Hello,
Anyone has a schematic to build a CW transmitter on the AM Band? I guess it's legal as long as the output power doesn't exceed 0.1 watt and the antenna length less than 10 foot.
Yves
You could use most any transmitter if you use MCW,modulated CW tone. Special care would be needed to make a true cw transmitter to prevent key click interference and proper waveform. Sure is legal,as is SSB or any other mode,search for "lowfers" for transmitter ideas.
Pure CW on the AM band would not even be noticeable to most potential listeners. Without a hetrodyning signal or BFO, the signal would appear to be periods of brief silence. Of course if, the transmitted signal was interfering with an existing signal, the hetrodyne tone would be present and very annoying to most listners.
However, MCW (modulated continuous wave) has been used for a long time on AM, FM and sideband with some success. I have used MCW on 2 meter FM and communicated from mountain top to mountain top over 300 miles on less than 3 watts. In fact I have a MCW code keyer for my hand held. Tons of fun and inexpensive too.
NDBs are popular with DXers because favorable atmospheric conditions can allow NDBs to travel much farther than normal. NDBs transmit their own Morse Code callsign and are easy to listen to and identify.
Medfers are just like legal part 15 am/mw, 100 mw on an antenna no greater than 3 meters in length from 530-1710 khz. Narrow band communication modes make these low power beacons readable over great distances. By decreasing the speed of the morse code signal we can achieve readability at lower signal to noise ratios.
Can you hear an NDB beacon? Tune a car radio to 530 AM during the commute to hear the LYQ NDB beacon morse code with voice weather.
Part 15 experimenters have done amazing
things with cw beacons in the AM band.
Also, they run some digital modes, which I
know nothing about.
I also don't know how to make a good stable
cw transmitter for that range, but somebody
must know.
OK, check the W4DEX Radio page. It can be found
on Google. That is a real good place to start.
His Medfer beacon, running on about 1704 kHz,
using a VERY slow digital mode, was received almost
700 miles away!
Best Wishes
Bruce, MICRO1690/1700