Hi all, as a full time cruiser I recently installed a amplified antenna at the top of the mast. As a test, I ran 50ft of quad shielded RG-6 with gold connectors outside the mast to the TV. The test worked perfect, I got in all the local TV stations. Next, I ran the same cable inside the mast to the TV and checked the reception. The reception is very bad. I get 3 channels instead of the 9 I had in the test run and those 3 cut in and out. I did a ohm check on the antenna cable and it is good. I disconnected all power wires in the mast to eliminate magnetic fields, this made little difference. I then ran a 2nd antenna cable (not as good as the 1st cable) outside the mast and got much better reception. SUMMARY: TV reception works great with the antenna cable outside the mast but bad reception with the cable inside the mast. Solutions appreciated.
TV Antenna Issue
- Thread starter AyeSea
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The shield on coax would prevent most attenuation from adjacent magnetic fields so this makes no sense. My guess would be either a bad connection to ground (the shield and mast should be at the same potential which is easy for you to check) or the amp for the antenna is connected in reverse to induce a current on the shield (which again would be obvious if you checked voltage between mast and shield).
This presumes all else being equal - same connections, same connectors, no bad connections on coax inside mast, etc.
This presumes all else being equal - same connections, same connectors, no bad connections on coax inside mast, etc.
Most amplified marine TV antennas have a LED 'pilot light' mounted on the 'dome' ... this insures that sufficient power is getting to the antenna. Is the LED 'on'? If the LED isnt ON then you get attenuated signal response. 
Possibly, depends on the cable used. RG59 is 80% shielded and could have issues but it's more likely skin effect inside the mast. If RG6X is used (95% effective sheilding) , there should be no issue with the cable inside or outside the mast.
There is a possibility that you have scraped some of the cover off the coax and the shield is making contact with the mast. Happens a lot, the other common problem is that the center wire is bent and not inserted right. If you installed twist on or crimp on ends yourself, they may be the problem. There is little or nothing that can happen in the mast to make you loose reception. The problem is the coax, connectors or connections. Chuck
My guess is that your antenna isn't doing much (perhaps no power as suggested above) and the coax was acting as the antenna. Once you shielded the coax with the mast, your reception went poof. Just for grins, try running the coax up outside the mast without hooking up to the antenna and see what kind of signal you get.
Cheers,
Brad
Cheers,
Brad
Former cable guy here to throw in some words about coax, fittings, and amplified antennae.
Signal ingress was the worst thing that could happen to cable, so I usually tried to prevent it. It looks like what you've got is an instance where the signal is better coming off of the RG-6 itself than it is coming from the antenna, there are a lot of reasons why this might be the case, you're getting better signal when it is outside of the mast is because the cable itself is your antenna and when it is inside the mast, the mast is shielding it.
1. The braid, or some small part of it is touching the center conductor at either end. This grounds the shield to the braid and turns the whole cable into an antenna.
2. The fittings are *so* awful that they aren't providing adequate electrical separation of the braid from the center conductor. Gold fittings for cable connections are actually usually an indication of really poor production quality. It doesn't make sense, but it was true for the seven years I was working as a field maintenance technician for Comcast.
3. The antenna itself is poorly built and connecting the two together.
To fix it, check that the braid isn't wrapped *anywhere* around the center conductor at either end of the cable. Disconnect the antenna but check picture with the cable inside and outside of the mast to determine if the antenna is the culprit. (If it is good with no antenna outside the mast and bad with no antenna inside the mast, the cable is serving as your antenna and the antenna unit itself might still be OK.)
Let us know what you find!
-Scott
Signal ingress was the worst thing that could happen to cable, so I usually tried to prevent it. It looks like what you've got is an instance where the signal is better coming off of the RG-6 itself than it is coming from the antenna, there are a lot of reasons why this might be the case, you're getting better signal when it is outside of the mast is because the cable itself is your antenna and when it is inside the mast, the mast is shielding it.
1. The braid, or some small part of it is touching the center conductor at either end. This grounds the shield to the braid and turns the whole cable into an antenna.
2. The fittings are *so* awful that they aren't providing adequate electrical separation of the braid from the center conductor. Gold fittings for cable connections are actually usually an indication of really poor production quality. It doesn't make sense, but it was true for the seven years I was working as a field maintenance technician for Comcast.
3. The antenna itself is poorly built and connecting the two together.
To fix it, check that the braid isn't wrapped *anywhere* around the center conductor at either end of the cable. Disconnect the antenna but check picture with the cable inside and outside of the mast to determine if the antenna is the culprit. (If it is good with no antenna outside the mast and bad with no antenna inside the mast, the cable is serving as your antenna and the antenna unit itself might still be OK.)
Let us know what you find!
-Scott
I agree with those who say the antenna is not working. And yes the line is acting as the antenna. Yes once the line is inside the mast, it probably would shield the line.
Here's a quick test. With the line inside the mast, disconnect the antenna.
Hang a clip lead or any length of wire a couple of feet long onto the center (only) conductor of the line at the top.
If you see stations then, most likely you have an antenna problem.
Here's a quick test. With the line inside the mast, disconnect the antenna.
