Well, with the remote autotuner you will have less RF in the shack...
But even then I would hang ground radials off the tuner case to keep
it at lower voltage potentials...

Definitely! One of the characteristics of the SGC autotuners is that
they seem to *require* a really good RF ground. Their tuning
circuitry "wants" to work into a ground connection which has a lower
impedance than the wire. SGC's manual makes this point repeatedly,
and identifies "grounding problems" (poor bonding, high inductance,
etc.) as the commonest cause of "Hey, this thing won't tune" problems
with their autotuners.

My own experience with a used, older-model SGC 230 (so old it's in a
non-waterproof metal case) seems to back this up. When used with a
relatively simple ground, the tuner has serious problems in achieving
a match, and frequently won't ever find one.

I tend to think that these arbitrary-wire tuners work best in their
original environment - bolted to a really big, solid chunk of metal
such as a ship body or a tank.

Another "gotcha" - the tuner I have, at least, can become seriously
"confused" if you try to use it with a radio that has aggressive "high
SWR power reduction" circuitry to protect the finals. In such a radio
(my Kenwood TS-2000 is one), the output power jumps around a lot as
the autotuner tries different L-network match settings, and the tuner
firmware seems to misinterpret these transmitter power changes and
never actually finds a low-SWR match. The same tuner, and the same
wire and grounding setup, will often match within a few seconds when
power is applied from another transmitter which doesn't alter its
output power so abruptly (e.g. a Ten-Tec Scout 555).

I've given up trying to use my old SGC-230 - it's so quirky that I
just can't depend on it to work acceptably in my environment, with my
radio.

Other vendors' autotuners may be less of a problem in this respect.

Since you are willing to spring for an SGC, etc. given your
description of your site I would think about an off center fed wire
antenna... Run your longwire through the trees... Roughly an 1/8 wave
lowest band back from one end of the antenna drop a vertical wire
to the ground and use the tuner to feed the end of the drop wire... A
ground stake and some radials and you are likely to be in business...

I'd recommend following SGC's recommendations... which probably add up
to "lots of heavy radials".

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Yeah, I noticed the same thing with the motorola triton, another antique....
maybe the newer ones aren't so quirky?
W

"Dave Platt" wrote in message
...
Well, with the remote autotuner you will have less RF in the shack...
But even then I would hang ground radials off the tuner case to keep
it at lower voltage potentials...

Definitely! One of the characteristics of the SGC autotuners is that
they seem to *require* a really good RF ground. Their tuning
circuitry "wants" to work into a ground connection which has a lower
impedance than the wire. SGC's manual makes this point repeatedly,
and identifies "grounding problems" (poor bonding, high inductance,
etc.) as the commonest cause of "Hey, this thing won't tune" problems
with their autotuners.

My own experience with a used, older-model SGC 230 (so old it's in a
non-waterproof metal case) seems to back this up. When used with a
relatively simple ground, the tuner has serious problems in achieving
a match, and frequently won't ever find one.

I tend to think that these arbitrary-wire tuners work best in their
original environment - bolted to a really big, solid chunk of metal
such as a ship body or a tank.

Another "gotcha" - the tuner I have, at least, can become seriously
"confused" if you try to use it with a radio that has aggressive "high
SWR power reduction" circuitry to protect the finals. In such a radio
(my Kenwood TS-2000 is one), the output power jumps around a lot as
the autotuner tries different L-network match settings, and the tuner
firmware seems to misinterpret these transmitter power changes and
never actually finds a low-SWR match. The same tuner, and the same
wire and grounding setup, will often match within a few seconds when
power is applied from another transmitter which doesn't alter its
output power so abruptly (e.g. a Ten-Tec Scout 555).

I've given up trying to use my old SGC-230 - it's so quirky that I
just can't depend on it to work acceptably in my environment, with my
radio.

Other vendors' autotuners may be less of a problem in this respect.

Since you are willing to spring for an SGC, etc. given your
description of your site I would think about an off center fed wire
antenna... Run your longwire through the trees... Roughly an 1/8 wave
lowest band back from one end of the antenna drop a vertical wire
to the ground and use the tuner to feed the end of the drop wire... A
ground stake and some radials and you are likely to be in business...

I'd recommend following SGC's recommendations... which probably add up
to "lots of heavy radials".

