Easy to build DIY detector

[diggerbarns]

I want to build something easy over XMAS did any one here build this one and does it work http://home.clara.net/saxons/bfo.htm

[ismail surek]

yes i was build that bfo machine

yes i was build that bfo machine but it is not recive clearly
and i dont advice that for over of 50 cm.
i was build it and it is work

[Largesarge]

I would use the top one on the projects page of this site. It only uses one IC, a varactor and a one coil on the board plus the odd assorted resistors and capacitors and such. I calced the coils and came up with the following:

L1
Inductance 0.083 mH
DC Resistance 2.15 Ohms
Wire Gauge 31 AWG
Wire Diameter 9.8 mils (1 mil = .001 in)
Coil Length 1 in
Coil Inner Diameter 0.375 in
Coil Outer Diameter 0.4142 in
Average Turn Diameter 0.3823 in
Wire Length 16.42 feet
Copper Weight 0.004 pounds
Turns 164
Levels 1.61
Maximum Turns Per Level 102 (Based on wire diameter)
Nearest British Wire Gauge 34 SWG
Metric Equivalent 0.249 mm, Includes Insulation Thickness.
Current Handling Capability 0.119 at 700 cm per Amp.

SEARCH
Inductance 0.094 mH
DC Resistance 0.38 Ohms
Wire Gauge 22 AWG
Wire Diameter 26.7 mils (1 mil = .001 in)
Coil Length 0.125 in
Coil Inner Diameter 4 in
Coil Outer Diameter 4.267 in
Average Turn Diameter 4.0946 in
Wire Length 23.58 feet
Copper Weight 0.046 pounds
Turns 22
Levels 4.7
Maximum Turns Per Level 4.7 (Based on wire diameter)
Nearest British Wire Gauge 23 SWG
Metric Equivalent 0.678 mm, Includes Insulation Thickness.
Current Handling Capability 0.9277 at 700 cm per Amp.

and

Inductance 0.097 mH
DC Resistance 0.55 Ohms
Wire Gauge 22 AWG
Wire Diameter 26.7 mils (1 mil = .001 in)
Coil Length 0.125 in
Coil Inner Diameter 8 in
Coil Outer Diameter 8.2136 in
Average Turn Diameter 8.0602 in
Wire Length 33.76 feet
Copper Weight 0.066 pounds
Turns 16
Levels 3.42
Maximum Turns Per Level 4.7 (Based on wire diameter)
Nearest British Wire Gauge 23 SWG
Metric Equivalent 0.678 mm, Includes Insulation Thickness.
Current Handling Capability 0.9277 at 700 cm per Amp.

You can use the same coil form type and engineer your own pole and enclosure.