229
Item nr.
Directional and tuned antenna.
Production | The Netherlands, 2003. |
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Bands | MW (522-2000kHz). |
Cabinet | Wood. Size (height) 124cm. |
Documents | Slide deck: Raamantennes. |
You can see the crystal receiver circuitry on this photo, but later I have removed it, because I use this construction mainly as a MW antenna for active receivers.
You can calculate the construction of Loop Antenna's approximately with my Excel sheet LoopAnt; see the TelRaam Calculation.
Obtained | 9/2003 from home made. |
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Condition | 8. |
Value (est.) | 10€. |
Sound sample | PLAY SOUND ![]() |
Dave writes on his page that one needs good ears, but a larger coil improves performance. So we made the coil a little bit bigger than Dave's: the width of the coil is 80cm and it has 13 turns. The 13 turns with variable capacitor form the resonance circuit, the coil is tapped 6 turns from the ground to connect the diode (1N34A).
An outdoor antenna can be coupled through a 2-turn coupling coil. But coupling also works the other way: through the coupling coil, you can feed the HF energy to another receiver. The set then works as a tuned, directional, magnetic coil antenna, which may improve your MW reception dramatically.
When tuning, especially in the higher MW regions, you will observe a considerable hand effect: touching the metal tuning knob will change the frequency, so if you tune to max signal and lose your hand from the knob, signal gets worse. To remedy this, I attached a large plastic disc to the tuning condenser. It size allows very exact tuning. Twenty years after building it, I still enjoy using it as a MW loop antenna. I mounted it on a rotating plate and put it on top of an azimuth indicator.
I recommend everybody who has a 10-year daughter to build this set. It is fun!