[Amps] Ten-Tec Titan 10 Meter Input SWR

[donroden at hiwaay.net]

Thank You Paul.

If you don't believe Paul, play around with a Smith Chart.
You absolutely CAN change the input Z by using a coax tuner
instead of discrete L / C  components.

For example 100 ohms measured
1/4 wave of RG-11
Now you have 50 ohms at the input of the coax and the transmitter is happy.


Don W4DNR


Quoting Paul Christensen <w9ac at arrl.net>:

>> "Like Bill said, changing the coax length does not change the swr so there
> is very little "tuning" going on. Using 1/4 wave or less will not fix the
> swr problem so something more is needed.  Changing from 50 to 75 ohm coax
> will cause some tuning to take place. Good luck finding a happy length
> though. 73, Gerald K5GW"
>
> It's not only about SWR.  Any line-to-load mismatch, no matter how small,
> will cause the complex impedance to change at the input end of the line with
> changing line length, even though the line SWR does not change with length.
> For example, if there's a 2:1 SWR load mismatch, then changing the line
> length may affect the operating performance of the driving stage by creating
> say...a 50+j0 or some other input Z, even though the line SWR hasn't
> changed.  The input Z changed, the line SWR didn't.
>
> In any line mismatch condition, SWR on the line remains the same provided
> the characteristic Z remains the same and the line is low-loss.  If the line
> characteristic Z changes (e.g., RG-11 to RG-213 transition), then the SWR on
> each portion of the line is different.  Changing the line length on one
> section of the transition will: (1) affect the SWR on the other section; and
> (2) cause the complex Z measured on each end to change.
>
> Paul, W9AC
>
>
> In a message dated 6/11/2017 7:22:17 A.M. Central Daylight Time,
> donroden at hiwaay.net writes:
>
> If you  change the length of the feed coax, you have created a "coax tuner".
> 1/4  wave or less is all that is required.
>
> Don W4DNR
>
>
> Quoting Bill  Turner <dezrat at outlook.com>:
>
>> ------------ ORIGINAL MESSAGE  ------------(may be snipped)
>>
>> On Sat, 10 Jun 2017 19:57:42  -0500, W7RY wrote:
>>
>>> Tried different lengths of coax between  the amp and the radio and
>>> still no better.
>>
>>  REPLY:
>>
>> The length of coax does not affect SWR unless it is  extremely long,
>> where line loss comes into play. Even then, the effect  is to reduce
>> SWR, not increase it.
>>
>> It does affect the  impedance the transceiver "sees", but not SWR.
>>
>> 73, Bill  W6WRT
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