A simple cardboard box provides the frame for a BOX LOOP

Subject:      Re: Select Antenna
From:         hugo@infobahnos.com (H. Caron)
Date:         1997/02/08
Message-ID:   <32fcc2b5.0@news.total.net>
Newsgroups:   rec.radio.shortwave

<edited>

I first heard of this subject when I joined this group last year. I'm not 'realy' in AM DX but thought it would be fun to experiment (just like cristal radio :) ) When someone suggested a desing of an 18" wooden frame loop I though I give it a try. I decided to use what I had on hand. A stiff cardbox box ~ 24H x 18W x 18D, some lenght of thin transfo wire AWG24?, wound 15 turns (~2" wide) around the box perimeter, and used a recycle 365 var. cap. My receiver is a portable
RS380/ATS808.

The nice thing about this setting is, when sit on its 18x18 side, the box makes a very light stiff enough 24" high sort of table on which I can put the rcver on and turn the whole thing very easely and comfortably for orientation. When I'm finished whith 'experimenting' I just remove the caps off and store the box in the closet, until next time.

I also did find that that relative position of the rcver ferrite loop to the 'box' loop is of importance for maximum coupling (energy transfer). Altough just bringing the receiver close to the loop will enhance target signal strenght, its maximum is obtained when its ferrite loop axis is 90 deg relative to the box loop plane, hence both
loop windings are parallel //. If I'd put the rcver inside the box insted than on top of it then I agree it will be concentric for maximal transfer (at least according to theory). I will give it a try, (the setup permits!). Who knows, I may end up with boom-box-loop :).

For the moment the receiver being on top, I remark that I get the stongest signal when the receiver is positionned so that its ferrite loop sits (90 deg). right on top of the loop winding. Moving it away sideway or higher, even few inches, reduces it quite drasticaly, although still stronger than without the loop at all.

For those who may want an idea of what kind of performance enhancement that kind of loop may give, here's a little test I've done that can be indicative.

I'm located on the north part of Montreal, Quebec. About 100 mile east is CHLN 550 (50KW?) in Trois-Rivières and about the same distance west is 1310 in Ottawa. Now, when the receiver on itself is properly oriented, in daytime, those signals are clean but rather week 0-1 on the signal strenght indicator (max=7) of the rcver with its AM sensitivity sw set to DX. When set to LOCAL, I dont hear nothing.

Using the loop those stations come in as if they were local with ss of 6 to 7. (4-5 when set on LOCAL). Mind you that ain't DX but still gives an idea. I know I have heard Washingtong DC stations or others (ST-Louis?) that the receiver wasen't even aware were there, without the loop. But as mentionned before, not realy being in AM-DXing I mounted this set-up just out of curiosity.

But there is a station I'd like to log. CFDA 1380 10KW(?) in Victoriaville (spent part of my yought there, first date, first... well you know). Its relative location from my present site is ~120 deg E (~40 miles S of Trois-Rivières (where I was born), at about 110 miles from my QTH. It's almost flatland in between except for two
bumps, Mont-Royal on Montreal Island at about 1000' (but I'm relatively close to it) and Mont St-Hilaire ~2500' 50 miles away both being almost straith on path line. I think the station goes off after midnight. There's a Maine (relativaly in the same direction but further away) italian station on the same frequency. I think I heard a very faint "Le Réseau des Appalaches" by which CFDA identifies itself on a sunday afternoon last october, with the above setup. But that was all.

15 years ago, when I was in Charlesbourg, just north of Québec City about 80 miles N-E of Vict. and no bumps in between, I could hear it sometimes on a Sony ICF2001 i had, but didn't know then about this loop :(

Any trick of the trade someone could suggest? Could Kiwa loop acheived it? Any other loop? (just curious!)

Thanks in any case and have fun,

H.C.

WHAMLOG Inductive Loops