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#1
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Dipole advice?
Hi
I got myself an old Alpha Delta DX CC now, it is old, very green. coils look green also. I want to rewind those coils or even rewire the entire thing. This is the 82ft no trap 80 through 10 dipole. Also includes 12, 17 and 30. Any advice from the group? I see the coils are using a much thinner wire, new ones look nice and copper, this one is very green. What size wire can those coils be? Can I just continue the copper length for the 80m leg and instead of separate copper winding just use the same copper and wind it around that winding core? With the coil is the critical factor its length or number of coils? Any advice from the group is greatly appreciated 73s 82' No Trap 80 thru 10 Dipole.And it is great ALL bands. This includes 12, 17, and 30. |
#2
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Dipole advice?
On 10/26/2012 6:22 PM, Tom wrote:
Hi I got myself an old Alpha Delta DX CC now, it is old, very green. coils look green also. I want to rewind those coils or even rewire the entire thing. This is the 82ft no trap 80 through 10 dipole. Also includes 12, 17 and 30. Any advice from the group? I see the coils are using a much thinner wire, new ones look nice and copper, this one is very green. What size wire can those coils be? Can I just continue the copper length for the 80m leg and instead of separate copper winding just use the same copper and wind it around that winding core? With the coil is the critical factor its length or number of coils? Any advice from the group is greatly appreciated 73s 82' No Trap 80 thru 10 Dipole.And it is great ALL bands. This includes 12, 17, and 30. There are a lot of variables here. Most of which I do not understand. I have enough experience to know that the number of turns in the coils is most important and the diameter of the coil is important. If you use the larger wire for the coils it will likely take a large coil form. You can certainly use the same wire for the whole antenna. I am just thinking that if they used thinner wire for the coils, you will not be able to get enough turns on the form to get the same inductance. If I were in your place, I would use some insulated stranded #14 house wire for the whole thing. I would also buy some pvc pipe to allow the same number of coil turns (and same diameter). If it worked fine before you started this project, copying it wire length for wire length and turn for turn would be my plan. Michael |
#3
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Throw it away.
Make a dipole for the longest frequency you desire to operate on. Formula is 33 / 66 Make the one leg 33% of the length of the frequency and make the other side so that when combined to the first leg equals 66% of the total length for the dipole. A true Dipole is a half wavelength at the center cut frequency. I use the term dipole loosely - because it is a non terminated antenna that has two sides... It will then be resonant somewhere on all frequencies above the center cut frequency as long as the Q of the coil is high. Don't use a low Q coil balun... Last edited by Channel Jumper : October 27th 12 at 08:52 PM |
#4
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Throw it away.
Make a dipole for the longest frequency you desire to operate on. Formula is 33 / 66 Make the one leg 33% of the length of the frequency and make the other side so that when combined to the first leg equals 66% of the total length for the dipole. I use the term dipole antenna loosly - because a true dipole antenna is only one half of the wavelength at the resonant frequency... It will then be resonant somewhere on all frequencies above the center cut frequency as long as the Q of the coil is high. Don't use a low Q coil balun... |
#5
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Dipole advice?
Thanks Channel Jumper,
but not sure which frequency I would most operate on. So with the tuner I have I want suitable access to as many as possible. I think rebuilding the DX CC is ok for what I want to achieve. Do you know what is the critical points regarding those coils? I found out the copper wire coil I have is 12ga and solid, 300meters of it, it has a nylon jacket with a plastic layer around that. Regular industrial stuff. So regarding those coils, could I simply replace that thinner transformer wire with windings of the same 12ga solid in jacket that will comprise of the rest of the dipole? Is it length of that coil's copper (badly oxidized) that is critical or is it coil turns? The present diameter of those coils is much smaller than the 12ga, so should I make new coils with that thinner transformer wire and make two solder connections there or can I simply weave the 12ga in its place? What would you recommend in this situation because I want to rebuild this good dipole with new copper. Thanks 73s "Channel Jumper" wrote in message ... Throw it away. Make a dipole for the longest frequency you desire to operate on. Formula is 33 / 66 Make the one leg 33% of the length of the frequency and make the other side so that when combined to the first leg equals 66% of the total length for the dipole. A true Dipole is a half wavelength at the center cut frequency. I use the term dipole loosely - because it is a non terminated antenna that has two sides... It will then be resonant somewhere on all frequencies above the center cut frequency as long as the Q of the coil is high. Don't use a low Q coil balun... -- Channel Jumper |
#6
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I'm not sure if this will be helpful or wanted.
