Hi to all,

Just got my new ATU. The specs mentionned:

Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

It sems that this is the standardized (?) way to mention
specifications...

But, since impedances have both a resistive and reactive compoment,
doses it means 6 to 600 Ohms "resistive"?

For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt
because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms..

Thanks de Pierre

ve2pid wrote:
Hi to all,

Just got my new ATU. The specs mentionned:

Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

It sems that this is the standardized (?) way to mention
specifications...

But, since impedances have both a resistive and reactive compoment,
doses it means 6 to 600 Ohms "resistive"?

For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt
because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms..

Thanks de Pierre

Only the manufacturer can tell you what they mean. It would be
interesting to see what they say when you ask.

Roy Lewallen, W7EL

ve2pid wrote:
Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

I once emailed a tuner company (don't recall which)
and asked them about their specs. They told me that
their ohmic specs were for resistive loads. They
didn't say where one would find an antenna with
a 600+j0 feedpoint impedance - maybe a 4-wire
folded dipole?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On May 21, 7:28*am, ve2pid wrote:
Hi to all,

Just got my new ATU. The specs mentionned:

Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

It sems that this is the standardized (?) way to mention
specifications...

But, since impedances have both a resistive and reactive compoment,
doses it means 6 to 600 Ohms "resistive"?

For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt
because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms..

Thanks de Pierre

It would be good if they plotted the range on something like a Smith
chart. It should be done for different frequencies; it's rare indeed
for a tuner to be able to match the same range of impedances over its
frequency range. Some tuner topologies even have "holes" in their
coverage.

Icing on the cake would be some additional lines on the Smith charts
showing the expected power loss, perhaps as constant-loss contour
lines. Many (most? all?) tuners get pretty lossy at some
adjustments.

As far as I know, none of the ham manufacturers do that. I expect it,
though, for commercial equipment, and we ought to hold the ham
manufacturers' feet to the fire to do something similar.

Cheers,
Tom

K7ITM wrote:
... we ought to hold the ham
manufacturers' feet to the fire to do something similar.

I suspect their average amateur radio customer
doesn't understand the meaning of 1000+j1000
much less comprehend graphs on a Smith Chart.

I recently published an article over on eHam.net
that contained a Smith Chart. One of the reactions
was that Smith Charts are obsolete and have been
replaced by software programs that just provide
the answers without all the effort and pain involved
with understanding a Smith Chart.

One doesn't need to know anything about hyperbolic
trig functions any more. Just point and click.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On 21 mayo, 19:41, Cecil Moore wrote:
K7ITM wrote:
... we ought to hold the ham
manufacturers' feet to the fire to do something similar.

I suspect their average amateur radio customer
doesn't understand the meaning of 1000+j1000
much less comprehend graphs on a Smith Chart.

I recently published an article over on eHam.net
that contained a Smith Chart. One of the reactions
was that Smith Charts are obsolete and have been
replaced by software programs that just provide
the answers without all the effort and pain involved
with understanding a Smith Chart.

One doesn't need to know anything about hyperbolic
trig functions any more. Just point and click.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Hello Cecil,

I was expecting that this only happens in the Netherlands. I have
some (modern) software where the default plot method is Schmit
Chart...

I agree with the contour plot on a Smith Chart showing losses (and
power handling) for Antenna Tuners.

Best regards,

Wim
PA3DJS
www.tetech.nl
forget first three letters of the alphabet in the PM

On Thu, 21 May 2009 07:28:25 -0700 (PDT), ve2pid
wrote:

Hi to all,

Just got my new ATU. The specs mentionned:

Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

It sems that this is the standardized (?) way to mention
specifications...

But, since impedances have both a resistive and reactive compoment,
doses it means 6 to 600 Ohms "resistive"?

For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt
because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms..

Thanks de Pierre

Well, a little Googleing found the missing maker and model number.
It's obviously made by LDG but which product?
http://www.ldgelectronics.com
The spec sheets aren't any more useful. I'm also rather suspicious
because ALL their products, regardless of size or technology, have the
same specification.

