Merschrod
123 Warren Road
Ithaca, NY 14850
www.merschrod.net
----- Original Message -----
From: <wow_chf@hotmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Monday, May 31, 2010 11:05 PM
Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
> Since you have already run some jumper experiments with no success, why
> not
> measure the 25 ohm shunting resister and see if it has changed value
> somewhat? You could start by just examining it visually, and reflowing
> the
> connections.
>
> 73,
>
> Mike
> W2AJI
>
>
>
> --------------------------------------------------
> From: "Kris Merschrod" <Kris@merschrod.net>
> Sent: Monday, May 31, 2010 10:58 PM
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>
>> Good evening Mike and Duane,
>>
>> I have tried two different alternatives to the short coax 1) 3 foot #213,
>> and 2) 25 feet or so of RG 58, and not a bit of change in the SWR. I
>> havbe
>> not tried the whittling down foot by foot b/c I am convinced that the
>> problem just was not in the design. I need to find the problem in the
>> 411.
>>
>>
>> The observation that there is only a 25 ohm resister in parallel with the
>> THREE 811s seems to be too simple, but perhaps elegant. If tghat is the
>> case though, thenthere should be similar mismatches on other bands.
>>
>> Kris KM2KM
>> Merschrod
>> 123 Warren Road
>> Ithaca, NY 14850
>> www.merschrod.net
>> ----- Original Message -----
>> From: "Duane Calvin" <ac5aa1@gmail.com>
>> To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
>> Sent: Monday, May 31, 2010 10:36 PM
>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>
>>
>>> Why not just try a different length of coax and see what happens - that
>>> is
>>> an easy experiment.
>>>
>>> 73, Duane
>>>
>>> Duane Calvin, AC5AA
>>> Austin, Texas
>>> www.ac5aa.com
>>>
>>>
>>> -----Original Message-----
>>> From: tentec-bounces@contesting.com
>>> [mailto:tentec-bounces@contesting.com]
>>> On Behalf Of Kris Merschrod
>>> Sent: Monday, May 31, 2010 9:31 PM
>>> To: Discussion of Ten-Tec Equipment
>>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>>
>>> Good evening, I am still fiddling and pondering the observations on
>>> this
>>> problem. Gary's observation means that no matter the band the input
>>> impedance is the same except for the "intervention" of the coax between
>>> the
>>> exciter and the AMP. That is hard to believe, b/c my 8"jumper cable
>>> seems
>>> to keep the 160, 80 and 20 meter input "happy" (No SWR) but on 40 it
>>> all
>>> goes to "pot."
>>>
>>> I can't believe that TT built non-matching rigs in the 1990s. Something
>>> else has to be wrong.
>>>
>>> Kris KM2KM
>>> Merschrod
>>> 123 Warren Road
>>> Ithaca, NY 14850
>>> www.merschrod.net
>>> ----- Original Message -----
>>> From: "CSM(r) Gary Huber" <glhuber@msn.com>
>>> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>>> Sent: Monday, May 31, 2010 10:16 PM
>>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>>
>>>
>>>> In the case of the Centaur 411, the input is simply a 25 Ohm resistor
>>>> in
>>>> parallel with the cathodes of the 4 811s (which are also in parallel).
>>>>
>>>> The input load impedance of the Centaur is always less than 25 Ohms and
>>>> thus
>>>> the length of input coaxial cable plays a significant role in
>>>> transforming
>>>> the SWR for the driving solid state transmitter.
>>>>
>>>> 73,
>>>>
>>>> Gary - AB9M
>>>>
>>>> (NOT an E.E.)
>>>>
>>>> --------------------------------------------------
>>>> From: <wow_chf@hotmail.com>
>>>> Sent: Monday, May 31, 2010 8:32 PM
>>>> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>>>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>>>
>>>>> Yes indeed. In fact, there were two different lengths in the Collins
>>>>> 30S1
>>>>> manual, one for their transceiver and one for their transmitter.
