Balanced AT

[Craig Smith]

<> Doesn't an SGC fit this bill? I use an SG237 to tune a portable inverted
V
<> fed by 300ohm (or thereabouts) ribbon - arms cut at 20m, on a 10m
telescopic
<> pole and it tunes up on 80m - 10m a treat.

Yes, the SG237 can work.  Lots of people seem to like them, and some people
report frustration.  Note that SGC only rates the 237 at 40 watts
continuous.  I'm sure there is some degree of safety margin in the spec, but
I personally would not feel too comfortable running 100W CW with it for any
significant amount of time during a contest, especially since the tune
algorithm does its thing at full power unless you manually turn down your
power for tuning.  ICOM, in my opinion, has a better idea with the AH-4,
with automatic tune power reduction (with ICOM rig) and termination of the
transmitter into a matched load during tuning.  I use one now with my
IC-7000 and a ladderline fed non-resonant doublet.  Alas, it is not
plug-and-play with Elecraft or other rigs.  

Given Elecraft's knowledge and success with their other tuners (I loved the
internal tuner in my K2), I think they could do a bang up world-class job
with a remote tuner with automatic interface with the K3.  There (relatively
soon) will be thousands of K3s out there waiting for tuning solutions.  I
will be first in line to purchase a remote tuner when Elecraft announces it.
And I'm sure they will find a way to provide excellent performance with
balanced loads such as ladderline fed doublets, loops, etc.  

         73
                   ... Craig   AC0DS




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[N2EY]

In a message dated 9/7/07 2:08:49 AM Eastern Daylight Time,
[hidden email] writes:


> I use an SG237

The SG-237 is an unbalanced tuner.




73 de Jim, N2EY


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[Geoffrey Mackenzie-Kennedy-2]

Craig D. Smith <[hidden email]> wrote on Friday, September 07, 2007
11:56 AM

Given Elecraft's knowledge and success with their other tuners (I loved the
internal tuner in my K2), I think they could do a bang up world-class job
with a remote tuner with automatic interface with the K3.  There (relatively
soon) will be thousands of K3s out there waiting for tuning solutions.  I
will be first in line to purchase a remote tuner when Elecraft announces it.
And I'm sure they will find a way to provide excellent performance with
balanced loads such as ladderline fed doublets, loops, etc

-------------------------------------------------------------------------

Craig,

If my understanding is correct, a remote tuner designed to interface with
the K3 would not allow the use of the tuner with any other type of rig. If
that is correct then the user of a rig other than the K3 would have to build
/ buy a control device which simulates the K3 control interface before the
tuner could be used. I believe that Elecraft's potential market would be
greatly enlarged if the remote tuner could be used with any type of rig (50
ohm load)? My apology if I have misunderstood what you mean by 'automatic
interface with the K3'.

My vote based on use of homebrewed remote tuners is for a tuner that tunes
itself for a match and which does not require to be given band data from the
rig. This reduces the number of wires between shack and tuner to 3  -  DC
supply, Remote VSWR indication and Ground. If the coax feeder is used to
route these rails it is possible to have no extra wires at all, but I prefer
not to do this.

73,
Geoff
GM4ESD





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[Julian, G4ILO]

The trouble with this approach is it requires a few seconds of RF to
tune up. I wonder how much RF pollution the K2 design has saved by
being able to remember and automatically tune to each band as you
switch? It's also far more convenient for those who like to switch on
and have a quick listen to see if 10 or 15 are open, say. It would be
well worth the trouble of extra cabling, in my opinion. It's just a
pity there isn't a universal standard of band data that would allow
such a device to be made for any rig.

Wouldn't it be cool if the K3 could peak the ATU for maximum noise in
the receiver, especially for using the GC RX in the non-ham bands...
--
Julian, G4ILO K2 s/n: 392  K3 s/n: ???
G4ILO's Shack: www.g4ilo.com
Ham-Directory: www.ham-directory.com


On 9/7/07, Geoffrey Mackenzie-Kennedy <[hidden email]> wrote:

> My vote based on use of homebrewed remote tuners is for a tuner that tunes
> itself for a match and which does not require to be given band data from the
> rig.
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[Edward Dickinson, III]

...remote tuners is for a tuner that tunes itself for a match and which does
not require to be given band data from the rig. ...

