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Antennas

Bertho All Messages By This Member #99709 开云体育 On the subject of antennas: Lo-VFH pager antennas surprisingly are using the person’s body as the antenna.? The body “antenna’ couples into the pager’s internal antenna when it is when worn on the belt.? Worse performance if used in the shirt pocket. Motorola’s Pageboy 2 series use the U-shaped metal case as the antenna.? I have spent too many weeks optimizing antennas and front-end designs for the Motorola pagers.? From low band-VFH-UHF and finally the first 900MHz pager. ? I like the info on the active antennas, and I am itching to build one. I got an SDR that I played with 5-6 years ago, but I have to relearn how to use it, or maybe get an updated unit. Bertho ?
wn4isx #99713 Antennas are fascinating, some of the simplest antennas work much better than one would expect and some extremely complex antennas that should work like magic are disappointing. ? As to SDRs, they've come a long way in 3 or 4 years in terms of performance. The more bits you A>D has, the better the performance, although there are tricks such as decimation to improve performance, sort of cheating to use math in the computer CPU to create artificial additional bits. But this 'steals' performance and can be quite demanding of CPU resources. ? I've had good luck with the SDRplay series, the RSP1 was their introductory product and OK, they rapidly learned from beginner's mistakes and all their newer models are OK.? ? The Perseus (original) is an amazing receiver, it was quite pricey but worth it. I'm an analog man, prefer my heavily modified, antique, Kenwood R2000 to any SDR, but the RSPdx is an OK receiver optimized for LW/MW but still does VHF to high UHF. I use it as a panadter [telling my age there] and it works very well for that function. It is very nice to be able to see what's on either side of where you are tuned, you can ID CW, AM, LSB, USB, digital from the 'squiggles' as my wife calls them. ?
Andy All Messages By This Member #99714 Bertho, ? You probably meant "VHF", right?? Not VFH ("very frequency high"?).? But this might be a non-English language issue, if English is not your preferred language. ? It is only somewhat right that the pager uses the human body as its antenna.? The antenna system includes both what's inside the pager and the effect of its environment including the human.? You can't fully separate one from the other.? That would be like saying that a Yagi antenna consists of just the longest wire, and it happens to have a bunch of other shorter wires nearby and then there's this dipole thingamajig that is in the way, between them. ? Every antenna has that "problem" of being part of its local environment, unless you can mount it in total isolation.? Dish antennas come close. ? Andy ?
Bertho All Messages By This Member #99715 开云体育 Thanks Andy, Yes, VHF ? Of course, the internal antenna in the pager is always active but at lowband, wearing the pager on the belt, the effect is not significant.? I have lots of antenna plots of a pager by itself showing a perfect figure-8 loop antenna pattern.? The same pager on the belt turns into a round omni-directional pattern. The effect is less at VHF. At VHF, holding an arm straight up and placing the pager near that arm, greatly increases the sensitivity. The analog pagers typically triggers at -3db Sinad but requires about 5dB Sinad for the voice message. Bertho ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Andy via groups.io Sent: 10 February, 2025 9:03 To: [email protected] Subject: Re: [electronics101] Antennas ? Bertho, ? You probably meant "VHF", right?? Not VFH ("very frequency high"?).? But this might be a non-English language issue, if English is not your preferred language. ? It is only somewhat right that the pager uses the human body as its antenna.? The antenna system includes both what's inside the pager and the effect of its environment including the human.? You can't fully separate one from the other.? That would be like saying that a Yagi antenna consists of just the longest wire, and it happens to have a bunch of other shorter wires nearby and then there's this dipole thingamajig that is in the way, between them. ? Every antenna has that "problem" of being part of its local environment, unless you can mount it in total isolation.? Dish antennas come close. ? Andy ?
wn4isx #99716 Sadly while English is my birth language I still manage to mangle it with frightening regularity. I'd blame it on being born in Appalachia but that'd be unfair. The truth is I am dyslexic and can be counted on to reverse letters at random. Everyone in my junior and senior high home room knew the combination to my locker because I couldn't ever open the !@#$ thing! And I'm sure you've heard of DAM..... ? ? Mothers Against Dyslexia. ? Yes if was VHF to what I guess I should have called SHF. ? It's? a narrow mind that can only think of one way to spell a word. [My mind must be wide open.] ?

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