But your dipole antenna needs to be resonant - 1/2 wavelength on the lowest frequency you desire to operate on. Because most amateur radio frequencies are multiples of other frequencies - 10 / 20 / 60 / 80 / 160 Some wavelengths will work with one antenna - as long as you do not try to tune up on a non resonant frequency. This is the problem with the G5RV The ladder line is the matching network and it only works on 20 meters. When you try to tune it up on 10 or 40 - it tries to damage the tuner - arcing and heating. At the same time, some will not be feasable - even with the tuner - such as 12 / 15 / 17 / 30 / 60 It does no good to transmit if you cannot hear. [quote='Tom[_8_];797940']Thanks Channel Jumper, but not sure which frequency I would most operate on. So with the tuner I have I want suitable access to as many as possible. I think rebuilding the DX CC is ok for what I want to achieve. Thanks 73s |
#7
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Dipole advice?
On Sunday, October 28, 2012 6:18:58 PM UTC-5, Channel Jumper wrote:
But your dipole antenna needs to be resonant - 1/2 wavelength on the lowest frequency you desire to operate on. Like the G5RV that you dislike, if one removed the feedline from a 1/2WL resonant center-fed dipole, it is no longer resonant. Resonance implies a low resistive feedpoint impedance. The G5RV antenna system has a low resistive impedance looking into the series matching section on 75m, 40m, and 20m (also on 12m). 3/2WL dipole + 1/2WL feedline = resonance on 20m 3/4WL dipole + 1/4WL feedline = resonance on 40m 3/8WL dipole + 1/8WL feedline = resonance on 75m. The (G5RV) ladder line is the matching network and it only works on 20 meters. Here's technical proof that it also works on 75m and 40m. http://www.w5dxp.com/G5RV.HTM The Smith Chart SWR arc indicates how series section transformers really work. The G5RV is a reasonably good antenna on 75m, 40m, 20m, and 12m. Not so good on 15m and not good at all on 30m, 17m, and 10m. A ZS6BKW is a better choice to obtain 17m and 10m but one loses 75m. The G5RV antenna system is what it is. It is neither a gift from Heaven nor a design straight from Hell. -- 73, Cecil, w5dxp.com |
#8
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Dipole advice?
Hi,
Yes you are very correct. The entire system apparently is working condition so why not just leave it alone. That is ok. But it is 16 years in the air and very green, coils are green. When looking at the photos online the new ones while exactly the same design are beautiful copper with a clear protective wrap around those coils. Mine doesn't have that wrap and those coils are very green. The coils are smaller diameter wire, looking like the transformer wire with that sholack on it but then there are soldered connections back to the larger diameter bare copper green wire running to the insulators. I would have to make another core if I were to wind the same new copper wire right from the center feed point to the ends of each leg. That would be basically the only difference other than instead of bare copper wire (new stuff) I have a big coil of solid copper wire with a jacket, I think it is 16ga. I was hoping to simply replace the exisiting bare green copper wire and the green coils with new copper wire with the jacket. So do you think the changing of the coil wire diameter but keeping the same number of wraps is the way to go? Or because the new copper wire has the jacket, this will change the number of wraps if I measure the length of the old coil wire. Lot of hardware in good shape on this old antenna, I just want to change all the copper. Thanks for the advice, 73s "Boomer" wrote in message ... On 10/26/2012 6:22 PM, Tom wrote: Hi I got myself an old Alpha Delta DX CC now, it is old, very green. coils look green also. I want to rewind those coils or even rewire the entire thing. This is the 82ft no trap 80 through 10 dipole. Also includes 12, 17 and 30. Any advice from the group? I see the coils are using a much thinner wire, new ones look nice and copper, this one is very green. What size wire can those coils be? Can I just continue the copper length for the 80m leg and instead of separate copper winding just use the same copper and wind it around that winding core? With the coil is the critical factor its length or number of coils? Any advice from the group is greatly appreciated 73s 82' No Trap 80 thru 10 Dipole.And it is great ALL bands. This includes 12, 17, and 30. There are a lot of variables here. Most of which I do not understand. I have enough experience to know that the number of turns in the coils is most important and the diameter of the coil is important. If you use the larger wire for the coils it will likely take a large coil form. You can certainly use the same wire for the whole antenna. I am just thinking that if they used thinner wire for the coils, you will not be able to get enough turns on the form to get the same inductance. If I were in your place, I would use some insulated stranded #14 house wire for the whole thing. I would also buy some pvc pipe to allow the same number of coil turns (and same diameter). If it worked fine before you started this project, copying it wire length for wire length and turn for turn would be my plan. Michael |
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