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article imYki.1884$YH3.394@trnddc08, "Woody"
wrote:

Yeah, I noticed the same thing with the motorola triton, another antique....
maybe the newer ones aren't so quirky?
W

Interesting you should notice that. The original Binary Switch Lump
Constant Autotuners were those designed for the Triton Series MF/HF
SSB Radio's, from Motorola, by Bill Schilb. When he left Motorola
and came west, to Northern Radio in Seattle, he brought that technology
with him and introduced it to the MF/HF Marine Market. First at Northern,
which never did anything with it, and then on to SEA, thru the
ex-Northern Engineering Team, that followed Dick Stephens, from
Northern, to SEA, as Northern was sinking into oblivian. The first
Marine Product with this technology, was the SEA-1601 Autotuner, Designed
by Bill Forgey, and Mark Johnson. A sucsession of improvments followed
culminating in the SEA-1612B Autotuner. This is the model that SGC
copied, for their original product, including the Firmware that still had
the SEA Copyright, compiled in the code. Most of the later Binary
Switched Autotuners are, either Copied, or Reverse Engineered,
adaptations of the SEA1612B System. All these tuners NEED a Low
Impedance RF Ground to work against, as well as a Longwire who's length
is SPECIFICALLY set up to put the 1/2 Wavelength Point in a non used
portion of the Spectrum. They will NOT tune within 2% of the Natural
1/2 Wavelenth point of the Longwire connected, where Antenna Impedances
near Infinity.

There has been considerable work done, over the years, on making this
type tuner, drive Balanced Antennas. Some have used a 4:1 Balun,
directly across the tuner Output, with limited sucess. Some have
decoupled the Tuner from it's Coaxial Feedline, Power, and Tuner
Indicator Lines, by running them thru a Bifilar Wound Torroid at
the Tuner end, and then putting the tuner in the Center of a Dipole
cut for the Lowest Desired Frequency of the System. This type has proved
a better system than the Balun, but I have used both at Limited Coast
Stations thruout Alaska, and most are still in operation today.
G & L Marine Radio in Seattle, once designed an SEA-1612B based Autotuner
that had two Tuner boards, one for each side of the Balanced Antenna,
that ran off a single MCPU and Detector System, and just latched
the same Data into both boards. I never actually heard how well Don Sr.
got it to work, but always thought that it was an interesting concept.

Bruce in alaska
--
add a 2 before @

Most of the later Binary
Switched Autotuners are, either Copied, or Reverse Engineered,
adaptations of the SEA1612B System.
Copied or reverse engineered might be a bit harsh..

The idea of a automatically driven LC tuner has been around a while,
with DC motors, servos, or steppers. Once you have the concept of a
variable L or C that's "remote controlled" using a binary switched array
is a pretty obvious thing to try. (e.g. I built a binary switched power
inductor for ballasting a tesla coil to replace the more traditional
sliding core inductor or variac with a cut core, and I doubt I was the
first to think about it.)

I think the subtle details in SEA's, SGC's, LDG's, or MFJ's tuners would
deal more with the means of detecting the mismatch and the actual tuning
algorithm. From that standpoint, the SGC and LDG tuners (which are the
two I'm most familiar with) are quite different. SGC uses a pi net, LDG
uses L net with cap switched between in or out. SGC and LDG use
different bridge and detector designs. I'm pretty sure, also, that the
actual tuning sequence is different, just based on the sounds they make.

Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?
thanks,
Woody


"Bruce in Alaska" wrote in message
...
In article imYki.1884$YH3.394@trnddc08, "Woody"
wrote:

Yeah, I noticed the same thing with the motorola triton, another
antique....
maybe the newer ones aren't so quirky?
W

Interesting you should notice that. The original Binary Switch Lump
Constant Autotuners were those designed for the Triton Series MF/HF
SSB Radio's, from Motorola, by Bill Schilb. When he left Motorola
and came west, to Northern Radio in Seattle, he brought that technology
with him and introduced it to the MF/HF Marine Market. First at Northern,
which never did anything with it, and then on to SEA, thru the
ex-Northern Engineering Team, that followed Dick Stephens, from
Northern, to SEA, as Northern was sinking into oblivian. The first
Marine Product with this technology, was the SEA-1601 Autotuner, Designed
by Bill Forgey, and Mark Johnson. A sucsession of improvments followed
culminating in the SEA-1612B Autotuner. This is the model that SGC
copied, for their original product, including the Firmware that still had
the SEA Copyright, compiled in the code. Most of the later Binary
Switched Autotuners are, either Copied, or Reverse Engineered,
adaptations of the SEA1612B System. All these tuners NEED a Low
Impedance RF Ground to work against, as well as a Longwire who's length
is SPECIFICALLY set up to put the 1/2 Wavelength Point in a non used
portion of the Spectrum. They will NOT tune within 2% of the Natural
1/2 Wavelenth point of the Longwire connected, where Antenna Impedances
near Infinity.

There has been considerable work done, over the years, on making this
type tuner, drive Balanced Antennas. Some have used a 4:1 Balun,
directly across the tuner Output, with limited sucess. Some have
decoupled the Tuner from it's Coaxial Feedline, Power, and Tuner
Indicator Lines, by running them thru a Bifilar Wound Torroid at
the Tuner end, and then putting the tuner in the Center of a Dipole
cut for the Lowest Desired Frequency of the System. This type has proved
a better system than the Balun, but I have used both at Limited Coast
Stations thruout Alaska, and most are still in operation today.
G & L Marine Radio in Seattle, once designed an SEA-1612B based Autotuner
that had two Tuner boards, one for each side of the Balanced Antenna,
that ran off a single MCPU and Detector System, and just latched
the same Data into both boards. I never actually heard how well Don Sr.
got it to work, but always thought that it was an interesting concept.

