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List:       elecraft
Subject:    Re: [Elecraft] Dusting off the old K3 & Considering a KAT3A
From:       Bob McGraw K4TAX <rmcgraw () blomand ! net>
Date:       2017-08-31 23:33:56
Message-ID: 1af74748-4fe7-7b3e-b75a-f2890b63e955 () blomand ! net
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One point to consider,  anytime one inserts a tuner in line at the 
transmitter, additional loss is also introduced. Additionally the SWR 
and related loss on the feedline is not reduced.   Some tuners, 
depending on load and frequency, can introduce as much as 25% power 
loss.   In many cases, a 2:1 SWR at the radio is better than using a 
tuner to show a 1:1 SWR at the radio due to added loss in the tuner and 
the feed line loss remains the same.


73

Bob, K4TAX




On 8/31/2017 5:09 PM, Bill Frantz wrote:
> Sorry Jim. You are indeed correct about the feedline SWR. While there 
> are other SWRs within the radio, they aren't of much interest.
>
> However, these radios do report a SWR in the UI, and that is what I 
> was referring to. Since a naive user might look at that figure and 
> say, "The SWR is 2. The antenna must be good.", it is important to 
> know that the tuners can produce a low figure on that meter with 
> nothing connected to the antenna connector.
>
> 73 Bill AE6JV
>
> On 8/30/17 at 11:25 PM, jim@audiosystemsgroup.com (Jim Brown) wrote:
>
>> Please don't perpetuate that myth, Bill. Tuners do NOT reduce the SWR 
>> unless they're at the antenna end of a transmission line. The SWR 
>> exists on the transmission line, and it is determined ENTIRELY by the 
>> match between the transmission line and the load.
>>
>> What tuners at the rig do is get the rig to put power into the tuner 
>> (and hopefully, onto the transmission line).  If the SWR is high 
>> without the tuner, it is equally high WITH the tuner. Depending on 
>> the cable, the frequency, and the SWR, much of the power that the rig 
>> puts into the tuner gets to the transmission line, but is turned into 
>> heat by the SWR in the line and doesn't get to the antenna.
>>
>> A better way to talk and think about this is to say that the tuner 
>> can match a wide variety of loads to the transmitter sufficiently 
>> well that the rig can pump the maximum power from its output 
>> terminals, whether it's feeding a short wet string or a nice long 
>> wire we've launched into a tree. And if there's no transmission line, 
>> SWR has no meaning!  So SWR is the wrong way to talk and think about it.
>>
>> 73, Jim K9YC
>>
>> On 8/30/2017 10:15 PM, Bill Frantz wrote:
>>> My experience with the tuners in both the K3 and KX3 are that they 
>>> will reach an acceptable SWR with anything. I always check the 
>>> antenna when they take a long time to reach a match. (I.e. lots of 
>>> clicking.) Most of the time I find I am trying to match an open 
>>> antenna connection.
>>
>>
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> -----------------------------------------------------------------------
> Bill Frantz        | Since the IBM Selectric, keyboards have gotten
> 408-356-8506       | steadily worse. Now we have touchscreen keyboards.
> www.pwpconsult.com | Can we make something even worse?
>
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