16-02-2016, 04:21 PM
(This post was last modified: 16-02-2016, 04:25 PM by Murphyv310.
Edit Reason: Added an extra line.
)
Hi.
My recent repair of the loop has driven me on to play about with the 1 metre loop I have.
These do perform very well but being tunable I thought it could be utilised for a crystal set.
Tapping off from the seven turns works but in usual crystal set fashion its far from selective with two or more stations fighting for first place.
Using the single turn just and no more resolves West Sound as there is insufficient drive for detection.
Adding a 7:1 RF transformer made from 22swg copper wire on a toroid ring with the smaller winding connected to the single turn on the frame and the "secondary" of the ring fed to an OA91, filter cap and phones produces excellent results, quite simply the best Crystal set I have heard. Considering my normal use of hearing Aids I can happily listen to four stations with at least two being just audible and that's less my hearing aids!
EDIT. If using crystal earpieces a resistor should be connected in parallel so there is a DC path for the diode. I usually find a 220K is sufficient, trial and error can often improve performance.
Cheers.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.