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Old 06-03-2008, 14:22   #16
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Well - I've gone for the M802 and a few of the bits are beginning to arrive so I now need to cast my mind to rigging up a ground and antenna for when I have everything. I'll refer to my amateur radio books for the ground. What I'm wondering is what I can use for an antenna. If back stays are good enough could I use any piece of copper wire of an appropriate length? I'm getting the auto tuner which should help. I have some electrical cable which has reasonably thick solid copper cores. This may sound a stupid question but could I get away with using this?
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Old 06-03-2008, 15:04   #17
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Yes, you can use just about any type wire for your setup at home. Copper, aluminum, stainless...whatever.

Easiest way to make the 802 work from home:

1. put up an antenna wire...string it to a tree or two....the longer the better but at least 25-30' overall;

2. for the RF ground, use 1/4-wave radials constructed of insulated wire of virtually any kind; at least one radial for each intended transmit band.

Example: you want to transmit on the 40m ham band. Put up the antenna wire and connect it to the tuner's antenna lug. Cut a piece of insulated wire 1/4-wavelength long (234/7.2mHz= 32.5 feet long) to serve as a radial. Connect one end of this radial to the ground lug on the tuner. String the rest of the wire around the floor or the earth outside, or wherever. Be careful to insulate the end...it's HOT when transmitting.

Bingo: you're up and running on the 40m band. Cut radials for the other bands of interest and connect them to the same lug on the tuner. Now you have an "all band" setup which will perform very well.

Bill
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DISCLAIMER: I am a working marine professional, providing fee-based training and services in marine electronics, communications, navigation, cruising skills, and related areas.
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Old 06-03-2008, 15:53   #18
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That sounds much simpler than I expected. Thanks. Out of curiosity though. On boats (the Icom manual says) it's critically important to use copper foil for the ground and not to run wires which are opaque. Why am I able to use wires in this case?
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Old 06-03-2008, 16:20   #19
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The short answer is that the Icom manual is both incomplete and misleading.

There are tons of posts re: RF grounds, and lots of opinions. Icom and lots of other "expert sources" tend to follow the long-established marine practice of trying to couple the RF ground system to seawater.

What you're doing with the radials is something else: you're creating a pseudo-ground. It need not be coupled to seawater or to the ground. In fact, it works a bit better with the radials elevated above the ground a bit.

In any case, in your situation just make up the radials, toss them about, and it will work fine.

Bill
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Old 06-03-2008, 16:50   #20
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2. for the RF ground, use 1/4-wave radials constructed of insulated wire of virtually any kind; at least one radial for each intended transmit band.

Example: you want to transmit on the 40m ham band. Put up the antenna wire and connect it to the tuner's antenna lug. Cut a piece of insulated wire 1/4-wavelength long (234/7.2mHz= 32.5 feet long) to serve as a radial. Connect one end of this radial to the ground lug on the tuner. String the rest of the wire around the floor or the earth outside, or wherever.
Bill,
For my home setup, can I leave my copper strap ground wire connected from my radios ground lug to my home copper plumbing pipes, or do I need to disconnect that ground and just go with the various radials for the bands of my choice?
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Old 06-03-2008, 17:02   #21
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tyrntlzrdking,

Depends on your setup. If you're using a tuner, I'd connect any and all ground connections to the ground lug on the tuner.

In contrast with the advice given in many radio manuals, sometimes it's better NOT to connect anything to the ground lug on the radio.

What kind of antenna do you use? Do you have a tuner?

Bill
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Old 06-03-2008, 17:10   #22
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In any case, in your situation just make up the radials, toss them about, and it will work fine.

Bill
Looking forward to trying this out. I don't yet have the cable to connect the auto tuner to the rig but I can get everything ready in advance.

Thanks
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Old 06-03-2008, 17:48   #23
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tyrntlzrdking,
What kind of antenna do you use? Do you have a tuner?
Bill
I have a Yaesu ft900 with an internal auto tuner.
I have a new slinky dipole antenna, but I want to try your setup.
My auto tuner is having a hard time tuning on different bands using the slinky antenna. Would I be better off keeping my current antenna, and buying an external antenna tuner or maybe a swr meter?
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Old 06-03-2008, 18:08   #24
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tyrntlzrdking,

As I've noted in PMs with you, the internal antenna tuner in the FT900AT is for balanced antennas only. Additionally, it is for antennas which are approximately resonant at the operating frequency. It is fine for a single-band dipole, i.e., one cut for the operating frequency. For example, for 20 meters you want a dipole with two equal legs, each about 16ft 6inches long.

If you want to use an end-fed random-length antenna with this radio, you will need an external tuner of some sort. The automatic ones are easiest to use, of course, because they tune automatically. Manual ones are a lot less expensive, but a bit trickier; however, with practice they will work OK.

For a marine installation, an automatic tuner is much to be preferred, partly because it's automatic and partly because it can be mounted under deck near the base of, e.g., a backstay antenna.

