Low-noise antenna amplifier 23 channel UHF
The amplification of 18 and 21 dB for voltage. Mounted on the mast near the antenna. Two outputs on coaxial cables reduce for 2 TVs. Food should be served on both cables (for independent) via a simple adapter and decoupling diodes. Contour and communication lines made of tinned pigtails approximately 1.5 mm in diameter (they Lipany from flow capacitors completion for the purpose of miniaturization). The output line is placed close to the last contour line.
Installation of the amplifier is made in hinged manner. Lower pins of the RMP 2/pF completely bitten off and the top terminal is bent and soldered as shown. Board, double-sided foil fiberglass 1.5 mm, wrapped a strip of tinned sheet metal 20 mm wide and soldered the seam on both sides. The parts which are not visible in the top compartment, located in the pan. Small circles show the ends of the bushing capacitors, on which hinged the entire installation. On Board, the ends of Proudnikov are 0.5-1 mm and soldered in a circle on both sides of the Board. Height contour lines on Board is determined by the height of trimmer capacitors. The top compartment is divided in half by a screen with a small hole for the condenser from the bottom. Two sides of the amplifier is closed and sealed lids of tin in which the drilled holes on the trimmers. Finally, the amplifier adjusts with lids. In the connection route sheet is pierced with an awl and unfolds some of the cone tool. The holes soldered to the tube sheet, the diameter of the cable. Cable core connected to the reference line on the patch 3x3 mm from scraps of boards are soldered thereto. Box is durable, but needs protection from corrosion.
I ask You to offer some recommendations on the amplifier on UHF channel 23.
1. Can I use the amplifier transistors GTA and is required if any changes to the scheme or design of the amplifier?
2. How using the device X1-50 to set this amplifier, what adapter, styli, etc. needed for the correct settings?
1. Yeah transistors GTA can be used instead CTA without any schema changes. You only need the output emitter of VT1 and VT2 base to make as short as possible, to pripiski-through capacitors. In planar transistors CTA I these findings were shortened to 2 mm and since the conclusions spatially separated them easy to solder. And yet, when replacing 2-3 dB gain is lost. If You make an amplifier with one output, on the contrary, the gain will be 3 dB more.
2. With X1-50 I'm not familiar worked with X1-44, X1-55. From X1-44 I only had the generator unit and I used a homemade detector (described on the website) to simple N. H. the oscilloscope. The signal to the input of amplifier I filed two attenuator 20 dB each, thus avoiding overload of the amplifier and at the same time provide great signals for control and synchronization of the oscilloscope removed from the detector BEFORE these attenuators. The output included the load (2) 75 Ohm and homemade oscilloscope detector. Associated pair of circuits at input and output of the amplifier was tuned to the operating frequency. Changing the distance between the contour lines have achieved the flat top of the resonance curve for a given bandwidth allocation (all operation adjusting the resonance). The distance between the lines is about 10 mm.
If you reduce the connection of taps in the input circuit to 1/3 and the resistors R9 and R10 to increase to 2 ohms, you can get the width of the bandwidth of the amplifier only 8-10 MHz, i.e. one channel, and still get 24-26 dB of gain. This is useful when interference from adjacent frequency channels. But I was limited to a bandwidth of 24 MHz (3 channels) a few losing gain, but large temperature differences, with an outdoor setting of the amplifier, no effect to strengthen possible temperature when the detuning of the circuits. Finally, the amplifier is arranged when closed and propane the caps through the holes opposite the tuning capacitor, and then soldered a patch for sealing. The trimmers type CFM - the smallest I have ever had. According to this scheme, but with a single output I do amplifiers on any UHF channel, changing only the set of contours and easily getting 24-26 dB of gain, which at these frequencies a lot! Amplifiers were placed directly into the receiving antennas and the power and signal passed through a single cable and got a big win signal/noise in the TV. Connectors on input and output I used, sealing the cable directly into the amp.
Success and good reception!
Author: E. shoustikov, UO5OHX ex RO5OWG; Publication: www.shustikov.by.ru, www.cxem.net