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Homemade Antenna and Radio theory.
- Thread starter LumpySnake
- Start date
Hey 'Doc, LS's setup shows a little basics, but no real understanding of how a simple 1/4 wave should/needs to work.
He will not see a decent match with a 1/4 wave radiator and four radials laying horizontal---unless like he is, on or near the Earth, and is able to match the feed point some. You are correct in telling him his antenna is likely showing him a very low resistance, but it may be as low as 3-15 ohms with an additional 35 ohms of ground losses. If so, then the Earth is sucking all the power out of his transmitter and he sees low output. His true SWR situation is not showing up on his RF meter due to these losses, and forget about what the SWR meter is showing even if it is setup correctly. I would, however, be surprised if he could even calibrate the SWR meter to full scale with all the losses.
"Doc, this is not to say a system similar to this could not work, but his system will not work without some form of feed point matching or a tuner. He did question what he was seeing, but he does not realize he is just seeing the results of heavy losses. That should be obvious to you.
This also says nothing about the PVC he uses to support his wire radiator. I think some of the colored PVC are heavy in metal content and will not make a good insulator and make an even poorer radiator. He needs to check this out however as I could be wrong on this issue.
He also needs to raise the radiator up high enough so that all the radials slant down about 140 degrees to vertical, leaving the tips at least 8' above Earth. Then he might be able to get a reasonable match to work with, and not hurt his radio any more. To this point I suspect his radio is just shutting down due to the high SWR. Maybe the little underpowered power supply he says he is using has saved his radio from smokin' without him knowing. Lumpy Snake, does your PS meter peg out with max volts or amps when you key you radio?
He will not see a decent match with a 1/4 wave radiator and four radials laying horizontal---unless like he is, on or near the Earth, and is able to match the feed point some. You are correct in telling him his antenna is likely showing him a very low resistance, but it may be as low as 3-15 ohms with an additional 35 ohms of ground losses. If so, then the Earth is sucking all the power out of his transmitter and he sees low output. His true SWR situation is not showing up on his RF meter due to these losses, and forget about what the SWR meter is showing even if it is setup correctly. I would, however, be surprised if he could even calibrate the SWR meter to full scale with all the losses.
"Doc, this is not to say a system similar to this could not work, but his system will not work without some form of feed point matching or a tuner. He did question what he was seeing, but he does not realize he is just seeing the results of heavy losses. That should be obvious to you.
This also says nothing about the PVC he uses to support his wire radiator. I think some of the colored PVC are heavy in metal content and will not make a good insulator and make an even poorer radiator. He needs to check this out however as I could be wrong on this issue.
He also needs to raise the radiator up high enough so that all the radials slant down about 140 degrees to vertical, leaving the tips at least 8' above Earth. Then he might be able to get a reasonable match to work with, and not hurt his radio any more. To this point I suspect his radio is just shutting down due to the high SWR. Maybe the little underpowered power supply he says he is using has saved his radio from smokin' without him knowing. Lumpy Snake, does your PS meter peg out with max volts or amps when you key you radio?
"The 4 ground plane wires are held in place by a state of the art red brick anchoring system."
lol
lol
Marconi,
I think the hardest part of answering a question on any of these forums is trying to gauge how much the question ask'er knows about what's happening. Most of the time, that guess is almost always wrong to some extent, in either direction, which just causes more confusion. If you ever figure that one out, please tell me!
There's almost always more than one way to do something, to make something 'work'. Keeping track of things, which suggestion might be 'best' for any particular situation, is another one of them head scratchers. Lots and lots of variables in all this stuff.
A 'one step at a time' sort of approach is probably the simplest way of going about it. Not the fastest by any means, but the easiest, sort of. It gives everyone involved a chance to keep up, maybe get an idea of why something works the way it does.
I know, you know, and I'll bet LumpySnake knows that this antenna isn't ever going to be the best in the world. But it'll be usable. And with a 'shoe string', 'budget', 'cheap axed' approach like this, what else can you really expect? (Except for MY 'cheap axed' antennas which are always perfect! Right?