Hang a clip lead or any length of wire a couple of feet long onto the center (only) conductor of the line at the top.
If you see stations then, most likely you have an antenna problem.
The coax impedance must match the antenna output impedance.
The coax must not have any kinks (which more the center conductor in relation to the shield changing the local characteristic impedance.) An ohm meter can't sort this out.
Do not exceed the published minimum bend radius for your particular coax.
The coax must not have any kinks (which more the center conductor in relation to the shield changing the local characteristic impedance.) An ohm meter can't sort this out.
Do not exceed the published minimum bend radius for your particular coax.
I haven't been that impressed with 'amplified' antennae. At home I've tried them, but I'm currently using two home-made antennae - one a simple array made from coathangers and a foil backplane, for stations across Lake Ontario, the other a simple 75 ohm dipole for local stations. My HD reception is now better than cable.
Like the cable guy mentioned, it's less about the specs for the components you used ("gold' connectors and the like), it's more about the mechanical quality of every connection. Ensure that every connection is well-made and is wrenched up tight.
Secondly... if all you're after is decent local reception when you're in port, just hoist a simple antenna, (or this 'amplified' antenna) on a halyard. Don't waste valuable masthead space (and weight) on something you don't use while sailing.
Like the cable guy mentioned, it's less about the specs for the components you used ("gold' connectors and the like), it's more about the mechanical quality of every connection. Ensure that every connection is well-made and is wrenched up tight.
Secondly... if all you're after is decent local reception when you're in port, just hoist a simple antenna, (or this 'amplified' antenna) on a halyard. Don't waste valuable masthead space (and weight) on something you don't use while sailing.
Its all about the ratio of siignal to noise. Powered antennas (atennai sounds weird) amplify both the noise and signal.
I also have to wonder about the amplified antennas, especially with DTV.
At the transmitter end we jump through hoops to keep the amplifiers in the transmitter linear. In fact the exciter constantly keeps making adjustments so the least amount of distortion comes out of the transmitter (best signal to noise).
And that's in a climate controlled environment. So you have to wonder about an amplified antenna that sits out there baked in the sun, cooled at night. Some of the manufacturers TV preamps were already suspect before DTV. They make tons of noise, some take off and oscillate on their own. Put them outside and your asking for trouble. Meanwhile others work quite well.
Keep in mind with DTV you're watching 19 Mbps data stream divied up to carry individual smaller data streams. With minimal forward error correction. No at all as forgiving as NSTC. It doesn't take much to disturb it enough that your error rate goes high enough for no picture.
At the transmitter end we jump through hoops to keep the amplifiers in the transmitter linear. In fact the exciter constantly keeps making adjustments so the least amount of distortion comes out of the transmitter (best signal to noise).
And that's in a climate controlled environment. So you have to wonder about an amplified antenna that sits out there baked in the sun, cooled at night. Some of the manufacturers TV preamps were already suspect before DTV. They make tons of noise, some take off and oscillate on their own. Put them outside and your asking for trouble. Meanwhile others work quite well.
Keep in mind with DTV you're watching 19 Mbps data stream divied up to carry individual smaller data streams. With minimal forward error correction. No at all as forgiving as NSTC. It doesn't take much to disturb it enough that your error rate goes high enough for no picture.
Paradoxically, I'm getting good reception of more signals now (I get most Buffalo stations from across the lake) than I did before DTV. This is probably because DTV got me into trying different antennae, from a simple 75 ohm dipole taped to the wall (great for local reception) to a DIY directional antenna in my attic that works a treat for pulling in Buffalo.
Thanks for all the great feedback everyone! My next step is to disconnect the antenna and try the reception with just the wire (inside & outside the mast) to check any difference. I do know the signal amplifier works since reception is worse without it. The antenna is a amplified indoor/outdoor Philips SDV2940/27. It is very light so I'm not concerned about weight issues. I did coat the connectors with a dielectric grease to prevent corrosion and wonder if that could be a cause of signal bleading. When I disconnect the antenna I'll post the results. Thanks again folks.
Rich H, There is no LED indicator on this unit (Philips SDV2940/27). But I know the amplifier is working since the reception is worse when the power is unplugged. Thanks for your response.
I agree the cable itself is picking up the reception but the mast blocks the reception inside the mast, thats why the cable outside works. This makes me suspect the antenna itself is not working. Next time I go up the mast I'll disconnect it and check the reception via the cable inside the mast with the cable end hanging outside the mast. I'll post an update when I do this. Thanks.
Former Cable Guy
At the time of installation I coated the connections with a dieltric grease to prevent corrosion. The product I applied is "Super Lube". The product states it is a "excellent dielectric and is impervious to salt water". Do you believe otherwise? Next time I go up the mast I will disconnect the antenna and post the results. Your expertise is much appreciated.
Keith
At the time of installation I coated the connections with a dieltric grease to prevent corrosion. The product I applied is "Super Lube". The product states it is a "excellent dielectric and is impervious to salt water". Do you believe otherwise? Next time I go up the mast I will disconnect the antenna and post the results. Your expertise is much appreciated.
Keith
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