Antenna Question
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I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have I been able to find a link to a description / design data.
The county ERC has a 'shortened fan dipole' with three parallel elements, spaced about 18-24" apart on each side. the longest element folds back around the mid-length element toward the shortest element. The antenna end insulator / guy rope is attached to the long element, where it folds back. There appears (from the ground) to be a 6~8" insulator / gap between the end of the shortest element, and the longest element where its been folded back. no traps, loading coils, or loading resistors that I can see. I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be interested in more technical details if anyone can decipher my text description above… Thanks Niel ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Neil,
When you see an antenna element folded back on itself like that, think "linear loading" (look it up in the ARRL Handbook or similar). There is no "magic", but it is one way of shortening an antenna. It is not as efficient as a full length antenna, but is more efficient than using loading coils. Everything is relative. If you have the space to put up full size half wave dipole antennas, that is the way to go. If you need shortened antennas for the lower bands, linear loading is one way to achieve resonance with shortened length. 73, Don W3FPR On 6/17/2012 11:26 PM, Niel Skousen wrote: > I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have I been able to find a link to a description / design data. > > The county ERC has a 'shortened fan dipole' with three parallel elements, spaced about 18-24" apart on each side. the longest element folds back around the mid-length element toward the shortest element. The antenna end insulator / guy rope is attached to the long element, where it folds back. There appears (from the ground) to be a 6~8" insulator / gap between the end of the shortest element, and the longest element where its been folded back. no traps, loading coils, or loading resistors that I can see. > > I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be interested in more technical details if anyone can decipher my text description above… > > Thanks > Niel > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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A note on folded back antennae. I have a 3 element SteppIR with the 30/40 kit. The antenna is mounted at about 67 feet above the ground. I have compared the folded antenna at 67 feet to a full sized inverted V at 40 feet and find it noticeably stronger. Even though it is only a dipole which is a little more than half length it is noticeably bi-directive with deep nulls off the element ends. It is quite effective as a DX antenna and I believe the SteppIR claim that it is only one or two dB down from a full sized rotatable dipole. Of course, its improved performance over the inverted V is mostly because of the elevation difference, but I would not hesitate to fold the ends of a dipole if restricted by lot size or other physical restraints.
Willis 'Cookie' Cooke K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart ----- Original Message ----- From: Don Wilhelm <[hidden email]> To: Niel Skousen <[hidden email]> Cc: Elecraft Reflector <[hidden email]>; [hidden email] Sent: Monday, June 18, 2012 6:18 AM Subject: Re: [Elecraft] Antenna Question Neil, When you see an antenna element folded back on itself like that, think "linear loading" (look it up in the ARRL Handbook or similar). There is no "magic", but it is one way of shortening an antenna. It is not as efficient as a full length antenna, but is more efficient than using loading coils. Everything is relative. If you have the space to put up full size half wave dipole antennas, that is the way to go. If you need shortened antennas for the lower bands, linear loading is one way to achieve resonance with shortened length. 73, Don W3FPR On 6/17/2012 11:26 PM, Niel Skousen wrote: > I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have I been able to find a link to a description / design data. > > The county ERC has a 'shortened fan dipole' with three parallel elements, spaced about 18-24" apart on each side. the longest element folds back around the mid-length element toward the shortest element. The antenna end insulator / guy rope is attached to the long element, where it folds back. There appears (from the ground) to be a 6~8" insulator / gap between the end of the shortest element, and the longest element where its been folded back. no traps, loading coils, or loading resistors that I can see. > > I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be interested in more technical details if anyone can decipher my text description above… > > Thanks > Niel > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
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Linear loading versus loading coils, top hats, etc. is a very complex subject that cannot be summed well in an email. Affordable programs that run on home computers, such as EZNEC are great tools and I use them. Professional programs that run on bigger computers are no doubt better, but I do not have access to them. But, the proof is in the pudding and to really know how well something works requires building the antenna and erecting it in the position it is to be used with the trees, buildings, soil type, etc. that will be present. Wire size is important, as is Q and the problem is very different for QRP versus medium power versus full QRO, particularly when wound coils are considered. The computer programs are great for deciding which antenna you want to try first. Trying an infinite number of variations might be better, but that would require infinite money and time. Some designs, such as the SteppIR are better with linear loading
because of mechanical considerations. As previously mentioned, the design of antennas for commercial or emergency use certainly considers different things than getting the last dB for busting a pileup. The mountain topper that plans to take his station to the top of a peak certainly has different antenna criteria than the avid contester who is building his antenna farm. I have been playing with antennas for 56 years now and I am a long way from knowing all there is to know, even way short of knowing all I want to know! I don't think I will live long enough to get there, Marconi certainly didn't. Isn't ham radio great? There is so much to do and learn that you never run out of something interesting. Willis 'Cookie' Cooke K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart ----- Original Message ----- From: James Rodenkirch <[hidden email]> To: [hidden email]; [hidden email] Cc: [hidden email]; QRP-L <[hidden email]> Sent: Monday, June 18, 2012 7:48 AM Subject: Re: [Elecraft] [QRP-L] Antenna Question Please treat this reply to the below thread where an emphasis on linear loading being mo betta than a loading coil as a dialectic discussion. Something about that posit - linear loading is more efficient than a loading coil - didn't ring true with me so I did a little digging. Now, keep in mind that what I ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Cookie
I agree that folding the low-current parts of an antenna is a good way to make it smaller.
