just out of curiousity has anyone used a end fed half wave antenna like the cushcraft ar-10. i have a homebrewed one for 11mtrs. just wondering if a ground plane would help since that was the whole purpose of the design to eliminate the ground plane? any feed back would be appreciated 73
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voltage fed antennas
- Thread starter rfoverlord
- Start date
What's going on?
I have one made by Wolf Radio. It is hard to tune and when you move it higher it changes. It makes a very strong signal according to local buds, but it is never matched well. I didn't check it out for skip, but it probably is pretty good there also.
I slipped a hub and radials from an A99 over the mast, but could not get it close enough to the coil. At least that is what I thought. It didn't help at all, it was like the radials weren't even there.
At some point I felt like maybe the coil was not quite big enough. What is the total length of your antenna's coil? I will dig mine out and check the measurement.
I have one made by Wolf Radio. It is hard to tune and when you move it higher it changes. It makes a very strong signal according to local buds, but it is never matched well. I didn't check it out for skip, but it probably is pretty good there also.
I slipped a hub and radials from an A99 over the mast, but could not get it close enough to the coil. At least that is what I thought. It didn't help at all, it was like the radials weren't even there.
At some point I felt like maybe the coil was not quite big enough. What is the total length of your antenna's coil? I will dig mine out and check the measurement.
the coil lenght is 36 in. one turn 1.5 inch spread start to end and tapped about half way it's pretty much a home brewed copy of an ar-10 the coax capacitor is 19 3/4 in. long. i wanted something without a ground plane thats why i went with it. it seems to working great for local i can work bases out about 25 miles . it,s only up 13 ft off the ground. it was one of those i have nothing to do today and i need a dedicated 11 mtr vert. ant. project.
Remember, With just about any vertical antenna, you need the "second half" of the antenna to work against. in this case, the counterpoise section. Preferably 1/4 wl at the lowest frequency you intend to work at and at least 8 wires (more is better but there is a diminishing return feature. That and commercial broadcasters are required BY LAW to have at least 120 radials in there counterpoise construction). Mind you, they arent like 00 B.A.C's #14 copper works well too! and the glory of it is, they dont even have to be straight. You can scalp the lawn. lay the counterpoise and staple it down with lawn staples then let the grass grow back. yer done! You dont worry about it much in the mobile because the vehicle acts as the counterpoise!
By design, verticals have a low take-off angle of RF energy and make great DX antennas. They sometimes suck for NVIS work but low dipoles work wonders for that. And again, dont forget about the polarization. you loose something like (gosh what is it) 30db(?) between vertical and horizontal polarization?
Another issue is RF feedback. since your working in the V vice the I plane, your going to get RF feedback into the shack or worse (the dreaded worked all neighbors or worked all consumer electronics award!). Since you didnt use a counterpoise so.... the shield of the coax is going to be used as the counterpoise. Not the best scenario. So if you are not going to use counterpoises (why not?) you had best invest in a good 1:1 current balun to force equal current between the two conductors to help prevent the junk that is going to happen. Good place to read up is at DX engineering.com (here is a good PDF on what baluns do and how to choose the correct one! Balun information )
Dont wanna buy one? Sometimes I dont blame ya here is a way to make a decent 1:1 current balun with the coax your using! The UGLY balun! If you are using RG-8/213, a hunk of 4" PVC conduit or sewer pipe works fine! Mini-8 would probably be good with uhh... 2.5" maybe? I built the RG-8 one and I had all the stuff around the house (yeah I packrat scrap PVC and PVC conduit. Ya never know....)
Anyhow, I think I have rambled on for a bit. Give that a read and see what you think. Anyone else wanna add in?
By design, verticals have a low take-off angle of RF energy and make great DX antennas. They sometimes suck for NVIS work but low dipoles work wonders for that. And again, dont forget about the polarization. you loose something like (gosh what is it) 30db(?) between vertical and horizontal polarization?
