[TenTec] G5RV

Sun Feb 1 16:29:30 EST 2009

```Another typo!100 metres
K4VMO

----- Original Message -----
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, February 01, 2009 3:23 PM
Subject: Re: [TenTec] G5RV

> There is a LOT of difference between 100 feet and 199 metres!
> Frank, K4VMO
>
> ----- Original Message -----
> From: "Steve Hunt" <steve at karinya.net>
> To: "Discussion of Ten-Tec Equipment" <tentec at 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.
>>>
>>>
>>
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>
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