Re: 130 mile contact on HT
Posted: Sun May 16, 2010 5:22 pm
CB SWR meters often do not have the frequency range for VHF, in fact I looked at mine and it doesn‘t . . . so I need to go buy a real one and test again. Live and learn. Who knows what numbers I have been using! I wondered why when I got done, it worked a bit poorly and a fine adjustment process for good Tx was done with the help of a friend listening on another radio. Dumb, I should have figured it out then.
How you tune an antenna is different for different antennas. CB you often trim the end or turn a screw on top (like Firesticks) until you get good SWR. The gamma match is basically what gets adjusted on what I built, but I got lucky in that I welded the one end of the rod in place so it cannot have the feed point and capacitor adjusted separately. It works but that was an error.
The elements are made from 0.125” steel round from Home Depot (where most of the materials came from) and are 40“, 37” and 35” (reflector, driven and director). Spacing is 16.25” reflector to driven element and 20.25” driven element to director.
Spacing and lengths could be done better, even eliminating the gamma . . . But I didn’t do that, . . .next time, maybe.
The gamma is made out of 8“ of 5/16” steel rod partially covered in heat shrink so as to be inserted into 7“of 1/2” steel tube. That heat shrink extends over the end to ensure the round cannot contact the tube The other end of the rod is left bare for about 1”. The tube has a 3” piece of fiberglass tent pole JB Welded in place 1" in the tube and the exposed 2" is inserted into a hole in the boom to hold the tube up.
A piece of 3/4” square with a small 1/8” hole for the driven element and another for the bare end of the 5/16” rod (where I welded but should not have). The element is held in place and good contact made by a small bolt, its nut and a spacer welded inside the square with another on the other side to prevent the element from being bent when the bolt is tightened.
Sprinkler headers of 36” and 12 “ are threaded into a PVC T for the boom. Caps are used to keep the elements in the boom when storing or traveling. Holes for the elements and gamma are drilled into those headers at the spacing described. The T is used for a 48” sprinkler header to hold it up (sometimes), vertically polarized.
The color tape matches that on the element that goes in that position. The tape on the element positions the element correctly in the boom. The white stripe on each element’s color tape tells me that end is “out” to make sure I put it together right. So green is the director, yellow the driven element and red the reflector. I put blue tape on the driven element as a stop for where the gamma match’s 1/2” square tube is attached there, in the place where it belongs.
The cables are just off the shelf BNC cables (and an adapter for the radio) from Orovac. The last one is BNC to Alligator clips, one then goes on the driven element on the opposite side as the gamma, and the other goes onto a little piece of 0.125 round welded onto the 1/2” tube. This could be done better as well.
The cables are held onto the boom with Velcro straps. One cable has a ferrite core installed and for over kills three poops held in place with cable ties, all to prevent any thing from going back down the coax shield. They were added before the gamma in an attempt to get rid of the annoying hiss and didn’t do that but were left in place. They may do nothing but do no harm.
The elements are heavy as is the over built gamma. Steele is an error, but at Home Depot they do not carry 0.125 aluminum and I was lazy. I should have gone down to the metal shop and will next time. Aluminum would work better for everything The boom is also heavy , long when disassembled and not as ridged as I’d like.
All the many shortcomings noted (and those I am sure to encounter) will be worked on in the next, lighter, more pack able, better looking version.
There, the way too long version!
If you do not plan to hike with one but want to be able to move around in the truck, something like these might work http://www.arrowantennas.com/ and save one from building one.
The Simley on my friend’s HT worked well. He has the same HT as me. I think he has the Super Stick. It worked well, I wondered about the weight and length impacting the connector but even then, I am probably going to get one to add to the arsenal. http://www.smileyantenna.com/ He really got out well with it. The only obvious downside is it is really long, but then again, the yagi isn’t small!!!! Plus it is only 25 bucks!
How you tune an antenna is different for different antennas. CB you often trim the end or turn a screw on top (like Firesticks) until you get good SWR. The gamma match is basically what gets adjusted on what I built, but I got lucky in that I welded the one end of the rod in place so it cannot have the feed point and capacitor adjusted separately. It works but that was an error.
The elements are made from 0.125” steel round from Home Depot (where most of the materials came from) and are 40“, 37” and 35” (reflector, driven and director). Spacing is 16.25” reflector to driven element and 20.25” driven element to director.
Spacing and lengths could be done better, even eliminating the gamma . . . But I didn’t do that, . . .next time, maybe.
The gamma is made out of 8“ of 5/16” steel rod partially covered in heat shrink so as to be inserted into 7“of 1/2” steel tube. That heat shrink extends over the end to ensure the round cannot contact the tube The other end of the rod is left bare for about 1”. The tube has a 3” piece of fiberglass tent pole JB Welded in place 1" in the tube and the exposed 2" is inserted into a hole in the boom to hold the tube up.
A piece of 3/4” square with a small 1/8” hole for the driven element and another for the bare end of the 5/16” rod (where I welded but should not have). The element is held in place and good contact made by a small bolt, its nut and a spacer welded inside the square with another on the other side to prevent the element from being bent when the bolt is tightened.
Sprinkler headers of 36” and 12 “ are threaded into a PVC T for the boom. Caps are used to keep the elements in the boom when storing or traveling. Holes for the elements and gamma are drilled into those headers at the spacing described. The T is used for a 48” sprinkler header to hold it up (sometimes), vertically polarized.
The color tape matches that on the element that goes in that position. The tape on the element positions the element correctly in the boom. The white stripe on each element’s color tape tells me that end is “out” to make sure I put it together right. So green is the director, yellow the driven element and red the reflector. I put blue tape on the driven element as a stop for where the gamma match’s 1/2” square tube is attached there, in the place where it belongs.
The cables are just off the shelf BNC cables (and an adapter for the radio) from Orovac. The last one is BNC to Alligator clips, one then goes on the driven element on the opposite side as the gamma, and the other goes onto a little piece of 0.125 round welded onto the 1/2” tube. This could be done better as well.
The cables are held onto the boom with Velcro straps. One cable has a ferrite core installed and for over kills three poops held in place with cable ties, all to prevent any thing from going back down the coax shield. They were added before the gamma in an attempt to get rid of the annoying hiss and didn’t do that but were left in place. They may do nothing but do no harm.
The elements are heavy as is the over built gamma. Steele is an error, but at Home Depot they do not carry 0.125 aluminum and I was lazy. I should have gone down to the metal shop and will next time. Aluminum would work better for everything The boom is also heavy , long when disassembled and not as ridged as I’d like.
All the many shortcomings noted (and those I am sure to encounter) will be worked on in the next, lighter, more pack able, better looking version.
There, the way too long version!
If you do not plan to hike with one but want to be able to move around in the truck, something like these might work http://www.arrowantennas.com/ and save one from building one.
The Simley on my friend’s HT worked well. He has the same HT as me. I think he has the Super Stick. It worked well, I wondered about the weight and length impacting the connector but even then, I am probably going to get one to add to the arsenal. http://www.smileyantenna.com/ He really got out well with it. The only obvious downside is it is really long, but then again, the yagi isn’t small!!!! Plus it is only 25 bucks!