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Can you figure out this antenna?
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=3077597082
This antenna is a mystery. No-one can identify it from the picture. It's made in Japan and model number is CA-815. I now have this antenna and can give the dimentions. | | A variable appx 17" (43 Cm) | | | B 4" (10 Cm) | | | | | C 59" (150 Cm) | | -------------X-------------- D D 28" (71 Cm) Tube A is adjustable it's about 17" long when in mid position. B from the outside looks like a 4" long metal tube. A enters the "tube" from the top, but is insulated from it. Likewise C enters the "tube" from below and also insulated from it. I wonder if within B is a coil. Tube C is 59" long. Radials D are 28" long, but it looks to me as if they have a loading coil which is located at the beginning. Coils not equal length for eachground plane radial. On the information sheet it shows a picture of a radio set they call "BASE UNIT" It highlights an antenna select switch and tells you to select external. So, to me, it looks like this antenna is meant for a receiver. This antenna is ground plane type, it looks like a ground plane. Hope it can now be identified. I've no idea what it's for. Is it either an AM or FM outdoor antennna? Or both? TIA. Rich. |
Richard wrote:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=3077597082 Are the 'tubes' solid, or hollow and contain mercury? |
All the vertical part of the antenna is made of
aluminum tubing. B is a short peice of fatter aluminum tubing than either A or C. C electrically connects with A, so I presume there is a coil within aluminium tube B. Tube B, at the bottom, looks rivited to tube C. So I'm saying B is like: | | A _____|__|_____ | | | | |____|__|_____| | | | | | x | | x | | x | B | x | | x | | x | | x | |____|__|_____| | | |-----| Rivet |____| |_____| | | C | | There are insulated collarsat both ends of B. X represents assumed coil connecting A to C. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] |
Richard wrote:
All the vertical part of the antenna is made of aluminum tubing. B is a short peice of fatter aluminum tubing than either A or C. C electrically connects with A, so I presume there is a coil within aluminium tube B. Tube B, at the bottom, looks rivited to tube C. So I'm saying B is like: | | A _____|__|_____ | | | | |____|__|_____| | | | | | x | | x | | x | B | x | | x | | x | | x | |____|__|_____| | | |-----| Rivet |____| |_____| | | C | | There are insulated collarsat both ends of B. X represents assumed coil connecting A to C. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] Okay I removed tube B and made measurements. Here are the details that ought to allow someone to do calculations for the vertical part of the antenna: | |------------------- | | | | | | | | | | | | | | p 19" (48 Cm) | | A | _____|__|_____ --- | | | | | | | | | | | | | | | | | q 1.25" | |____|__|_____| | (3Cm) | | | | |------------| | x | | x | | x | B | x | | x | | x | | x | | | | |------------------ | | | | | | |____|__|_____| r 1" (2,5 Cm) | | | | | | | | | |ooooo|--- Rivet | |____| |_____| connecting | | | tube B | | | to tube C | | | | | | s 60" (153 Cm) | | C | | | | | | | | | | | |------------------------ ^ Feedpoint Tube B is a 4"(10 Cm) long tube. Tube B connects to tube C 1" (2,5 Cm)from the top of tube C. Tube B in fact shrouds the top 1" of tube C. Top of tube C connects to the bottom end of a coil shown by x's. The top end of the coil connects to tube A which is 19" (48 Cm)long.The top part of tube B shrouds over the bottom part of tube A by 1.25"(3Cm). I got the inductance of the coil to be appx 3uH. Length: 24mm O.D. coil: 23mm Turns:13 Spacing: Closewound Wire diameter:1.5mm So I suppose next task is to calcuate the resonant frequency of the vertical part of the antenna. Thing is,is it meant to be a quarter wave half wave 5/8th wave or what. The feedpoint impedance I reckon will be 50 or 75 Ohms. I don't know how to calculate this. The 3 radials are 28" (71 Cm)long, but appear to have small coils at the beginning of the radials. The coils on two of the radials look the same, and the coil on the third radial looks about twice as long as the other two coils. The smaller coil inductances seems to be very approximately 0.330 uH, so the inductance of the larger coil on the third radial is about 0.660 uH. Smaller radial coils data: Length: 7.5mm O.D. of coil: 12mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm larger radial coil data: Length: 7.5mm O.D. of coil: 24mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm Perhaps now these data might help figure out what frequency this antenna is for.I hope. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] |
