02-03-2016, 08:25 AM
Hi.
Nice work there Gary
To clarify, there are two types of loop that we have been talking about here.
The active magnetic loop, & the tunable frame aerial. Both have disadvantages and advantages.
The tunable frame aerial cant be successively mounted any distance from the operator and receiver, simply as you need to track the frequencies your tuning unless you make a remote drive for the tuning gang, Varicap diodes have been tried but these will rectify strong signals and cause addition of harmonics and distortion.
The frame can supply a large amount of signal and will pull in weak signals that a long wire will struggle with, 8 turns round a 1 metre frame equates to 32 meters of a long wire and will perform far better than those 32 metres of wire will stretched out!
So the frame can give a very strong signal, its excellent for weak signals, it falls down due to the need for tuning and can also be noisy.
The active single turn loop requires no tuning, they function better with a larger cross sectional area wire or tube and are pretty well immune to mains derived noise. The signal level from the single turn is low so a balanced amplifier is needed to boost the signal to a usable level. No matter what type of amplifier is used some noise is generated but selecting low noise transistors or chip this needn't be an issue.
The single turn loop can be remotely mounted as no tuning is required, this can be an advantage to get some extra height.
They also can cover from Long Wave to above 30mhz dependant on the amplifier design.
Both frame and loop have very strong nulls and this can be a big plus for DXing adjacent stations.
Have fun
Nice work there Gary
To clarify, there are two types of loop that we have been talking about here.
The active magnetic loop, & the tunable frame aerial. Both have disadvantages and advantages.
The tunable frame aerial cant be successively mounted any distance from the operator and receiver, simply as you need to track the frequencies your tuning unless you make a remote drive for the tuning gang, Varicap diodes have been tried but these will rectify strong signals and cause addition of harmonics and distortion.
The frame can supply a large amount of signal and will pull in weak signals that a long wire will struggle with, 8 turns round a 1 metre frame equates to 32 meters of a long wire and will perform far better than those 32 metres of wire will stretched out!
So the frame can give a very strong signal, its excellent for weak signals, it falls down due to the need for tuning and can also be noisy.
The active single turn loop requires no tuning, they function better with a larger cross sectional area wire or tube and are pretty well immune to mains derived noise. The signal level from the single turn is low so a balanced amplifier is needed to boost the signal to a usable level. No matter what type of amplifier is used some noise is generated but selecting low noise transistors or chip this needn't be an issue.
The single turn loop can be remotely mounted as no tuning is required, this can be an advantage to get some extra height.
They also can cover from Long Wave to above 30mhz dependant on the amplifier design.
Both frame and loop have very strong nulls and this can be a big plus for DXing adjacent stations.
Have fun