Another issue is RF feedback. since your working in the V vice the I plane, your going to get RF feedback into the shack or worse (the dreaded worked all neighbors or worked all consumer electronics award!). Since you didnt use a counterpoise so.... the shield of the coax is going to be used as the counterpoise. Not the best scenario. So if you are not going to use counterpoises (why not?) you had best invest in a good 1:1 current balun to force equal current between the two conductors to help prevent the junk that is going to happen. Good place to read up is at DX engineering.com (here is a good PDF on what baluns do and how to choose the correct one! Balun information )
Dont wanna buy one? Sometimes I dont blame ya here is a way to make a decent 1:1 current balun with the coax your using! The UGLY balun! If you are using RG-8/213, a hunk of 4" PVC conduit or sewer pipe works fine! Mini-8 would probably be good with uhh... 2.5" maybe? I built the RG-8 one and I had all the stuff around the house (yeah I packrat scrap PVC and PVC conduit. Ya never know....)
Anyhow, I think I have rambled on for a bit. Give that a read and see what you think. Anyone else wanna add in?
ed,
i went to the wolf point site. i originally designed mine without the coax capacitor and i had all kinds of issues tunning it. it wasn't as broad banded and the swr's were right around 1.5- 2:1 . for the 26.965-27.405 spread. after adding the coax cap. tunning was a breeze, 26.500 /1.3:1 - 27.950/1.4:1 even though i don't normaly operate that low or that high as it's hooked up to a stock madison base. BTW i started with 1/2 watt and raised the pwr to 100W the swr change was barely noticeable on the meter(hairs width). so i think i got it right.
i went to the wolf point site. i originally designed mine without the coax capacitor and i had all kinds of issues tunning it. it wasn't as broad banded and the swr's were right around 1.5- 2:1 . for the 26.965-27.405 spread. after adding the coax cap. tunning was a breeze, 26.500 /1.3:1 - 27.950/1.4:1 even though i don't normaly operate that low or that high as it's hooked up to a stock madison base. BTW i started with 1/2 watt and raised the pwr to 100W the swr change was barely noticeable on the meter(hairs width). so i think i got it right.
bunnieman,
i did use an ugly balun on it, at the ant.feed point. and i use a GROUNDED low pass filter at the rig end. as far as worked all nieghbors i have already talked with everyone around me, nothing they still don't know when i'm the air. and we have a cheap off the air kitchen tv less than 6 ft. below it with coax running on the other side of the wall by it. but i have been accused of my tower cuasing cell phone interference even when there was nothing hooked up to it when i first moved here. now everytime i get a new nieghbor and their cell phone does'nt work in the house i hear about it. Hell my cell phone does'nt work that good in the house, it couldn't be that most of the homes around here were built by the same contractor and they used aluminum studs. or that 50 kw am broadcast ant. array 2 miles away. naw it's got to be those guys with the towers and ants. everywhere doing it. my newist niebor casually asked me 1 week after they moved in if there were some city odinances for that thing in my yard. growing weary of the whole situation i told him to talk with his nieghbor next door who i had gone through this with last summer. she even called her brother the deputy to come talk with me and the city. after he talked with her. he was a lot nicer to me, i did tell him if he did get any interference from me, don't hesitate to let me know. i then offered a tour of my shack. HI HI
thanks for the input though, i appreciate it 73
i did use an ugly balun on it, at the ant.feed point. and i use a GROUNDED low pass filter at the rig end. as far as worked all nieghbors i have already talked with everyone around me, nothing they still don't know when i'm the air. and we have a cheap off the air kitchen tv less than 6 ft. below it with coax running on the other side of the wall by it. but i have been accused of my tower cuasing cell phone interference even when there was nothing hooked up to it when i first moved here. now everytime i get a new nieghbor and their cell phone does'nt work in the house i hear about it. Hell my cell phone does'nt work that good in the house, it couldn't be that most of the homes around here were built by the same contractor and they used aluminum studs. or that 50 kw am broadcast ant. array 2 miles away. naw it's got to be those guys with the towers and ants. everywhere doing it. my newist niebor casually asked me 1 week after they moved in if there were some city odinances for that thing in my yard. growing weary of the whole situation i told him to talk with his nieghbor next door who i had gone through this with last summer. she even called her brother the deputy to come talk with me and the city. after he talked with her. he was a lot nicer to me, i did tell him if he did get any interference from me, don't hesitate to let me know. i then offered a tour of my shack. HI HI
thanks for the input though, i appreciate it 73