Tiny Toy!

[Albert H]

Here's 500mW carrier, 2.1 Watts peak in a tobacco tin! Built for battery-powered use at a music festival.

Little MW.jpg

[sinus trouble]

HaHa!! back in the day, you could cover it in 'Baccy' with a pack of Rizla and smuggle it anywhere!!

[Albert H]

I fired it up into the wire aerial that was plugged into it. With a 12V Lantern battery, the range was astonishing! I hung the aerial (about 5m of wire) out of an upstairs window, plugged an MP3 player into the 3.5mm jack on the side of it, and connected the battery. I walked off up the road with a portable in my pocket. It was still perfectly audible about ½ mile away!

I then tried it again, with the tin body connected to my house earth, and the aerial connection connected to an inverted-L going down the garden. A couple of phone calls and I found that it was a reasonable signal at 2 miles!

It's on 1602kHz, and I put it on the bench and tested it. The output impedance was designed to be fairly high, in an effort to match it to the short wire aerial that I'd be able to throw up a tree on the site. The output is a beautifully clean sinewave (that was quite unexpected) and the frequency is stable (despite it being a VFO circuit) to within about 80 Hz. Carrier power was 521mW and peak mod was 2.035W, so it's pretty much 100% modulated!

It's amazing what you can squeeze into a tobacco tin!

[Gigahertz]

Clearly your not in West London Albert ; ) as a certain community station gets out well on 1602KHz around here! shame about its output!!!

[Albert H]

It'll go up to 1611kHz or even 1620kHz, or down as far as 1557kHz. It takes a few minutes to tweak the VFO core and then tweak the output match for maximum. I'll try it a couple of channels down. The VFO was designed for a fairly small range of frequencies, in an effort to keep it stable. 1602kHz was found to be the best at the music festival site as there was nothing on that frequency for many miles.