Posted: 8/7/2011 10:40:29 AM EDT
| I want to install an antenna in the attic so i can be on the air more and have the convenience of not having to set it up every time i want to get on the air so my question is, my house is 54' long so figure 52' for a wire antenna. its WAY to short for 40m but would a tuner tune a 52' wire to a decent SWR on 40m? im thinking not but im hoping someone her would know. |
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IF you have a counterpoise, a "random wire" about 33' will work just fine. Run some counterpoises (just wire laying on the ground) about the same length. Do several, off in various directions.
The counterpoises are the other half of your dipole. A halfwave dipole is 66' for 40 meters. An OCFD (aka "Windom") is also 66' for 40 meters. Maybe you could bend those to fit? An OCFD would be usable on 20, 17, and 10 meters. A 40 m dipole is not. A friend has a 66' OCFD zig-zagged in his attic with good results. AFM |
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Quoted:
IF you have a counterpoise, a "random wire" about 33' will work just fine. Run some counterpoises (just wire laying on the ground) about the same length. Do several, off in various directions. The counterpoises are the other half of your dipole. A halfwave dipole is 66' for 40 meters. An OCFD (aka "Windom") is also 66' for 40 meters. Maybe you could bend those to fit? An OCFD would be usable on 20, 17, and 10 meters. A 40 m dipole is not. A friend has a 66' OCFD zig-zagged in his attic with good results. AFM well, i want 40/20/17 in the attic, 10 i can mount outside on an old telephone pole. i will have to get up there and measure how much height is up there. dont think its enough room for me to stand up but it should be 4ft or so. i will have to look into the OCFD. |
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OR.... try this on for size.
And instead of the Jetstream center insulator and ferrite beads, use a 1:1 current balun. This is the Buxcomm B15C11. There are others you can use. http://www.packetradio.com/catalog/index.php?main_page=product_info&cPath=11&products_id=2248&zenid=mf6pr33ts2nnhuvlib3fng09q3 
So, what the hell is that? The two legs with the red and blue coils are a 75 m coil loaded dipole. You will need a tuner to help expand the bandwidth a bit. The coils are not quite symmetrical, nor are the lengths. This is to help RAISE the impedance up closer to 50 ohms. When a dipole is in free space it is 72 ohms. Closer to the ground at more realistic heights (30'-50') it is closer to 50 ohms, which we want. But lower still, the impedance drops below 50 ohms, such as the Buddipole at 16', which can be down around 20 ohms or so. So, the offset raises impedance. So the whole red and blue leg assembly gives 75 meters. But at higher frequencies the coils act as chokes, electrically cutting off the outer portions of that dipole. The coils are located so as to act like a 20 meter dipole between coils. So, there are two bands, 75 and 20 meters. Looking at the other two legs, with brown and green coils. The whole thing is a coil loaded dipole for 40 meters. The coils are located so that between the coils it is 15 meters. The offset gets the whole thing closer to 50 ohms. Keep it all as far from metal ductwork, pipes, as possible. Use your tuner to get a tune on 75, 40, 20, 17, and 15 meters. Tie the ends off with insulators, and keep the ends away from everything, just hanging in the air. (the ends are high voltage) ( ETA: It might tune on 10 meters, try it.) |
| i will have to see what i can do once the temp drops some. to damn hot to be up there right now. if we get a cooler day and maybe some rain to cool it off up there i may just deal with the heat thats left to get it up there. going to order a PS and tuner when i get paid next monday. |
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http://www.powerwerx.com/batteries-chargers/powerwerx-30-amp-desktop-switching-power-supply-powerpoles.html
This new supply from Powerwerx looks good. I like the Powerpoles on the front for small acc, but you can put a 10-ga zip on the back with Powerpoles going to a RigRunner strip. Price looks good, too. I've seen some good buys on tuners on QRZ, QTH, and eHam. You might look for good/used on those sites. |
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same with the PS, its between the 1223 and another that i cant think of the model number right this min. im on a budget so im shopping around. http://cgi.ebay.com/33-Amp-12-Volt-10-13-8V-HAM-Radio-Power-Supply-12V-/150642246046 The 36/40 amp version of these has a 5.0 rating on eham reviews. It's not much higher in price so I guess most get that one instead of this lower power version, since there are no reviews of this one. I've been seriously contemplating one of the 36/40amp versions to power my 2m SSB amp, to replace the heavy room heater linear supply I have now, which I suspect doesn't have enough amperage capacity for the amplifier. |
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http://www.powerwerx.com/batteries-chargers/powerwerx-30-amp-desktop-switching-power-supply-powerpoles.html This new supply from Powerwerx looks good. I like the Powerpoles on the front for small acc, but you can put a 10-ga zip on the back with Powerpoles going to a RigRunner strip. Price looks good, too. I've seen some good buys on tuners on QRZ, QTH, and eHam. You might look for good/used on those sites. i like that. its niceand small and wont take up to much room in my radio box. have to hunt around and see if i can find it cheaper though. |
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same with the PS, its between the 1223 and another that i cant think of the model number right this min. im on a budget so im shopping around. http://cgi.ebay.com/33-Amp-12-Volt-10-13-8V-HAM-Radio-Power-Supply-12V-/150642246046 The 36/40 amp version of these has a 5.0 rating on eham reviews. It's not much higher in price so I guess most get that one instead of this lower power version, since there are no reviews of this one. I've been seriously contemplating one of the 36/40amp versions to power my 2m SSB amp, to replace the heavy room heater linear supply I have now, which I suspect doesn't have enough amperage capacity for the amplifier. thats not bad but i went to there website and it says they are both the same size but the 36/40 has some type of box connected to the bottom of it. not sure how they are claming its the same size when one has a box thats just as big as the PS attached to the bottom of it. |
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If you specifically need very small size for a power supply, this came highly recommended by a friend that uses one in his "go kit".
http://www.gammaresearch.net/hps-1a.html 3.37" x 1.55" x 5.25" "It is especially useful when used with smaller transceivers. It is much smaller than the Icom IC-706, IC-7000, FT-100D, etc." It specifically mentions your radio. |
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thats not bad but i went to there website and it says they are both the same size but the 36/40 has some type of box connected to the bottom of it. not sure how they are claming its the same size when one has a box thats just as big as the PS attached to the bottom of it. I made the same assumption from the photo when I first started looking at these, but the photo on the website and ebay of the 36/40 is highly deceptive. The photo is of two units, one on top of the other so as to show the front and back. If you look at the eham review one of the reviewers gives the dimensions. The website mentions that the photo is of two stacked on top of each other. The 36/40 amp one is $10 more than the 30/33... up to you whether the extra capacity is worth it. A 30 continuous/33 peak should run a 100w HF radio along with a couple of VHF/UHF mobiles and other accessories simultaneously. Quoted:
If you specifically need very small size for a power supply, this came highly recommended by a friend that uses one in his "go kit". http://www.gammaresearch.net/hps-1a.html If you read the actual specs on that, it's only a 5 amp power supply, just that it has some capacitors on the output to boost the peak current. 10 watt FM mobile would likely outtax that supply. Not what I would recommend, especially not considering the cost. |
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Yeah, but the caps really do the job. It apparently keeps up with SSB and CW at 100w, as born out by my friend's experience with it. Just wondering why you'd want to handicap yourself with a power supply of limited capacity, that's 2~4 times the cost of a standard full capacity supply. |