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, Walter M. Subject: RE: A-1 minicaster Here`s the pix of the A-1 minicaster, top and bottom plus schematic. I didn`t have a DP switch, so I had to kluge a second SP underneath for the HV. Note the neon indicator for HV-on. Small cap to osc grid is. 001 (noticed it was too small to read on schematic. ) This radio construction project, including all descriptions, diagrams, photos, and the underlying electronic design, is published here for the noncommercial use of radio hobbyists. You may print and reproduce these project instructions for your personal use. Commercial use of this material is strictly forbidden.


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