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"news" wrote in message
... I need to improve my ground system, and am thinking of burying some radials under the lawn. [I realise this is not the most efficient way to do it from an electrical point of view, but the alternative approach of installing the radials above the ground is completely out of the question, for aesthetic reasons]. Some practical questions: ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. What is the "best" type of wire (or braid) to use for the radials? Whatever you can get cheaply, as you need a lot. Insulated is fine- the soil (rf) conductivity is poor (or you'd not need radials) so the benefit from have bare wire is minimal. Insulated will stop it corroding. 2. How do I bond the radials together? (I guess my 15-watt soldering iron won't be up to the job ...). 3. What kind of solder and flux should I use? Bring them to a 'star point' which is your earth point and it should have a normal earth stake. Make sure this is bonded to you PME point for safety by 10mm^2 wire. If you solder, use ordinary multicore solder. 4. What precautions should I take to minimise the effects of corrosion at the joints? Self amalgamating tape or use conduit boxes and 'pot' with epoxy. 5. How deep should I bury the radials? Two inches, six inches, 12 inches? Depends- this is as much to do with what the land is used for. In the past I've used a spade to make a shallow 'slit', maybe 2" deep, in the lawn and pushed wires into that. In a flower bed or vegetable patch that wouldn't be deep enough. Don't forget patios. Our patios have radials under them. Also, you can run wires around the bottom of fences etc, by paths. 6. Is there anything else I should know? Don't forget that safety bonding! -- Brian Reay www.g8osn.org.uk www.amateurradiotraining.org.uk FP#898 |
"news" wrote in message ... I need to improve my ground system, and am thinking of burying some radials under the lawn. [I realise this is not the most efficient way to do it from an electrical point of view, but the alternative approach of installing the radials above the ground is completely out of the question, for aesthetic reasons]. Some practical questions: ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. What is the "best" type of wire (or braid) to use for the radials? 2. How do I bond the radials together? (I guess my 15-watt soldering iron won't be up to the job ...). I would use a blowtorch (But I am used to using one). The secret is not to overheat things. Its a kind of dabbing technique to get up to temperature. |
Hi Ian
I had over 3,500 feet of radials under my HF9VX/w160. They were buried only about 1 inch deep overall. I used a meat cleaver and rubber mallet, placing an open eyehook through the hanging hole on the meat cleaver. I stretched the wire out first, then let it pass through the eyehook. As I cut along the edge of the wire to make the hole in the ground, the eyehook would pull it down below the surface. The job went fairly quickly! I used some 12 and some 14 guage insulated solid copper wire, whatever was on sale the cheapest, hi hi..... At the antenna base, I drove an 8 foot ground rod, allowing it to stay above ground about 4 inches. Each radial came up to this ground rod and made a 90 degree turn upwards. I used a cheap pencil flame propane blowtorch and Copper Phosphorus Bronze brazing rods (low melting point, good adhesion to copper), affixing each wire to the ground rod. I then welded an insulated braided 8 guage wire to this for later connection to the antenna. After all the radials were in place and welded to the rod, I slipped a 3/4 inch copper pipe over the ground rod and down to the radials and filled it with silicone caulk. Then, using a hose I washed out the dirt under the radials around the ground rod so that I could (after it was dry) get about a 1 inch deep layer of silicone around the ground rod and ends of all the radials so that the insulation was covered back about 1 inch and about 1/2 inch above the copper pipe. Because the HF9VX has a COIL near ground level, I cut the bottom out of a vinyl Cylindrical flower pot and slipped this over the antenna mount and ground rod. It was stuck into the ground about an inch or two, down to the tops of the radials. To keep grass/weeds from growing, I also dumped a 4lb box of rock salt into the container. I used a PVC sleeve over the antenna mount, so the salt would not get to the aluminum. TTUL Gary |
Another way is to go to your local electrical wholesaler
(assuming he will deal with you now we're past Jan 1st/Part P) and buy one of those chocolate-box-like strips for commoning up 6mm green-and-yellow to clamp all the wires together. "Gary V. Deutschmann, Sr." wrote in message ... I used a cheap pencil flame propane blowtorch and Copper Phosphorus Bronze brazing rods (low melting point, good adhesion to copper), affixing each wire to the ground rod. |
On Sun, 09 Jan 2005 11:33:44 GMT, news wrote:
I need to improve my ground system, and am thinking of burying some radials under the lawn. [I realise this is not the most efficient way to do it from an electrical point of view, but the alternative approach of installing the radials above the ground is completely out of the question, for aesthetic reasons]. Some practical questions: ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. What is the "best" type of wire (or braid) to use for the radials? Some of my literature recommends against braided or woven conductors as having too high a surface resistance to lightning and RF, especially if they get corroded. Wide smooth surfaces are better. You might try Lowe's Home Improvement or Home Depot -- they both sell 500-ft. rolls of #12 copper wire for about $20. That'd save you going to the poorhouse, on this :-) 2. How do I bond the radials together? (I guess my 15-watt soldering iron won't be up to the job ...). A Weller SP-120 (120 watts, 1/2" tip) or SP-170 (170 watts, 5/8" tip) would do the job. Either of these is also great for soldering coax plugs (I have the SP-170 & it's a barnburner). If you can't find the irons locally at a hardware or hobby shop, a Google search brings them up, online. Bob k5qwg 3. What kind of solder and flux should I use? 4. What precautions should I take to minimise the effects of corrosion at the joints? 5. How deep should I bury the radials? Two inches, six inches, 12 inches? 6. Is there anything else I should know? ~~~~~~~~~~~~~~~~~~~~~~~~~ We are on heavy clay soil that alternates between being very dry and very wet. My main interest is in the lower hf bands (40/80/160) and possibly 136kHz. |
