Re: Topband: small rx loops and ferrite
Looking at the front cover brings to mind this web page. Yep, their ferrite rods are very expensive! http://www.stormwise.com/ 73, Mike WA5POK -Original Message- From: Mike Waters Sent: Tuesday, July 03, 2012 6:24 PM To: topband Subject: Re: Topband: small rx loops and ferrite Speaking of ferrite RX loops... I picked up the July 2012 issue of Popular Communications from the local grocery store's magazine rack, just to see what the unusual antenna on the front cover was all about. It's called a "ferrite sleeve loop", and is made from a bunch of ferrite rods arranged into a cylinder with many turns of wire --connected to a variable capacitor-- wrapped around the center of it. You hold your little portable AM radio next to it to pick up signals from Uranus, supposedly. ;-) A photo is at http://www.popular-communications.com/pc_current_issue.html(for now). And a video of this thingy is at bit.ly/Ifhpiy . Anybody ever see anything like this? What's the advantage (if any)? And can you imagine what all those ferrite rods cost?! 73, Mike www.w0btu.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: small rx loops and ferrite
Speaking of ferrite RX loops... I picked up the July 2012 issue of Popular Communications from the local grocery store's magazine rack, just to see what the unusual antenna on the front cover was all about. It's called a "ferrite sleeve loop", and is made from a bunch of ferrite rods arranged into a cylinder with many turns of wire --connected to a variable capacitor-- wrapped around the center of it. You hold your little portable AM radio next to it to pick up signals from Uranus, supposedly. ;-) A photo is at http://www.popular-communications.com/pc_current_issue.html(for now). And a video of this thingy is at bit.ly/Ifhpiy . Anybody ever see anything like this? What's the advantage (if any)? And can you imagine what all those ferrite rods cost?! 73, Mike www.w0btu.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: small rx loops and ferrite
Sam Morgan wrote: > Since the topic of ferrite seems to be at the top of the lists focus > I'd like to ask about what ferrite mix to use at the feed of a small rx > loop I > have built > You might want to look at the feed technique described here: http://www.n6rk.com/loopantennas/NCJ_loop_antenna_N6RK.pdf Although this article talks about a shielded loop, it will work equally well on your unshielded loop. The article recommends Fair-Rite 67 material because it is very low loss at 160 meters. This gives maximum antenna sensitivity. If you want to broadband a loop, the thing to do is to reduce the turns ratio on the transformer so that you reduce the *loaded* Q. This will result in better sensitivity than simply adding loss to the system (ie reducing the *unloaded Q*) by using a lossy ferrite core like 31. That sort of "broadbanding" reduces sensitivity at all frequencies, but reduces it more at the center. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
