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Medium Wave (MW) AM broadcast band loop antenna. Built using cheap 4 pair (8 wire) telephone 'ribbon' cable,& (optionally) housed in cheap garden 13mm...
The compact version allows easy storage -suitable portable & traveling needs. 3 metres (~10 feet) of cheap 8 wire cable will resonate nicely over most...
The idea with such a loop relates to tuning the simple coil (L) capacitor (C) parallel combo so that the pair "resonate" at a frequency in the band of...
There's nothing new about loop antennas, as they dominated receivers for ~50 years until the 1960s transistor radio ferrite rod takeover-itself still ...
Rather than tediously winding multiple strands of wire around a frame,the approach here is to simply connect the cables offset wire ends,thus making a...
In fact,with the same 60-160pF varicap,6m of 4 wire flat phone cable gave LC resonance in the mid-upper MW band almost as well as 3m of 8 wire cable. ...
If you can't locate the preferred flat 8 wire cable, then perhaps hot melt glue 2 x 4 wire "silver satin" grade phone cables together side by side! Wi...
If your soldering is not up to it, then these wire ends can even be joined by cheap screw terminal connectors. Naturally this will also give design ve...
Trimmed with a scapel these terminals will also just fit (perhaps end to end) inside the 13mm plastic pipe.
A serial D9 pair could also be used, but these are tricky to solder & more costly.
Just basic household tools will do - the compact version can be mounted on a short piece of trellis offcut.
Cut off 3 metres of cable & remove about 4 finger widths of the outer insulation.
Avoid nicking (& thus weakening) the 8 inner wires- carefully bend back the outer insulation as you cut.
A scapel will often do this most cleanly- side cutters are usually too savage.
If soldering the pairs then "stagger" the joins by about 10mm to avoid shorting.
Use both fine pliers & sidecutters to reveal the copper wire.
An electronic "3rd hand" or "Helping Hand" will greatly assist in holding the wires steady during soldering.
After soldering (or connector joining), use a DMM on resistance to check the wires are not shorted or broken. About 5 Ohms resistance is normal (subtr...
Rather than forcefully pushing the wires into the protective irrigation hose, it's probably easier to slit a short length with scissors. The hose sadd...
Hot melt glue can be used to keep any wire joins well apart- don't use too much insulating glue here or later resoldering may be difficult!
Further hot melt glue can be used at the tube ends to secure the cable.
Only low value (typically 60-160 pF)"polyvaricons" (plastic insulated variable tuning capacitors) are now usually available. Mounting for these can ne...
Punch a hole through the thin aluminium, trim with scissors & fold the wings to suit the mount. Even use 2 such brackets if the first seems too flimsy...
Voila-it looks quite professional. Discard the 2 side screws,as if screwed down too far these will usually hit the plates inside the varicap & stop t...
IMPORTANT: Before fastening the capacitor to the mount, adjust the 2 small trimmers to a minimum (thus NOT overlapping)- this determines the upper fre...
Finished. The portable design easily folds up for storage or travel.
Clothes pegs fastened to a curtain make for a neat holding system. The loop doesn't need to be perfectly formed either, although it's directional pick...
Spot the antenna. Here the variable capacitor is up on the bookshelf, with the radio simply placed near the loop on the lower table. Simply move the r...
As most doors are about 2m high by 800mm wide, consider even simply fastening (Blu-Tack ? Velcro?)the antenna to the door itself! Even the lengthy 4 w...
Simply tune the variable capacitor for maximum band signal- it can be quite sharp (thus a high "Q" factor). Signal enhancement on some stations is so ...
Quite aside from now hearing NUMEROUS remote AM stations,some at night 1000s of km away,a sunset test with a cheap semi-digital radio found a weak NDB...
YouTube demo of a weak 1630kHz NDB (Non Directional Beacon)signal being received with a (curtain pegged!) portable loop & a cheap semi-digital rece...
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