)
For me, half of the fun of playing with antennas are the mistakes. After making enough of those mistakes it gradually sinks in that something or other just ain't gonna work that way. That's probably one of the stupidest ways of learning something, but I'm very good at it (unfortunately)!
Oh well.
- 'Doc
I think the hardest part of answering a question on any of these forums is trying to gauge how much the question ask'er knows about what's happening. Most of the time, that guess is almost always wrong to some extent, in either direction, which just causes more confusion. If you ever figure that one out, please tell me!
There's almost always more than one way to do something, to make something 'work'. Keeping track of things, which suggestion might be 'best' for any particular situation, is another one of them head scratchers. Lots and lots of variables in all this stuff.
A 'one step at a time' sort of approach is probably the simplest way of going about it. Not the fastest by any means, but the easiest, sort of. It gives everyone involved a chance to keep up, maybe get an idea of why something works the way it does.
I know, you know, and I'll bet LumpySnake knows that this antenna isn't ever going to be the best in the world. But it'll be usable. And with a 'shoe string', 'budget', 'cheap axed' approach like this, what else can you really expect? (Except for MY 'cheap axed' antennas which are always perfect! Right?
)For me, half of the fun of playing with antennas are the mistakes. After making enough of those mistakes it gradually sinks in that something or other just ain't gonna work that way. That's probably one of the stupidest ways of learning something, but I'm very good at it (unfortunately)!
Oh well.
- 'Doc
'Doc you are not giving yourself any credit as usual, sorta.
My idea did not really change anything (materials) that LS was using. I did mention the PVC however. The problem he saw and did not understand, that probably stimulated his question, was what I meant when I said "...you should know that."
I did not mean we had to read his mind. He was thinking "problem" while saying at the same time everything was good. That does not jive. He did not see or suspect the obvious, and I think you should have---just based on what he showed us and your understanding.
You say it will work, and that begs the question. It will work of course, but work just about as badly as you could make it. He said it worked quite well, so ask yourself---why did he think he needed to fiddle with it all to find out the SWR went up? If it is good, why does he feel the need to fix it? We can't read his mind of course, but we should be able to make some conslusions about what folks say, don't say, or the way they say it.
Now LS is talking about co-phasing with another antenna and in the same breath almost he is saying in his nice little video walk-around: "...that I can't even get this thing to work."
And again a little later after some more changes he is saying the following, while the antenna remains basically on the ground:
He will not overcome his biggest problem until he raised this antenna to at least 8' to the tip end of the ground radials or puts down many more radials. Mother Earth is taking all of his signal.
He needs some steady direction, not a lot of talk about how to co-phase. He will have to tell us what he is really thinking, but right now he needs a little better understanding and once he gets that antenna right he won't have to guess or wonder about how good or bad it is working, he will be amazed to compare it to what he currently is using.
Lumpy Snake is a bright young man and he will figure it all out sooner or later.
My idea did not really change anything (materials) that LS was using. I did mention the PVC however. The problem he saw and did not understand, that probably stimulated his question, was what I meant when I said "...you should know that."
I did not mean we had to read his mind. He was thinking "problem" while saying at the same time everything was good. That does not jive. He did not see or suspect the obvious, and I think you should have---just based on what he showed us and your understanding.
You say it will work, and that begs the question. It will work of course, but work just about as badly as you could make it. He said it worked quite well, so ask yourself---why did he think he needed to fiddle with it all to find out the SWR went up? If it is good, why does he feel the need to fix it? We can't read his mind of course, but we should be able to make some conslusions about what folks say, don't say, or the way they say it.
Now LS is talking about co-phasing with another antenna and in the same breath almost he is saying in his nice little video walk-around: "...that I can't even get this thing to work."
And again a little later after some more changes he is saying the following, while the antenna remains basically on the ground:
He will not overcome his biggest problem until he raised this antenna to at least 8' to the tip end of the ground radials or puts down many more radials. Mother Earth is taking all of his signal.
He needs some steady direction, not a lot of talk about how to co-phase. He will have to tell us what he is really thinking, but right now he needs a little better understanding and once he gets that antenna right he won't have to guess or wonder about how good or bad it is working, he will be amazed to compare it to what he currently is using.
