Two Tube Regenerative Homemade Radio
Hi there! Here is another radio in the series of tube radios that I have been building in 2002. Little by little they are getting better.
This is a two tube radio built with a pair of 1T4 tubes. These tubes have a 1.4 volt filament at 50 ma current draw. The B+ supply is made of 5 - 9 volt batteries connected in series. On this page I am featuring my battery box. This is a small box with two D batteries and ten 9 volt batteries. There are 6 connections on the front for 0, 1.5, and 3 volts for the filaments and 0, 45 and 90 volts for the B+ supplies. There are connections on the front panel and a 6 pin connector. The 6 pin connector makes it easy to switch between sets without fear of plugging something in wrong. I made a cable for each set. Each cable has 4 or 5 wires. A battery box is easy to build and makes using batteries for these tubes sets more convenient.
This is a 2 stage radio. The first tube is an untuned RF amplifier. This stage not only makes the signal to the detector somewhat stronger, it isolates the detector from the antenna. Regenerative sets can cause interference to other local receivers when the set oscillates. Since the signal can't travel backwards through the tube the signal won't radiate from the antenna.
The second stage is the regenerative detector. The coupling between the first and second stage is done by inductive coupling. The signal passes from the primary of the main coil to the secondary. Another way to couple is to have an rf choke in the plate circuit of the first stage and then capacitor couple to the second stage. The method is up to you.
The output will drive a high impedance headphone. A crystal earphone will not work here unless you add a resistor across the headphone connections. A walkman style headphone may be used if you add a small audio output transformer.
The construction is much like my #12 crystal set. The base is the bottom of a box that I cut for the crystal set. I still have another 1/3 of that box. 3 sets from one box! A cheapskates delight. I used the Garolite® for the top. Just love that stuff. I used a 3/4 inch chassis punch to cut the holes where the tubes come through. I recessed the tube sockets. I didn't have to do all that, but I wanted to have the tops of the tubes sticking above the panel. This is a parody of the early tube radios that had the tubes sticking out the top of the box.
73, Dave - N2DS