1. I never tried to restrict the term "tuning" to only bringing
something to resonance. I merely was allowing for the sensibilities of
might be more accurate ... such as the term "matching" would be in the
case where impedances differed. Reread the part where I said that I
2. I know exactly how transmission lines operate and that is why I say
"matched" ... it can be done at the antenna or in the shack and
is exactly the same. Whether doing so results in a narrower response is
only be accurately applied at the antenna. Go back and read the earlier
about ... at least from the point at which I entered it.
3. I'm not in any way dismissing losses in the feedline due to SWR as
being unimportant. They are of course a significant factor to be
function. Those losses do not, however, have anything to do with
> David, remember becoming 'nit free' leads to becoming 'lice free'. You are
> correct that 'tuning' may have something to with bringing the circuit into
> resonance but the term 'tuning' has other meanings too. For instance if we
> equate tuning as bringing into resonance then we could not use the term
> 'tuning' applied to non-resonate antennas. You see the term is more
> frequently applied to impedance matching and band centering.
> Matching at the antenna is quite different than matching at transmitter.
> Transmission lines are only pure transmission lines if they are matched at
> both ends. If either end is mismatched the transmission line becomes a
> circuit element. A transmission line inverts the reactance every quarter
> wave. Hence R+jx becomes the complex conjugate R-jx after a quarter wave in
> length. This increase the effects of frequency change requiring more
> frequent retuning across the band. The higher the VSWR the higher the copper
> losses in the coax. You seem to dismiss copper losses as being
> insignificant. The higher the mismatch the more significant they become so
> those losses can be saved if the match occurs at the antenna.
> If you want to run your own little proof experiment take your favorite coax
> feed antenna and measure and note the SWR at the transmitter. Make sure
> there is a high SWR to measure like your 40 meter doublet running an 80
> meters. Then add a long length of same impedance coax in series, say a 100',
> and re-measure the SWR at the transmitter. The SWR will usually be much
> different because of the additional attention from the longer coax.
> 73
> Fred, AE6QL
>
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of David Gilbert
> Sent: Wednesday, September 19, 2012 1:10 AM
> To:
[hidden email]
> Subject: Re: [Elecraft] KX3 ATU
>
>
> That's pretty much picking nits, in my opinion. It doesn't really matter
> whether you physically locate needed complex reactance at the antenna or
> present it to the antenna via the transmission line physics of a feedline
> ... the net result that exists at the antenna is exactly the same
> (neglecting transmission line losses, of course) in either case. The only
> relevant distinction I can see is that "tuning" more accurately refers to
> bringing something to resonance rather than also transforming it to a
> different load impedance, but that falls into the category of useless
> semantics for me and I can give you all sorts of examples where it would be
> next to impossible to distinguish electrically where an antenna ends. The
> dividing line between an antenna and the rest of the system is not at all as
> definitive as you suggest, and pretending it is seems more likely to give a
> false impression of how things really work than not.
>
> 73,
> Dave AB7E
>
>
>
> On 9/18/2012 11:52 PM, Adrian wrote:
>> Matt, Of course I don't question Don's technical stature, however
>> "tuning the antenna" is a poor choice of explanation, and can give a
>> false impression to those weak on the subject. Adding 'system' would
>> have been a good move as you indicate. We tune where we measure.
>>
>> -----Original Message-----
>> From: Matt Maguire [mailto:
[hidden email]]
>> Sent: Wednesday, 19 September 2012 3:35 PM
>> To: vk4tux
>> Cc:
[hidden email]
>> Subject: Re: [Elecraft] KX3 ATU
>>
>>
>> On 19/09/2012, at 2:48 PM, vk4tux <
[hidden email]> wrote:
>>
>>> Don, When you say "The ATU will tune the antenna to an acceptable
>>> SWR", you are contradicting yourself, because as you rightly said the
>>> tuner does not change the antenna feedpoint swr.
>> It is clear from the context that Don meant the ATU will tune (ie.
>> match) the antenna *system* to the radio, where the antenna system
>> consists of the ATU, antenna and connecting feedline considered as a
>> single unit. This of course does not mean that the VSWR is 1:1 everywhere
> within that system.
>> The theory predicts that the measures VSWR will be constant along a
>> *lossless* feedline. As you point out, practical feedlines do have losses.
>> This will include I^2.R copper losses, but there can be losses from
>> other sources as well, such as dielectric losses. Often such losses
>> will be modelled as some sort of equivalent series resistance.
>>
>> 73, Matt VK2ACL=
>
>