To: Jamie Danter, KF4VOP and the group.
Changing from analog display to digital display is an excellent idea. But
before you do it, I suggest you change your C21 from having a single RIT pot
to having two. I call the mod, "Dual RIT". The advantage of Dual RIT is
that by putting one RIT above and one below the transmit frequency on a DC
receiver, you can dodge audio image qrm at the flip of a switch.
If you plan things correctly, you can make your Dual RIT without making any
new holes in the front panel. Only then should you add the digital display
and a toggle switch to choose whether the counter counts up or down and with
what offset.
I am travelling at the until June 17th, but I will send scan my Dual RIT
schematic for you once I am back in the office.
In the meantime, here is a description of the new controls:
Delete the spot button. Delete the tune button.
Remove the RIT pot. Break apart the RIT pot and save the brass shaft
bushing, washers, and nuts. Obtain a 5 or 6 position dual switch with a 1/4
inch shaft. Mount the post from a bracket behind the subpanel. Run the
shaft through the recycled bushing. This bushing is again used to support
the front panel as it did when it contained the shaft of the RIT pot.
5 of the 5 or 6 positions of this switch are used for the following:
(1) Left RIT and 2.5kHz selectivity,
(2) Left RIT and selectivity as chosen by the 3-position selectivity switch
in the lower right corner of the front panel,
(3) Center position: No RIT and 2.5kHz selectivity,
(4) Right RIT and selectivity as chosed by the 3-position selectivity switch
in the lower right corner of the front panel, and
(5) Right RIT and 2.5kHz selectivity.
Each new Dual Rit pot (called left and right) should be 5k with linear
taper. Mount each on the front subpanel using homemade one- inch by one
inch square washers. Their shafts appear through the front panel using the
holes vacated by the original Spot and Tune switches.
In actual operation, use positions 2, 3, and 4 of the switch to dodge the
audio image qrm and to zero beat the other station. Use positions 1 and 5
for tuning quickly and for compatibility with SSB stations.
This particular modification is quite simple to do as you will see when I
send my scanned schematic directly to you. But again, to keep the front
panel of the C21 clean and symmetrical, you should do the Dual RIT mod
before the digital readout mod.
73, Tom Hamblin, sine HN
VA3HN, VE3TMH, VE3HIE
The original message was
Message: 12
From: "jdanter" <jdanter@mail.i-america.net>
To: "TenTec List" <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Sat, 8 Jun 2002 14:24:19 -0400
Subject: [TenTec] Q-Century 21 mods
I would appreciate info on mods for the Century 21 analog.
I would like to add a digital readout.
Product recommendations?
I would like to change the sidetone from the factory 'buzzer',
to a more pleasing audio.
Thanks,
KF4VOP
Jamie Danter
Troutman NC
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