TenTec
[Top] [All Lists]

## Re: [TenTec] Ten-Tec 411 Centaur Amp Problem

 To: "Discussion of Ten-Tec Equipment" Re: [TenTec] Ten-Tec 411 Centaur Amp Problem "Kris Merschrod" Discussion of Ten-Tec Equipment Mon, 31 May 2010 22:31:48 -0400 mailto:tentec@contesting.com>
 ```Merschrod 123 Warren Road Ithaca, NY 14850 www.merschrod.net ----- Original Message ----- From: "CSM(r) Gary Huber" To: "Discussion of Ten-Tec Equipment" 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: > Sent: Monday, May 31, 2010 8:32 PM > To: "Discussion of Ten-Tec Equipment" > 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" >> Sent: Monday, May 31, 2010 8:15 PM >> To: "Ten Tec" >> 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 >>>> TenTec@contesting.com >>>> http://lists.contesting.com/mailman/listinfo/tentec >>> >>> _______________________________________________ >>> TenTec mailing list >>> TenTec@contesting.com >>> http://lists.contesting.com/mailman/listinfo/tentec >>> >> _______________________________________________ >> TenTec mailing list >> TenTec@contesting.com >> http://lists.contesting.com/mailman/listinfo/tentec >> > _______________________________________________ > TenTec mailing list > TenTec@contesting.com > http://lists.contesting.com/mailman/listinfo/tentec > _______________________________________________ TenTec mailing list TenTec@contesting.com http://lists.contesting.com/mailman/listinfo/tentec ```
 Current Thread Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, (continued) Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Jim Brown K9YC Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, James Duffer Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, wow_chf Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, CSM\(r\) Gary Huber Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Kris Merschrod Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Duane Calvin Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Kris Merschrod Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, wow_chf Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Kris Merschrod Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Alan Sewell N5NA Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Kris Merschrod <= Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Kris Merschrod Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, wow_chf Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, mike bryce Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Mike Schatzberg Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Ken Brown Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Jim Brown K9YC Re: [TenTec] Ten-Tec 411 Centaur Amp Problem, Tony Berg