Lumpy Snake is a bright young man and he will figure it all out sooner or later.
Marconi,
I'm not sure I'd agree with that raising the antenna up 8 feet thingy. I've known of some very nice ground mounted vertical antennas. The radial system with them were not exactly simple or few, though. One way of improving that ground mounted vertical would be to add more radials. How many? As many as possible till you get sick and tired of the whole thing, then maybe one or two more.
That adding more radials tends to make the input impedance go down, which isn't really bad. Just means you have to do some impedance matching. It will also tend to make the SWR start going up after some point. That's not really bad either, just means that the impedance matching still needs some work. Both of those things also mean that the antenna is getting more efficient, doing it's job better. 10,000 of them commercial broadcast stations can't all be wrong, can they? Most of them use a ground mounted vertical antenna.
Do ground mounted verticals out perform verticals higher off the ground? Not always, but they do sometimes. Mainly because of the care/attention put into building them. It also depends on what's around that ground mounted vertical, or if it's in a hole, sort of. But then, it's still better than nothing.
- 'Doc
(You're right about certain kinds of PVC pipe being worse than useless due to the metal content. To the best of my knowledge, the white stuff works okay. The darker colored stuff tends not to. Which could possibly be part of any 'problem'.)
I'm not sure I'd agree with that raising the antenna up 8 feet thingy. I've known of some very nice ground mounted vertical antennas. The radial system with them were not exactly simple or few, though. One way of improving that ground mounted vertical would be to add more radials. How many? As many as possible till you get sick and tired of the whole thing, then maybe one or two more.
That adding more radials tends to make the input impedance go down, which isn't really bad. Just means you have to do some impedance matching. It will also tend to make the SWR start going up after some point. That's not really bad either, just means that the impedance matching still needs some work. Both of those things also mean that the antenna is getting more efficient, doing it's job better. 10,000 of them commercial broadcast stations can't all be wrong, can they? Most of them use a ground mounted vertical antenna.Do ground mounted verticals out perform verticals higher off the ground? Not always, but they do sometimes. Mainly because of the care/attention put into building them. It also depends on what's around that ground mounted vertical, or if it's in a hole, sort of. But then, it's still better than nothing.
- 'Doc
(You're right about certain kinds of PVC pipe being worse than useless due to the metal content. To the best of my knowledge, the white stuff works okay. The darker colored stuff tends not to. Which could possibly be part of any 'problem'.)
Wow a lot happened overnight.
Okay lets see here.
The PS is slightly underpowered. It can crank out 1.2 amp's.
When I dead key, the radio pulls about .9 amp's. When talking normally, it goes to about 1.1, and when I whistle only then does it peg the meter and I see a slight voltage drop (Between 1 and 2 volts).
Lol indeed my friend
One of the reasons I am having so much fun with this is because its just so darn cheap (Both in construction and price). The antenna is far from a proper base station setup, and yet I can talk to everyone I know on this side of town. The furthest being 5 miles away. I dont know anyone further out.
You and me both when it comes to finding a way NOT to do something.
Thank you very much Marconi.
I am actually quite thrilled with what this little 'hatchet' antenna is doing.
And yes I am kinda getting carried away with the co-phasing part.
But hey if I wasnt looking forward to trying that, then what would I have to do?
I already got this antenna to suit my needs. Now I have a reason to keep pursuing the knowledge of how to do such a setup.
Also in response to raising the antenna height. I live in a homeowners association. So I kinda have to keep it hidden from sight.
Okay lets see here.
The PS is slightly underpowered. It can crank out 1.2 amp's.
When I dead key, the radio pulls about .9 amp's. When talking normally, it goes to about 1.1, and when I whistle only then does it peg the meter and I see a slight voltage drop (Between 1 and 2 volts).
Lol indeed my friend
I know, you know, and I'll bet LumpySnake knows that this antenna isn't ever going to be the best in the world. But it'll be usable. And with a 'shoe string', 'budget', 'cheap axed' approach like this, what else can you really expect? (Except for MY 'cheap axed' antennas which are always perfect! Right?