But there are several things at work in the comparison between the Steppir element and the V. Of course the height is one of them. But if you model an inverted V (90 degree angle between wires) and a dipole at the same height you will see that the dipole has significantly more gain. Many inverted V's are constructed with even smaller angles, which are worse. The V pattern also has smaller nulls on the ends. Finally, the Steppir undoubtedly has some kind of balun, and its feedline runs perpendicular to the antenna for 1/2 wavelength. All of these things improve the nulls. They also reduce noise pickup on the feedline. On 6/18/2012 5:26 AM, WILLIS COOKE wrote: > A note on folded back antennae. I have a 3 element SteppIR with the 30/40 kit. The > antenna is mounted at about 67 feet above the ground. I have compared the folded > antenna at 67 feet to a full sized inverted V at 40 feet and find it noticeably > stronger. Even though it is only a dipole which is a little more than half length it > is noticeably bi-directive with deep nulls off the element ends. It is quite effective > as a DX antenna and I believe the SteppIR claim that it is only one or two dB down from > a full sized rotatable dipole. Of course, its improved performance over the inverted V > is mostly because of the elevation difference, but I would not hesitate to fold the > ends of a dipole if restricted by lot size or other physical restraints. > > Willis 'Cookie' Cooke K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart > > > ----- Original Message ----- From: Don Wilhelm<[hidden email]> To: Niel > Skousen<[hidden email]> Cc: Elecraft Reflector<[hidden email]>; > [hidden email] Sent: Monday, June 18, 2012 6:18 AM Subject: Re: [Elecraft] > Antenna Question > > Neil, > > When you see an antenna element folded back on itself like that, think "linear loading" > (look it up in the ARRL Handbook or similar). There is no "magic", but it is one way > of shortening an antenna. It is not as efficient as a full length antenna, but is more > efficient than using loading coils. Everything is relative. If you have the space to > put up full size half wave dipole antennas, that is the way to go. If you need > shortened antennas for the lower bands, linear loading is one way to achieve resonance > with shortened length. > > 73, Don W3FPR > > On 6/17/2012 11:26 PM, Niel Skousen wrote: >> I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have >> I been able to find a link to a description / design data. >> >> The county ERC has a 'shortened fan dipole' with three parallel elements, spaced >> about 18-24" apart on each side. the longest element folds back around the >> mid-length element toward the shortest element. The antenna end insulator / guy >> rope is attached to the long element, where it folds back. There appears (from the >> ground) to be a 6~8" insulator / gap between the end of the shortest element, and the >> longest element where its been folded back. no traps, loading coils, or loading >> resistors that I can see. >> >> I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a >> 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be interested in >> more technical details if anyone can decipher my text description above… >> >> Thanks Niel -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Indeed! The purpose of the inverted V was for local NVIS coverage and was mentioned anecdotally to illustrate that folded back elements can be very effective if needed. They reduce the mechanical problems of erecting and turning a rotating dipole with minimal degradation. I can see a significant advantage where a shorter antenna is needed. We are fortunate to have a wide range of designs for our wide range of antenna problems.
