Ultimate rejetiton more than lOOdb signals, especially the guy down the street with the big linear. In this respect, the Swan filter is superior to others being used in amateur sideband gear.
In Swan transceivers, the filter is also used when transmitting, of course, and in this mode the shape factor determines what your unwanted sideband suppression will be. We have been advertising 40 db, but this is a conservative figure, since it is really better than 50 db. Also, we've been advertising only 400 watts [:>EP input to the 350. but actually the average production unit peaks over 500 watts before flat-topping, which is why the 350 gets out so well, and sounds so good. Compare these features with any other sideband transceiver, and they all sell for more money' 73 Herb johnson W6QKI
One of the reasons why the Swan-350 is the top selling transceiver today is its exceptional selectivity provided by a new crystal filter which we began installing in all production units a few months ago. This amazing little gem is made exclusively for Swan bv C-F Networks, The selectivity it provides for voice communication is as good or better than the selectivity provided in any other sideband equipment, regardless of price.
There are 3 important factors about a filter which determine what the overall selectivity will be. One of these is its bandwidth at the 6 db points, and here we have carefully selected 2.7 KC in order to give you good channel separation. and still retain the smooth, natural audio for which Swan transceivers are so well known,
The next consideration is shape factor, or the ratio between bandwidths at 6 and 60 db. In this respect the Swan filter eives you a "shape factor1' of 1,7 to I. This is substantially better th;in the 2 to I ratio of the mechanical filter, or 3 to 1 of the average 9 rnc crystal filter. Best shape factors are achieved right around 5 mc, and this is one of the main reasons for selecting 5175 KC for the Swan I.R (This choice of I,F. also permits single conversion design which results in fewer images and spurious signnls. The only thing better than single conversion is no conversion at all.)
The third important factor, but by no means the least, is the measure of utthiwte rejection, or how far the skirts fall before flaring out. Take a look at the graph and you'll see that this is better than lOOdb with the Swan filter! Ultimate rejection determines how well your receiver attenuates those strong adjacent channel
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