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Drake 2880 additional mod



I did one more mod to my Drake 2880 and will now quit while I am ahead.  I
had reported a gain of 38 dB and a 1.9 dB noise figure achieved by replacing
the first amplifier stage with a MGA-86563 MMIC and doing the other mods
described at the G3PHO site.  The next step was to protect this IC from
static on the input connector without loosing performance.  I plan to use
this converter with a helix that is not DC grounded.

A photo of my modified input circuit can be found at:
http://www.msnusers.com/wc0y/files/LNA.jpeg

You will see two chip inductors, one in the MMIC bias circuit, and one at
the input connector, from the input trace to ground.  The chip inductors
have blue markings.

These inductors are Coilcraft 0805CS-220X_BC part number.  I chose this one
because it is designed to have a series resonant frequency (SRF) around 2400
MHz.  It is a wire-wound chip inductor, so it should help with static
discharge.  I am happy to report that placing it across the input circuit to
ground had no measurable effect on gain or noise figure.

Coilcraft has a good web site at www.coilcraft.com, and they do direct
sales.

If you downloaded the photograph, you will see the MMIC placed between two
"huge" eyelets that I inserted to get a low impedance path to the ground
foil on the underside.  These eyelets are 0.055 inches in diameter on the
body, and 0.10 inches in diameter at the collar that is visible.  That shows
how tiny the MMIC IC is.

Hope this helps some of you with your plans.

73,
Ward - WC0Y

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