Post by lamplighter on Mar 3, 2010 12:07:49 GMT -5
I have a broken down rotor and had to put the vertical back up. The 2el Quad i made is looking for a new home. It is a freebie to anyone near enough to Rogers, AR to make it worth their while.
The antenna found a new home today - 03/04/2010.
For those who may have an interest in the antenna here is the info:
1 1/4" fence top rail (boom and top mast section)
1 1/4" PVC (2 pieces for boom end sleeves holding spreader tees)
1" PVC ( 8 sections for spreaders)
1" x 48" wood dowel (inside spreaders for rigidity)
1" PVC 4-way cross (2 for spreader center joints)
3/4" PVC (8 sections for spreaders)
1" PVC couplers (8 for spreader joints)
1" x 3/4" PVC bushings (8 for spreader joints)
3/4" PVC caps (8 for spreader tips)
3/4" PVC tee (1 for driver wire/feedline terminal connection)
16" wire shelf supports (8 for spreader rigidity)
project box (1 for 75ohm match section to pl239 solder joint)
u-bolts (2 for boom connection to angles)
threaded eye bolts (2 for PVC cross spreader center joints)
myriad bolts, screws, and nuts
Steel shelf angle brackets (2 for mast to boom connection)
wood squares (2 for spreader rigidity)
14ga wire of sufficient length
PVC boom end sleeves were shaped to match profile of 1" PVC crosses joining center of spreaders. 1/4"hole was drilled through the center of PVC crosses, 1/4" x 3" eye bolts were reversed through the holes into the 1 1/4" PVC boom end sleeves and secured with 1/4" bolts across sleeves through the eye of eye bolts. Sleeves allow for both mounting and sliding spreaders in or out to tune.
SWR
28.755 --------- 1.7:1
28.305 --------- 1.2:1
27.855 --------- 1.2:1
27.405 --------- 1.2:1
26.965 --------- 1.1:1
26.515 --------- 1.0:1
26.065 --------- 1.5:1
25.615 --------- 4.0:1
25.165 --------- 4.0:1
Got it up to 35 feet at the boom.
As stated above the match was achieved by using a quarter wavelength 75ohm section at the feed point on the driven loop (available length to cut with online calculators). The antenna was still in need of tweaking with the length I cut for the 75 ohm 1/4^ section, so someone suggested the coax choke you see in the photo inline with the match section. The details of the choke are:
1.) 1 1/2" x 6" piece of PVC white schedule 40
2.) drill 2 holes in the side of the PVC on same side each about 3/4" from the center of the pipe's length (this is for zip ties to hole the coil)
3.) run the coax down the center of the 6" joint of PVC and back along the outside of the same. Make 5 wraps of the coax around the PVC between the 2 holes drilled earlier, zip tie them into place permanently, continue along the 6" joint with the coax running it out the other end to connect it to the 75ohm matching section.
You can see from the posted SWR readings how it matched.
I have no analyzer or such so my stuff is make it, get the SWR as good as I can, and run it for fun.
The antenna in the background is/was another homebrew. It's a 5/8^ vertical that has done a great job for me. Comparative performances are only anecdotal. as for locally, I've talked on both up to 40 - 50 miles. Regarding DX, it has been about conditions. The 5/8^ was in the air before conditions opened up last year, but I've made some very good contacts for the sporadic conditions I had. The quad did real good. I talked to and received everywhere it was opened to me. I know it outperformed the 1/2^ A99 I had up before. The backdoor rejection on the Quad was about 2 "S" units from about 3 miles out locally, and skip being what it is, about the same it seemed, although I had no way of being sure what I experienced was anything other than fluctuating conditions. I thought it did well for a two element beam.
Additional info from a helpful source:
Couple of points that might be helpful for anyone thinking of making one. I used a commercial 1:1 current balun on mine, helps to take the stress away from the wire/coax connection, if you use a balun you don't need the choke.
For a 2 ele you need the 1/4 wave 75 ohm coax for impedance matching, which for RG-59 would be 1.82M long @ 27.185 MHz.
