[Antennas] Hy-gain AV-640 issues

Mon Apr 25 19:33:36 EDT 2011

On 2011年4月25日 19:00:10 -0400, you wrote:
> Anthony R. Gold <ham-radio-mail-lists at ahjg.co.uk> wrote:
>>> Thanks for your various comments on transmission lines, but they did not
>> answer my question. You deleted the paragraphs I was commenting on so let
>> me recap: you wrote that VSWR reduces with increased line losses, which
>> agrees with the arithmetic, but then you added that this relationship was
>> only true if one used the line in some particular manners. I did not
>> understand that last part. Can you give an example of a situation where
>> one's manner of use of the line will change the relationship between
>> increased losses and reduced VSWR?
>> I thought that was the question I answered.
>> Yes, I wrote that VSWR reduces with increased line losses; but I
> qualified that by saying that it applies when you are using a line at
> its intended characteristic impedance.
>> If you use a line at other than its characteristic impedance ... my
> example being that you use a 125 ohm coax in a 50 ohm system ... then
> the VSWR measured in your 50 ohm system, with increased line loss, can
> increase rather than decrease.
>> Re-read what I wrote. With a half-wavelength piece of 125 ohm coax,
> between a 50 ohm antenna and a rig designed to see 50 ohms, the rig
> sees 50 ohms (a nice low VSWR) when the coax losses are low. But as
> the coax losses increase, the VSWR the rig sees increases towards
> 2.5:1. In this case, higher loss causes higher VSWR, not lower.

Okay, so you're not talking about the VSWR on the line but somewhere else.
> Did you need another example?

No thanks, that one was more than enough :-)
Tony