Thread: Rca ant751
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Old 5-May-2017, 5:30 PM   #40
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,738
Inside the GE 34792 Attic Antenna

Originally Posted by OTAFAN View Post
If you decide to open your GE Indoor up and discover its mysteries, I'll be interest, rabbit73.
Well, here it is:

I have used the conventional terms for top and bottom of the board. The top is where the components are mounted and the bottom is where the ground plane is located. In actual use, the coax connector faces down.

The GE 34792 Attic Antenna includes a REAL UVSJ, not shorting stubs, to keep the UHF and VHF signals separated before combining. Each section of the antenna has its own balun. The UVSJ and the well designed reflector are responsible for the good performance of this antenna.

Here is a circuit of a UVSJ by SM0HX (amateur radio callsign for a ham in Sweden). The UVSJ UHF/VHF Separator-Joiner belongs to the filter family of Diplexers. All UVSJs are Diplexers, but not all Diplexers are UVSJs; Diplexer is the more general term. A HLSJ is also a Diplexer, but for VHF-Low and VHF-High.

The UHF highpass filter section has 3 series capacitors and 2 shunt inductors. The VHF lowpass filter section has 3 series inductors and 2 shunt capacitors.

Here are the curves for the Radio Shack UVSJ:

Attached Images
File Type: jpg GE34792_board_botom.jpg (173.6 KB, 10986 views)
File Type: jpg GE34792_board_top.jpg (152.5 KB, 10623 views)
File Type: jpg VHF-UHF Diplexer SM0HXrev.jpg (40.4 KB, 11903 views)
File Type: png RS15-2586UVSJ FreqResp3.png (118.9 KB, 11189 views)
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 8-May-2017 at 10:54 AM.
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