For me, half of the fun of playing with antennas are the mistakes. After making enough of those mistakes it gradually sinks in that something or other just ain't gonna work that way. That's probably one of the stupidest ways of learning something, but I'm very good at it (unfortunately)!
Oh well.
- 'Doc
One of the reasons I am having so much fun with this is because its just so darn cheap (Both in construction and price). The antenna is far from a proper base station setup, and yet I can talk to everyone I know on this side of town. The furthest being 5 miles away. I dont know anyone further out.
You and me both when it comes to finding a way NOT to do something.
Thank you very much Marconi.
I am actually quite thrilled with what this little 'hatchet' antenna is doing.
And yes I am kinda getting carried away with the co-phasing part.
But hey if I wasnt looking forward to trying that, then what would I have to do?
I already got this antenna to suit my needs. Now I have a reason to keep pursuing the knowledge of how to do such a setup.
Also in response to raising the antenna height. I live in a homeowners association. So I kinda have to keep it hidden from sight.
Well I agree 'Doc, but in this case I would advise LS to raise the antenna even higher. The 8' of height for the tip ends of the radials was just a minimum height I would think he needs to try and avoid the large effects of Earth with just four radials.
I wouldn’t compare this setup to a broadcast radio antenna either, so I think LS should wait a while before starting such a project and give you some time to produce a plan.
LS should try his radio with a friend's setup, on a traditional base antenna, or in a good mobile setup that is known to work well. Check his meter output for responses and see how it acts---with a good load and his power supply. I suspect right now he is probably seeing little to no drive from his radio hooked up to this antenna and hopefully he has not hurt the radio. He has already told us though that the dead key and output was low from the get-go.
I think I will wait for LS to make some more comments 'Doc.
I wouldn’t compare this setup to a broadcast radio antenna either, so I think LS should wait a while before starting such a project and give you some time to produce a plan.
LS should try his radio with a friend's setup, on a traditional base antenna, or in a good mobile setup that is known to work well. Check his meter output for responses and see how it acts---with a good load and his power supply. I suspect right now he is probably seeing little to no drive from his radio hooked up to this antenna and hopefully he has not hurt the radio. He has already told us though that the dead key and output was low from the get-go.
I think I will wait for LS to make some more comments 'Doc.
This radio use to be my mobile until I got the Galaxy 959. But this radio always had a bad habit of not putting out a lot of power so im thinking the radio itself might have problems. Its pretty old and not to mention when I first got it I didn't know jack about radios and I keyed the thing up a few times with no antenna. :blushing:
Heck I always wanted to try a properly mounted antenna. You know like, 30' in the air.
you and I come from both ends of the spectrum here.
Quote:
" One of the reasons I am having so much fun with this is because its just so darn cheap (Both in construction and price). The antenna is far from a proper base station setup, and yet I can talk to everyone I know on this side of town. The furthest being 5 miles away. I dont know anyone further out."
That is probably the best part of homebrewing is doing and learning for yourself! And when you are done you have bragging rights and pass your new found knowledge on to others!
Now for my two cents.... Change the radiator to something with a larger diameter like copper pipe or aluminum. (salvage is best!) Then you can get rid of the PVC, self supporting! Raise the radiator so the the ground radials appear like an upside down "Y" , maybe not as steep. This will change the feed point impedance and lower the "takeoff" angle of the signal.
Height above terrain has always given more distance so raise the whole thing as high as you can. I have a ground mounted Chushcraft AV3 and it works well on 11 meters and the feed point is only a foot above ground level. I feel it would do better at 10 to 50 feet! I have many ground radials, maybe 25.
Try a tuning capacitor as a shunt at the feed point to adjust the impedance. Shunt between the shield and center conductor. You could also use a coil of stiff copper wire as an inductor, connect one end to the ground radials and the other end to the bottom of the radiator then feed the coil at different points with the center conductor. A choke coil can be helpful as mentioned.
Think of an antenna and your radio like you would a speaker and an audio amp, keep them balanced and they will sound great!
mechanic
" One of the reasons I am having so much fun with this is because its just so darn cheap (Both in construction and price). The antenna is far from a proper base station setup, and yet I can talk to everyone I know on this side of town. The furthest being 5 miles away. I dont know anyone further out."
