I don't think most 11 meter amp manufacturers are to concerned about
inter mod. The tuned circuit is there to transfer maximum power from the
50 ohm radio.
73
Gary K4FMX
Will Matney wrote:
> Tony,
>
> Even the old 10-11 meter sweep tube amps had a tuned input, or at least the
> better ones of them. They even knew it was better than not having any at all.
> Most of those used a tuned transformer feeding either the cathode(s) or the
> grid(s). Same thing applies to any amp IMHO.
>
> Best,
>
> Will
>
> *********** REPLY SEPARATOR ***********
>
> On 3/28/05 at 10:57 PM Tony King - W4ZT wrote:
>
>
>>Tomm Aldridge wrote:
>>
>>
>>>This is an interesting thread to me not because of the AL-811 vs
>>>MLA-2500 but because I am designing and building an amp. If I
>>>understand this correctly, using a TS570 transceiver to drive my amp
>>>implies I really don't need a tuned input circuit as I can just use the
>>>built-in tuner of my rig to achieve a good enough match to the input of
>>>the tubes. That saves me money and complexity.
>>>
>>>However, some on this list advise that the proximity of the output C of
>>>the tuned input to the cathode of the PA is very important for its
>>>"flywheel" or energy storage effect during the wide swings in impedance
>>>during a cycle of operation.
>>
>>I have gotten the same advice / impressions. A tuned input adjacent to
>>the cathode appears to be the only true way to get a good flywheel
>>effect. I suppose, if you didn't care about improving the IMD that it
>>might not matter. I hope that some of the experts will chime in on this.
>>
>>
>>>My question is, which strategy should one employ and what are teh pros
>>>and cons? Assuming, of course, a built in AT such as in the TS570.
>>
>>There is a good link at <http://www.somis.org/SB220ci.html> where Rich
>>discusses the need for a good tuned input. This article is about the
>>SB-220 but the idea is the same. Go to the link and scroll down to
>>"Improving Input SWR" about two thirds of the way down. I think that
>>will help us understand why it's more complex than matching the radio
>>output to the cathode input.
>>
>>My questions to the group are these:
>>How many of those running homebrew amps use a tuned input? How many are
>>not?
>>Now how many of those running a COMMERCIALLY manufactured amp are NOT
>>running a tuned input?
>>
>>
>>>Regards,
>>>
>>>KD7QAE
>>>Tomm
>>><snip>
>>
>>73, Tony W4ZT
>>
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>
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