Ham Radio Homebrew Informations: RE: [HamBrewers] 73 watts okay but.........

Dev,

I remember, Vishay and ATC were making those RF grade capacitors, I have not only bought them from their distributors in US, but also I’ve seen those in some of the BEL HF PA boards.

If you are incorporating VSWR protection beyond 3:1, then these must withstand the nominal X 3 times the voltage as you are aware.

I have seen some of those orange colored Mica capacitors in the .001 range rated for 3KV being used in some of the kilowatt class tube amps as the Plate blocking / coupling capacitor.

Several of them in parallel might be able to handle the higher current requirements at 30Mhz.

Also, in a lot of Motorola Application notes where HF LPF are shown, you will find a number of 600V or 1000V dc rated Disc ceramic capacitors used at power outputs close to 400W

73s

vu2ttp

From: HamBrewers@yahoogroups.com [mailto:HamBrewers@yahoogroups.com] On Behalf Of Dev Ramaprabhu
Sent: Wednesday, May 11, 2011 4:14 PM
To: HamBrewers@yahoogroups.com
Subject: Re: [HamBrewers] 73 watts okay but.........

Dear Satyan (or shall I address you as my dear Sarath!),

I have seen those circuits and we do use them in Morning QTH ,,,,, BUT..... the rating for those Capacitors as specified is a bit on the lower side, you see my dear friend ...... It is okay for them as they can make a few ohms in after sales etc...... but Knowing fully well 200 watts implies 141Volts on DUMMY load I would like to use higher rating......

Best regards,

dev

From: vu3mes <satyansarath@gmail.com>
To: HamBrewers@yahoogroups.com
Sent: Wed, May 11, 2011 4:07:34 PM
Subject: Re: [HamBrewers] 73 watts okay but.........

http://www.w6kan.com/ssamp.html

Dev - try this link, this is a time-tested circuit and many ham brewers have it up and running.

73s

vu3mes

On 11 May 2011 16:03, Dev Ramaprabhu <vu2dev@yahoo.com> wrote:

Dear All,

As you might have seen the pics in the previous mail we have managed to combine two PAs and get almost 100watts but.......

100 watts on dummy load is 100volts peak and alas all our Capacitors are rated for 100Volts only so obviously we got to run at 73watts or below for safety!( on real ANTENNAS, not NOT DUMMYS)

Now, dear all could you suggest some vendors/ shops/ types for Capacitors which would work let us say at 200 volts or more so that we could run a lil more output; somewhat like 400w d.c.input (I am afraid that's all we are allowed to run in our beloved India shining!) And just for info I am using a Wilkinson Combiner to get more output ( and run those Mosfets very Cool!!!!!) We would need the following values:

47pF,

100pF,

300pF/320pF,

470pF!

Of course any one wants I could send the full schematic etc and the photo ( I Can't send as I need some youngster to convert from Camera to PC, hi hi hi hi)

All the best and Do run full Legal limit!

( Not exactly anti-QRP but pls do experiment)

dev, vnk, pwt

73s de vu3mes satyan sarath qth link -
http://www.findu.com/cgi-bin/find.cgi?call=vu3mes www.qrz.com/callsign/vu3mes www.chennaihams.blogspot.com
www.satyansarath.param.mobi [mobile webpage]
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