20-02-2016, 03:28 PM
Hi Guys.
Peter, I wonder how the modified Wellbrook loop compares to your 1 year old genuine Wellbrook? I also wonder what difference a 1 meter loop made from the same diameter alloy tubing as the Wellbrook would compare with their Ferrite/Alloy construction.
Wellbrook themselves can supply a replacement amplifier but it connects just like the mod I've done with the two transistor amp. I just wonder if the Ferrite/Alloy is the real answer.
I'm going to my local engineering shop in the two or three weeks and will ask them to make up a 1.5 meter loop made of alloy tube to try a slightly bigger loop.
This brings me to Gary's post. If you look at the calcs the cross sectional area of the "wire, tubing etc" makes a difference to the signal level so I personally wouldn't use alloy tape. It may work but perhaps not as good as it could.
The 1:1 toroidal transformer is there for two reasons.
1, to add the phase differences between each side of the loop/amp
2, to allow 12v to the amp and couple the RF to the down lead.
A multi-turn loop will be tunable, a 1 meter loop with 7 turns requires a tuning capacitor up to 500pf to cover the MW band, to cover Long Wave satisfactory you need around 20 turns plus the cap. Tunable frame aerials have really good gain but the sharp tuning can be a pain if the aerial isn't close to the radio, they also are not as good as a single turn loop in noisy situations.
Peter, I wonder how the modified Wellbrook loop compares to your 1 year old genuine Wellbrook? I also wonder what difference a 1 meter loop made from the same diameter alloy tubing as the Wellbrook would compare with their Ferrite/Alloy construction.
Wellbrook themselves can supply a replacement amplifier but it connects just like the mod I've done with the two transistor amp. I just wonder if the Ferrite/Alloy is the real answer.
I'm going to my local engineering shop in the two or three weeks and will ask them to make up a 1.5 meter loop made of alloy tube to try a slightly bigger loop.
This brings me to Gary's post. If you look at the calcs the cross sectional area of the "wire, tubing etc" makes a difference to the signal level so I personally wouldn't use alloy tape. It may work but perhaps not as good as it could.
The 1:1 toroidal transformer is there for two reasons.
1, to add the phase differences between each side of the loop/amp
2, to allow 12v to the amp and couple the RF to the down lead.
A multi-turn loop will be tunable, a 1 meter loop with 7 turns requires a tuning capacitor up to 500pf to cover the MW band, to cover Long Wave satisfactory you need around 20 turns plus the cap. Tunable frame aerials have really good gain but the sharp tuning can be a pain if the aerial isn't close to the radio, they also are not as good as a single turn loop in noisy situations.