That is probably the best part of homebrewing is doing and learning for yourself! And when you are done you have bragging rights and pass your new found knowledge on to others!
Now for my two cents.... Change the radiator to something with a larger diameter like copper pipe or aluminum. (salvage is best!) Then you can get rid of the PVC, self supporting! Raise the radiator so the the ground radials appear like an upside down "Y" , maybe not as steep. This will change the feed point impedance and lower the "takeoff" angle of the signal.
Height above terrain has always given more distance so raise the whole thing as high as you can. I have a ground mounted Chushcraft AV3 and it works well on 11 meters and the feed point is only a foot above ground level. I feel it would do better at 10 to 50 feet! I have many ground radials, maybe 25.
Try a tuning capacitor as a shunt at the feed point to adjust the impedance. Shunt between the shield and center conductor. You could also use a coil of stiff copper wire as an inductor, connect one end to the ground radials and the other end to the bottom of the radiator then feed the coil at different points with the center conductor. A choke coil can be helpful as mentioned.
Think of an antenna and your radio like you would a speaker and an audio amp, keep them balanced and they will sound great!
mechanic
More a Minimalist May Make to Maximize, mmm...
Hey LumpySnake,
Here's something you might wanna try, and it's real cheap.
Get hold of a Wilson 1000/5000 whip, a 3/8" thread x 2" brass bolt with a flat hex head and two or three brass nuts with a couple washers to fit it, and a PVC cap to fit the top of your PVC mast.
Drill a hole in the center of the top of the hex head bolt so the Wilson whip fits tightly when hammered into it. I used a pair of vice grips which were squeezed onto the whip to hit with the hammer forcing the whip into the interference-fit hole I drilled.
It helped to file the end of the whip into a little beveled edge so it would seat into the brass easier.
Drill a small hole into the top of the PVC cap for the brass bolt to screw into it, and if you're careful you should be able to match the hole size to the brass bolt so it will actually thread into the PVC cap and be self-sealing, but you might also want to add a small rubber O-ring between the bolt head and the PVC cap to seal it from all that Arizona rain.
You'll be connecting the center wire of your coax to the brass bolt from underneath and inside the PVC.
You will need to make sure it's 106" total height to the top of the whip from where the coax is split to reveal the shield and center conductor.
Don't assemble yet.
Now drill three or four holes through the side of the PVC mast where the coax split will hang, inside the PVC.
Solder or twist onto the braid three or four lengths of 108" of wire and send them out through the holes by pulling their ends through with 3 or 4 strings you pushed into the holes from outside so you could tie the ends of the wire and pull them out through those 3 or 4 holes drilled in the side of the PVC mast. You may want to tape over those holes to seal the antenna from all that Arizona humidity and to keep the baby scorpions out.
Those 1/4 wave long 108" wires or 'ground radials' attached to the braid are called a counterpoise and should go outward and downward toward the ground at a downward angle.
Your ground conductivity appears to be so minimal that I doubt it will much hinder the performance even though they won't be at least a 1/4 wave from the ground.
One thing we did was to drill another hole in the side of the PVC mast about a foot below the point where the coax splits inside. Out through that hole we pulled the mini-8 (RG-8X) coax and then wrapped 12 feet of it around the PVC in a tight coil to act like a choke (common mode current choke) which helped the tuning by keeping the outer braid from radiating back down the coax.
You should see real close to a 1.5:1 or less SWR, and your signal strength should increase by several S-units!
- You might want to paint everything flat black or flat gray primer to keep the visibility to a minimum.
I built one of these for my nephew in the outer parts of the Reno area for a little CB rig he was given. The furthest we made it was 8 miles south of Carson City, or about 60 miles!! - It was an SSB rig, Cobra 140, but the guy we talked to had a PDL II beam pointed our way.
As a local guy out here is always saying, "It's all about the fun!!" so have fun! - As it sounds like you
already are.
73zzzzz
Hey LumpySnake,
Here's something you might wanna try, and it's real cheap.