Richard,
Why don't you go to the web site you referenced, and click on "Ask seller a question", or doesn't he know? I did not read the whole thing. With the loading coils, it might be an 11 meter antenna. TYam/WB2TT "Richard" wrote in message ... http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=3077597082 This antenna is a mystery. No-one can identify it from the picture. It's made in Japan and model number is CA-815. I now have this antenna and can give the dimentions. | | A variable appx 17" (43 Cm) | | | B 4" (10 Cm) | | | | | C 59" (150 Cm) | | -------------X-------------- D D 28" (71 Cm) Tube A is adjustable it's about 17" long when in mid position. B from the outside looks like a 4" long metal tube. A enters the "tube" from the top, but is insulated from it. Likewise C enters the "tube" from below and also insulated from it. I wonder if within B is a coil. Tube C is 59" long. Radials D are 28" long, but it looks to me as if they have a loading coil which is located at the beginning. Coils not equal length for eachground plane radial. On the information sheet it shows a picture of a radio set they call "BASE UNIT" It highlights an antenna select switch and tells you to select external. So, to me, it looks like this antenna is meant for a receiver. This antenna is ground plane type, it looks like a ground plane. Hope it can now be identified. I've no idea what it's for. Is it either an AM or FM outdoor antennna? Or both? TIA. Rich. |
"Richard" wrote in message - Is it either an AM or FM outdoor antennna? Or both? Both. |
Richard wrote:
Richard wrote: All the vertical part of the antenna is made of aluminum tubing. B is a short peice of fatter aluminum tubing than either A or C. C electrically connects with A, so I presume there is a coil within aluminium tube B. Tube B, at the bottom, looks rivited to tube C. So I'm saying B is like: | | A _____|__|_____ | | | | |____|__|_____| | | | | | x | | x | | x | B | x | | x | | x | | x | |____|__|_____| | | |-----| Rivet |____| |_____| | | C | | There are insulated collarsat both ends of B. X represents assumed coil connecting A to C. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] Okay I removed tube B and made measurements. Here are the details that ought to allow someone to do calculations for the vertical part of the antenna: | |------------------- | | | | | | | | | | | | | | p 19" (48 Cm) | | A | _____|__|_____ --- | | | | | | | | | | | | | | | | | q 1.25" | |____|__|_____| | (3Cm) | | | | |------------| | x | | x | | x | B | x | | x | | x | | x | | | | |------------------ | | | | | | |____|__|_____| r 1" (2,5 Cm) | | | | | | | | | |ooooo|--- Rivet | |____| |_____| connecting | | | tube B | | | to tube C | | | | | | s 60" (153 Cm) | | C | | | | | | | | | | | |------------------------ ^ Feedpoint Tube B is a 4"(10 Cm) long tube. Tube B connects to tube C 1" (2,5 Cm)from the top of tube C. Tube B in fact shrouds the top 1" of tube C. Top of tube C connects to the bottom end of a coil shown by x's. The top end of the coil connects to tube A which is 19" (48 Cm)long.The top part of tube B shrouds over the bottom part of tube A by 1.25"(3Cm). I got the inductance of the coil to be appx 3uH. Length: 24mm O.D. coil: 23mm Turns:13 Spacing: Closewound Wire diameter:1.5mm So I suppose next task is to calcuate the resonant frequency of the vertical part of the antenna. Thing is,is it meant to be a quarter wave half wave 5/8th wave or what. The feedpoint impedance I reckon will be 50 or 75 Ohms. I don't know how to calculate this. The 3 radials are 28" (71 Cm)long, but appear to have small coils at the beginning of the radials. The coils on two of the radials look the same, and the coil on the third radial looks about twice as long as the other two coils. The smaller coil inductances seems to be very approximately 0.330 uH, so the inductance of the larger coil on the third radial is about 0.660 uH. Smaller radial coils data: Length: 7.5mm O.D. of coil: 12mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm larger radial coil data: Length: 7.5mm O.D. of coil: 24mm Turns: 5 Spacing: Closewound Wire Diameter: 1.5mm Perhaps now these data might help figure out what frequency this antenna is for.I hope. [Best viewed with a monospaced font like courier new. ToolsOptionsReadFont Proportional Font:Courier New] This post is perfect for this group. Now that I've posted all the necessary the data it ought to be fathomable.. Reg, you must be able to work this antenna out. |
