Tv antenna help
- Thread starter planoron
- Start date
Sounds like a Plan. Bring some dielectric grease and fill the coax connector "F-Fitting" with it before screwing it onto the new antenna. That should slow down the moisture intrusion, and corrosion of this connection.
It is a disc shaped omnidirectional antenna. Not as powerful as a directional antenna, but you keep your signal while spinning at anchor.
take a look at the original picture (hopefully I have posted it below). The RF cable has the plastic stripped from the shield and then a captive bar is screwed down over the shield to make the ground. The center conductor goes to screw terminal on the board. Very unconventional method for terminating an RF cable and probably doesn't perform that well plus likely prone to corrosion problems. However.. it looks like not that difficult to just cut the cable back a little and re-do everything using fresh ground and center conductor on the cable. That RF cable connection looks like someone didn't care if it worked for a long time. If nothing else.. that would be an easy thing to try.
FYI, it is not the tiny voltage from an ohm meter that you need to worry about if you probe that circuit, it is electro static discharge (ie, ESD or shock). The cable going up to the antenna will have 12 volt plus the RF signal on it. The meter will screw up the RF performance if you touch that cable but not the slightest damage problem with measuring voltage or resistance.
On the consumer products I have worked on in the past (25 years in that bushiness) we would always test all ports (such as the DC plus RF ports on that board) for ESD in the design phase. This would be a very fast transient pulse with a peak of 8000 volts to simulator ESD so that it had spectrum in the RF range of interest.. Whatever the device had to perform perfectly after the test. Why do this.. customer returns are very expensive and its not at all hard or expensive to make electronics withstand ESD.
FYI, it is not the tiny voltage from an ohm meter that you need to worry about if you probe that circuit, it is electro static discharge (ie, ESD or shock). The cable going up to the antenna will have 12 volt plus the RF signal on it. The meter will screw up the RF performance if you touch that cable but not the slightest damage problem with measuring voltage or resistance.
On the consumer products I have worked on in the past (25 years in that bushiness) we would always test all ports (such as the DC plus RF ports on that board) for ESD in the design phase. This would be a very fast transient pulse with a peak of 8000 volts to simulator ESD so that it had spectrum in the RF range of interest.. Whatever the device had to perform perfectly after the test. Why do this.. customer returns are very expensive and its not at all hard or expensive to make electronics withstand ESD.
This is similar to the capture systems used in Cable TV street level hardline distribution taps and amplifiers. Should work fine. The connection I was speaking of was thou one up the mast connecting to the omni antenna.take a look at the original picture (hopefully I have posted it below). The RF cable has the plastic stripped from the shield and then a captive bar is screwed down over the shield to make the ground. The center conductor goes to screw terminal on the board. Very unconventional method for terminating an RF cable and probably doesn't perform that well plus likely prone to corrosion problems. However.. it looks like not that difficult to just cut the cable back a little and re-do everything using fresh ground and center conductor on the cable. That RF cable connection looks like someone didn't care if it worked for a long time. If nothing else.. that would be an easy thing to try.
FYI, it is not the tiny voltage from an ohm meter that you need to worry about if you probe that circuit, it is electro static discharge (ie, ESD or shock). The cable going up to the antenna will have 12 volt plus the RF signal on it. The meter will screw up the RF performance if you touch that cable but not the slightest damage problem with measuring voltage or resistance.
On the consumer products I have worked on in the past (25 years in that bushiness) we would always test all ports (such as the DC plus RF ports on that board) for ESD in the design phase. This would be a very fast transient pulse with a peak of 8000 volts to simulator ESD so that it had spectrum in the RF range of interest.. Whatever the device had to perform perfectly after the test. Why do this.. customer returns are very expensive and its not at all hard or expensive to make electronics withstand ESD.
Will do. I also use uv rated liquid tape on any exterior or weather proneSounds like a Plan. Bring some dielectric grease and fill the coax connector "F-Fitting" with it before screwing it onto the new antenna. That should slow down the moisture intrusion, and corrosion of this connection.
Since you probably dont have a spectrum analyzer..
