Amateur Radio Emergency Antenna

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skiptaylor
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Amateur Radio Emergency Antenna

Postby skiptaylor » Sun Mar 08, 2009 12:54 pm

What antenna do you use at your Stake center for emergency communications? How is it setup, permanent or temporary? How did you mount it if permanent?

We have a two meter copper Jpole on about 15 feet of 5' per section masting. Looking for a better way.

I guess another question is whether your emergency comms are permanently mounted or kept apart till needed?
Skip Taylor :eek:
Lancaster CA.

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Mikerowaved
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Postby Mikerowaved » Sun Mar 08, 2009 5:41 pm

Skip, it can depend on many things, like, how geographically large your stake is; what the terrain is like; how much of that you are trying to cover; if you're trying to communicate simplex to 5W HT's with rubber ducks, 50W radios with elevated gain antennas, local repeaters; etc., etc. For example, from our stake center I can hit 1 of our ward buildings with a wrist-rocket and the other is only a mile or so away. For me, an elevated J-Pole might be overkill, unless I was trying to reach the nearest Bishop's Storehouse, then it might not be enough.

For our situation, instead of a permanent fixture, a couple of us have fiberglass dual-band collinear antennas with portable tripods (and guy ropes/stakes, if needed) that can easily be setup on the stake center property. Mine fits in a duffel bag (with other things, of course) and takes about 15 minutes to put up. With a couple of RG-8 and/or RG8x sections, I can easily make it reach indoors to a command center.

Every situation is different, so you will have to experiment and see what works and what doesn't for you. That's one of the reasons holding regular nets is important. Over time, you will know exactly which areas are solid and which are completely deaf to your location. Or... which repeaters you can reach and which alternate repeaters you can't.

It all comes down to what it is you are trying to accomplish and what's keeping you from accomplishing it. ;)
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skiptaylor
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Postby skiptaylor » Sun Mar 08, 2009 6:06 pm

The Stake is geographically large. Something like 40 by 45 miles or so. It's an easy thing to cover if you have mountaintop repeaters.

We have 50W 2m mobile radios. Each location has a jpole and 2 or 3 five foot pole sections. The problem is it takes quite a few people to set it up. We had been looking toward a permanent mounting, but the FM group says that's not allowed.

I think what we really need is going to be directionality (and gain) or height above ground (and gain) or both. Did I mention gain yet? One of the wards is located on the far side of a small mountain range as well.Our contact Storehouse is on the other side of a large and tall mountain range. Some portions seem better suited to lower bands in my mind but those radios cost a lot more than a 2m mobile. It just seems to be stretching the ability of 2m without a lot of antenna or height.

I was hoping someone had a really nifty portable 2m setup they use that's fast, simple to do and easily guyed for the local winds we have. We are in a desert and it seems like the average wind is about 30mph around here sometimes a lot higher though.

What kind of collinear do you use with yours - commercial or did you make them?

Maybe someone will come up with some more ideas.

Thanks!
Skip Taylor :eek:
Lancaster CA.

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Postby russellhltn » Sun Mar 08, 2009 6:42 pm

I'm not sure what the prohibition is for antennas. We've got antennas mounted on a church-owned building next door to the stake center. It might be a aesthetics issue or it might be a risk issue that can be mitigated by using a professional installer. However, even if permanently installed, one needs to figure out ways to erect a replacement should it be damaged by high winds.

From the description of your stake, I think you're looking at a passive reflector to bounce your signal off of, a relay station or a repeater you can depend on. Unless the mountains come to a sharp peak (quite a bit less then 2m), I don't think you can get a 2m signal over those hills.

Also be careful about antenna gain. Antennas do not amplify - they can only direct. And all gain figures assume the desired station isn in the direction favored by the antenna - whatever direction that happens to be. J-poles are generally good for base stations, but since they have a slight upward angle to the direction, they aren't so good for mountain top repeaters that need to direct their signal downward. Likewise high gain vertical antennas tend to beam the energy sideways which may be the wrong thing to do in a hilly area or if surrounded by taller buildings where a higher angle of take-off is needed to get out. Bottom line, always look at the radiation pattern, not the gain number to decide if a given antenna is the right one for you.

Without knowing if there's any alternatives avaialble, I think you're going to be stuck going to HF radios and NVIS antennas.
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Hijt
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Building mounted 2 meter antennas

Postby Hijt » Sun Mar 08, 2009 11:03 pm

About 10 years ago we installed a vertical 2 meter antenna on the roof of our Stake building. It has been used for several drills, both city and stake. I don't think it has ever been questioned as to whether it was allowed or not. One of the issues might be that it is not allowed in the city that you live in. Also it has been a rule of thumb that antennas are not to be mounted on the steeple. We used a fiberglass commercial antenna that tends to be less obtrusive because of the simplicity of design.

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Postby Mikerowaved » Sun Mar 08, 2009 11:55 pm

avskip wrote:I was hoping someone had a really nifty portable 2m setup they use that's fast, simple to do and easily guyed for the local winds we have.

I'll see if I can dig up a recent picture of our's all setup and guyed.

avskip wrote:What kind of collinear do you use with yours - commercial or did you make them?

I use a Diamond X200A (or equivalent*), mainly for the trade-off of having reasonably good gain without too flat a pattern (like Russell mentioned). On 2M, at 20° up from the horizon you are still holding -3dB of your max. signal level. Factored in with that is good ruggedness in winds (only 10' tall), and easily broken down into 2 sections for transport.

*There are cheaper versions of the X200A, made by companies such as Tram, Workman, Jetstream, and others, that seem to perform on par with the Diamond (YMMV). To be clear, I'm not endorsing Diamond, nor any other company mentioned here. Just tossing out some examples.
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brentcase
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Postby brentcase » Fri May 22, 2009 9:38 pm

Instead of installing equipment or antennas at our buildings, we use our car 2m mobile antenna's. (and use APRS!)

Our Stake has plenty of repeaters and backup repeaters in the area that we will use that are reachable with HT and mobile radio's. In an emergency (after the hurricane in our case) We will drive to the Stake house or Ward building and use our 50-65 watt dual bander 2m/70cm mobiles in the car. Our mode is to drive to the nearest command post (Ward buildings/Bishop/Stake President House etc) and use our vehicle mobile rigs to either use a repeater or relay information via simplex nets. You have a built in portable power supply and generator (car battery and ample gas in the tank(s) of the cars in the parking lot). I also keep a portable yagi satellite antenna made by arrow antennas with adapters for the HT and moble rig. My car is also rigged with APRS so coordinates at the location of an emergency are relayed to the internet and other APRS equipped land stations that might have normal communications available. My car mobile is equipped with a keyboard adapter so I can also send tactical information via packet e-mail. (http://aprs.fi/?call=K4BSC). Using APRS, you don't really need to punch your signal to a distant repeater. APRS blasts your signal to nearby APRS equipped mobiles or fixed locations monitoring 144.390 and with 2 - 3 hops, your message will reach it's destination via a gateway to the internet. My mobile communicated with 287 radios over the last 48 hours, heard on radio by 17 known stations, 10 known iGates.

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Postby russellhltn » Fri May 22, 2009 10:06 pm

BrentC wrote:My car mobile is equipped with a keyboard adapter so I can also send tactical information via packet e-mail.


Kenwood D700 with adapter?
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