Bruce in alaska
--
add a 2 before @

In article t3ali.3392$Y_3.570@trnddc04, Woody wrote:

Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?

I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,
alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

For what it's worth, SGC sells a longwire antenna 60' in length, which
they say works well on both lower and higher HF bands. It might or
might not be a good choice for MARS frequencies.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

(Dave Platt) wrote in
news
....

I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,

You probably mean't any integral multiple of a half wave.

alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)

Problem is that it probably unecessarily constrains the solution.

The input impedance and the feed point voltage of an end fed wire at its
higher parallel resonances falls, so that whilst you might want to avoid
the first such resonance, the impedance (and feed point voltage) at the
third or higher resonance might well be low enough to not worry about it.

To demonstrate that life isn't simple, the antenna efficiency (Rr/Rtot at
the feedpoint) improves closer to those parallel resonances that everyone
wants to avoid.

Owen

Hi Owen. 5% was just a number picked out at random by me for clarification
of my question.
So you wouldn't want to share your 'sweet' findings, would you??
thanks!
W


"Owen Duffy" wrote in message
...




I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)
Owen

In article ,
Owen Duffy wrote:

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,

You probably mean't any integral multiple of a half wave.

You're right... integral multiple of a half-wavelength, or even
multiples of a quarter-wavelength are two alternative ways for stating
the lengths to be avoided (high feedpoint Z).

alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

I have done just that, and searched for "sweet" wire lengths that aren't
within say 5% of band edge for all HF bands. It sounds like a solution to
the problem doesn't it. (5% implies that you have a pretty determinate
scenario, which is a big assumption. IIRC 10%+ will not give a practical
result on the higher bands.)

Problem is that it probably unecessarily constrains the solution.

Entirely possible!

The input impedance and the feed point voltage of an end fed wire at its
higher parallel resonances falls, so that whilst you might want to avoid
the first such resonance, the impedance (and feed point voltage) at the
third or higher resonance might well be low enough to not worry about it.

And, even if it was a bit high, you might not need to be more than a
couple of percent away from it to get it down to a length that might
work.

Odds are that some amount of experimentation is going to be required,
at any given installation, to find a wire length which tunes up well
with these ATUs. The orientation of the wire (vertical, inverted-L,
etc.), height about ground, presence of trees and metallic objects,
and (perhaps most importantly) the details of the ATU's grounding
system, are likely to change the impedances around enough to make the
"textbook" answers less than completely effective.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
In article t3ali.3392$Y_3.570@trnddc04, Woody wrote:


Well.. a million thanks for that. Quite a cool history lesson as well. So
now I'm looking for an SEA tuner... LOL...

Listen, that all makes perfect sense but just to clarify, a.) now I know why
that triton did so poorly when tested. We calc'd 1/2 wavelength for the
longwire, and b.) Again, for continuity and clarity of this thread for
future surfers...... what then, considering our discussed auto-tuners, would
be the optimal length for a longwire that would be used for amateur/MARS,
3-30MHz?
Pick 1/2wavelength on say 2.8Mhz and just cut it? Or calc 1/2wavelength on
the lowest and add 5% or some arbitrary odd number??
Which plan will offer the least chance of dropping a 1/2wl further up the
band on a desired frequency?


I think you'll need to run a a simple calculation, based on the
frequencies you actually want to use.

What you'll want, is a wire whose length is not particularly close to
any multiple of 1/2 wavelength, on any frequency you want to use. A
wire which would match easily on 80 meters (e.g. 1/4 wavelength long)
would be a bad choice if you want to work on 40 meters as well, as
it'd be 1/2 wavelength long.

A simple program or spreadsheet ought to be able to do the necessary
calculations... try every wire length from 66 feet to 132 feet and see
if you can find a length which is a comfortable percentage away from
an even multiple of 1/2 wavelength on each frequency. Or,
alternatively, iterate through each frequency, calculate the
1/2-wavelength multiples, and "blacklist" every possible length which
is too close to these multiples.

For what it's worth, SGC sells a longwire antenna 60' in length, which
they say works well on both lower and higher HF bands. It might or
might not be a good choice for MARS frequencies.


The other strategy is to use two wires of appropriately different
lengths connected together at the feedpoint. (the SGC whips do this, for
instance).. Space the wires some distance apart (a few inches would
do).. What this does is put multiple bumps in the impedance curve and
eliminates the pathological cases where you have very high Z when the
(one) wire is a half wavelength or multiple thereof. At those
frequencies where one wire *is* a half wavelength, and presents a high
Z, the other one is likely NOT a multiple of a half wavelength, and so,
will present a reasonable impedance. Sure, they interact (as folks
making multiband dipoles find when trying to cut and trim), but all that
really does is shift the resonances around.

An interesting question would be what is the optimum ratio of lengths..
probably something like 1:1.618 or 1:2.7183