I would just clean up the connector like was suggested by Pateco but I would also consider the cable connections on the circuit board.. A very simple thing to measure with a volt meter is to make sure the cable center conductor that goes "to the mast mount antenna" has the same voltage as the "from the 12 volt breaker". That bottom board is all passive and unless you get a giant static shock, you wont damage anything. Also, take the volt meter and measure the voltage between the ground coming into the board and the shield of the cable going up to the antenna while the antenna is powered (ie, you can see the red LED ON at the top so you know some current is flowing). If both of these grounds are well connected, this should read zero.zero volts.
If you clean up the cable (I would on both ends..) and it still doesnt work.. time to get something new.
FYI, since I "whined" about the cable connections on the off air circuit board, I attached a picture of what a higher performance F cable to circuit board looks like (from a consumer satellite switchbox I worked on in the past). . We had to have a very good cable ground and maintain the transmission line characteristics all the way to the termination on the circuit board. Something like the cable shield ground clamp used by that off air antenna that partially crushed the cable would have screwed up the specs we needed to achieve (mainly insertion and return loss). .But.. when the connections are good (like when new), that set up is probably good enough.
I would just clean up the connector like was suggested by Pateco but I would also consider the cable connections on the circuit board.. A very simple thing to measure with a volt meter is to make sure the cable center conductor that goes "to the mast mount antenna" has the same voltage as the "from the 12 volt breaker". That bottom board is all passive and unless you get a giant static shock, you wont damage anything. Also, take the volt meter and measure the voltage between the ground coming into the board and the shield of the cable going up to the antenna while the antenna is powered (ie, you can see the red LED ON at the top so you know some current is flowing). If both of these grounds are well connected, this should read zero.zero volts.
If you clean up the cable (I would on both ends..) and it still doesnt work.. time to get something new.
FYI, since I "whined" about the cable connections on the off air circuit board, I attached a picture of what a higher performance F cable to circuit board looks like (from a consumer satellite switchbox I worked on in the past). . We had to have a very good cable ground and maintain the transmission line characteristics all the way to the termination on the circuit board. Something like the cable shield ground clamp used by that off air antenna that partially crushed the cable would have screwed up the specs we needed to achieve (mainly insertion and return loss). .But.. when the connections are good (like when new), that set up is probably good enough.
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Agreed, the deformation of the cable will cause signal issues, but only at the higher frequencies used by Satellite or newer digital cable plants. For the signals received off air, this issue should be minimal.
Yep..
I attached a blowup of the OP's cable (at the circuit board) going to the antenna. The black arrow points to the cable shield. It could just be the picture but the black color of the metal shield mesh doesnt look healthy.. I dont think it looked like that when new - but Im just going from the picture. .
I attached a blowup of the OP's cable (at the circuit board) going to the antenna. The black arrow points to the cable shield. It could just be the picture but the black color of the metal shield mesh doesnt look healthy.. I dont think it looked like that when new - but Im just going from the picture. .
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I agree,,,who knows how much is degraded and where so that is why I'll get a whole new upgrade. It would be kinda like fixing that 15yr old refrigerator.
Well its raining outside and we're sitting in a marina doing stuff to keep busy. So how about the TV antenna? Tried the co-ax fitting at the mast bottom, well unplugging and plugging back together didn't do anything. Tear into the Nav Station to get to the UFO power inserter box. There is supposed to be a LED light when working. This is a pre LED board. Call NASA, its their fault. Look at the co-ax cable and take it apart while the wife balances the board with the chart plotter, autopilot display screens, and wire jumble. Just as I thought, a big wire with metal around a small wire covered with thick plastic. Ask the wife if it looks good. Put it all back because I didn't want to strip the wire without a good stripper. (I somehow broke the one I had)
Time for the test. My wife does the TV Air search. Three stations found. Tried the radio, many stations found. Time for a drink and a movie, I'm such the radio man.
All U Get
Time for the test. My wife does the TV Air search. Three stations found. Tried the radio, many stations found. Time for a drink and a movie, I'm such the radio man.
All U Get
So Tom, does the TV work or not? I do have the board and UFO antenna if you need parts to swap for T/S.
It works but we're in a marina surrounded by Cyprus trees along the Waccamaw River. If you remember the movie "The Patriot" about the "Swamp Fox" raiding the British troops during the Revolution, that's where we are just a little north of the Pee Dee and Santee Rivers. When we get to Charleston the stations will come rolling in.
All U Get
All U Get
Absolutely not. The 75 ohm characteristic is at the operating frequency. If you put an ohm meter on it you will be dealing with DC resistance.
Ken