplane with openwire.
It's not a lot different than the vertical dipoles which I have been feeding
with openwire of 20 years.

73
Rick

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Steve Hunt
Sent: Thursday, January 26, 2012 5:52 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] Re. [Ten Tec] Grounds and balanced fed verticals

Here's some calculations to support that last comment:

Solid dielectric coax Vf=0.66 and foam dielectric coax Vf=0.85, 
therefore relative dielectric constants must be 2.29 and 1.38 respectively.

So, if we keep the coax outer diameter the same, the foam inner 
conductor must increase by SQRT(2.29/1.38)=1.288; that makes the RF 
resistance 0.776 times what it was.

If we assume a loss of 1.8dB in a particular length of solid dielectric 
cable, that reduction in RF conductor resistance reduces the losses to 
1.5dB - *exactly the quoted figure*.

In other words the increased centre conductor diameter and the 
consequent reduced copper losses *exactly* account for the quoted 
difference in cable loss; *losses in the dielectric are not a 
significant factor*.

73,
Steve G3TXQ


On 26/01/2012 15:57, Steve Hunt wrote:
> If you look at the technical data for a Belden solid dielectric RG58
> (say 8259) and compare it with a foam dielectric RG58 (say 7807) you'll
> see that the centre conductors are significantly different diameter:
> 0.035" vs 0.044" - they have to be to achieve the same 50 Ohm
> characteristic impedance with different dielectric materials.
>
> The difference in loss is almost totally down to the smaller conductor
> diameter, not to differences in dielectric loss.
>
> 73,
> Steve G3TXQ
>
>
> On 26/01/2012 13:43, Carl Moreschi wrote:
>> Here is some data taken from the ARRL handbook on losses for various
>> transmission lines at 14 mhz per 100 feet.
>>
>>
>> RG-58 hard dielectric 1.8 DB
>> RG-58 foam dielectric 1.5 DB  These two have the same I squared R loss
>>
>> RG-8 hard dielectric 0.85 DB
>> RG-8 foam dielectric 0.6 DB  These two have the same I squared R loss
>>
>> Open wire line air dielectic TV type  less then 0.1 DB
>>
>> As you can see from above, the dielectric has significant meaning to the
>> loss.
>>
>> Carl Moreschi N4PY
>> 121 Little Bell Dr.
>> Hays, NC 28635
>> www.n4py.com
>>
>>
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