"Tam/WB2TT" wrote in message ... Richard, Why don't you go to the web site you referenced, and click on "Ask seller a question", or doesn't he know? I did not read the whole thing. With the loading coils, it might be an 11 meter antenna. The seller does not know. Funny, but figuring out what frequency an antenna might be for, even with the physical and electrical parameters spelled out must be more difficult than I imagined. I'm really surprised that after giving these details lower down in the thread, the antenna cannot be figured. I'm gobsmacked. |
On Sun, 29 Feb 2004 12:58:41 -0000, "Richard"
wrote: "Tam/WB2TT" wrote in message ... Richard, Why don't you go to the web site you referenced, and click on "Ask seller a question", or doesn't he know? I did not read the whole thing. With the loading coils, it might be an 11 meter antenna. The seller does not know. Funny, but figuring out what frequency an antenna might be for, even with the physical and electrical parameters spelled out must be more difficult than I imagined. I'm really surprised that after giving these details lower down in the thread, the antenna cannot be figured. I'm gobsmacked. You are right in the case of a simple antenna. Loading coils and similar make a determination without actually examining it far more difficult. You may not have provided every bit of data required for people to VOLUNTARILY provide you with an answer. An antenna design book might help, as would some careful testing. You don't need to determine exactly what it is, you just need a "go/no go" test for your frequencies of interest. Low power Xmit and an SWR meter would help. Happy trails, Gary (net.yogi.bear) ------------------------------------------------ at the 51st percentile of ursine intelligence Gary D. Schwartz, Needham, MA, USA Please reply to: garyDOTschwartzATpoboxDOTcom |
Have you tried to put the model number (I couldn't read it in the
picture) into Google to see what it returns? |
"Richard" wrote in message ... "Tam/WB2TT" wrote in message ... Richard, Why don't you go to the web site you referenced, and click on "Ask seller a question", or doesn't he know? I did not read the whole thing. With the loading coils, it might be an 11 meter antenna. The seller does not know. Funny, but figuring out what frequency an antenna might be for, even with the physical and electrical parameters spelled out must be more difficult than I imagined. I'm really surprised that after giving these details lower down in the thread, the antenna cannot be figured. I'm gobsmacked. It can be figured out, but it is a lot of work. If you have the actual antenna, I would measure the SWR at some frequencies, starting at 10 or 11 meters. Of course, if you have access to an MFJ Antenna analyzer, you are in luck. Tam/WB2TT |
"Stevens" wrote in message ... Have you tried to put the model number (I couldn't read it in the picture) into Google to see what it returns? Yea, done that and nuthin'. I wonder what the quarter wave frequency would be for a length of wire 30" long with a base coil of approximately 0.330uH. Same wonder with a 0.660 uH coil. |
On Sun, 29 Feb 2004 12:58:41 -0000, "Richard"
wrote: I'm really surprised that after giving these details lower down in the thread, the antenna cannot be figured. I'm gobsmacked. Hi Richard, You would be even more so if you had sat through a cycle of correspondence of trying to make sense of the Patent for that same antenna. We get a lot of that too, and at that point, some may respond briefly because Patents don't have to make sense. Would you care to delve into the mysteries of a Faster than Light antenna? Just needs magnets in the right place (or was that for better gas mileage?). Some details just don't add up to better understanding. We even get Patent holders who come here to proclaim their latest invention, and then ask us how it works - or worse, proclaim it does work and it is our bound obligation and duty to prove it. 73's Richard Clark, KB7QHC |
I wonder what the quarter wave frequency would be for a length of wire 30"
long with a base coil of approximately 0.330uH. Same wonder with a 0.660 uH coil. ==================================== Rich, wonder no longer. Download program BOTLOAD2. For a 30" rod - With base loading coil 0.33 uH, Fres = 69.1 MHz. With a base loading coil 0.66 uH, Fres = 55.7 MHz. ---- Reg, G4FGQ .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
