There is a LOT of difference between 100 feet and 199 metres!
Frank, K4VMO
----- Original Message -----
From: "Steve Hunt" <steve@karinya.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, February 01, 2009 2:50 PM
Subject: Re: [TenTec] G5RV
> Jerry,
>
> Yes, I'm sure. According to the VK1OD on-line calculator, at 3.8 MHz
> 100m of RG213 with 14-j1 as a load has a loss of 1.9dB; 100m of Wireman
> 551 with 14-j1 as the load has a loss of 3.1dB. I'm not saying the
> difference is particularly significant - I'm just pointing out that
> ladderline is not always lower loss than coax - it depends on the load
> impedance.
>
> Incidentally, be wary of those ARRL charts which tell you what the
> "excess loss" is for a particular VSWR - they are approximations. There
> are some particular situations where a 1:1 VSWR produces more loss than
> with a higher VSWR. here's an example:
>
> Take 15ft of RG213 with a load of 100+j100. At 3.8 MHz the loss with
> this 4.3:1 VSWR is 0.025dB, whereas the matched loss is over twice this
> at 0.055dB. I know these are ridiculously small losses, but I'm just
> illustrating the fallacy of thinking you can add a fixed "extra loss"
> figure for some particular VSWR value.
>
> 73,
> Steve G3TXQ
>
> Dr. Gerald N. Johnson wrote:
>> Are you sure? Using data and formulae in the 1994 ARRL Antenna Book, I
>> see 100' of RG213 has 0.6 dB loss at 4 MHz when matched, and 1.066 dB
>> with a 3.6:1 SWR. 1" spaced window line has 0.027 dB (had to stretch the
>> loss chart by a factor of ten for that line) per 100' matched and 0.41
>> dB loss with the SWR of 32:1.
>>
>>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|