Well, if all else fails, I guess I have to read one of the manuals:
http://www.ldgelectronics.com/assets/manuals/Z-817Manual.pdf
No help in the Theory of Operation section.
The manual has a slightly expanded specification:
"Tunes 6 to 600 ohm loads (16 to 150 on 6M), 24 to 2400 ohms
with optional 4:1 Balun."

My guess(tm) is that they're refering to the vector sum of the complex
impedance, which is what one ends up measuring on a VSWR guess-meter.
Disclaimer: This is only a guess.

As for the proper way to specify antenna tuners, I vaguely recall a
marine band antenna tuner that we sold at Intech in the 1970's. (Not
my project). The matching range was specified as anything that landed
inside a constant VSWR circle on a Smith Chart and was limited to a
conservate 8:1 VSWR range. It also excluded any resonant antennas,
which would automatically fall outside of the 10:1 range. We also
derrated the maximum power handling spec at the 1.6MHz end to avoid
high voltage flash over. I'll dig through my box of old Intech data
sheets and manuals later and see what I can excavate.

Meanwhile, call LDG and ask.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

K7ITM wrote:
On May 21, 7:28Â*am, ve2pid wrote:
Hi to all,

Just got my new ATU. The specs mentionned:

Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about
3:1)

It sems that this is the standardized (?) way to mention
specifications...

But, since impedances have both a resistive and reactive compoment,
doses it means 6 to 600 Ohms "resistive"?

For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt
because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms..

Thanks de Pierre

It would be good if they plotted the range on something like a Smith
chart. It should be done for different frequencies; it's rare indeed
for a tuner to be able to match the same range of impedances over its
frequency range. Some tuner topologies even have "holes" in their
coverage.

Icing on the cake would be some additional lines on the Smith charts
showing the expected power loss, perhaps as constant-loss contour
lines. Many (most? all?) tuners get pretty lossy at some
adjustments.

As far as I know, none of the ham manufacturers do that. I expect it,
though, for commercial equipment, and we ought to hold the ham
manufacturers' feet to the fire to do something similar.

Cheers,
Tom

SGC used to publish the capacitance and inductance range of their
tuners from which you could calculate what it would do at a specific
frequency.

I haven't looked in a long time so I don't know if it is still there.


--
Jim Pennino

Remove .spam.sux to reply.

...; it's rare indeed
for a tuner to be able to match the same range of impedances over its
frequency range. Some tuner topologies even have "holes" in their
coverage.

This is why it is so pointless to specify the resistive SWR range. It is
really only an indication. If your antenna system winds up with an
impossible match at some frequency, you need to try something different
anyway or suffer loss or damage. Hope the autotuner algorithm knows how to
deal with that.

There was a QST test review years ago that compared several popular tuners.
Old and new.

On May 21, 11:30*am, wrote:
....
I was expecting that this only happens in the Netherlands. *I have
some (modern) software where the default plot method is Schmit
Chart...

I agree with the contour plot on a Smith Chart showing losses (and
power handling) for Antenna Tuners.

Best regards,

Wim
PA3DJSwww.tetech.nl
forget first three letters of the alphabet in the PM

Since the points plotted on a Smith chart are simply complex
reflection coefficient plotted on a linear grid, it would be fine with
me if they'd just plot the range of complex reflection coefficient
over which the tuner will operate (perhaps plus contours of constant
loss and power handling ability). The graphs would look identically
the same, except for the grid. I don't suppose any more hams
understand complex reflection coefficient than understand Smith
charts, though.

The Smith chart, to me, remains a very valuable _visualization_ tool.
It matters not how the points on it were calculated or measured. I
think it will always be the case that information properly presented
graphically will generally be easier to understand and easier to draw
conclusions from than information presented in text in tabular form.
Some graphical tools, such as the Smith chart, are worth getting to
know, even if you don't use the chart itself to do calculations,
deferring instead to other calculators for that part. Pictures,
often, are worth much more than 1000 words.

Cheers,
Tom