"Reg Edwards" wrote in message ... I wonder what the quarter wave frequency would be for a length of wire 30" long with a base coil of approximately 0.330uH. Same wonder with a 0.660 uH coil. ==================================== Rich, wonder no longer. Download program BOTLOAD2. For a 30" rod - With base loading coil 0.33 uH, Fres = 69.1 MHz. With a base loading coil 0.66 uH, Fres = 55.7 MHz. The antenna has three radials, and each has a loading coil right at the begining. Now I would have thought that at the feedpoint, the impedance would be low, so I think then one would assume the radials are suppossed to acting as 1/4 wavelength radials. If that were true, then the freqency at which the radials are quarter wavelength would be the operating frequency of the antenna. I've remeasured the coils after removing the rubber insulation to get a better look. For Radial #1 Length: 6mm O.D.: 11mm Turns: 9 Pitch: closewound For Radial #2 Length: 6mm O.D.: 11mm Turns: 9 Pitch: closewound For Radial #3 Lenngth: 13mm O.D.: 11mm Turns: 20 Pitch: closewound I wonder if the coils should all be different, but by mistake the radials 1 & 2 are identical. I just don't know. The new length of the radial is 72mm orabout 28.5". They are 2mm diameter stainless steel rods. I tried to use Botload2, but not sure what I'm doing. Can you please do the two calculations again Reg? Ta. |
I see, you wish to know the two resonant frequencies of the radials.
Measure the dimensions of the radial loading coils and calculate their inductance. Make no attempt to measure inductance. First you will have to enter a crude frequency into program BOTLOAD2. Then insert the overall length of a radial into the program. You MUST include the length of the loading coil in the length. Also insert the diameter of the radial in the program. Use keys 1 and 2 to VARY frequency up and down until the program indicates the value of loading coil is equal to its actual value. ie., the value you have calculated from its dimensions. The frequency at which the indicated coil inductance is equal to the value you have calculated is the resonant frequency of the radial. You don't really need the coil-design part of the program. Initially just enter some crudely correct values for the dimensions. But you can use it to check your calculation of coil inductance. You will be using the program in a somewhat different manner to its primary purpose. You are using it to measure frequency whereas frequency is really a program input parameter. The only output parameter you are interested in is coil inductance. Let me know how you get on. ---- Reg, G4FGQ ================================== "Richard" wrote in message ... "Reg Edwards" wrote in message ... I wonder what the quarter wave frequency would be for a length of wire 30" long with a base coil of approximately 0.330uH. Same wonder with a 0.660 uH coil. ==================================== Rich, wonder no longer. Download program BOTLOAD2. For a 30" rod - With base loading coil 0.33 uH, Fres = 69.1 MHz. With a base loading coil 0.66 uH, Fres = 55.7 MHz. The antenna has three radials, and each has a loading coil right at the begining. Now I would have thought that at the feedpoint, the impedance would be low, so I think then one would assume the radials are suppossed to acting as 1/4 wavelength radials. If that were true, then the freqency at which the radials are quarter wavelength would be the operating frequency of the antenna. I've remeasured the coils after removing the rubber insulation to get a better look. For Radial #1 Length: 6mm O.D.: 11mm Turns: 9 Pitch: closewound For Radial #2 Length: 6mm O.D.: 11mm Turns: 9 Pitch: closewound For Radial #3 Lenngth: 13mm O.D.: 11mm Turns: 20 Pitch: closewound I wonder if the coils should all be different, but by mistake the radials 1 & 2 are identical. I just don't know. The new length of the radial is 72mm orabout 28.5". They are 2mm diameter stainless steel rods. I tried to use Botload2, but not sure what I'm doing. Can you please do the two calculations again Reg? Ta. |
Richard Clark wrote:
"---patents don`t have to make sense." A search to show the patent application is for something not already patented is, I think, a part of the process. This patent search may favor the impractical to the extent that sane knowing people choose not to pursue the impractical, so no prior patent may be found. The patent office may issue a patent for a Yagi / Uda antenna in which the director is longer than the driven element and the reflector is shorter than the driven element. Many patents either don`t work as claimed or have such limited utility that they aren`t imitated. Best regards, Richard Harrison, KB5WZI |
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