Build a Portable AM Radio Transmitter

After we published the original Li`l 7 AM Transmitter plans, fellow experimenter Scott Todd sent us information about his design for a similar portable, battery-powered transmitter. -Original Message- From: Scott Todd Sent: Wednesday, April 12, 2000 8:58 AM To: Walter Heskes Subject: A-1 minicaster I noticed that you have yet to get around
Build a Portable AM Radio Transmitter - schematic

to developing a battery operated part 15 transmitter for swap meets (or if you have, it`s not on the net. ) Well, I decided to take matters into my own hands and did one myself. Actually it was nothing more than a variation on a converter circuit in a farm radio using a 1A7 (hence the name A-1 Minicaster. ) Since I`m no computer genius and don`t own a scanner, I`ll have to describe the schematic. Should be simple enough- Pins 1 & 2 [base shell and A- respectively] to gnd. Pin 3 [plate]- RF choke >1mH (will be replacing with tuned circuit for better performance and lower spurious output) to B+, and. 01 to antenna terminal. Pin 4 [screen] through 47K to B+, and. 05uF cap to gnd. Pin 5 [osc. grid]- 220K to gnd, and. 001u cap to secondary of osc. coil; other end of same to gnd. Pin 6 [osc "plate"]- primary of osc. coil to B+. Pin 7 through 1/2 DPST sw. to +1. 5v. The other half of the DPST switches B+. Cap grid- 1M ohm to gnd, and >/=. 05uF cap to input jack (RCA). Additional touches- NE-2 neon indicator across B+ for power on; a low resistance (8-24ohm) that can be switched in or out as needed across the RCA jack for proper loading of audio source, such as when using a small pocket size tape recorder speaker output jack for source of programming. Built mine on an old cake pan that developed holes and was no longer useable. Scott Todd N0BST -Original Message- From: Scott Todd Sent: Wednesday, April 26, 2000 8:24 AM To: Heskes,...

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