But with the internal tuner in the FT900AT, you're limited to resonant, mostly balanced antennas....dipoles, yagis, inverted vees, slopers, etc. One exception: a tuned vertical will work fine, like the Hustler mobile whip antennas with changeable resonators for each band. When setup properly, these are essentially tuned antennas which don't require a tuner, but the internal tuner in the FT900AT can trim out any small amount of mismatch.

And, yes, an SWR meter is a very good thing to have. IMHO, all vessels should carry one aboard, since they are the only practical and easy way to check up on the health of your radio and antenna system. Don't skimp on them: be sure to get a good one. Among the new ones, this Daiwa is popular and is an excellent meter: Daiwa CN-101L HF/VHF RF Wattmeter Peak/Average SWR - eBay (item 270185775999 end time Mar-09-08 08:46:16 PDT)


Bill
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Old 06-03-2008, 20:42   #25
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Re tuners - I just researched the field and chose the Wavenode WN-2. It's the smallest of the digital ones, can provide lots of information if you plug it into a PC (USB) but works fine stand-alone, and senses RF with external modules (up to 4). This lets me cycle among the backstay, marine masthead VHF, dual-band ham antenna, and any external antenna (Buddipole setup, hoistable wire dipoles, etc). It nestles into my comm console, and is about the same panel size as the SCS PACTOR modem.

Cheers and 73,
Steve
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Old 06-03-2008, 21:58   #26
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Steve,

The WN-2 is an interesting multipurpose device (principally for power and SWR monitoring), but it is NOT a tuner. It will not tune out the reactance of a mismatched antenna system to present a 50-ohm load to your transceiver (which is what a tuner does). Rather, it can give you loads of information, has a digital USB interface so you can play with the data on your computer, and looks very neat.

A tuner or coupler suitable for marine operation has to be considerably larger than this puppy (to handle the 150 watt output of marine transceivers), and it has to have a wide tuning range to accommodate the extremely wide range of reactance to be found at the base of the typical backstay antenna.

73,

Bill
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Old 08-03-2008, 15:16   #27
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Well - I am gradually making progress here. I have my M802 hooked up to the AT-140. I have the connector cable and antenna running between them. I have a 30 ft "antenna" strung up indoors (lousy weather in NJ today - I am not climbing trees today) and I have a couple of counterpoise lines running across my floor.

I can pick up a few things but haven't tried transmitting yet. Having unlocked a HAM bands I was able to pick up one side of some chatter in the 20m band. I'm also trying to download a weatherfax using SeaTty 2.0

The fax is pretty fuzzy but you can see that it is a weather map but the detail is lost. A HAM friend of mine says the indoor antenna is a loser so I'll have to see how much better it gets when I can stick an antenna outside.

One question. Given the setup you recommend Bill - do I have to ground the M802 unit in any way?
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Old 08-03-2008, 16:48   #28
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The 1/4-wave radials will serve as all the ground you need for effective reception and transmission.

However, understand two things:

1. the tuner won't tune until you push the "TuneThru" button, so you won't get the strongest reception until you do this. REMEMBER TO DO THIS ONLY IF YOU HAVE A RADIAL SET UP FOR THE BAND YOU'RE USING. If you try it on other bands, the tuner won't be happy at all.

2. it would be very good to set the radio up for low or medium power transmission while you're getting used to it. Push the F 7 buttons for low power or F 8 buttons for medium power.

It wouldn't hurt a bit to run a DC ground wire from the tuner ground lug as well, to help bleed off static and transients. Not mandatory, but good practice.

Also, when the rain lifts by all means get that antenna up in the air! Much better than inside.

The Icom manual for the 802 has a long discussion of antennas and grounds. They label these "non-technical" and "technically-speaking", or some such. To be nice, I can only say they ought to be ashamed of all the misinformation and misleading proclamations therein. Really atrocious stuff in places, viz the diatribe against "round wires". What the devil do they think a wire antenna or a backstay antenna is? The idea that and RF ground/counterpoise cannot use round wires is just plain wrong. I suppose the author never thought of a simple wire dipole...one of the most effective antennas you can put on a boat....which consists entirely of round wires.


Have fun,

Bill
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Old 08-03-2008, 17:00   #29
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Bill - I really appreciate your input. Some questions about the counterpoise. What is the tolerance around counterpoise length? Clearly one doesn't use a counterpoise for each fractional turn of the dial. So there must be some range of lengths involved where it's ok. Next - do I need to keep the counterpoise wire straights (as the Icom manual says) or can they bend around a bit. Also - do I need to keep them apart or can I lay them along side each other?
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Old 08-03-2008, 17:18   #30
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Good questions.

1. There's quite a bit of tolerance. Figure the radials for the middle portion of the BAND you wish to operate on. For example, for the 20m ham band (14150-14350 kHz if you're an Extra Class), cutting the radial for about 14250 would be fine, and would cover the entire band.

2. They don't need to be straight. You can curve them around the room some what.

3. They don't need to be separated. You can run them together. Remember my TV twinlead example? And my 5-conductor cable example?

Sounds like you're on your way.

Bill
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