See the latest QST! CW and SSB 5 watt rig for $50!
73,
Gary - AB9M
----- Original Message -----
From: "Ken Brown" <ken.d.brown@hawaiiantel.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, April 19, 2008 3:44 PM
Subject: [TenTec] Cheap SSB and not CW rig
> 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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