It would be a good idea to clear your cache from time to time, to make sure your browser loads the latest version of this post. As an example, I just found an error on the schematic, and uploaded a newer, correct diagram. The review from Adventure Radio Society was quite positive. The sidetone level does vary with the volume control, as opposed to being a fixed volume, but I only find this to be an issue when I have the AF gain all the way up, in which case I either quickly adjust the volume knob, or partially pull the earbuds away from my ears while sending. By the way, the sidetone on this little rig sounds really nice.

Author:Tojarg Shaktinris
Language:English (Spanish)
Published (Last):19 December 2015
PDF File Size:7.66 Mb
ePub File Size:5.71 Mb
Price:Free* [*Free Regsitration Required]

It fits perfect. It fits perfect, then back out of bolt. Sqeeze all the wraps real close I also took off the insulation on the 18 gauge wire to make the air-core coils. It was originally a mW unit, without the universal power stage added.

Together with the power amp MRF , it then became a 7-watt unit. I used this transmitter with a half-wave open-end dipole in a vertical position 50 feet above ground. Together with about 70 feet of coax, this transmitter delivered great audio at a distance of 10 miles This circuit worked well for me, as I had experimented with it for nearly a year.

Of course, one would be better off with more equipment than I have had That was, by far, one of the hardest things to capture. It was thru trial and error, with the FM tuner, in finally finding out how to grab the right frequency. With the transmitting antenna at 50 feet above ground, I decided to see how well I could receive the transmitter signal from an overpass than is exactly 15 miles from the transmitter. I now undersand what is meant when one says FM signal travels best in a line of sight.

Well, being on that overpass, if I had a strong telescope with me, I am sure I could see the 50 foot antenna in my oak tree. I surrender this circuit to anyone who likes to experiment in things like this Together with a DVM, these two homemade devices can aid you in fine-tuning the unit and also giving you an rough idea of how much wattage you are putting out. The three test devices above is what I had used in the complete makings of the transmitter.

I had nothing else. A lot experimentation came in when I had to govern myself and get the unit to function well with just these three items


MRF237 NPN Silicon RF Power Transistor, 12.5 V, 90 MHz, 15 W, Motorola



A Scratch-Build of N6KR and Wilderness Radio’s SST for 20M


Related Articles