73,
Geoff
GM4ESD
-----------------------
Hi Greg.

I support your notion.


Regards,
Dick - KA5KKT/4

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[Jack Brindle]

While such a tuner might be fun to work with, it would unfortunately  
have a very short life due to burnout of the relay contacts when  
tuning at full power. There are also very high voltages created for  
various combinations of L and C while tuning is going on, which would  
undoubtedly shorten the life of the other components.

For such a tuner to work, it would need the ability to have the  
exciter drop to low power while tuning, then return to full power  
when the tuning task is done. This is far worse than telling the  
tuner before transmission occurs the frequency for operation.

Note that this same situation exists whether the tuner needs to tune  
for each transmission or it has frequency memories. Quite simply, the  
problem is switching the relays at full power.

My belief is that the best way to handle the situation is to  
communicate the operating frequency to the tuner so it can use its  
memories, or to send the actual relay settings whenever they need to  
change. Of course, this should be done during receive, when no power  
is applied. This is the method used in the K2 tuners, and I am sure  
Wayne is also doing it in the K3 ATU.

It's awfully hard to do in a remote tuner, although perhaps the best  
example is the method used in tuning the Steppir (which uses  
frequency data from the radio).


On Sep 7, 2007, at 9:08 AM, Edward Dickinson, III wrote:

> ...remote tuners is for a tuner that tunes itself for a match and  
> which does
> not require to be given band data from the rig. ...
>
> 73,
> Geoff
> GM4ESD
> -----------------------
> Hi Greg.
>
> I support your notion.
>
>
> Regards,
> Dick - KA5KKT/4
>
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- Jack Brindle, W6FB
------------------------------------------------------------------------
---------------------


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[Geoffrey Mackenzie-Kennedy-2]

Jack Brindle <[hidden email]> wrote on Sunday, September 09, 2007
at 4:15 AM :

> While such a tuner might be fun to work with, it would unfortunately  have
> a very short life due to burnout of the relay contacts when  tuning at
> full power. There are also very high voltages created for  various
> combinations of L and C while tuning is going on, which would  undoubtedly
> shorten the life of the other components.

 ----------------------------------------------------------

Hot switching can be / usually is a recipe for disaster as you point out.
The trick is to design the system so that the tuning of the antenna matching
unit (ATU) is done at milliwatt power levels, which also helps to reduce RF
pollution. Methods to achieve band switching or coarse tuning of the remote
AMU, depending on the type used, include the use of either DC comparators or
frequency selective switches and no doubt simple digital schemes, but I have
not used digital. Frequency selective switches do require a shot of a few
milliwatts of RF input to work of course.

Keeping the size of any control cabling between the shack and remote unit to
a minimum is a personal requirement. My main feeder, control cable for a
remote 5 way coax switch and 3 wire cable for the remote AMU used with a
reference doublet all run together underground in plastic pipe.

73,
Geoff
GM4ESD


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[David Cutter]

Whatever happened to "silent tuning?"  I know it's not entirely silent, but
monitoring across a dummy load with a bridge circuit means the auto
tuner/matcher can sniff the incoming rf and adjust for best match/tune and
then switch to full connection.  On most HF bands, say >20m, there might be
only one optimum point in the middle of each sub-band, so re-tuning/matching
would not delay things by much.

David
G3UNA


----- Original Message -----
From: "Jack Brindle" <[hidden email]>
To: "Elecraft Discussion List" <[hidden email]>
Sent: Sunday, September 09, 2007 4:15 AM
Subject: Re: [Elecraft] Balanced AT

