The AM Forum

What was the value of the shunt capacitor (I believe they were vacuum types) used with The B & W CX-58B capacitor.  This unit is equipped with "fuse-clips" mounted on the front that will mount a Jennings 20kv vacuum capacitor - 13/16" diameter at the clips by about 6-1/2" overall length.   This amplifier uses B & W
HDVL style coils.  I have checked resonance with a grid dip meter - okay on 10 meters.  Cannot get resonance with the HDVL-40 Coil in place.  Were shunt capacitors of different values used for 160 / 80 and 40 meters? 

tnx... Cid K8JLY

I've seen those clip-in cap in values of 50, 100 and 200 pF. Which ones get plugged in depended on the band and the tube parameters.

I have several of those plug-in types here. I forget the voltage ratings
Fred

Cid,

I just scanned all the information your looking for from my B&W archives but the PDF file is to large to post.  I do not have PDF writer so I am guessing that's why I can't compress them in size to do an attachment.  I could just email the information to you, but I wanted to share it with all here.

Here is my text from the post I tried to send, minus the attachments.

Cid,

Here is the catalog for the B&W butterfly capacitors.  You can see the model of air variable you have on the sheet.  B&W offered various version based on what you were building.  With the proper butterfly condenser selected you do not need a padder capacitor when working 160 through 10 meters.  Saying that, the fix vacuum capacitors do work quite well if your do not have enough capacity in your lesser capacity butterfly capacitor.      

I have also attached the page talking about the coils and what capacitance required to resonate down from 160 through 10 meters.  Look all the way down at the bottom of the page and you will not that 100pf is required for 160M operation.  

Concerning the voltage rating of the padder, since this is a parallel resonant circuit it will need to be a very high voltage capacitor.  I believe I used a 10 or 15KV in mine when I built my push pull class C amp using a pair of 833A's.  

Hope that helps!

73,
Joe, W3GMS    


  

Send it to my email Joe. I'll figure out how to post.

Thanks Steve....
Joe

I've used the CX series caps in 3 of my HB TX. The 58 and 62 are my favorites.
My HB PP T-200 transmitter (Taylor T-200 triodes) uses the TX-62C, Johnson 80 M
coil and 25 pF fixed padder cap (N-4 neutralizing caps).
This tx L-C circuit resonates nicely on 75m and I've had it on 80 m
CW a few times too. This handles more RF output than you can imagine!

To get this RF into 50 ohms, a 6 turn swinging link coil and a 40-1000 pF
are variable L-C does the job.
(Come off the link with a short piece of coax. Take the ground of the coax to
the are variable; the center conductor to the coax antenna connecter; the air
variable is chasis mounted thus is grounded) The 1956 West Coast Handbook
has the circuit.

Good luck!
73
Steve w8tow

The data sheets Joe supplied are now available in the Handbook section under Printed Material. Links below.

http://amfone.net/Amforum/index.php?topic=35680.0

http://amfone.net/Amforum/index.php?topic=35679.0

Should work now. Thanks for the heads up Ralph.

B&W Butterfly Cap Info (http://amwindow.org/misc/pdf/B%26W%20Butterfly%20Cap%20info.pdf)

Thanks very much Steve for downsizing the document size and posting it.

Joe, W3GMS