>>>>>
>>>>> In my article the explanation as to why this works is as follows:
>>>>>
>>>>> "In cases involving RF signals, some time will pass during the 'round
>>>>> trip
>>>>> of the reflected energy and the phase of the reflection will also
>>>>> depend
>>>>> upon this length of time. Imagine that a resistor in a black box is at
>>>>> the
>>>>> end of a length of cable. From the outside world this length of cable
>>>>> will
>>>>> give the reflection from the resistor a phase shift since the signal
>>>>> must
>>>>> make a round trip through the length. If a 100 ohm resistor has an SWR
>>>>> of
>>>>> 2,
>>>>> a cable long enough to invert the signal after the round trip will
>>>>> make
>>>>> it
>>>>> look like a 25 ohm resistor, also with an SWR of 2 but with inversion
>>>>> (a
>>>>> cable with a multiple of 1/4 wavelength would do the trick). Since the
>>>>> impedance looking into this black box is a function of the SWR and the
>>>>> cable
>>>>> length, it can be seen that intentionally mismatched lines can be used
>>>>> to
>>>>> transform one impedance into another. Notice that the 1/4 wave cable
>>>>> inverts
>>>>> the impedance and preserves the SWR. This impedance inversion may be
>>>>> used
>>>>> to
>>>>> match two impedances at a particular frequency by connecting them with
>>>>> a
>>>>> 1/4
>>>>> wave cable with an impedance equal to the geometric mean of the two
>>>>> impedances. (The geometric mean is the square-root of their product.)
>>>>> A
>>>>> 50
>>>>> ohm, 1/4 wave cable will match a 25 ohm source to a 100 ohm load :
>>>>> sqrt(25
>>>>> x
>>>>> 100) = 50. Of course, it is not always easy to find the desired
>>>>> impedance
>>>>> cable!
>>>>>
>>>>> Multiples of 1/2 wavelength will give enough delay that the reflection
>>>>> is
>>>>> not inverted and the impedance will be the same as the load. Such
>>>>> cables
>>>>> may
>>>>> be used to transfer the load impedance to a remote location without
>>>>> changing
>>>>> its value (at one frequency).
>>>>>
>>>>> Other cable lengths will transform an impedance which differs from the
>>>>> cable's impedance with a reactive component. If the load is a lower
>>>>> impedance than the cable, a length below 1/4 wave will have an
>>>>> inductive
>>>>> component and above 1/4 (but below 1/2) wave a capacitive component.
>>>>> If
>>>>> the
>>>>> load is a higher impedance than the cable, the reverse is true. Above
>>>>> 1/2
>>>>> wavelength, the reactance will alternately look capacitive and
>>>>> inductive
>>>>> in
>>>>> 1/4 wave multiples. This reactance will combine with the load's
>>>>> reactance
>>>>> and offers the possibility of resonating the reactive component of the
>>>>> load.
>>>>> Therefore, a cable with the "right" length and impedance can match a
>>>>> source
>>>>> and load with different resistance and reactance values. Obviously,
>>>>> these
>>>>> calculations can become quite involved and most engineers resort to a
>>>>> Smith
>>>>> chart, a computer program or perhaps the most common method, trial and
>>>>> error
>>>>> with a SWR meter or return loss bridge!"
>>>>>
>>>>> Sorry for so much bandwidth.
>>>>>
>>>>> 73 and Happy DXing,
>>>>>
>>>>> Mike
>>>>> W2AJI
>>>>>
>>>>>
>>>>>
>>>>> -------------------------------------------------
>>>>> From: "James Duffer" <dufferjames@hotmail.com>
>>>>> Sent: Monday, May 31, 2010 8:15 PM
>>>>> To: "Ten Tec" <tentec@contesting.com>
>>>>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>>>>
>>>>>>
>>>>>> I recall from some Collins manual for their amp 30S1 they specified a
>>>>>> length for the coaxial cable between the KWM-2 and the amp. In that
>>>>>> case
>>>>>> that was their fix.
>>>>>>
>>>>>> Jim de wd4air
>>>>>>
>>>>>>> From: k9yc@audiosystemsgroup.com
>>>>>>> To: tentec@contesting.com
>>>>>>> Date: Mon, 31 May 2010 13:19:38 -0700
>>>>>>> Subject: Re: [TenTec] Ten-Tec 411 Centaur Amp Problem
>>>>>>>
>>>>>>> On Mon, 31 May 2010 15:55:31 -0400, wow_chf@hotmail.com wrote:
>>>>>>>
>>>>>>> >I submitted the article draft to QST, and it was questioned by the
>>>>>>> >Technical
>>>>>>> >Review folks, and although I have been published in QST before,
>>>>>>> >they
>>>>>>> >could
>>>>>>> >not see how this would "transform" the apparent input SWR.
>>>>>>>
>>>>>>> Because it's a POOR fix for the fundamental problem, which is
>>>>>>> something
>>>>>>> wrong
>>>>>>> in the input circuit of the power amp causing a mismatch. The proper
>>>>>>> fix
>>>>>>> is
>>>>>>> to find and correct the problem in the input circuit. Adding coax is
>>>>>>> a
>>>>>>> band-
>>>>>>> aid.
>>>>>>>
>>>>>>> 73,
>>>>>>>
>>>>>>> Jim K9YC
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> TenTec mailing list
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>>>>>>
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