01-15-2012, 06:18 PM
[Image: http://i487.photobucket.com/albums/rr233...ant1-1.jpg]
[Image: http://i487.photobucket.com/albums/rr233...ant2-1.jpg]
[Image: http://i487.photobucket.com/albums/rr233...ant3-1.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant4.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant5.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant6.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant7.jpg]
I'll refer to the antenna pic numbers for reference. The X arms are 1/2" molding stock from Ace Hardware. You'll need 4 total at 36". Then use the extra you cut off to make the center wire (tank coil) support dowels. The center tank coil dowels are 2 3/4", though 2 1/2" would work fine also(pics 5 & 7). The center box support piece adds strength against flexing, it is the same width of 2 3/4" but is 1" stock molding(pic 4). I used 3/4" long brass screws. One on each end to attach the main loop supports to the main X arms. I used fairly small screws and drilled the holes for them. If you don't, you'll split the wood turning them in. Sorry I do not have complete screw dimensions as I had them in the screw box. I just know their length.
Now I set the tank coil support dowels in 1/4", to help bring the wire inside the X arms. Then should you choose, get some balsa wood, and attach them parallel to the wire to protect it against bumps and falls. I already dropped my 30" loop and destroyed the wire. I re-wound it, but had I included this protection nothing would have happened when I dropped it. Doesn't look as sexy, but sure protects it well.
Next I worked on the tank coil dowels. I cut about 20 slots using a hand-held wood saw. If you have access to a band saw, that would save time and look more precise. Anyhow I cut them about 1/16" deep across the dowel. I used 20 cuts to allow for more winds than are needed. With this setup only 15 turns are needed. Though when you wind it, use 17 turns. That way when you tune the antenna for both the bottom and top end of the band, you can remove wire as needed. Easier than adding it. Some folks use taps with gator clips to achieve proper BCB band tune. But again doesn't look as sexy.
Next the sense coil (loop) is 3/4" from the main loop. I used very small eye screws to support the sense loop. The eye screws were purchased at Home Depot some time back for whatever reason. Again the actual size I do not have other than they were about 1/4" in length.
The main support bar that supports the X arms is 1" molding stock cut to 15" in length. Another warning if you do not work with wood. Drill all holes for the screws including the eye screws. If you do not, you stand a good chance of splitting your wood. The base board can be anything for the most part. I used counter top wood which is thick/dense and heavy. Though it's very smooth, sands out nice. Then add rubber feet to the bottom. For this loop I used a 10" x 7". Use your common sense and keep in mind you don't want it to easily tip over. For the tuning cap I used a 10/pf - 470/pf. Though I found a 10/pf - 400 works well in allowing you to tune the entire BCB. With a smaller one you can add capacitance to the tuner if needed.
Parts used:
Wood
#26 awg
25" x 25" with 15 turns
1 turn loop sense
Tuning cap that has the range of 10/pf - 450/pf
Attach the sense loop to antenna and ground. Remember, many of the 1935 - 39 sets have multiple antenna connections. The reason is if you're using a simple long wire or doublet/dipole antenna. Many of the manufactures sold these readymade. Now they have shorting bars on the connections for use depending on your antenna type. I found the best performance is seen when keeping these connections in their default settings for use with a long wire. Also do not connect a ground to the chassis when using a loop. With your new antenna connected up. Start at the top of the band and see if you get a fairly sharp tune. Then move to the bottom end and check the same. Removing windings brings the resonate freq higher(shorter antenna length). Also adding capacitance to the tuning cap drops the resonate freq lower.
Last here is my thoughts on this. I'm no wood worker, I'm no electronics engineer. Forgive my noobish approach for those that probably can be called experts. But I built this simple antenna sitting on my butt with nothing more than a drill, small wood working saw, soldering gun, screw driver, ruler and extra parts laying around and a couple of trips to the hardware store. Plus no plans, I built it as I went. Drawing up the idea in my head. There is nothing special here and no magic. It's been done to death and explained in painful detail on the net within 100s of web pages. There are probably 1000 different ways to build this to serve your needs or curiosity. Different shapes types and sizes. Some like spiral designs, others (myself) prefer the box style. Some could care less as long as it does the job, picking up the desired signal and leaving out the crud that gets normally dragged in. Remember this is the same tuned antenna on the back of your late 30s and post WWII sets. It's the same antenna in your transistor radio (at least in principle). Like those antennas it works the same way and allows your 30s sets that require a long wire to run without it. Performance can be dramatic against other forms/styles of antenna depending. These help eliminate some of the noise brought into your set(in effect a tuned circuit). It allows directional use, thereby eliminating or reducing an interfering station. Remember it's a hobby, so have fun and experiment
[Image: http://i487.photobucket.com/albums/rr233...ant2-1.jpg]
[Image: http://i487.photobucket.com/albums/rr233...ant3-1.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant4.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant5.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant6.jpg]
[Image: http://i487.photobucket.com/albums/rr233...6/ant7.jpg]
I'll refer to the antenna pic numbers for reference. The X arms are 1/2" molding stock from Ace Hardware. You'll need 4 total at 36". Then use the extra you cut off to make the center wire (tank coil) support dowels. The center tank coil dowels are 2 3/4", though 2 1/2" would work fine also(pics 5 & 7). The center box support piece adds strength against flexing, it is the same width of 2 3/4" but is 1" stock molding(pic 4). I used 3/4" long brass screws. One on each end to attach the main loop supports to the main X arms. I used fairly small screws and drilled the holes for them. If you don't, you'll split the wood turning them in. Sorry I do not have complete screw dimensions as I had them in the screw box. I just know their length.
