how do you wire it if you only want one dipole?
Thanks for the information prcguy. I have another question i forgot to ask. If i use 1/2 inch copper pipe how would that affect the SWR's, design, and reception? I was thinking of using 1/2 pipe as my old projects are. Plus 1/2 inch is cheaper and lighter. would the measurements be the same?
thanks again, Eric
Is this design required for the dipole to be on the metal mast for good swr's? Reason why i ask is i have a dipole out the window on a 2 ft PVC support arm with no metal mast on the antenna. the arm is mounted directly to the wall mount. Another dipole is on a PVC mast for portable base station use. those designs are much like yours but on 3/8 inch pipe not the 1/2 i stated earlier. and the measurements are copied off of a Decibel folded dipole antenna and cut to around 17 3/4 inches. 3/8 inch tubing matches a 1/2 aluminum tubing.
I'm thinking the metal mast is part of the matching device. What if the top element is about the metal mast?
sorry for so many questions. I'm just learning the ins and outs of these designs.
Eric Burris kc0ldt
I was wondering if you could help me with phasing harness? I want to make a 2 dipole array instead of 4 because of mast space. 4 is too big and i wouldn't know how to mount something that big and the landlord is already concerned that 3 antennas is too much. I am using my previous built dipoles. they are aluminum equivalent to 3/8 copper pipe. i think it's 3/8, smaller then 1/2 inch. The support arm is 4 inches from center of element to the end of pipe, not counting the T connector to the mast. What would the dimensions be for the harness? would you build it for me if i can't do it? I have some RG59 but i think it's all the foil shield type. without buying the commercial brands how would i know the velocity factors and stuff? Radio shack doesn't list those specs nor would anything from walmart.
I was wondering since the commerical antennas have metal support arms do i have to use PVC on mine? I don't know if it matters. I put mine on my mast outside a few feet of the ground and tested it. flat match on ham band. i cut the support arm to around 5 inches instead of 6 to match that of my other one that was copied from the DB ant and the SWR went from a flat match to 1:5:1 in the middle of the 2m band and it was shifted up the band a bit. So i think it would stretch closer to the RR band that way. i'm not sure how to figure out the spacing to the mast without guessing.
not sure what those snap-n-seal connectors are but i am interested. how much would you charge? Would you include the Pl259 with it? I'm kind of short on those.A metal or PVC sopport arm doesn't matter as long as you tuned the individual dipoles to frequency with 50 ohm coax and it was attached to a metal mast while tuning. Most current CATV type RG-59 is foam type and will have a similar velocity factor to what I used in the article, so the phasing harness dimensions in the article should be close and you would only make half the harness for two elements.
The metal mast is a reflector and part of the antenna. Each dipole becomes a 2-element beam in this case and that's why its directional when all elements are arranged on one side. If you don't use a metal mast the coax will interact with the pattern and that would require a lengthy study to see the effects.
The spacing of the elements to the mast will affect several things including the pattern, efficiency and impedance. I used a common spacing measured from several commercial antennas and if you change it very much your on your own.
To make a proper harness for a 2-element version you would use PL-259s and a T adapter so the antenna is fed with 50 ohm coax. I don't have time to solder connectors but if you were planning on using 75 ohm coax I could make a harness in about 5 min using T&B Snap-N-Seal connectors and an F type T adaptor for your coax interface. I would leave it to you to strip the ends and make the dipole connections and I don't to start a harness making business for everyone on the forum. I have never tested the antenna with 75 ohm coax and can't guarantee the result.
not sure what those snap-n-seal connectors are but i am interested. how much would you charge? Would you include the Pl259 with it? I'm kind of short on those.
So i can use 50ohm coax for this? I thought i would have to use 75 or is that just as with 4 bays only? If we go 75ohm then would you include the Pl-259 if i put it on myself? I'd hate to use a F-pl259 adapter cause of signal loss. I'm excited to play with this antenna. btw i have a single dipole built like yours out the window now with lightweight aluminum from an old antenna for the mast.I can easily make a 2 dipole harness that terminates with an F type T adapter but I don't have time to make one with PL-259s. You can feed it with 75ohm TV coax and take a small hit on VSWR or get a male F to SO-329 adapter to use 50ohm coax. The F type T adapter is about $3.50, Snap-N-Seal connectors are about $.35 ea, so I could make you a 2 dipole harness for about $5 + shipping. You will have to strip and prep the ends with lugs to connect to your dipoles.
So i can use 50ohm coax for this? I thought i would have to use 75 or is that just as with 4 bays only? If we go 75ohm then would you include the Pl-259 if i put it on myself? I'd hate to use a F-pl259 adapter cause of signal loss. I'm excited to play with this antenna. btw i have a single dipole built like yours out the window now with lightweight aluminum from an old antenna for the mast.
i see want you meaning on the adapter and loss. you were talking about going 75ohm all the way to the radio. My scanner right now has 75ohm with the ST-2 on it.Each individual dipole is tuned for 50 ohms and the common feed point for the entire antenna is 50 ohm but the phasing harness is all 75 ohm coax. You can use 75 ohm coax to feed the entire antenna if you don't mind the additional loss and VSWR.
i see want you meaning on the adapter and loss. you were talking about going 75ohm all the way to the radio. My scanner right now has 75ohm with the ST-2 on it.
If you can send me the PL-259 with the cables i can put that part on myself. Unless you have an N connector. I have an xtra LMR400 cable that also needs a connector on one end as it is bare. It has a N female on the other which hooking to a jumper cable would eliminate a coupler. that'd be sweet!!! tell me how much and i'm ready to send some money your way.
I'm sorry for the misunderstanding. I looked at RS website and they don't even have RG59 that is solderable. So i'm not sure if it's easy to come by locally. Then i've have to order online and then order connectors and all that. I don't even know what F T connector to use as RS site only shows splitter and diplexers. I didn't realize you were going to test it. we can do it your way if you still want.If I'm going to "make" the harness I would tune it and that requires having the connectors installed. I can make and tune an entire harness in minutes using F connectors (have hundreds on hand) but PL-259s take more time to properly install than I am willing to spend right now and I only have a few PL-259s left. If you have the ability to solder on your own PL-259s the rest is just some RG-59 foam type TV coax. The coax lengths listed in the instructions should be close for most foam type RG-59 coax. I thought you didn't have the ability to solder or install connectors and that's why I offered.