In the weeks leading up to the ARRL DX Phone contest this year, Eric, WG3J and I did some extensive antenna planning at his QTH in Maryland in preparation for the upcoming contest. One of this biggest concerns was the amount of coax coming into the station. During a contest last year, we encountered a ton of RF affecting computers and audio causing an RF burn or two. Fun times.
How to resolve this? Reduce your coax run length and quantity by using antenna switches.
I reviewed a number of designs online and ended up designing my own, 2 position antenna switch which injects 12VDC onto the coax, so we didn’t require additional long lengths of control wire which could end up resonating RF.
Control board REV114-Feb-2011 22:47, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 111
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Control board REV114-Feb-2011 22:47, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 131
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Relay switch board. REV112-Feb-2011 02:25, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 107
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Relay switch board. REV112-Feb-2011 02:25, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.017 sec, ISO 134
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Relay switch board. REV112-Feb-2011 02:25, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 80
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Relay board with components. 10KW relay.14-Feb-2011 22:50, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 457
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Relay board with components. 10KW relay.14-Feb-2011 22:50, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 483
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Relay board with components installed. 5kW relay.01-Mar-2011 00:30, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 355
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Relay board with components installed. 5kW relay.01-Mar-2011 00:30, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 318
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Relay board with components installed. 5kW relay.01-Mar-2011 00:30, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 375
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Control Panel front22-Feb-2011 22:20, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 800
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Rear of control panel22-Feb-2011 22:23, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 613
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Control board under test15-Feb-2011 20:56, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 244
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2 position DPDT rotary switch15-Feb-2011 20:56, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 188
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Control board mounted25-Feb-2011 00:21, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.008 sec, ISO 96
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The makeshift assembly line in the shack.02-Mar-2011 08:58, EASTMAN KODAK COMPANY KODAK Zi8 Pocket Video Camera, 2.8, 6.34mm, 0.033 sec, ISO 357
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For the next 3 weeks part of my station would be turned into an assembly line, etching circuit boards, fabricating cases, etc.
A week before the contest, Eric and I put the switches through their paces by dumping 2.5kW at 100% duty cycle for about 10-20 seconds. This would help us assure that they would hold up to the contest pace.
I ended up building five switches, 2 rated at 10kW and 3 rated at 5kW. I’m happy to report success with the design with no smoke emissions. One thing we did find was a high SWR at 15m and above, which I believe I have a fix, that needs future testing.
