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Author Topic: Mysterious receive boost  (Read 1812 times)
ND9B
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Posts: 52




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« on: March 07, 2013, 07:18:09 PM »

The SWR on my HF antenna recently went to hell in a hand basket. It turned out to be a corroded SO239 barrel connector splicing two lengths of coax together outside. After replacing the connector, I noticed the local AM broadcast station (that I'm very close to) went from +60 over 9 to +80 over 9. (Now I need a BCB filter, but that's a different topic.) After making some contacts, I believe reception in general is stronger.

Now the corrosion on the barrel connector probably didn't happen over night. Is it possible that it was affecting RX but not TX for a period of several years? And, then finally got bad enough to affect TX?

Bobby Dipole ND9B
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K8AXW
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« Reply #1 on: March 07, 2013, 08:00:13 PM »

Very possible.  In the RX mode the signal is in the microvolt range and a little resistance goes a long way.  In the TX mode the high RF voltage would probably blow through.
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WA7RBC
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« Reply #2 on: March 09, 2013, 10:06:37 PM »

It would have been interesting to measure the SWR with a (relatively) low-power analyzer.

73,  Ron.
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KE3WD
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Posts: 5689




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« Reply #3 on: March 10, 2013, 04:03:00 PM »

The dissimilar metal junctions in the barrel connector, aggravated by corrosion, can act like diodes...


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K1DA
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« Reply #4 on: April 17, 2013, 08:58:04 AM »

I thought voltage drop was related to current.
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K8AXW
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« Reply #5 on: April 17, 2013, 09:05:58 AM »

Quote
I thought voltage drop was related to current

It does but basic ohm's law contains 3 elements.....Voltage, Current and Resistance.
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KB5ZSM
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Posts: 70




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« Reply #6 on: April 17, 2013, 06:11:32 PM »

Another thought is the transmit power may have been arcing across or the connection may have been acting like a capacitor.
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