Now I set the tank coil support dowels in 1/4", to help bring the wire inside the X arms. Then should you choose, get some balsa wood, and attach them parallel to the wire to protect it against bumps and falls. I already dropped my 30" loop and destroyed the wire. I re-wound it, but had I included this protection nothing would have happened when I dropped it. Doesn't look as sexy, but sure protects it well.
Next I worked on the tank coil dowels. I cut about 20 slots using a hand-held wood saw. If you have access to a band saw, that would save time and look more precise. Anyhow I cut them about 1/16" deep across the dowel. I used 20 cuts to allow for more winds than are needed. With this setup only 15 turns are needed. Though when you wind it, use 17 turns. That way when you tune the antenna for both the bottom and top end of the band, you can remove wire as needed. Easier than adding it. Some folks use taps with gator clips to achieve proper BCB band tune. But again doesn't look as sexy.
Next the sense coil (loop) is 3/4" from the main loop. I used very small eye screws to support the sense loop. The eye screws were purchased at Home Depot some time back for whatever reason. Again the actual size I do not have other than they were about 1/4" in length.
The main support bar that supports the X arms is 1" molding stock cut to 15" in length. Another warning if you do not work with wood. Drill all holes for the screws including the eye screws. If you do not, you stand a good chance of splitting your wood. The base board can be anything for the most part. I used counter top wood which is thick/dense and heavy. Though it's very smooth, sands out nice. Then add rubber feet to the bottom. For this loop I used a 10" x 7". Use your common sense and keep in mind you don't want it to easily tip over. For the tuning cap I used a 10/pf - 470/pf. Though I found a 10/pf - 400 works well in allowing you to tune the entire BCB. With a smaller one you can add capacitance to the tuner if needed.
Parts used:
Wood
#26 awg
25" x 25" with 15 turns
1 turn loop sense
Tuning cap that has the range of 10/pf - 450/pf
Attach the sense loop to antenna and ground. Remember, many of the 1935 - 39 sets have multiple antenna connections. The reason is if you're using a simple long wire or doublet/dipole antenna. Many of the manufactures sold these readymade. Now they have shorting bars on the connections for use depending on your antenna type. I found the best performance is seen when keeping these connections in their default settings for use with a long wire. Also do not connect a ground to the chassis when using a loop. With your new antenna connected up. Start at the top of the band and see if you get a fairly sharp tune. Then move to the bottom end and check the same. Removing windings brings the resonate freq higher(shorter antenna length). Also adding capacitance to the tuning cap drops the resonate freq lower.
Last here is my thoughts on this. I'm no wood worker, I'm no electronics engineer. Forgive my noobish approach for those that probably can be called experts. But I built this simple antenna sitting on my butt with nothing more than a drill, small wood working saw, soldering gun, screw driver, ruler and extra parts laying around and a couple of trips to the hardware store. Plus no plans, I built it as I went. Drawing up the idea in my head. There is nothing special here and no magic. It's been done to death and explained in painful detail on the net within 100s of web pages. There are probably 1000 different ways to build this to serve your needs or curiosity. Different shapes types and sizes. Some like spiral designs, others (myself) prefer the box style. Some could care less as long as it does the job, picking up the desired signal and leaving out the crud that gets normally dragged in. Remember this is the same tuned antenna on the back of your late 30s and post WWII sets. It's the same antenna in your transistor radio (at least in principle). Like those antennas it works the same way and allows your 30s sets that require a long wire to run without it. Performance can be dramatic against other forms/styles of antenna depending. These help eliminate some of the noise brought into your set(in effect a tuned circuit). It allows directional use, thereby eliminating or reducing an interfering station. Remember it's a hobby, so have fun and experiment
-Brian
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