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Old 04-05-2010, 07:53 AM   #1
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Re: Antennas

I have the Winegard antenna that came with the bread truck, the one that looks like a little AWACS disc antenna. Works pretty well, I get more OTA channels in the RV than I do with 2 Terk antennas indoors.
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Old 04-05-2010, 10:04 PM   #2
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Re: Antennas

We are using RG6 coax attached to the TimeWarner cable pole! We currently have TimeWarner's cable & internet (wireless router) but will not have service when we pull out from here (cable doesn't run that far). In NM (back to the campground we stayed in before) we will have cable TV but no internet... back to cell phone on a Wilson Truckers antenna? Breakdown and buy an aircard? I will figure that out when I need to. Previously we simply used my daughters netbook.

DIY Wifi Booster might help. As for TV, we have a Dish but the box messed up and we haven't used it in a while (shut the service off last winter)
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Old 04-06-2010, 12:57 AM   #3
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Re: Antennas

Originally Posted by Smitty
I thought that an external antenna would boost reception? I've also read that using a router that the air card plugs into was better, since the router stays in one spot, unlike the laptop, so less chance of damaging the card or the USB port. I know (read) alot of full timers use a Wilson Truckers antenna on their routers (or maybe a signal amplifier?).

There are at least two antennas in the set-up you describe. The one (or two)to get the service from the source (WiFi and/or cellular), and the other for wireless connection to the laptop. I'm not going to address the internal signal routing, just the internet or voice source. While losses inside cables at cellular frequencies are bad (880 and 1900 MHz), and pathetic at WiFi (2400 MHz), they aren't anything compared to the shielding of the source signal that will be experienced inside a metal-skinned bus. What might work to pick up a signal inside a lath and plastic death trap RV will not have the same performance in an armored Skoolie.

The tiny 1/8" cable they give you with devices is the most pathetic of all. It is necessary in short lengths so the equipment can move a bit without snapping the socket off of the case, but bigger cable is better. You should notice weak-signal improvement even with 1/4" RG-58/U cable like on a mobile CB set. Also, the shorter you can make the antenna cable, the better. Park the router in an overhead cabinet or shelf if possible to keep the antenna cable the shortest.

The best place for antennas is on a ground plate, outside above all other obstacles. Normally, this is the bus roof. If you still had a sign compartment over the windshield, drill the antenna into the roof, and mount the router in the shelf just below it to keep the cable short. This would be a few inches behind your middle marker light. If you wanted to put the router in an overhead cabinet on the side, mounting the external antenna on a metal angle bracket above the windows and have a short cable come in to the router is fine, though the signal may be blocked toward the opposite side of the bus.

The ground plane is a necessary part of most antennas at lower frequencies, and many in these bands, too. Some others are "elevated feed" antennas and are at least twice as tall. These antennas have the cable run up through the bottom of the "whip" to attach in the center, and do not need a ground plate. They are also most subject to performance-robbing mechanical damage. The Wilson Trucker is one designed to be on a mirror mount, so it is elevated to see over the roof of a semi. Because the designers know the mirror does not provide a ground plate, it uses an elevated ground. Most of the height is mast, not antenna, and I have seen that they break. They are good for what they are, but I would prefer to drill a mount for a 3" whip into the roof first.

The good news is that at these small wavelengths, A 4-inch square of metal is an adequate ground plate, and a 6-inch or 8-inch square is all you will ever need. If you are worried about omni-directional pickup, mount a plate up between your solar panels so that the whip is at the highest (and most vulnerable to damage) point on the bus.

My first choice would be for an antenna whip and mount with no cable, one that goes through a drilled hole and attaches with a nut on the bottom. The threads for the nut should also be a female socket for a Type 'N' or type 'TNC" connector. Then you provide a heavy main cable that attaches to this socket.

Avoid antenna kits that have the industry-standard Motorola "NMO" mounts. The whips and external button of these mounts are mostly designed OK. The problem is that the way the cable attaches to the mount internally in most models of mount sold does not provide maximum signal transfer between the cable and whip. If you can look under the cover of the underside of any mount, and see the bare center conductor of the coax stretched out in the open and soldered to the center contact, do not use this model mount. The exception is when you have to look down into a grounded tube surrounding the solder connection to see it. Some of these tubes are sealed on the bottom, the ones left open are acceptable. It is most preferable to only use models where the outer braid or an extension of it goes out through the ground plate, keeping the signal sealed inside the coax and tube until it gets to the business side. (Don't anyone bother telling me about all the brands of mount that work fine when operating mobile near a tower that has 40 db of signal over the minimum required. I'm worried about exchanging signals all the way out to the limits of coverage. It's a lot different trying to access the only tower when it's 10 miles away versus accessing coverage inside a city served by 50 towers.)

There are "thick panel" NMO mounts that have no cable, they are just the rooftop button and a nut and female connector inside, these are no problem for signal transfer.

