07-12-2011, 10:00 PM
Lawrence: my comment earlier about what I see as so many Radio Amateurs not having an understanding of the basics of the hobby was not directed at Amateurs and SWLs like yourself. By virtue of the comments in your last post, your obviously do have such an understanding: I hope you did not take offence at my post: it was not intended, nor aimed at you or enthusiasts with your level of comprehension.
Here are some examples of what I have actually heard - to illustrate my previously mentioned point:
1. "If I double the voltage on that resistor, it'll get twice as hot."
► No: P = V²/R: it'll get four times as hot.
2. "I'm not getting out very well: I need to "swarr in" my antenna." ("swarr" as in 'S.W.R'.)
3. "I'm using a half-wave dipole. But when I measure the resistance across the coax at my rig, I don't get 75 ohms. That's why I'm not 'getting out' ".
► Antennas and matching probably rank as the most misunderstood sub-topic of all aspects of communications amongst this group.
4. "Well, I've been calling CQ DX through the 2m. repeater for ages"
► If you really want a DX contact, you don't do it via a repeater! That is a self-defeating exercise! (Not to mention pointless!)
5. "A half-wave dipole is only resonant at one frequency, yes?"
► No: it will be resonant at (2n + 1).f, where n takes all integers from 0 to infinity, and f is the lowest frequency it is resonant at - the fundamental.
So a dipole cut for 7 MHz is resonant on its 3rd. harmonic (21 MHz) and its 5th. (35 MHz) ~ and so on.
I could go on - but that'll do. Enjoy the hobby; you're in good company here.
Al.
Here are some examples of what I have actually heard - to illustrate my previously mentioned point:
1. "If I double the voltage on that resistor, it'll get twice as hot."
► No: P = V²/R: it'll get four times as hot.
2. "I'm not getting out very well: I need to "swarr in" my antenna." ("swarr" as in 'S.W.R'.)
3. "I'm using a half-wave dipole. But when I measure the resistance across the coax at my rig, I don't get 75 ohms. That's why I'm not 'getting out' ".
► Antennas and matching probably rank as the most misunderstood sub-topic of all aspects of communications amongst this group.
4. "Well, I've been calling CQ DX through the 2m. repeater for ages"
► If you really want a DX contact, you don't do it via a repeater! That is a self-defeating exercise! (Not to mention pointless!)
5. "A half-wave dipole is only resonant at one frequency, yes?"
► No: it will be resonant at (2n + 1).f, where n takes all integers from 0 to infinity, and f is the lowest frequency it is resonant at - the fundamental.
So a dipole cut for 7 MHz is resonant on its 3rd. harmonic (21 MHz) and its 5th. (35 MHz) ~ and so on.
I could go on - but that'll do. Enjoy the hobby; you're in good company here.
Al.
