[JMS] 250 Watt modulator for 90881

[Bill W2DGB]

Cal,

Just for your background information, the 12th Edn of the Radio Handbook
(Editors and Engineers, 1949) details a 100-watt 811 modulator using parts
from the ART-13. I would think you could easily get it up to 125 watts, and
would only have to be concerned about any mismatch, and how significant it
would be.

Bill Fizette   w2dgb

----- Original Message ----- 
From: "Dennis Petrich" <dpetrich at wavecrest.com>
To: "'The James Millen Society Members Email Reflector'"
<james_millen_society at mailman.qth.net>
Sent: Wednesday, July 26, 2006 9:46 AM
Subject: RE: [JMS] 250 Watt modulator for 90881


> Hi Cal,
>
> I don't exactly what you have but it sounds like it has the right size to
> work.  Most military transformers were under rated so I would suspect it
> would handle the power OK.  Now if it can hit the impedances you need,
> you'll be in like Flint....
>
> Ciao, Dennis
>
> -----Original Message-----
> From: james_millen_society-bounces at mailman.qth.net
> [mailto:james_millen_society-bounces at mailman.qth.net]On Behalf Of C E
> Sent: Tuesday, July 25, 2006 8:48 PM
> To: james_millen_society at mailman.qth.net
> Subject: [JMS] 250 Watt modulator for 90881
>
>
> All:
> After reading Dennis Petrich article on making a plate
> modulator for the 90881 amp, I've got the "itch" to
> make one myself. I initially thought of using an
> ART-13 item but some have said that it might not have
> enough power handling capabilities (which I'm almost
> inclined to believe might not be all that true since
> it is rumored that the xfrmr has been used at the 250
> watt levels).
>
> I have, however, stepped across a unit that contains
> an 811 modulator. It is marked "Modulator Panel
> PN-10-B" and with a red lable "Modulator Unit Type
> 5001A AM #29. It is a Signal Corps/Air Ministry unit
> that came from the 1950's. The modulator transformer
> is a hefty piece of iron about twice the size of an
> ART-13 iron with large ceramic standoffs for the
> modulator unbal out and B+ in.
>
> Does anyone have any idea what I have? If so, let me
> know. Cal, N6KYR/8
>
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