Re: An IF in search of a radio
|
We introduced the first SDR based Telemetry system as well. Our analog designs had bandwidths down to 1 KHz, without crystal filters. Have fun, but between my work with Telemetry and Microwave TV relays, I take group delay quite seriously. I also dealt with it in designing Cable TV return systems.
I do have one question. How will you prevent the IF signal from modulating the tuning voltage on your Varicaps?
On Sat, May 13, 2023 at 8:31?PM Reginald Beardsley via <pulaskite= [email protected]> wrote: I'm a little confused. How is this related to implementing very narrow filters by using isolated sequential, partially overlapping filters? The Icom 705 will give single signal reception with stronger stations within 50 Hz. That blew my mind and I've been doing this stuff a very long time.
In modern professional work you use DSP, but for portable ham use, analog is much better if power is a concern.
Digital filters are my forte. I just need to know what you want done. Analog is a bit more ambiguous.
Have Fun!
Reg
I worked with high end Telemetry receivers at the factory. All tuned circuits were Lc or RC. The only crystals were for LO or system clock applications. The LC were aligned on HP Network analyzers. RC filters were Sallen-KKey, used to shape the baseband output. For testing these, I used a HP3325A and a Fluke 8921 True RMS Voltmeter that worked out to 20 Mhz. I could measure the -3dB point with ease, and quickly to test each of 16 computer selected filters
Telemetry needs very low phase delay, especially on very weak signals. We used a 70 MHz IF? which could be recorded to instrumentation recorders to allow recovery of multiple channels of frequency multiplexed data.
|
Michael A. Terrell