Get hold of a Wilson 1000/5000 whip, a 3/8" thread x 2" brass bolt with a flat hex head and two or three brass nuts with a couple washers to fit it, and a PVC cap to fit the top of your PVC mast.
Drill a hole in the center of the top of the hex head bolt so the Wilson whip fits tightly when hammered into it. I used a pair of vice grips which were squeezed onto the whip to hit with the hammer forcing the whip into the interference-fit hole I drilled.
It helped to file the end of the whip into a little beveled edge so it would seat into the brass easier.
Drill a small hole into the top of the PVC cap for the brass bolt to screw into it, and if you're careful you should be able to match the hole size to the brass bolt so it will actually thread into the PVC cap and be self-sealing, but you might also want to add a small rubber O-ring between the bolt head and the PVC cap to seal it from all that Arizona rain.
You'll be connecting the center wire of your coax to the brass bolt from underneath and inside the PVC.
You will need to make sure it's 106" total height to the top of the whip from where the coax is split to reveal the shield and center conductor.
Don't assemble yet.
Now drill three or four holes through the side of the PVC mast where the coax split will hang, inside the PVC.
Solder or twist onto the braid three or four lengths of 108" of wire and send them out through the holes by pulling their ends through with 3 or 4 strings you pushed into the holes from outside so you could tie the ends of the wire and pull them out through those 3 or 4 holes drilled in the side of the PVC mast. You may want to tape over those holes to seal the antenna from all that Arizona humidity and to keep the baby scorpions out.
Those 1/4 wave long 108" wires or 'ground radials' attached to the braid are called a counterpoise and should go outward and downward toward the ground at a downward angle.
Your ground conductivity appears to be so minimal that I doubt it will much hinder the performance even though they won't be at least a 1/4 wave from the ground.
One thing we did was to drill another hole in the side of the PVC mast about a foot below the point where the coax splits inside. Out through that hole we pulled the mini-8 (RG-8X) coax and then wrapped 12 feet of it around the PVC in a tight coil to act like a choke (common mode current choke) which helped the tuning by keeping the outer braid from radiating back down the coax.
You should see real close to a 1.5:1 or less SWR, and your signal strength should increase by several S-units!
- You might want to paint everything flat black or flat gray primer to keep the visibility to a minimum.
I built one of these for my nephew in the outer parts of the Reno area for a little CB rig he was given. The furthest we made it was 8 miles south of Carson City, or about 60 miles!! - It was an SSB rig, Cobra 140, but the guy we talked to had a PDL II beam pointed our way.
As a local guy out here is always saying, "It's all about the fun!!" so have fun! - As it sounds like you
already are.
73zzzzz
Last edited:
As a local guy out here is always saying, "It's all about the fun!!" so have fun! - As it sounds like you
already are.
73zzzzz
Hey Thanks for the info CDX. I might have to try that sometime sounds like it would get out a lot further than mine is. And yes I am enjoying myself very much with this. It really is all about having fun. However there are a few local ppl here that make it kinda hard to have fun.
I made a dipole antenna. Formula for this is- 468/Frequency.
Example 468/27.205=17.2 feet. I cut the #14 wire in half then stipped end of wire and connected one piece to the center lead of rg58 coax and the other to the shield sie of the coax. My center lead is HORIZONTAL (attached to the ceiling) and the shield is Vertical and I get a 1.2:1 match. Keep in mind that this in my basement because I live in a Condo, no antennas allowed outside. I can get out around 4 to 5 miles running a Galaxy DX959 and D104 M6B Mic powered by a Pyramid 12 amp power supply. What more can you ask for.
Example 468/27.205=17.2 feet. I cut the #14 wire in half then stipped end of wire and connected one piece to the center lead of rg58 coax and the other to the shield sie of the coax. My center lead is HORIZONTAL (attached to the ceiling) and the shield is Vertical and I get a 1.2:1 match. Keep in mind that this in my basement because I live in a Condo, no antennas allowed outside. I can get out around 4 to 5 miles running a Galaxy DX959 and D104 M6B Mic powered by a Pyramid 12 amp power supply. What more can you ask for.
- No one is chatting at the moment.
