Up conversion design

[Georges Ringotte F6DFZ]

Hi to the group

Even though I own and appreciate very much my K3, in fact I believe it's the best sounding receiver I ever had, I have always been an advocate of up conversion design, namely because it's the only way to get general coverage and also because some characteristics, for a given cost, are better with an up conversion design (IF and image rejections for example). The probability is low, but if in the future a WARC give a new band very near the IF of a down conversion design, it will not be able to cover it.

Due to the Sherwood chart, and the way receivers are classed, there is a trend for manufacturers to propose down conversion design, even though some characteristics may be poor ; I think of the Yaesu FT5000 for example, very high in the Rob Sherwood chart, but with poor image rejection, and extremely poor IMD2 figure for the second receiver.

I always thought the key to success was an up conversion design with very good gain distribution, like RS XK2100 transceiver for example.
Ten Tec tried this with the Omni 7, but with limited success.

Now the 1st transceiver on Rob's chart is an up conversion design, with a VHF roofing filter 50 kHz wide, proof of the validity of optimized gain distribution ; it has 105 dB dynamic range with signals separated by only 1 kHz.

Perhaps, after the current trend to develop down conversion receivers (Elecraft's rigs, Eagle, FT3K, TS-590) it will revert trend and we will see up conversion design with large dynamic range for closed spaced signals.

Yes this german made transceiver, built like a measuring instrument, is very expensive, but surely it's concept can  be used to market simpler rigs (100W, 13,8V, only one receiver, no VHF, not so luxurious...) for a more correct price.

Any comments?

Best regards.




Georges F6DFZ
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