[Elecraft] Questions and K3 options? Please!

[David Yarnes]

Bill and All,

I would think (hope?) it would.  My concern is that it takes 
the ATU a while to achieve the 2:1 match on 160.  When I do 
it, I do it at reduced power, so that the K3 is hopefully 
not working too hard in the process.  This may be done 
automatically now, but I was under the impression that for a 
time there was no power fold back during tuning.  Easy 
enough to verify though, by just putting a power meter on 
it.  Anyway, I then crank the power back up, but generally 
only to around 70 or 80 watts.  That's may be another 
unnecessary precaution, but 80 watts vs. 100 watts won't be 
noticed at the other end anyway.  But if my ATU had to 
struggle a bit getting that 2:1 match, I feel that I could 
easily loose that match very quickly just because the R8 
might be bending around in the wind or something.  If 
anything up there is a little loose, that 2:1 could become 
15:1, or something like that,  in a heartbeat.  Supposedly 
the SWR protection would kick in, but I'm just a little shy 
about trusting it.  Loading a 26 ft. vertical on 160 meters 
just seems a little scary I guess.  I may be kidding myself 
thinking I'm making it less risky with these precautions, 
but intuitively it seems prudent.  Of course, trying this at 
all may be anything but prudent!

It kind of interesting though.  On 80 meters the K3 gets a 
1:1 match very quickly.  And that is just about anywhere on 
the entire 75/80 meter band.  I expected it to struggle 
there a bit too, but it just doesn't.  But results aren't so 
hot, and the efficiency is probably pretty sorry.  Since the 
R8 is supposedly a "half-wave" system, it presumably is 
something like a 1/4 wave on 80 without an effective ground 
system to compliment it.  It makes me wonder if there would 
be much improvement noticeable by putting up 2 or 3 tuned 
radials for 80 meters.  One of these days I may do a little 
tinkering with that.

Dave W7AQK

----- Original Message ----- 
From: "Bill W5WVO" <w5wvo at cybermesa.net>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, July 02, 2008 7:17 AM
Subject: Re: [Elecraft] Questions and K3 options? Please!


> David Yarnes wrote:
>
>> but I don't--at least not routinely.  I really only get
>> about 2:1 there, and that tells me "watch out!"  If you
>> can't get something close to 1:1 using the ATU, you 
>> probably
>> need to be cut the power back a little or a lot...
>
> I would think the SWR protection circuitry in the K3 would 
> do this for you
> automatically. I guess I always assumed that, like 
> virtually every other rig
> out there, the K3 has automatic SWR foldback to protect 
> the finals... Am I
> wrong about that?
>
> Bill W5VWO
>
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