----- Original Message -----
From: Jim VE7RF <jim.thom@...>
Reply-To: <[email protected]>
To: <[email protected]>
Sent: 29/12/2019 15:12:42
Subject: Re: [ham-amplifiers] Plate blocking caps YC156


The??problem??with??broadcast?? mica's (or??any??mica)??is??they??won't handle?? any current??on??higher??freqs.??But??they are??NPO.?? Drake used switchable mica's??in their??MN-2000??ant??tuner (along??with??2 x air??variables).?? Drake??used??7 (SEVEN)?? mica's??in??parallel....just??for 10m??band.....just to handle 1200w??pep into??some??swr.??

Drake??used??a single??700 pf??(NPO) mica??to??pad??the 1600??pf??load??cap on??80m band....??on their L4B??80-10??amp.

Those CDE and??similar??mica??caps??are??typ rated??at?? 1??mhz??for??max current.??> 6??mhz, they??have??fallen??off really??fast.??>20??mhz,??they??are??down??to??nothing.

Mica's??work??superb??on??low??bands (<6 mhz)....??and ceramic??caps work??superb??>2-3 mhz.

For??a plate??block??cap, ceramic??is??used,??since??we??require??a cap(s) that??will??handle loads??of??current on??21-29.7??mhz. (+6M).????On lower??bands,??plate??block??cap??current??drops??way??off.....non??issue.

HEC??is??still made??in PA...amish??country.??

Download??the??main??catalog for??CERAMIC????

Draloric is??still??made in??germany.

Centralab??was??bought??out??by??ITT-Jennings.??Centralab??(ITT-Jennings)????857 /??859??is??the??same??as a HEC?? HT-57??/??HT-59

Everything??else??is??a chinese copy.?? Also??factor??in??the??heat??from??the??anode??will??travel??down??the strap..to??one??side??of??plate block??caps.

Jim?? VE7RF