I actually ordered them from Ten-Tec as parts. That was at least 10 years
ago though.
73
Jim W7RY
--------------------------------------------------
From: "Paul Christensen" <w9ac@arrl.net>
Sent: Sunday, December 12, 2010 1:53 PM
To: "AMPS" <amps@contesting.com>
Subject: Re: [Amps] PI-L Thoughts!
> Jim,
>
> Recycling the basic RF deck from an HF amp carcass seems like a great way
> to
> start on a homebrew HF amp project. Your amp looks great. Well done!
>
> Paul, W9AC
>
> ----- Original Message -----
> From: "Jim W7RY" <w7ry@inbox.com>
> To: "Ulf (SM0NOR)" <ulf@sm0nor.com>
> Cc: "AMPS" <amps@contesting.com>
> Sent: Sunday, December 12, 2010 4:39 PM
> Subject: Re: [Amps] PI-L Thoughts!
>
>
>> The tank coils and the band switch is from Ten-Tec. They used this in the
>> Titan 425. The tune-load knobs and Jackson Brothers drives are from them
>> too.
>>
>> The 4th switch deck is to control the band switching relays on the WD7S
>> tuned input board. I don't remember how I switched the large tune cap
>> into
>> the circuit but if you look at a Titan 425 schematic, you will see.
>>
>> You will also notice a large string of orange caps mounted on a piece of
>> perf board and connected to the lager tune cap. This is the 160 meter
>> tune
>> padder. These are 33 PF 6KV caps from Mouser. The caps are all in
>> parallel
>> of course.
>>
>> Thanks for all the kind words!
>>
>> 73
>> Jim W7RY
>>
>>
>>
>> --------------------------------------------------
>> From: "Ulf (SM0NOR)" <ulf@sm0nor.com>
>> Sent: Sunday, December 12, 2010 12:49 AM
>> To: "Jim W7RY" <w7ry@inbox.com>
>> Subject: Re: [Amps] PI-L Thoughts!
>>
>>> Hi Jim,
>>>
>>> Really nice work!
>>> How did you switch in the larger cap? I see you have a three deck
>>> switch.
>>> One would go to the input network, one to the Pi and and to the L.
>>>
>>> Carefully scrutinising your pictures it looks like you actually added a
>>> fourth deck. In that case I understand how you did it.
>>>
>>> 73's
>>> Ulf
>>>
>>> Sent from my iPad
>>>
>>> On 12 dec 2010, at 04:35, "Jim W7RY" <w7ry@inbox.com> wrote:
>>>
>>>> Please look at the way I handled a low minimum value cap in my 3CX800
>>>> amp. I used a small cap for 10, 15 and 20 meters. Then switched in a
>>>> larger cap for 40, 80 and 160.
>>>>
>>>> Pictures @
>>>>
>>>> http://s900.photobucket.com/albums/ac206/w7ry/3CX800%20Amplifier/
>>>>
>>>> 73
>>>> Jim W7RY
>>>>
>>>> --------------------------------------------------
>>>> From: "Ulf (SM0NOR)" <ulf@sm0nor.com>
>>>> Sent: Saturday, December 11, 2010 10:26 AM
>>>> To: <Amps@contesting.com>
>>>> Subject: [Amps] PI-L Thoughts!
>>>>
>>>>> Hi all,
>>>>>
>>>>> I'm looking for some advice regarding the tank.
>>>>>
>>>>> I'm about 2/3 on the way to complete my first amplifier build and I'm
>>>>> having some thoughts about how to get C1 to low enough to load on 10
>>>>> meter.
>>>>>
>>>>> To no surprise the 25-300 pF capacitor measured a min of 40 pF when
>>>>> mounted in the RF deck. This will give me trouble on the higher bands.
>>>>> I
>>>>> know this is discussed a lot in the literature, but I'd like your
>>>>> thoughts on one specific solution.
>>>>>
>>>>> The obvious solutions are to either get another C1 with a lower min
>>>>> capacitance or to get a vacuum variable. Maybe I could do the first
>>>>> solution, but that would probably make it necessary to rebuild the
>>>>> switching section with another deck to be able to switch in different
>>>>> sections of a split stator cap. The vacuum solution is really easy,
>>>>> but
>>>>> I have not really budgeted for that.
>>>>>
>>>>> This makes me think of a third solution mentioned in the handbooks but
>>>>> not really discussed in depth; and that is to tweak the Q to make it
>>>>> work. And I would like to have the opinions of all you experienced
>>>>> builders out there!
>>>>>
>>>>> Here are my calculations (based on one of the handbooks)
>>>>>
>>>>> C1 C2 L1 Q
>>>>>
>>>>> 160 330 1400 30.4 11
>>>>> 80 174 716 14.1 12
>>>>> 40 96 388 7.2 12
>>>>> 20 43 182 3.9 11
>>>>> 15 45 161 1.7 16
>>>>> 12 43 151 0.7 18
>>>>> 10 43 143 0.6 20
>>>>>
>>>>> For simplicity I did not add the values for L2 in this post.
>>>>>
>>>>> Ok, what do you think of this? Is it Ok with a Q of 20 on 10 meter?
>>>>> I'm
>>>>> using 5 mm copper tubing in the 10-20 coil. Or would it be better with
>>>>> one of the other solutions? Tweaking the Q is by far the most simple
>>>>> solution given the components I already have.
>>>>>
>>>>> Thanks for any advice!
>>>>>
>>>>> By the way..... the build is based on a GU74B and I'm aiming for a
>>>>> 1KW
>>>>> PEP.
>>>>>
>>>>>
>>>>> 73's
>>>>>
>>>>> Ulf (SM0NOR)
>>>>> ulf@sm0nor.com
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>>
>>>>>
>>>>>
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>>>
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