Re: [softrock40] Re: RXTXv6.1, production RXTX kit schematic / board now posted
- At 03:25 AM 12/30/2006, you wrote:
But that "filter" is going to allow a lot of stuff into the very nonlinear switch, in this case anything from 3.5 to 7.3 MHz, which will include the high power shortwave broadcast band from roughly 5.5 to 6.3 MHz. I cannot believe that will not cause problems, intermod, desens, etc.
Quite right Bill-a fact that disturbs me, but that others find this issue NOT to be a problem::>
As a weak signal enthusiast, I have a tremendous problem with tuning down to the noise level and spending a long time listening for a weak signal that isn't even on the band where you THINK you are listening::>
For my lowfer softrock, I have the front end set to admit only the lowfer band (from 160 to 190 KHz) with the filter attenuating 3 db at 160 and 190 Khz. My filter needs 5 toroids and does not fit on the softrock board, so I have the front end filter mounted on a small breadboard to accommodate the litz wire wound oversized toroids.
It's large, bulky and heavy, but I feel the bullet proof front end is a necessity, especially since the softrock does not hetrodyne the adjacent band signals out of existence as a typical superhet does.
With the QSD's response to odd harmonic signals, a sharply tuned front end seems like a necessity to me. Your mileage may vary.
PS:I'm not so sure I'd call the switch a non linear element. Although it is an active device, it is far more linear than the best diode detector you could ever hope to build::>