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- DaveFred 1:47AM
- Nicholas_23 1:47AM
- rjj45 1:47AM
- traw 1:47AM
Antenna DIY
Built the below antenna and had some questions. While it does great in the high vhf/low uhf band, it appears to be a black hole above ~300mhz. I've experimented with every phase possibility without altering the length/angle/mounting point of the elements. Started with only the two middle high vhf elements connected, and worked up to all elements in various phase connections. Nothing stuck out. Built a 60"x36" reflector, mounted it 4.5" behind the elements and reception decreased for all channels. Even those stations the antenna was facing.
The high vhf elements are 12.5" w/7" spread between elements, tuning@1/2 wavelength ~470mhz, @1/4 wavelength ~250mhz.
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The small elements are 9" w/5" spread between elements, tuning @1/2 wavelength ~650mhz, @1/4 wavelength ~310mhz. The highest channel in my area is 606-608mhz.
The channels received are in the high vhf/low uhf range, ~180mhz to 204mhz. One channel is ~60miles but transmits at high power = large coverage area. The other is 180* from the first, 84miles away, and transmits at modest power levels. It was a complete surprise. We are missing 2local stations that should be easily received, 476-482mhz, and 606-608mhz.
Attempted to contact the diy youtube'r with no luck. After a search of the name/location, it appears he may have passed a couple year ago. He reported excellent results with this antenna.
Gave 4nec2 a try and that is so far over my head it wasn't even funny.
So, anyone on here into this kind of stuff?
Comments
Wish I could help. I've always aspired to get into amature radio, but have never truly crossed over. Very interested to see the correspondence here!
You're just a ham, Drew!
InDIYana Event Website
Years ago I went down the rabbit hole and found the antennas I would need to buy to get the channels I wanted. Living in downtown Grand Rapids I needed 2 antennas to the stations I wanted. One was very much like your picture the other was a yagi.
Getting them aimed correctly was pretty hard back then, new telivisions have pretty good feedback on their signal strength. Getting the mast and 2 anttena mounted took a Saturday. After that I never had to touch them again.
Moved 10 years ago and never really set things up again.
Maybe cross talk ? Can you attenuate the RF signals ? Gees going waaay back on this one.
I know Ive messed with some off air channels that would come and go with a off air antenna . Get some off air then some times of the year nothing adjusting was hit or miss. I can hit up a guy at the previous employment
Looking at the element's ½ and ¼ À they seem to be in the thick of things. Odd thing, while experimenting, I unhooked all but the middle two 12.5" elements and it received the high vhf channels like normal, but when hooking up the other smaller 9" elements, one at a time, signal strength of those channels increased a little with every element added, but no new stations.
Hooked up a really old bowtie, probably 30years old, and it picked up one of the high vhf channels with a low signal level, nothing else, no uhf at all. It had 7" elements.
Hmm ... what happens when a balun goes bad? They are just a matching transformer.
I have a "just in case" DIY 2 element antenna in the garage. It's been 4 years since I've had to use it, but we got our local HD broadcasters that are 30-40 miles up the interstate. I have both elements in phase - not sure if that's correct, but it worked. I have a copper PCB behind the elements because that's the design I found online.
Bowtie?
No luck finding baluns locally so they are on the slow boat from China.
This all started because of a $49 tv, but it is kind of neat fiddling with this stuff.
Yep - bow tie type. I think I built it when we were having cable problems in the neighborhood quite a while ago. Probably a really old design.
After watching this other video testing different types of metal for the elements, I decided to build the original antenna elements from twisted galvanized wire, basically three strands of electric fence wire twisted together. Lots of that around here, so it was basically free. That got me to wondering ... that wire has to have higher resistance than copper. Is the higher impedance having an affect on what frequencies it receives?
Another thing of plenty laying around here is aluminum wire. Hmm. Cut the coating off some urd aluminum wire exposing the strands, which looked to be about 12gauge, twisted three strands together, and bent up more elements.
Same results.
Drat.
The commercial bowties use stamp cuts from flat aluminum. And I'm pretty sure most other designs use aluminum as well.
Every manufactured antenna I've seen is aluminum. Most of the diy ones are copper, and it appears size of wire does matter. Don't have a lot of copper laying around, though, and this video gave me the galvanized wire idea. He simply swaps out different types of metal for the receive loop and runs a crude reception test.
But yeah, figured the twisted galvanized wire thing might have thrown off the numbers, but according to the reception bars on the tv, and a channel rescan, they are even. Go figure.
Should have some new baluns and an ota tuner here in a couple days. The tuner appears to give much more signal information but it was hard to tell from the aliexpress add copy.
Baluns and other stuff were scheduled for delivery today. Snow had other plans. Since the roads were messy and the needed parts didn't arrive, I decided to stay around the house and build another type of tv antenna, the Gray-Hoverman w/tophat. Used more aluminum wire salvaged from the urd cable. urd cable is stiff and running it through conduit is a real headache, but to my surprise, the individual al strands bend as easy as the equivalent size copper wire. Laid the element diagram out on a piece of scrap plywood and built a wire bend fixture. The backbone came from a scrap piece of 1x4. Other than the screws, everything else in the build was salvage. Total cost, maybe $1.20.
FYI, if you have a crooked piece of cu or al and want a straight piece, put one end of the wire in a vice, and the other end of the wire in a drill, twist slowly with a slight pull and presto, it straightens right out.
Results ... same as the previous ff6. Hoping the new standalone tv tuner has a more sensitive signal strength meter than the 4bars of the current tv as this might show any smaller differences in signal not shown by the tv's rather vague signal meter.