[Elecraft] KAT500 Remote Version

[Wes Stewart]

What Don says is true as far as it goes.  The L-network tuner has only one solution, but it isn't necessarily a good one.

Way back in 1998 when correspondence was via typewriter and snail mail, I went around with Dean Straw, N6BV, then Editor of the ARRL Antenna Book, about tuner losses.  This was in conjunction with the editing of my paper, "Balanced Transmission Lines in Current Amateur Practice" that appeared in the Sixth Edition of the ARRL Antenna Compendium.

Remarkably (coincidence I'm sure ;) it wasn't long before favored authors were contributing articles to QST about how to measure tuner losses and TLW was written.

Tuner and line losses really do matter.

Wes  N7WS



--- On Thu, 9/20/12, Don Wilhelm <w3fpr at embarqmail.com> wrote:


David,

Those who have mentioned "tuner loss" may or may not be correct - it all 
depends on the tuner.  If the tuner is of the "T match" variety, it will 
have multiple points where it can show a match, but many of those 
"matched" points will result in high circulating currents in the tuner 
and high losses.

Elecraft tuners are "L-match" tuners, and do not suffer from those false 
tuning points - it will either match the load or it will fail.

You LMR600 coax is very low loss and at frequencies below 30 MHz. I 
would offer that a 100 foot run could have an SWR as high as 5:1 and the 
loss would be acceptable.  If your coax run is longer than that, or your 
SWR is higher, then, yes, I would feel more comfortable with a remote 
antenna tuner to keep the SWR on the coax down to a reasonable level.

73,
Don W3FPR

On 9/20/2012 3:59 PM, David Bunte wrote:
> I have been trying to decide between the KAT500... and a remote tuner at
> the base of my 30' vertical.  I have measured the SWR on each band, at the
> shack end of my 125' of LMR600.  If I take that length, frequency and SWR
> information and plug it into the chart for SWR loss of LMR600, I can see
> what my loss is on each band... but I am not sure that tells the entire
> story.
>
> Intuitively it seems that I want the ATU as close to the antenna as
> possible.  I could shorten my feedline to about 65'.  I could mount an ATU
> just inside my basement at about 30' from the antenna (and avoid a
> weatherproof box - as long as the ATU does not need to be seen or touched),
> or I could mount it at the base of the antenna, but that would be very much
> more challenging.
>
> Is the SWR loss, based on my cable type, length & frequency all I need
> consider, or am I missing something?
>
> Some people have told me that I need consider nothing else... others have
> said that "tuner loss" is critical, and that will be greater than the line
> loss.  That sounds bogus to me, but I really don't know.
>
> I also know that the ATU in my K3 can make the rig very happy on 80 through
> 6 with this antenna and 125' of cable... but I don't know if matching the
> antenna at the end of 1', 30' or 65' will be harder, or easier.
>
> It was suggested that the TLW program by N6BV, that is packaged with the
> ARRL Antenna Book would help, but I have not been able to figure out how to
> use it, and can find no instructions for that program.
>
> Any and all help will be appreciated.
>
> Dave - K9FN
>
>