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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Sun 05, 2019 6:33 am 
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Posts: 3597
Location: Lincoln City, OR
Greetings to Cadmandu and the Forum:

In answer to your questions:

Quote:
Is the Hw-32 a grid driven tetrode or a grounded grid cathode driven amp?


The PA stage of your HW32A consists of a pair of 6GE5 beam power pentodes operated in parallel. They are grid driven, RF drive being supplied from the plate of the 12BY7 driver tube to the 6GE5 control grids through C54.

Quote:
When you are reading about tank circuits like my L4 coil and my final tune cap 5-50 pf do all of these descriptions mean the same thing or the same car cap?


Quote:
Final tune cap
Plate tune cap
Tank tuning cap


These three are the same; Plate Tune or Final Plate Tune would be preferred.

Quote:
Output cap

This is somewhat ambiguous, as it could refer to the plate blocking capacitor, C67 or the loading capacitor, C77.

Quote:
Load cap


This would be C77 in your HW-32A; In your case, it is not tuneable; the output Pi network is optimized for a 50 ohm load.

Quote:
Antenna coupling control


In your case, no gots. If C77 were variable, it could be referred to as an antenna coupling control, but loading capacitor or loading control is more appropriate.

The term antenna coupling control is more correctly applied to a different PA topology known as "link coupling" where the degree of coupling is adjustable by mechanically moving the link closer to or further from the output tank circuit.

Regards,

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Jim T.
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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Sun 05, 2019 5:29 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 244
Location: Butler, PA
Thanks Jim what great answers. I need to ask more now if you guys got the time.

1)Which is better grid driven tetrode or a grounded grid cathode driven
2) That C77cap must be really important component. Should i put a new one in?
3) What do you mean the link-coupling?
4)Can a dipole cross over the roof diagonally?

See my pretty HP


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Dan W3DKY
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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Mon 06, 2019 8:59 am 
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Joined: Nov Mon 02, 2009 7:01 am
Posts: 3597
Location: Lincoln City, OR
Greetings to Dan and the Forum:

You asked:

Quote:
1)Which is better grid driven tetrode or a grounded grid cathode driven


That's sort of like asking which is better... Ford or Chevy? The two different designs have different characteristics which lend themselves to different applications.

Grid driven PA's require less driving power. For this reason, they are the usual design choice for a ham transceiver of moderate power as the drive power requirements for grounded grid circuits would require more stages and higher power driver tubes than the 12BY7. Their disadvantages are that it is almost mandatory to use tetrodes or pentodes because of the difficulty of neutralizing triodes in such applications. Attention to detail in screen bypassing and parasitic suppression are necessary due to the higher sensitivity of such tubes.

The grounded grid circuit is more often found in high power amplifiers designed to be driven by moderate power transmitters such as your HW-32A. Because the grounded grid circuit requires substantially more drive power than grid driven designs, the entire power output of the driving transmitter can be effectively utilized to drive the grounded grid stage. For amplifiers that use grid driven circuitry (such as the Johnson Desk Kilowatt) an attenuator is required to turn most of the driving transmitter power into heat so that the drive power supplied to the amplifier is not excessive. In the case of the grounded grid amplifier, the drive power in the cathode circuit is in phase with and added to the stage's output power, so it is not lost. In addition, the grounded grid design can utilize triode tubes without worrying about neutralization in most cases... after all, as an instructor of mine once said, the grid is GROUNDED!


Quote:
2) That C77cap must be really important component. Should i put a new one in?


If you experience difficulty in realizing the design nominal output power into a 50 ohm load, you might consider it. Generally speaking, such caps are not overly stressed and do not require replacement on general principals. If the cap is a disc ceramic, then it is probably fine. If it is a mica, then it is still probably fine, although there are some older micas used in Johnson transmitters (such as the Ranger) which are beginning to exhibit age related failures. I wouldn't change it out on general principals, though.

Quote:
3) What do you mean the link-coupling?


Link coupling is a technique used to transfer energy out of a PA tank circuit by magnetically coupling a coil (link) to the tank coil. The degree of coupling is controlled by the mechanical position of the link with respect to the tank coil. Since there is no direct connection to the link coil, there is no danger of high voltage DC appearing on the link. In the photo below, the link is mounted on a brown insulated lever which allows the degree of coupling to be adjusted.

Attachment:
Link Coupler.jpg
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Quote:
4)Can a dipole cross over the roof diagonally?


Sure... why not? The further from the roof you can get the dipole (higher) the less finicky it will be and the better it will work, but it's orientation with respect to the roof ridge line makes little or no difference.

Regards,

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Jim T.
KB6GM


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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Mon 06, 2019 1:58 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 244
Location: Butler, PA
Beautiful link coupler. Did you build that? Thanks for the great answers to my questions. My second HW-32A is being delivered today.

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Dan W3DKY
Butler, PA


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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Mon 06, 2019 8:39 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 244
Location: Butler, PA
You can't believe the nice hw-23a I just got for for a c note. All new mylars and a great he mike

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Dan W3DKY
Butler, PA


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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Mon 06, 2019 10:26 pm 
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Joined: Nov Mon 02, 2009 7:01 am
Posts: 3597
Location: Lincoln City, OR
Greetings to Dan and the Forum:

I did not build the gear in the photo. The photo was downloaded from an internet search for "link coupling", images.

Regards,

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Jim T.
KB6GM


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 Post subject: Re: HW-32A Tank Circuit L4 Coil
PostPosted: May Tue 07, 2019 4:26 pm 
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Joined: Jan Sun 06, 2013 2:14 am
Posts: 244
Location: Butler, PA
Here it is i paid 50.00 plus 50.00 for shipping from BC
Which is the better mic?


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Dan W3DKY
Butler, PA
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