Qubical Quad Construction has some great tips to help you build your quad, and the calculator there to give you element lengths and boom spacing. Found this site really useful when I made mine.
73
The antenna found a new home today - 03/04/2010.
For those who may have an interest in the antenna here is the info:
1 1/4" fence top rail (boom and top mast section)
1 1/4" PVC (2 pieces for boom end sleeves holding spreader tees)
1" PVC ( 8 sections for spreaders)
1" x 48" wood dowel (inside spreaders for rigidity)
1" PVC 4-way cross (2 for spreader center joints)
3/4" PVC (8 sections for spreaders)
1" PVC couplers (8 for spreader joints)
1" x 3/4" PVC bushings (8 for spreader joints)
3/4" PVC caps (8 for spreader tips)
3/4" PVC tee (1 for driver wire/feedline terminal connection)
16" wire shelf supports (8 for spreader rigidity)
project box (1 for 75ohm match section to pl239 solder joint)
u-bolts (2 for boom connection to angles)
threaded eye bolts (2 for PVC cross spreader center joints)
myriad bolts, screws, and nuts
Steel shelf angle brackets (2 for mast to boom connection)
wood squares (2 for spreader rigidity)
14ga wire of sufficient length
PVC boom end sleeves were shaped to match profile of 1" PVC crosses joining center of spreaders. 1/4"hole was drilled through the center of PVC crosses, 1/4" x 3" eye bolts were reversed through the holes into the 1 1/4" PVC boom end sleeves and secured with 1/4" bolts across sleeves through the eye of eye bolts. Sleeves allow for both mounting and sliding spreaders in or out to tune.
SWR
28.755 --------- 1.7:1
28.305 --------- 1.2:1
27.855 --------- 1.2:1
27.405 --------- 1.2:1
26.965 --------- 1.1:1
26.515 --------- 1.0:1
26.065 --------- 1.5:1
25.615 --------- 4.0:1
25.165 --------- 4.0:1
Got it up to 35 feet at the boom.
As stated above the match was achieved by using a quarter wavelength 75ohm section at the feed point on the driven loop (available length to cut with online calculators). The antenna was still in need of tweaking with the length I cut for the 75 ohm 1/4^ section, so someone suggested the coax choke you see in the photo inline with the match section. The details of the choke are:
1.) 1 1/2" x 6" piece of PVC white schedule 40
2.) drill 2 holes in the side of the PVC on same side each about 3/4" from the center of the pipe's length (this is for zip ties to hole the coil)
3.) run the coax down the center of the 6" joint of PVC and back along the outside of the same. Make 5 wraps of the coax around the PVC between the 2 holes drilled earlier, zip tie them into place permanently, continue along the 6" joint with the coax running it out the other end to connect it to the 75ohm matching section.
You can see from the posted SWR readings how it matched.
I have no analyzer or such so my stuff is make it, get the SWR as good as I can, and run it for fun.
The antenna in the background is/was another homebrew. It's a 5/8^ vertical that has done a great job for me. Comparative performances are only anecdotal. as for locally, I've talked on both up to 40 - 50 miles. Regarding DX, it has been about conditions. The 5/8^ was in the air before conditions opened up last year, but I've made some very good contacts for the sporadic conditions I had. The quad did real good. I talked to and received everywhere it was opened to me. I know it outperformed the 1/2^ A99 I had up before. The backdoor rejection on the Quad was about 2 "S" units from about 3 miles out locally, and skip being what it is, about the same it seemed, although I had no way of being sure what I experienced was anything other than fluctuating conditions. I thought it did well for a two element beam.
Additional info from a helpful source:
Simon004 said:
Simon004 said:Couple of points that might be helpful for anyone thinking of making one. I used a commercial 1:1 current balun on mine, helps to take the stress away from the wire/coax connection, if you use a balun you don't need the choke.
For a 2 ele you need the 1/4 wave 75 ohm coax for impedance matching, which for RG-59 would be 1.82M long @ 27.185 MHz.
Qubical Quad Construction has some great tips to help you build your quad, and the calculator there to give you element lengths and boom spacing. Found this site really useful when I made mine.
73