Yeah, a "panadapter" is almost as good as turning the tuning dial <G>. The panadapter lets one scan the band faster with a nice visual display, but it may not show you all the signals.
There's a *huge* performance tradeoff involved in trying to "see" the a wide frequency range on a 'scope and trying to hear *one* weak signal. In receivers with a front end that is "broad as a barn" (including the first I.F. in modern receivers), the panadapter can show you many signals within that passband, but not all the signals. As others have pointed out all of those signals coming through for display compromise the dynamic range. They can't be filtered out or they won't show up on the panadapter. The strongest among them defines the response to all the signals, no matter how weak. If there's a really strong signal in the passband it'll either overload the receiver, creating hash and spurs in the passband or the gain has to be reduced, making weak signals even weaker. An ideal receiver would filter out everything but the signal of interest at the antenna terminal! Nothing would enter the first stage except that one signal we want to hear. We'd do that on all receivers except no one has yet devised a suitable tunable filter. That's why we have "superheterodyne" receivers. They convert a tunable range of signals to a single intermediate frequency (I.F.) where we can have a very effective fixed-frequency filter that stops all but the desired signal. The K3 offers a selection *narrow* roofing filters designed to provide the minimum practicable bandwidth needed for various modes from a few hundred Hz for CW to several KHz for ESSB or AM, etc. Many receivers on the market today don't use such a filter. They have a very broad first I.F. (roofing) filter that allows the desired signal and many signals around it through. They are, frankly, a compromise design that the K3 avoids. It's a compromise that one can usually get away with unless conditions are tough (e.g. a contest or DX pileup). But isn't than when you want the best performance? So it's not practicable to pass a swath that incorporates most of a Ham band, or even a CW or phone sub-band without seriously endangering the receiver performance under the toughest conditions. And if you don't pass a swath of frequencies through the first I.F. you can't show them on a "bandscope" or "panadapter". I think my interest in such a device would be to have it running on its own receiver, not the one I'm trying to use to hear weak signals in a pileup. Whether or not it's worth doing that is debatable except to show general band activity or the presence of a group of quite strong signals. It may not show some signals thanks to its performance being limited by the strongest signal in the passband, but I'm sure it's a very useful tool if, like any tool, one understands its limitations. Ron AC7AC -----Original Message----- Jack Smith <[EMAIL PROTECTED]> wrote: > First, I have a definite bias to stand-alone equipment that works > without a computer. I'll second that! >.On HF, a panadapter can show you a pile up quickly, or in general give >you a good idea where the activity is at any given instant. In a pile up situation I have found it very useful to be able to turn on a line marker which shows where my transmitter frequency is positioned with respect to the other callers, before transmitting, and using a span which covers the DX station's frequency and his listening frequencies. If the DX is working SSB 'wide split' e.g. transmitting on 7205 kHz and listening 7060 kHz, I would monitor 7060 kHz +- with the panadapter (and audio) while listening to the DX's audio on 7205 kHz. > For these uses, in my view, a panadapter requires a span of at least > 100 KHz, and preferably more. The Z90 has a maximum default span of > 200 KHz, and maximum user-defined span of 250 KHz. In retrospect, I > wish that I had made it 500 KHz, with perhaps 3 KHz resolution > bandwidth, as it would provide a greater overview of most of an HF > band (excluding 10 meters, of course). With respect my personal view is that a span of 200 - 250 kHz is ample for routine monitoring purposes at HF and VHF. For greater spans the receiver can be put into SCAN mode while using the panadapter as long as the receiver's scan rate is not too high. My K2 scans too rapidly for my purposes at VHF. 73, Geoff GM4ESD _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
