Topband: MFJ 259B bridge diodes [HSMS2820]

[Tod -ID]

Several people have asked me where to find the RF bridge diodes.

According to the PDF schematic I have of the MFJ-259B unit the RF diodes are
HSMS2820 surface mount RF Schottky Barrier diodes. They are packaged as
'singles' in an SOT-23 package. The datasheet is found under HSMS-2820 at 

http://www.avagotech.com/pages/en/rf_ics_discretes/schottky_diodes/surface_m
ount/

They are available from Mouser as part number 630-HSMS-2820-BLKG with a unit
price of $0.42 in single unit lots.

http://www.mouser.com/catalog/catalogUSD/637/430.pdf . They may also be
available from DigiKey but I did not check that out.



I found the schematic for the MFJ-259B at 

http://www.we0h.us/Amateur_Radio_stuff/MFJ/MFJ-259B/MFJ-259B-schematic.jpg

I cleaned it up a bit so that it is easier to read the component values and
the component codes [R1, C24, etc.] and created a PDF scaled to print as an
11 x 17 page or two letter sized pages that one pastes together -- much
easier for me to read. I also cropped and expanded the section of the
schematic dealing with the actual components [diodes, resistors, etc.]used
in the bridge so it can be printed as an 8.5 x 11 inch page. One can analyze
how the bridge works by doing little circuit re-arranging for clarity.

If someone wants a copy of that stuff correspond directly with me rather
than copying the entire Topband list.

I think that probably completes this topic for the time being.

Tod, K0TO
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