KAT500 update

[gm3sek]

Ross Primrose N4RP wrote:

>On 12/9/2011 6:09 PM, Jim Brown wrote:
>>
>>>    If it is an automatic antenna tuner, that is less of a problem.
>> Except that the automatic circuitry, and it's power supply must also be
>> isolated from ground. That part of the design problem seems non-trivial.
>>
>
>Seems fairly simple to me, use a transformer in the PS, and float the
>secondary side...
>

Nope - there will be a large capacitance between the transformer
windings. In parallel with this will be the capacitance between the
entire RF sub-chassis and the outer metal case. If the choke balun is
connected on the input side of the ATU, these quite large parallel
capacitances will partially unbalance the output.

Worse yet (as Alan points out), if you select a coaxial output with the
SO-239 socket grounded to the case, the balun becomes short-circuited
from end to end. Alpha are working on a very similar auto-ATU but their
proposed schematic shows exactly how 'broken' this concept is:
<http://www.rfconcepts.com/PRODUCTS/New-Products/Alpha4040>

Elecraft have done well to avoid this trap, and to decide that the
KAT500 will be all-coaxial - because there simply isn't a "one way fits
all" solution for a balanced ATU. Different user installations will
require different solutions on different bands, so the optimum solution
will always involve some customization, swapping or switching between
1:1 balun, 4:1 balun and 'no balun'.

Please don't be confused by some ATU manufacturers' efforts to sell us a
"one way fits all" balanced ATU. They're only doing that because a fully
versatile engineered solution would be too complex and expensive. So
Engineering steps back and Marketing takes over instead - bending *your*
perceptions to fit what they have to sell.

Again, Elecraft have done well to avoid this.

Some time ago it was suggested that an all-coaxial KAT500 should also
include programmable band-switched relay control outputs (rather like
DIGOUT0 and DIGOUT1 on the K3) so that users have the option to
configure their own custom relay switching if they need it. Did anything
happen to that suggestion?


--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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[alorona]

I followed the link, Ian. I think it's amazing that an *antenna tuner*:

1. has to be plugged in to AC power to work
2. has cooling fans
3. runs the Linux operating system

I am just old enough to find that somewhere between humourous and preposterous.

Al  W6LX




________________________________
> Alpha are working on a very similar auto-ATU but their
> proposed schematic shows exactly how 'broken' this concept is:
> http://www.rfconcepts.com/PRODUCTS/New-Products/Alpha4040 

--
73 from Ian GM3SEK
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[Matthew Pitts]

I think this design is summed up nicely by the term "overkill".

Matthew Pitts
N8OHU

Sent from my Wireless Device

-----Original Message-----
From: Al Lorona <[hidden email]>
Sender: [hidden email]
Date: Sat, 10 Dec 2011 20:46:11
To: <[hidden email]>
Subject: Re: [Elecraft] Balun on tuner input?

I followed the link, Ian. I think it's amazing that an *antenna tuner*:

1. has to be plugged in to AC power to work
2. has cooling fans
3. runs the Linux operating system

I am just old enough to find that somewhere between humourous and preposterous.

Al  W6LX




________________________________
> Alpha are working on a very similar auto-ATU but their
> proposed schematic shows exactly how 'broken' this concept is:
> http://www.rfconcepts.com/PRODUCTS/New-Products/Alpha4040 

--
73 from Ian GM3SEK
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[Mike Reublin]

4. Costs 3Kbux.

73, Mike NF4L

On 12/10/2011 11:46 PM, Al Lorona wrote:

> I followed the link, Ian. I think it's amazing that an *antenna tuner*:
>
> 1. has to be plugged in to AC power to work
> 2. has cooling fans
> 3. runs the Linux operating system
>
> I am just old enough to find that somewhere between humourous and preposterous.
>
> Al  W6LX
>
>
>
>
> ________________________________
>> Alpha are working on a very similar auto-ATU but their
>> proposed schematic shows exactly how 'broken' this concept is:
>>   http://www.rfconcepts.com/PRODUCTS/New-Products/Alpha4040

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[mike]

Three connectors works for me! Did Wayne say he was going to post pictures? I am starting my pre-purchase Jonesing for the missing piece in my K-line shack.

..mike AI6II