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Joined: Sat, Apr 4th 1998, 00:00 Roles: N/A Moderates: N/A

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Why are cellular bands blocked on receivers? Aug 3rd 2011, 15:28 10 5,570 on 25/5/12

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Longwire Antenna WB8ZTP on 8/8/11
One more thing. Once one masters the methods of a long wire antenna, they are a more agile operator since a big advantage of this antenna is its simplicity. In a major emergency, this could be the first antenna you can get up and running. Knowing how could make a difference.
Longwire Antenna WB8ZTP on 8/8/11
If you can match your longwire to a coax feed, then you can use the coax to get in through the metal walls with no impact to the impedance.

I'd recommend the ARRL Antenna Book, though it is currently out of stock until early October.
BPL is back w1rfi on 7/8/11
One thing about BPL and its brethren like HomePlug is that expanding the bandwidth gets to be very hard to do as the expectations of users keeps going up. BPL itself was doomed because of the increasing demands for higher and higher speeds. Do you think you can push UHF and SHF down those widely space electrical distribution lines? Even for in-the-home use, look at the cable type being used (NM and UF type electrical power cabling you can see at home building supply store). They made Cat5 and Cat6 cable with twists at varying pitches for a reason. The power cable in the walls is just not going to go very high reliably.

Electrical power distribution companies really need to consider putting fiber on their existing right-of-ways, and take it all the way into the customer premise. They could be very competitive in the internet market that way, rather than being left behind in the BPL dust as other companies keep moving ahead.
Organization of the ARRL.org web page menus w1rfi on 7/8/11
I'd like to see the arrl.org web site use real video (via WebM standards for managing it), instead of Flash (which is based on the web server loading software into the browser, an always unsafe idea which has been proven to be true many times by exploits in the Flash plugins over the years).
Have you done radio physics experiments? LeeM on 7/8/11
Having a big interest in wave physics, one area I've always wanted to set up some "observability" experiments is how antennas establish their directionality. And it's more than just knowing that in some directions, the signal cancels out while in other directions it adds, because that alone does not explain the whole effect.

A single radiator (fed with say 100W) will give a specific field strength at some distance. If you split that 100W into two radiators so each is now at 50W, some people might think that in the direction where the phasing adds together, you'd just have the original field strength. If that's all that ever happened, antennas would not have gain. But in fact at that point in the far field, the strength is now doubled even though the total power radiated remains the same.

That should be a relatively simple experiment to set up to show the real effect. How to illustrate why this happens would be a lot harder (the only "illustration" I've ever seen is mathematics).

BTW, I've seen a few different variations on this, addressing different wave effects. In physics they are called "the two slit experiment" where it is argued that individual particles not just can, but always will, behave like waves. I personally believe waves are the foundation of all existence. Related effects of interest include X-ray crystallography (scale it way up and you can do the same thing at radio frequency) and diffraction (scale that way up and you can consider knife edge effects of hills on radio propagation). Fun stuff, these waves.

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