I did the mod to my first L-7 after I bought it new.
1. You remove a set stop screw on the bandswitch so it can go into the 10
meter slot position.
2. You remove a coax assembly which is made up of two pieces of coax and a PC
board in between the two. (It filtered out any 11 meter RF that was feed into
it.
This removed assy went between the coax input so-239 connector and the
grid input coils.
You then but in a new piece of coax between the input coax jack and the
input coils. It did not contain the 11 meter trap.
3. You then changed out a silver mica cap on the 15 m coil to I think a
smaller size. You then used the 15 meter input coil for both 10 meters and 15
meters.
The coil was then peaked between the two bands so the tubes so grid
current on both bands.
This is what I remeber I did to make the mod.
----- Original Message -----
From: [email protected]
To: [email protected]
Sent: Monday, August 31, 2009 7:41 PM
Subject: [Drakelist] L7 linear 10 m mod question
Had a question about the L7 with 10 meter coverage, either the export version
or the modified/upgraded version. The 10 m coverage is achieved by adding a
couple of 68 pf capacitors, aligning an input coil, etc. Does anybody know the
theory or philosophy behind this design? Electrically, the same thing can be
achieved by using just a single 68 pf cap on the S1A input switch, the side
going to the RF input, and then short the 10 m and 15 meter contacts together.
The output side of the input pi-network then functions the same as if two caps
were installed, one for 10 m, and one for 15m. There is no need to put the
other 68 pf cap near coil L4. Since companies try to save pennies on parts,
plus labor costs, I was wondering why Drake went to the extra trouble to use
this design. I'm sure there is a reason and, inquiring minds want to know...
Enjoy those Drakes.
73,
Evan
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