> While such a tuner might be fun to work with, it would unfortunately  have
> a very short life due to burnout of the relay contacts when  tuning at
> full power. There are also very high voltages created for  various
> combinations of L and C while tuning is going on, which would  undoubtedly
> shorten the life of the other components.
>
> For such a tuner to work, it would need the ability to have the  exciter
> drop to low power while tuning, then return to full power  when the tuning
> task is done. This is far worse than telling the  tuner before
> transmission occurs the frequency for operation.
>
> Note that this same situation exists whether the tuner needs to tune  for
> each transmission or it has frequency memories. Quite simply, the  problem
> is switching the relays at full power.
>
> My belief is that the best way to handle the situation is to  communicate
> the operating frequency to the tuner so it can use its  memories, or to
> send the actual relay settings whenever they need to  change. Of course,
> this should be done during receive, when no power  is applied. This is the
> method used in the K2 tuners, and I am sure  Wayne is also doing it in the
> K3 ATU.
>
> It's awfully hard to do in a remote tuner, although perhaps the best
> example is the method used in tuning the Steppir (which uses  frequency
> data from the radio).
>
>
> On Sep 7, 2007, at 9:08 AM, Edward Dickinson, III wrote:
>
>> ...remote tuners is for a tuner that tunes itself for a match and  which
>> does
>> not require to be given band data from the rig. ...
>>
>> 73,
>> Geoff
>> GM4ESD
>> -----------------------
>> Hi Greg.
>>
>> I support your notion.
>>
>>
>> Regards,
>> Dick - KA5KKT/4
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>  http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>
> - Jack Brindle, W6FB
> ------------------------------------------------------------------------
> ---------------------
>
>
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[AC7AC]

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[AC7AC]

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[Geoffrey Mackenzie-Kennedy-2]

Ron AC7AC wrote:


Another issue with a balanced AT is that they tend to be used in multiband
systems fed with open wire line where high SWRs are expected. High SWRs mean
very, very high RF voltages at a current "loop", demanding relays, etc.,
that can safely deal with thousands of volts of RF at any power level much
above QRP.

---------------------------------------------------------------

A timely warning Ron. This is one reason why commercial remote antenna
matching units designed to handle such high voltages and / or currents
without going up in smoke tend to be expensive. Fortunately for those of us
who homebrewed in ancient times suitable vacuum relays and and Mil Spec wide
spaced air variable capacitors were available at bargin basement prices.

73,
Geoff
GM4ESD



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[David Cutter]

If I had a doublet I would seriously consider feeding it like the W5DXP which uses switched ladder line for matching .  Looks cheap, low loss and easy to do: any residual mismatch should be compensated by the K2/K3 auto-matching system.

http://www.w5dxp.com/notuner.htm

David
G3UNA

>
> From: "Geoffrey Mackenzie-Kennedy" <[hidden email]>
> Date: 2007/09/10 Mon AM 05:09:13 BST
> To: "Ron D'Eau Claire" <[hidden email]>
> CC: Elecraft Discussion List <[hidden email]>
> Subject: Re: [Elecraft] Balanced AT
>
> Ron AC7AC wrote:
>
>
> Another issue with a balanced AT is that they tend to be used in multiband
> systems fed with open wire line where high SWRs are expected. High SWRs mean
> very, very high RF voltages at a current "loop", demanding relays, etc.,
> that can safely deal with thousands of volts of RF at any power level much
> above QRP.
>
> ---------------------------------------------------------------
>
> A timely warning Ron. This is one reason why commercial remote antenna
> matching units designed to handle such high voltages and / or currents
> without going up in smoke tend to be expensive. Fortunately for those of us
> who homebrewed in ancient times suitable vacuum relays and and Mil Spec wide
> spaced air variable capacitors were available at bargin basement prices.
>
> 73,
> Geoff
> GM4ESD
>
>
>
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>

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[N2EY]

In a message dated 9/10/07 1:10:42 PM Eastern Daylight Time,
[hidden email] writes:


> If I had a doublet I would seriously consider feeding it like the W5DXP
> which uses switched ladder line for matching .  Looks cheap, low loss and easy
> to do: any residual mismatch should be compensated by the K2/K3 auto-matching
> system.
>

Cecil's "linear tuner" setup works - I've heard it on the air. He's used it
for a number of years.

The problem is that it's a bit of a mechanical nightmare, with all the
switches and different lengths of window line.  Remember that the window line has to
be separated from other conductors by a couple of line-spacings.

You also don't have a lot of flexibility on how much line there is from the
antenna to the first switch.

If you don't QSY a lot, it's certainly doable.

73 de Jim, N2EY


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