2
Figure 1
Improved CW Operation:
In the CW mode the rig’s relays are energized by the CW sidetone amplifier's sidetone
output driving the vox relay amplifier. The audio (sidetone) drive to the vox amp is a bit
on the low side for fast relay action, and at speeds approaching 20 wpm the first dot sent
is heard in the sidetone but isn’t transmitted due to the slow relay response time.
Correcting this is a very simple modification – simply replace the 470KΩ resistor R328
on the audio board with a 1KΩ resistor (Figure 2). This increases the drive to the vox
amp enough to cause the relays to pull in quicker. Now the rig will key reliably at 20
wpm. The first dot tends to become shortened at 25 wpm but the rig is useable at this
speed.
Another annoying problem with these rigs is the fact the sidetone can be heard when the
rig is in the CW mode without the key actually being pressed. Although the sidetone
amplifier is in deep cutoff, there is enough coupling through the inter-electrode
capacitance of the tube to allow the output of the sidetone oscillator to be heard at a
constant low level even when the key isn’t being pressed. Fortunately this is also fairly
easy to correct:
To Next Page
Loading...
Need help?
General