For cable, you want the 1/2" cable like hams and CBers use at a home station - RG-213/U is my first choice, RG-8/U is the standard and slightly less good. Try to get Belden or another good brand, the Radio Shack cables have historically been made to minimum performance construction. After that, I would use a mid-sized cable like RG-8X, Mini-8 or Pro-Flex before using mobile cable. Try to keep this main cable down to 7 feet or less, limiting it to about 18 inches or so is better. When you get within 1-2 feet of the receiver box, then have connectors that switch down to the micro cable needed to attach to your equipment. If you are plugging straight into a laptop card, you may want to have a wall box with a double female drilled into a blank panel, and have your mini jumper cord go to the wall plate with the large cable hidden on the other side.

An alternate idea that has been used successfully is the use of receivers that are embedded into USB dongles instead of antenna installations. As you arrive at each campsite, find the window with the best reception, and tape the dongle to the glass with clear shipping tape. Then use a male-female USB extension cord between the dongle and the data device. Since there is no Radio Frequency, just 5 volts up to the circuit plus data up and down, there is no RF loss in the cable. The 5 volts may get weak in a long or poor cable, or from an overloaded data device supply, so for some set-ups maximum power for the dongle radio would require adding an externally-powered USB hub in between extension cords.
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Old 04-06-2010, 09:46 AM   #4
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Re: Antennas

My plan was to get an old Direct TV dish, get an old Direct TV box, build a little mount so I can setup the dish on our bus roof and then run some cables. I am interested to see what you guys say about WiFi though. I wrote it down as an optional idea for our bus, but if it is actually do-able I think it would be awesome to setup.
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Old 04-06-2010, 11:08 PM   #5
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Re: Antennas

Originally Posted by Smitty
Redbear I'm sure there's alot of useful info in your post, if I could understand it I don't know (or understand) scat about computers other than how to email, and post on forums (along with pics), the technical part of it is over my head (and likely always will be)

Well, it sounds like I need to go back to adding an external antenna for the wi-fi. Just to be sure I'm making myself clear, I'm not worried about signal from the router to the laptop (doubt if I'll ever worry about taking it outside), I'm wanting to pull in the best signal I can for the strongest internet connection I can get.

How does this sound.... getting a paint-roller handle that extends from sat 6 to 12' in length, and mounting the antenna to the end, then mounting the "mast" to the side of the bus so it could be raised when parked & lowered for travel. Is there anything with that idea that would interfere with a signal? I could mount it next to the front door since most of my computing will be done at the table right behind the stairwell. Of course I'd need a loop of cable to allow the mast to extend/raise.

Doable....or am I wizzing-up a rope?

OK, I answered your 'other' question with an exact antenna for the air card. It's the dual-band version of the mono-band cell antenna I've used for myself for (16?) years, ever since I had cell phone S/N 760 (or was it S/N 740?). Not the cheapest but the best there is. The reference price on the website is not the selling price, that's usually 1/2 to 3/4 of the reference, depending on how much you buy.

The push-up pole has been done, I've seen it on stick-n-staple rear ladders. I saw a detailed construction article a year or so ago, but can't put my finger on it tonight.

If you are going to do the push-up pole, you might want to consider a directional antenna that you could rotate toward the hot spot for maximum signal. Here is one I regularly recommend for $30: In Greek: the 15 dbi equals 12.8 dbd. Since a gain of + 12 db makes a 1 watt radio look like about 15.6 watts, and a gain of + 13 db makes it look like 20 watts, aiming this antenna at the hot spot should give you about 18 times the power both transmitting and receiving, or in other words work about 2.5 times the distance compared to a whip. Of course, there's nothing wrong with pushing up a whip, either.

You will have to have the outside antenna connected to electronics that are designed to HEAR a hot spot, not CREATE one. Most wireless routers are designed to connect to the internet through a LAN jack, or cable, fiber, or DSL modem. A router with BRIDGE mode is designed to either create or receive hot spots. The other option is to get one of the adapters that plugs into a USB and lets a desktop become part of a wireless LAN. Use that to hear the hot spot, and your normal router to reach the PC.

One bit of advice: if the budget allows it, use a laptop and router with 802.11a for the downlink, and use 802.11g or n for hot spot access. If your internal LAN is on 5000 to 6000 MHz, and your access is on 2400 MHz, your uplink and downlink will not interfere with each other. Also, your internal network won't be seen by the majority of people who have only one band, and your internal network will not interfere with your neighbors' ability to hear the hot spot. The only time this will be an issue is if a park uses 802.11a to link remote hot spots back to the office, but with low power, a metal bus, and shifting channels it should be completely manageable.
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Old 04-07-2010, 02:17 PM   #6
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Re: Antennas

I don't know anything about wi-fi signals- but as for the TV, I used my giant hunk of steel- the bus body. Picks up digital channels for miles... not so good for analog. Sand off a bare spot. drill a hole, self tapping screw to a wire lug- right to the digital wire on the t.v. Or the center pole of the coax- watched the superbowl on this set-up from way off in BFE.
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Old 04-07-2010, 09:16 PM   #7
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Re: Antennas

Originally Posted by Smitty
I appreciate you're trying to help, but I'm telling you I'm unable to understand what it is you're trying to say. If it's not something that can be explained in laymans terms, save your fingers the typing, 'cause I'm not gonna get it.

