Home |
Search |
Today's Posts |
#21
|
|||
|
|||
Horizontal loop antenna
Dave Platt wrote:
On the other hand, page 16 of the SGC-230 manual PDF specifically shows a balanced dipole, being fed through "balanced line feeders, 300-600 ohms, up to 40 feet". My 1990 manual shows nothing like that. Maybe they changed their minds about balanced line feeders. -- 73, Cecil http://www.w5dxp.com |
#22
|
|||
|
|||
Horizontal loop antenna
On the other hand, page 16 of the SGC-230 manual PDF specifically
shows a balanced dipole, being fed through "balanced line feeders, 300-600 ohms, up to 40 feet". My 1990 manual shows nothing like that. Maybe they changed their minds about balanced line feeders. Could be... I was using a PDF copy of the manual I downloaded from the SGC website. Possibly the newer versions of their couplers have more flexibility in their tuning algorithm? -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#23
|
|||
|
|||
Horizontal loop antenna - Dual Wire
On Tue, 19 Feb 2008 22:55:20 -0500, Buck
wrote: I seem to remember an article about someone taking a full-wave horizontal loop antenna and making two loops (or was it a half-wave loop?). The second loop caused the antenna to match 50 ohms so it could be fed with coax and (I think) it operated multiple bands. Anyone remember this article and know where it might be? Hi Buck, It is a small tuned loop (less than a tenth wave) with a smaller loop (about a third to a fifth in size of the first loop) inside it. Not much else to say except that polarity is vertical/horizontal when the loops are in the horizontal/vertical plane. Make every effort to build low Ohmic connections and elements. The capacitor will have to stand off a high voltage (and many caps suffer from ESR). 73's Richard Clark, KB7QHC |
#24
|
|||
|
|||
Horizontal loop antenna
Roy Lewallen wrote:
"I don`t see anywhere in the response which explains how "radiation is a function of loop area" and why increasing the loop circumference would be advantageous." Didn`t want to bore with details. Terman knows all and tells all. His loop antenna story begins on page 907 of his 1955 opus: "The radiation resistance of a loop antenna is less the smaller the loop area. For the radiation resistance to be large enough to give good antenna efficiency, it is necessary that the loop perimeter be of the order of a wavelength. This introduces a difficulty, since when the perimeter approaches or exceeds a half wavelength, then the loop current in Fig. 23-40 will not be constant, nor will its phase nnecessarily be the same in different parts of the loop. The prectical solution is to build up the loop in such a way that the perimeter consists of resonant antennas so arranged that the current everywhere in the loop perimeter flows in the same direction around the loop. A variety of practical physical arrangements for achieving this result have been devised, three examples of which are illustrated in Fig. 23-41." Yet another elegant phase inverter from Kraus as applied to a colinear dipole appears on Cecil`s webpages. Best regards, Richard Harrison, KB5WZI |
#25
|
|||
|
|||
Horizontal loop antenna
Roy Lewallen wrote:
"Perhaps you build antennas for radiation resistance, but I think most people build them to maximize radiation in some particular direction.." You must have some radiation resistance or you have no signal, but not all antennas are highly directional. Page 8-10 of the 20th edition of the ARRL Antenna Book has (Eq 5): Efficiency = radiation resistance / radiation resistance + loss resistance Zero radiation resistance = zero efficiency. Best regards, Richard Hsarrison, KB5WZI |
#26
|
|||
|
|||
Horizontal loop antenna - Dual Wire
On Tue, 19 Feb 2008 22:44:48 -0800, Richard Clark
wrote: On Tue, 19 Feb 2008 22:55:20 -0500, Buck wrote: I seem to remember an article about someone taking a full-wave horizontal loop antenna and making two loops (or was it a half-wave loop?). The second loop caused the antenna to match 50 ohms so it could be fed with coax and (I think) it operated multiple bands. Anyone remember this article and know where it might be? Hi Buck, It is a small tuned loop (less than a tenth wave) with a smaller loop (about a third to a fifth in size of the first loop) inside it. Not much else to say except that polarity is vertical/horizontal when the loops are in the horizontal/vertical plane. Make every effort to build low Ohmic connections and elements. The capacitor will have to stand off a high voltage (and many caps suffer from ESR). 73's Richard Clark, KB7QHC The antenna article I was referring to is either full size or 1/2 size horizontal loop and he used window line (twin-lead) wire for the loop crossing the connection of the coax so that the wire made a continuous loop twice going from the center conductor to the shield (he may have used a balun, but you get the idea). This was a large loop running around his yard. Thanks, tho. Buck N4PGW -- 73 for now Buck, N4PGW www.lumpuckeroo.com "Small - broadband - efficient: pick any two." |
#27
|
|||
|
|||
Horizontal loop antenna
|
#28
|
|||
|
|||
Horizontal loop antenna
Jon, LA4RT wrote:
"---but presumably there`s a reason that you`re using a small loop in the first place." True. In Norway I specified large dishes for scatter communications with North Sea platforms but the government sponsored the geosynchronous satellite program and ignored scatter. In the many tunnels I specified 300-ohm twinlead which works about as well as Andrew`s leaky coax and costs much less. I think Norway is too rich to care about cost. Best regards, Richard Harrison, KB5WZI |
#29
|
|||
|
|||
Horizontal loop antenna
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Size of horizontal loop? | Antenna | |||
Horizontal HF Loop | Antenna | |||
Intuitively {To My Way of Thinking} for an In-the-Attic Antenna the Horizontal [Flat] Loop Antenna offers these Benefits : | Shortwave | |||
For Shortwave Listening (SWL) here is a "Simpler" Horizontal Loop Antenna in the Attic using common TV type Parts | Shortwave | |||
80 Meter Horizontal Loop | Antenna |