Sent from my iPhone On Jun 18, 2012, at 10:27, Vic K2VCO <[hidden email]> wrote: > I agree that folding the low-current parts of an antenna is a good way to make it smaller. > > But there are several things at work in the comparison between the Steppir element and the > V. Of course the height is one of them. But if you model an inverted V (90 degree angle > between wires) and a dipole at the same height you will see that the dipole has > significantly more gain. Many inverted V's are constructed with even smaller angles, which > are worse. The V pattern also has smaller nulls on the ends. > > Finally, the Steppir undoubtedly has some kind of balun, and its feedline runs > perpendicular to the antenna for 1/2 wavelength. All of these things improve the nulls. > They also reduce noise pickup on the feedline. > > On 6/18/2012 5:26 AM, WILLIS COOKE wrote: >> A note on folded back antennae. I have a 3 element SteppIR with the 30/40 kit. The >> antenna is mounted at about 67 feet above the ground. I have compared the folded >> antenna at 67 feet to a full sized inverted V at 40 feet and find it noticeably >> stronger. Even though it is only a dipole which is a little more than half length it >> is noticeably bi-directive with deep nulls off the element ends. It is quite effective >> as a DX antenna and I believe the SteppIR claim that it is only one or two dB down from >> a full sized rotatable dipole. Of course, its improved performance over the inverted V >> is mostly because of the elevation difference, but I would not hesitate to fold the >> ends of a dipole if restricted by lot size or other physical restraints. >> >> Willis 'Cookie' Cooke K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart >> >> >> ----- Original Message ----- From: Don Wilhelm<[hidden email]> To: Niel >> Skousen<[hidden email]> Cc: Elecraft Reflector<[hidden email]>; >> [hidden email] Sent: Monday, June 18, 2012 6:18 AM Subject: Re: [Elecraft] >> Antenna Question >> >> Neil, >> >> When you see an antenna element folded back on itself like that, think "linear loading" >> (look it up in the ARRL Handbook or similar). There is no "magic", but it is one way >> of shortening an antenna. It is not as efficient as a full length antenna, but is more >> efficient than using loading coils. Everything is relative. If you have the space to >> put up full size half wave dipole antennas, that is the way to go. If you need >> shortened antennas for the lower bands, linear loading is one way to achieve resonance >> with shortened length. >> >> 73, Don W3FPR >> >> On 6/17/2012 11:26 PM, Niel Skousen wrote: >>> I'm pretty sure I've seen this antenna on the net, but don't recall the name nor have >>> I been able to find a link to a description / design data. >>> >>> The county ERC has a 'shortened fan dipole' with three parallel elements, spaced >>> about 18-24" apart on each side. the longest element folds back around the >>> mid-length element toward the shortest element. The antenna end insulator / guy >>> rope is attached to the long element, where it folds back. There appears (from the >>> ground) to be a 6~8" insulator / gap between the end of the shortest element, and the >>> longest element where its been folded back. no traps, loading coils, or loading >>> resistors that I can see. >>> >>> I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a 75m dipole, a >>> 40m dipole (with 15m as a freebie), and a 20 m dipole. but would be interested in >>> more technical details if anyone can decipher my text description above… >>> >>> Thanks Niel > > -- > Vic, K2VCO > Fresno CA > http://www.qsl.net/k2vco/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Antenna Question
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In reply to this post by Niel Skousen-2
Neil,
Were you able to see if the shortened fan dipole used by the county ERC has the feeder connected to all three elements, as would be the case with a typical fan dipole? If the feeder is connected *only* to the mid-point of the longest element, and the two shorter elements are unbroken lengths of wire running parallel to the longest wire, then this antenna would belong to the family of multiband antennas known as "Coupled Resonators". It would be tricky though to use linear loading with these antennas. 73, Geoff LX2AO On Monday, June 18, 2012 at 5:26 AM, Niel Skousen wrote: > I'm pretty sure I've seen this antenna on the net, but don't recall the > name nor have I been able to find a link to a description / design data. > The county ERC has a 'shortened fan dipole' with three parallel elements, > spaced about 18-24" apart on each side. the longest element folds back > around the mid-> > length element toward the shortest element. The > antenna end insulator / guy rope is attached to the long element, where it > folds back. There appears (from the > ground) to be a 6~8" insulator / gap between the end of the shortest > element, and the longest element where its been folded back. no traps, > loading coils, or loading > resistors that I can see. > I'm assuming three or four band coverage (80, 40, 20, and 15 ??) with a > 75m dipole, a 40m dipole (with 15m as a freebie), and a 20 m dipole. but > would be > interested in more technical details if anyone can decipher my text > description above… ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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