[Elecraft] OT: pwr rating of RG6, etc

[Don Wilhelm]

Peter (and interested others),

You might want to peruse the article "Antennas, Transmission Lines, and 
Tuners" at my website http://w3fpr.qrpradio.com.

The article tries to flatten several myths in terms that should be 
understood by most hams - no math, but I believe a good explanation of 
principles.

73,
Don W3FPR

Peter Howson wrote:
> I have been following this thread and find it very interesting, 
> particularly as a Mechanical Engineer I have to read it slowly but may 
> I comment --
> 1, I don't know the details of Icom's protection system, but the ones 
> I have seen sense reflected power, well actually it will be the 
> voltage detected at the sensor against an assumed impedance of 50 ohms 
> (50+j0). The actual SWR at which the protection will come into play 
> will be a function of  feedline impedance (which will, in practice, 
> have a reactive element), feedline losses, antenna impedance and 
> efficiency. -- If it's a problem - just add a few feet of coax!!
>
> 2, It shows an underlying belief in SWR as the be all and end all of 
> antenna systems.
>
> 3, Many years ago now I had the opportunity to visit the main Naval 
> transmitting station in the UK. Utilising frequencies from VLF to VHF 
> their antenna systems were out of this world. But the majority were 
> fed with 600 ohm open line across many kilometres of open ground. I 
> recall one of our guys asking about SWR. The station chief just 
> shrugged. One of the main HF transmitters was opened for maintenance 
> and contained a large number of 4CX250 valves connected in parallel - 
> not the easiest valve to run.
>
> So what should we be doing; as an instructor I see and hear a hell of 
> a lot of myths about SWR and do try to correct them within my own 
> understanding of the subject. But I do have to hand it to those who 
> fully understand the subject and who take the time to explain it at 
> the level of our examination system, which cannot be easy.
>
> Perhaps we should send this to the mythbusters and see if thay can 
> blow it away!!
>