Re: questions about fundamentals
- --- In email@example.com, Jack Smith <Jack.Smith@...> wrote:
>Yeah ok, I'm only interested in a fancy "IF strip" where my IF freq is
> > Thanks Jack for the rundown...
> > I'm scratching my head a bit here... but at 455kHz. it doesn't seem on
> > the surface that all that much is required to buffer the signal going
> > into the SRL??
> Depends. It's a lot easier to do it at 455 KHz than 73 MHz, and the
> Z10000 is designed to work between 50 KHz and 100 MHz.
either 455kHz. or 500kHz.
> > Is 70db really that good a figure?Right, but I'm only at 455kHz or so...
> I think so, but I stand to be corrected. More recent measurements show
> it's closer to 90 dB.
> > Would not a fairly standard opamp or buffer that has the requisite
> > bandwidth do as good a job, or nearly as good a job?
> At 455 KHz probably. Not at 73 MHz.
> > How about just a FET run as a follower - no feedback connection backAre we driving something with a very low input impedance in the SRL?
> > to the input? That any good?
> FET source followers have issues with output impedance for most small
> JFETs. A bipolar transistor is a better choice from this prospective.
I don't know. I suppose if it is 50 ohms then yeah, a single FET will
probably not cut the mustard.
> > A simple resistive divider, or capacitive divider won't drop urgain 6dB.?
> A capacitive or resistive divider provides no isolation to speak of.
> might be OK with a -40 dBm leakage signal being fed backwards into yourthe
> receiver's IF, but I'm not. It's a matter of what precautions one wants
> to take to prevent degradation of receiver performance. I don't like
> thought of strong signals hanging around just outside the IF filterI meant after a buffer...
> bandpass. In many cases, it will be OK, but in other cases, I strongly
> suspect it is not going to be OK.
I was wondering about the need for a special buffer that can do
negative gains... that was my context. Sorry I wasn't clear on this point.
>Well fine Jack! :_)
> > Honestly, I don't know the answers, so I ask the questions.
> > _-_-WBear2GCR
> I have 50 Z10000 buffer amplifiers in the hands of owners for about a
> year and half now and so far all owners are happy with the results.
> Jack K8ZOA
No doubt they work ok!
But I guess it depends on your application, as to the need and/or
As I said at the top, I'm trying to take the express lane to figure
out how to use these things - once I get one. ;_)