Is there any validity to the notion that deleting CW functionality from
a rig could make it cheaper?
Let's see, what additional parts are needed to make a SSB capable rig
operate in CW mode?
For receiving:
Any rig with a BFO and product detector can receive CW. Sure it would be
nicer to have some narrower filter options available, and perhaps a
faster AGC than when using SSB. The filters could be add on options, but
let's include the cost of the PCB space and connectors, and switching
diodes necessary to accomodate a narrower filter....No on second
thought, lets not include that, because an optional narrow filter could
just as easily be used for a narrow SSB filter, so this is not a CW
specific additional cost to the rig. And you don't need that filter for
basic CW functionality. How about the cost of a switch and a capacitor
and resistor for the other AGC speed? Lets say $2.
For transmitting:
There are two really simple ways of making an SSB transmitter send a CW
signal. One is to have an audio tone generator feed the balanced
modulator, and the other is to apply a DC bias to the balanced
modulator, unbalancing it and letting carrier through. The second method
is probably preferable, requiring fewer parts. The purity of the tone
from a tone generator would be very important and might require
adjustments or selected value parts in order to work right. So, if we go
with the unbalanced balanced modulator method, we need a switch and a
few resistors to get the proper DC bias to unbalance to modulator. We
could either bypass the sideband selecting filter, or use a different
BFO/carrier crystal to get the CW carrier well into the filter bandpass.
So we need a crystal, a couple of resistors, a few diodes for crystal
switching and a switch of some sort to apply the DC offset to the
balanced modulator. This might all add up to $8 if the crystal cost is
$5. We'll use the PTT line on the microphone connector for the key
input, so we don't need to include the cost of one phone or phono jack.
So our total is $10. This is for basic CW operation, since we were
talking about a cheap rig, that seems appropriate. In order to have fast
QSK operation and a few other nice features for CW, we might need a bit
more careful engineering, with not many more parts.
I'm not sure what price range this discussion was centering on for the
cheap rig, was it $200 or $500? Lets go with $200. Now suppose you have
two rigs to choose from, a SSB only rig for $200 and a SSB/CW rig for
$210. Will the $210 SSB/CW rig collect dust on warehouse shelves, while
the $200 SSB only rig sells like hotcakes?
DE N6KB
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