Radio is my livelihood, just like HVAC has been yours. I try to make everything simple, but I can't always. I also don't expect people to automatically trust what I say. I'm not so much about "Do this" as I am about "Do this, and here's why," just like you often are. Some people stop after "Do this," and take it at face value, others want to understand a little more. This is especially true in cases where instead of copying each other's work, we use each others' ideas as take-off points for our own. If my suggestions were 100% for you only, I'd send a PM. But something I type might trigger a cool idea in someone else's plans. That's why I ask myself "why" about the cool ideas I see in various topics from others in this group.

If I can figure out the part that someone "gets," I can go in another direction starting from there.

Originally Posted by Pied Typer
Okay redbear,

The directional antenna that you linked to is set up for 2400 mhz, and by the limited knowledge I have about antennas, that is set in stone due to the distance of the vertical bars from one another (which are set at a optimal distance to mesh with the 2400mhz wavelength). That being set in stone, why pick 2400mhz? Is that the standard for wifi or will I be SOL in some places that may operate on a different frequency?

Yes, the frequency band of best performance is set in stone, but not primarily by the space between the bars. Antennas have one or more "driven elements" that actually attach to the cable. The remainder of the antennas are reflectors, directors, or support pieces. In this type of antenna (Yagi), the length of the vertical bar that attaches to the cable makes the primary determination of the frequency band. The other lengths are important, too. The bars in front of the driven element are shorter so that they act as directors, the ones in back are longer so that they act as reflectors. The spacing is set so that the signals that hit them going to or from the driven element bounce in a way that increases the amount of in-phase waves arriving from or going to the desired direction. Waves coming or going to the side are somewhat out of phase and cancel each other. "In phase" means the pluses hit at the same time as other pluses, and minuses hit at the same time as other minuses. These waves combine in a way that results in the pluses being higher and the minuses being lower. +1+1+1+1 = +4; -1-1-1-1 = -4 That means a stronger signal. If pluses and minuses hit at the same time but "out of phase," they cancel, +1-1+1-1 = 0; -1+1-1+1 = 0 A satellite dish is just another kind of reflector, and one or two tiny bars under the plastic cap out front pick up the focused signal waves. Enough on antennas.

I would expect all WiFi hot spots would have at least 2.4 GHz, also known as 2400 MHz. Some may have added bands, I don't know; but I would be surprised to find no 2.4 GHz. If you notice laptop and wireless device specs, they will have 802.11b/g/n built in, but only rarely 802.11a. Now I am not a data expert, so maybe someone else can correct what I'm saying. These 802.11 specs, I believe, are actually information transfer arrangements and are not really locked to one band, but in practice 802.11a is usually on 5.? GHz and b/g/n is on 2.4 GHz. As far as interference, if I understand correctly these devices are never locked in transmit, but burst bits back and forth which include the desired data, signaling, and error checking. They use the signaling codes to separate different traffic streams on the same frequencies from each other.

Having a "clear" frequency might speed the data throughput by reducing collisions of different devices bursting on the same channel, and therefore not requiring the error checking to request repeated re-sends of your data.

I don't know if WiFi has this, but some data transfer protocols have dynamic burst length, depending on the errors. For example, If I try sending you whole sentences, and I find you don't stop me for errors, I might try sending whole paragraphs to speed up the data transfer. If you copy paragraphs without error, I will keep sending them. If that starts causing errors, I will go back to sentences. If sentences are a repeated problem, I will slow down and send one or two words at a time, and see if you got them before continuing. Again, I know dynamic length is out there, and I'm not sure if it's part of WiFi, but it serves as an example of how a busy frequency can slow down a data transfer.

There are 11 USA channels in the 2.4 GHz band, and they overlap each other. The signaling separates the information transfers. This proves you do not need a completely sterile frequency. Out of the group, Channel 1, Channel 6, and Channel 11 do not overlap each other. Channel 2 overlaps the upper 80% of Channel 1, and the lower 20% of Channel 6. Channel 4 overlaps 40% of Channel 1 and 60% of Channel 6, and so on, up through Channel 10 being 20% over Channel 6 and 80% over Channel 11.

In summary, Channel 1 is overlapped by 2 through 5, Channel 6 is overlapped by 2 through 10, and Channel 11 is overlapped by Channels 7 through 10. You will find a lot of devices default to Channels 1 or 11 for minimum channel overlap, but if too many are all left on those default channels, it may be better to pick one of the channels with more overlaps to get away from the crowd. Or get really away from the crowd onto a different band with 802.11a.

I think the best source for accurate WiFi information I've run across is Jack Mayer over at SKP. From what I've read, he has worked at 'wiring' campgrounds for wireless, and maybe even for fixing other people's installation problems.
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