Mag loop aerial for the Den

[Radio Fixer]

Thanks Sam and Lawrence for the PW link. I did wonder if the 2 transistor cct we have been using could be tweaked such as using a current source tail and balancing but Hey! for me it works fines as it is so why complicate it.

Love all the old Ads in those mags.

Gary

[boater sam]

Came across the article by pure chance, nothing else to read out here. There are years worth of browsing on the site.
Wish we could buy some of the stuff advertised these days, and at those prices. If only we had known........

Is it ferrite, or is it iron loaded clay like coil slugs? Ferrite is a ceramic, fired at high temperature, it could be molded in any shape but how then do you get it into the loop? Is it a mystery or  Ad Hype?

[pwdrive]

As yet I've not read a full description about the ferrite in the loop (Wellbrook) that's been mentioned, maybe a more precise description or a photo would shed some light on it.

Lawrence.

[Murphyv310]

As yet I've not read a full description about the ferrite in the loop (Wellbrook) that's been mentioned, maybe a more precise description or a photo would shed some light on it.

Lawrence.

Mine is rebuilt so difficult to photograph. I may have an old picture on the PC of the ends. I'll look later on.

[Murphyv310]

The preamp in PW is intended for a frame aerial taken from the high impedance resonant section at the tuning capacitor connections. There is a very strong signal at this point on locals. Not sure how well it would work.
I'm going to make it up and try it on a single turn loop.

[pwdrive]

I know very little about antennas and propagation so these may be daft questions.

What is so special about these loop antennas that gives them such good performance? How important is the amplifier? Is it dependent on modern transistors or could you design a valve circuit that interfaced well with such an antenna?

Here's an old film about the ionosphere and propagation Jeffrey, for those new to it and oldies that have forgotten (including me):

https://archive.org/details/effectsofthe...ropagation

And another one, there are at least two parts to this film, links to the others will be seen on the Utube page:

https://www.youtube.com/watch?v=7bDyA5t1ldU

Hope this is of some use.

Lawrence.

[Radio Fixer]

Morning all

Trevor you said:
"The losses though on the coax will be down to the bifilar winding on the output toroid which I reckon could be around 150 ohms, I was going to reduce the secondary turns by 50% on mine to see what effect it has. A job for later in the year though."

Did you find this other link and see how this chap has reduced the bifilar turns to 10 rather than 15?

http://www.qsl.net/m0ayf/active-loop-rec...diagram_is

Gary

[Terry]

I don't see the point there, Gary.

He has reduced the number of turns from 15 to 10 but on both windings, so the turns ratio is still 1:1.

I assumed Trevor intended to reduce the number of turns on the secondary only, so that it becomes a step down transformer to get a better match to the coax feed.

[Radio Fixer]

Good point Terry.

Might need a bit of experimentation to see if any benefit. Wonder why he reduced the turns though?

Gary

[Radio Fixer]

For the application why was bifilar winding chosen? Thinking of making my next model just have say a 15 turn primary and a 15 turn secondary with a tap half way and use two coax output sockets. Then I could easily see which matches the long garden coax the best.

Thanks for ideas Gary