G'say Jerry,
First of all let me try to clarify my mention of a random wire. I see from re reading my earlier post that one could fairly assume that I was promoting same. What was really back of my mind was the diversity of antenna that can be matched using an ATU rather than a good choice of antenna.
An ATU, for those unfamiliar with these things, is a device that at its simplest, requires no battery or power supply, it is merely a box with a few coils and a variable capacitor, an 'in' socket and an 'out' socket; it is used to present a 'good look' for a receiver/transmitter and at the same time a 'good look' for an antenna.( a master of negotiation
)
I guess I should say at this point that I personally have about as much or less interest in Radio Astronomy as I do in knitting a jumper out of spaghetti, so if my lack of enthusiasm shows through, please don't be discouraged from trying anyway.
Jerry, I think we are looking at this from different perspectives.
To me, when someone says they are dealing with a 12db s/n ratio, I have a mental picture of a very weak carrier wave burried under a pile of QRN/QRM.
I think of front to back and side lobe rejection and capture area, forward gain. I think of being able to switch in a narrow band pass filter etc;
not a dipole.
But with static, and lets remember Radio Astronomy listens to static, not ET phoning home (sorry Seti
). Any simple low gain antenna will be like looking at the sky through a piece of ground glass. You can see that there is light if the sun or moon is up, but have little idea of direction or anything else about that light.
It is all very well to talk about VSWR, but without a transmitter and a bridge I'd think the concept purely accademic.
To get the optimum match with an antenna, say on the 15M band using a receiver only, we could tune to a moderate to weak nearby station and tweak the matching section till we get max signal strength, and as long as there is little or no fading we might achieve reasonably good results.
I question the practicality of this method when listening to static, and even by tuning to a nearby carrier signal, because one will still be plagued with QSB.(fade)
That is why I think an ATU would be the way to go, because without leaving the receiver, one could quickly (measured in mere seconds) tweak for loadest noise or highest S meter readings without much risk of confusion caused by the variability of the ionoshere.(fade)
If we were matching to an antenna usung a transmitter and VSWR, we could easily see it we were moving toward or away from match.
Count the equipment cost to do the same thing for a (receiver only) antenna set up. How does that compare to the cost of a basic ATU?
BTW a "match box" used for CB might only be $50 or so from Dicksmith etc.
But not as good as the $189 job......you only get what you pay for.
cheers,
Doug