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The Riddler Strikes Again!




 
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W3SLK
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« on: December 23, 2020, 09:55:19 AM »

One of my favorite classic episodes of Batman, (Adam West & Burt Ward), are reading a clue left to them by the Riddler, (Frank Gorshin). 'Robin' reads the clue, "When is a door not a door?" After contemplating he recites the answer: "When its ajar!!!" So to paraphrase this, when is an antenna not an antenna? When its a resistor! A few years ago prior to 'darkening' my station, I discovered that people were having a difficult time hearing me even when running the 'big rigs'. So I turned my attention to the radiating element and discovered that my 160M dipole that I fed with coax, had developed a hard ~750K~1.5M (DC)resistance. I had some 600Ω ladder line and decided to feed it with that. I had quite a bit of difficulty getting it to play on 160, (as I would later learn) but my slopbucket rig with the auto tuner in it was able to accommodate it and so I didn't worry. 8 years later, (yeah I know!) I decide to get back on the air. Once again I find that 160, 1.885Mhz. for that matter, still would not work, (I expected a miracle to occur over all those years). I could find satisfactory response on 75 but 160 was a no-go, (about 5~6:1 SWR). So the other night I discussed this with my friend and fellow antenna gumbah Pat, KN2T. He brought me back to some of the realizations that I had forgotten about a dipole: 1)the characteristic impedance is ~70Ω; 2)the added open line changed the resonant point from 1.9Mhz. to somewhere around 1.6Mhz.
So to return to the beginning, the dipole was fed with RG-213, (yeah a slight mis-match but very managable). I used an 'N' connector, (for whatever reason, I ignored the words of my buddy Eric, WB4VVI(SK) echoing in my head about the center pin being too small and causing issues during cold weather), but I felt if it was good enough for the military it was good enough for me. It was at this connection point that I discovered the resistance and some corrosion. I (thought) I had sealed the connection well enough with rubberized splicing tape and covering that with a layer of vinyl tape. Obviously over the years moisture still managed to migrate into the junction. So now the plan is to reconnect with RG-213 again until I have the components in place to remotely tune the antenna system. The reason I am putting this out there is that should you find yourself in a similar situation I will have seeded your minds and not have to 'trod over plowed ground'! As always, constructive comments and criticism are welcome!
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Jim, W5JO
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« Reply #1 on: December 23, 2020, 01:25:36 PM »

To help avoid this kind of thing fill the void in your type N connectors with Dow Corning 4 and seal.  Keeps condensation down and prevents corrosion because  of that.  I used it on PL 259 connectors that is on an Ameritron Remote Coax Antenna Switch about 8 years ago.  Recently I replaced the switch with a new one and the connectors were all just fine.
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Steve - K4HX
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« Reply #2 on: December 23, 2020, 10:14:36 PM »

I second the dielectric toothpaste in the coax connector. I've been using that stuff for years. Never had any moisture get in any of my antenna coax connections.
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W3SLK
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« Reply #3 on: December 23, 2020, 10:43:49 PM »

I'll do that if I can find some at the local hardware store. I'm going to reinstall it with a SO-239 and seal it up with splicing tape. If I can get a photo that is reduced in pixels, I will post a picture of the N connector.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Jim, W5JO
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« Reply #4 on: December 24, 2020, 07:30:25 AM »

Mike, I suggest you look for "spark plug" grease or whatever they call it  Take a look at the MSDS of DC 4 and see if the spark plug isn't about the same.  DC 4 is expensive but the stuff they put on spark plugs is not quite so bad and all auto stores have it. 
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W3SLK
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« Reply #5 on: December 24, 2020, 10:19:36 AM »

Jim said:
Quote
Mike, I suggest you look for "spark plug" grease or whatever they call it  Take a look at the MSDS of DC 4 and see if the spark plug isn't about the same.  DC 4 is expensive but the stuff they put on spark plugs is not quite so bad and all auto stores have it.
Thanks for the tip Jim. I'll do that. BTW its no longer referred to as a 'MSDS'. It is now 'SDS' as part of 'Global Harmonization', in particular with Europe. All the pictograms, hazardous materials schedule, (was 1-5 now 5-1), etc. is all changed. I'm a HAZMAT guy I had that drilled into my head. Sorry for off topic!  Wink
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Jim, W5JO
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« Reply #6 on: December 24, 2020, 10:28:59 AM »


Thanks for the tip Jim. I'll do that. BTW its no longer referred to as a 'MSDS'. It is now 'SDS' as part of 'Global Harmonization', in particular with Europe. All the pictograms, hazardous materials schedule, (was 1-5 now 5-1), etc. is all changed. I'm a HAZMAT guy I had that drilled into my head. Sorry for off topic!  Wink

Good to know, I was not aware.  Merry Christmas to you and all the guys and gals here.
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W3SLK
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« Reply #7 on: December 24, 2020, 11:27:37 PM »

Merry Christmas Jim and to all the others!
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
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