458
Item nr.
Loop for pirate and ham hunt.
| Production | The Netherlands, 2017. |
|---|---|
| Bands | L (1400-6000kHz), H (4.2-7.0MHz). |
| Semi- conductors | BC337. |
| Cabinet | None. Size Height 26cm. Weight 350gr. |
| Power | Batt 9V (draw 6mA). |
| Documents | Schema, Amplifier. |
They consist of a tuneable, rotateable tank circuit, coupled to the radio with an extra winding. This object was a test for my loop calculator LoopAnt, and the test went reasonably well. The inductance of the coil came out as anticipated, which was good. But the capacity of my tuning condensator turned out to be lower than measured, so with just the "50pF" section, the antenna just didn't tune the 80m Ham band. So I added a switch and the larger section of the capacitor (see schema). This resulted in an antenna tuneable from roughly 1400 to 7000kHz in two "bands". Here find the calculations for the loop with 265pF of capacity. Reception is good! On the first evening I already got good results with this loop and my Yupiteru MVT-7100.
| Obtained | 5/2017 from Home built. |
|---|---|
| Condition | 8. |
| Value (est.) | 4,7€. |
| Sound sample | PLAY SOUND On December 25, 2017, I received a 60m band station for the first time, on 4810kHz. By Short-Wave.info, you either hear the Voice or Armenia speaking in Yezidi from Yerevan, 3300km away, or Air Mumbay in Hindi from Bhopal, 6800km away. |
I started the construction by computing the coil with my aid LoopCalc, to find out that I needed about 16 turns. To keep the spacing OK, I glued paper strips with 2mm spacing on the coil form (a CD box), and fed the wire through a small hole. 
To avoid losing the wire during winding, I fixated each turn with some hot glue. In this way, laying 16 turns around a coil is a work of several minutes, after which I could mount the coil on the rotating stand I had produced earlier.
I had an old box of construction toy material, which looks a bit like the well known Meccano but actually is called Construction. I use it sometimes for radio related constructions. 
In March, 2024, I improved the antenna by building in a small, one stage amplifier. The resistors on the right provide the bias for the BC337, and are decoupled by 4n7. A green LED was added because I usually forget to switch off my battery operated projects.