"news" wrote:
I need to improve my ground system, and am thinking of burying some radials under the lawn. Good idea. Bury anything that will conduct, eg biscuit tins! I spent ages unwinding and burying the coils from old TV CRTs. 40 years ago (I was a 160m nut) I bought a very large reel of bare 18 swg "garden wire" from local hardware store. It looked like copper but too light and seemed to be an ali alloy. It was buried in around 2"-4" slits in 100 - 150' lengths in clay-ish non-acid soil. Still looks in good shape. I used choc block connectors to join the wires in pairs or triplets, soldered the group and left a tail to make the next larger group. Used heavy auto earthing braid for final lead into ground floor shack. Was it worth the trouble? Yes. With a ~200' inverted L (3/8th wave on topband), no problem working Ws on a 500mW transistor (germanium!) box. Dead band with earth disconnected. Alf GW3SRG |
On Sun, 09 Jan 2005 11:33:44 GMT, news wrote:
I need to improve my ground system, and am thinking of burying some radials under the lawn. [I realise this is not the most efficient way to do it from an electrical point of view, Why not? Some practical questions: ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. What is the "best" type of wire (or braid) to use for the radials? Something that is cheap (so you can have lots of it) and non-corroding (so you don't have to re-lay it every year). 2. How do I bond the radials together? (I guess my 15-watt soldering iron won't be up to the job ...). Use a car battery clamp and plenty of grease. 3. What kind of solder and flux should I use? None at all. See above. 4. What precautions should I take to minimise the effects of corrosion at the joints? See above. 5. How deep should I bury the radials? Two inches, six inches, 12 inches? Whatever you find most convenient. 6. Is there anything else I should know? You will never lay enough radials to turn your garden into a highly-conductive metallic mirror, the next best thing you can do is to provide the lowest ohmic contact for your vertical. If your vertical has a radiation resistance of R ohms and the ohmic contact with the ground is Z ohms, the efficiency of your system is given by R/(R+Z). Consider a short vertical with a ground rod might have R = 10 and Z = 150, you can see the efficiency is pretty low at ~6 percent. So 94 percent of your RF is heating up the earthworms &c. We are on heavy clay soil that alternates between being very dry and very wet. I suggest you start with a couple of tons of well-rotted farmyard manure. You need to work on that clay and turn it into something better both horticulturally and electrically. My main interest is in the lower hf bands (40/80/160) and possibly 136kHz. In that case at 136 kHz R above might be .0001 ohms or worse, and your efficiency will be very low. Get as much metal in the ground as possible. Avoid loops. -- from Aero Spike |
Ian J wrote:
I need to improve my ground system, and am thinking of burying some radials under the lawn. [I realise this is not the most efficient way to do it from an electrical point of view, but the alternative approach of installing the radials above the ground is completely out of the question, for aesthetic reasons]. Some practical questions: ~~~~~~~~~~~~~~~~~~~~~~~~~ 1. What is the "best" type of wire (or braid) to use for the radials? Whatever you can get a lot of at a cheap price, and isn't going to corrode immediately it's buried. That means NOT braid or bare stranded either. Bare or insulated solid wire is fine, and likewise insulated stranded wire. 2. How do I bond the radials together? (I guess my 15-watt soldering iron won't be up to the job ...). I used a horizontal busbar of copper tube, supported by a token ground rod. Each radial was looped round the busbar and secured with a twist, and finally the whole lot was soldered with a blowtorch (used at a careful distance). 3. What kind of solder and flux should I use? Ordinary tin/lead. I used Fluxite paste and rinsed it off afterwards. 4. What precautions should I take to minimise the effects of corrosion at the joints? Clear polyurethane spray has worked perfectly for several years. I chose clear so I'd be able to check for corrosion underneath, but there hasn't been any. 5. How deep should I bury the radials? Two inches, six inches, 12 inches? Zero inches, if you can. Cut the grass very short in a few weeks' time, and staple the radials down. This part of the question was discussed here, only a week ago. 6. Is there anything else I should know? You're going to have backache. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
As suggested, lots of wire. Doesn't matter to the RF if
it's insulated or not (it will matter as far as corrosion is concerned). No soldering, use heavy clamps instead. Coat with some kind of noncorrosive 'goop'. Bury it deep enough so the lawn mower doesn't get into it. when you think you have enough metal in the ground, add another mile... 'Doc PS - If you're going to use 136 Khz, make that 10 miles. |
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