I built this Antenna today CM4228 clone almost.
This is a discussion on I built this Antenna today CM4228 clone almost. within the DTV | HDTV Reception and Antenna Discussion forums, part of the Over-the-Air (Antenna TV) category.
Last edited by SWHouston; 03-07-2010 at 09:55 PM.
UPDATE: NEW DISCOVERY
Here is the antenna I am talking about http://i43.photobucket.com/albums/e3...y350/Ant-6.jpg
Very interesting discovery. I built a second antenna identical to the first antenna. While experement with it upstairs one of the balun wires came loose and the signal got stronger. Hum.
I disconnected both baluns from the antenna. Each balun has 2 wires. If I touch the wires 1 at a time to the antenna terminals I get a signal for only 1 of the balun wires. I tied a small piece of string to the wire that picks up the signal, lets call this the hot wire.
There is a left bay and a right bay each bay has 2 terminals. Starting from left to right lets name the terminals A and B on the left bay and C and D on the right bay. If I touch the balun hot wire to terminal A no signal, terminal B signal is 20, terminal C no signal, terminal D signal is 20.
Next I touch the other balun wire to each terminal A, B, C, D and the signal is ZERO.
Next I attach the hot wire of one balun to terminal B signal is 20 then I attach the other wire of the same balun to terminal A signal is now 30. I tried this balun on both bays and I get the same signal reading. I tried the other balun on both bays I also get a signal of 20 and 30.
Next with both baluns connected, left side hot wire of one balun is on terminal B and the other bay the other balun hot wire is attached to terminal D combined signal 30 + 30 is 60 on the TV field strength meter.
I have no idea why each balun has a hot wire. I am not sure how a factory made balun is made inside. I looked in Amature Radio Handbook to see how a balun is made. Not sure why a balun seems to have 1 hot wire?
I have another balun made by a different company it does not appear to have a hot wire but it does make a difference which way the 2 wires are connected. With the wires connected to the 4 bay side one way the signal is 21 when I swap the wires the signal is 32.
It makes a different how the baluns are connected for some reason? With the baluns connected so the signal is 60 if I reverse the wires on either balun signal drop to 45. If I reverse the wires on both baluns signal drops to 30.
Now I am wondering what would happen if I swapped the input wires on the combiner. I swapped them and the signal stays the same.
Next I am wondering what would happen if I put the coax cable in front of the screen instead of behind the screen, the signal goes up 7%. This doesn't seem to make sense it looks like it work better behind the screen.
Next I tilted the antenna up a few degrees toward the sky and the signal goes up 5% more.
Next thing I have noticed is the signal from channel 5 = 692 MHz is the hardest one to receive. The transmitter is at 322 degrees. I have been rotating the antenna by hand and one morning the antenna had to be aimed at 305 degrees to receive channel 5. That same day from 1 pm to 6 pm the antenna had to be aimed at 360 degrees to receive channel 5. Today the antenna is aimed at 340 degrees. I need a rotor.
Does anyone have suggestions for a good rotor?
I built the second antenna and was planning to put up 2 antenna and running 2 coax cables to the TV with an A - B switch so I can use each antenna one at a time. I was planning to aim one antenna about 310 degrees and aim the other antenna at about 340 degrees but not I think a rotor is the best choice.
Last edited by gary350; 03-09-2010 at 04:07 AM.
Gemini Orbit 360 (OR-360)
CDE AR 40
RadioShack/Archer(otor) 1225A 1225B
Channel Master 9510* Colorotor
The CDE TR-44 and CD-45 are the most stout, however I like the Gemini the best. All of these are made in USA.
There are several good Rotators available, one I have use is the...
ChannelMaster CM-9521A .
which has a Remote and Digital readout and operates on a separate cable.
A couple of things I'll say just to possibly prevent future problems...
Get a Rotator that operates on a separate (usually 3-conductor) cable.
There are ones which you just slip into the Coax cable for the antenna, but if you at some point want to add an Amp, that can be rather problematic. Also, each component added into the Signal Line, in some way (even if only a Little) reduces your signal strength.
Several of the Rotators now have displays which tell direction in degrees.
One thing common with all, is that they're SLOW !
One can arrange a list of channels by direction, and call them up in that order, therefore reducing the time it takes the Antenna to zero in on that channel.
Also, one does not have to set the original North, to North.
If you have several stations that are between 300° and 20° (for instance), one can set the 0° at 90° or 250°, just to keep the Rotator from turning completely around the circle, saving a LOT of time to acquire a station.
Who cares what the actual readout is on the Display, as long as you know where it's actually pointing.
Lastly, there are Converter Box's which control Rotators automatically, and Rotators which are designed to operated by that technology. I am NOT sure how reliable that technology is, but it is designed to work like a Sat Dish Rotator, the DiSEqC 1.2.
I say this if you/anyone would require that. Some Televisions have this technology installed in them as well. Systems like this operate on a single Coaxial Cable, which as I stated above, can be a problem when other components are required.
Have a good Day !
Last edited by SWHouston; 03-08-2010 at 11:23 AM.
I assume I have to run a 120 VAC wire up on the roof to the rotor?
Originally Posted by SWHouston
Does the rotor return to 0 every times I turn off the TV or does the rotor stay where it is?
I would like to set the antenna at 322 degrees if channel 5 mores south then I only have to rotate 20 degrees to find it but if it moves north I only have to move about 40 degrees to find it. All the other channels come in perfect at 322 degrees plus or minus 20 degrees.
Running a seperate control wire to the rotor is not a problem.
Rotor stays where it is aimed on the controller box, its separate from the TV.
The Gemini Orbit 360 is 5 wires as well as the CDE AR-40.
18 gauge solid core should do good up to 300 ft....20 gauge is good for up to 75 or 100 ft. You can get a nice 18/5 solid core copper, sprinkler wire 100 ft for $35 shipped anywhere in the US, which is what I use. It has a tough waterproof jacket, works great.
The CDE TR-44 and CD 45 are 8 wires I believe.
The RadioShack/Archer(otor) 1225* and Channel Master 9510* are 3 wires. These are both made in USA, the newer CMs are made in China and not as high quality. The fancy remote control controller units that are available for current production CM rotors work with these older units...if that is your fancy.
Hope that helps.
Last edited by EscapeVelocity; 03-08-2010 at 01:53 PM.
In addition to what EV has offered...
110v to the Rotator...not likely, it will send a lower voltage to operate the Rotator, the 110 is just to the Controller.
Have a good Day !
Its low voltage current from controller box to the mast mounted rotor.
Last edited by EscapeVelocity; 03-08-2010 at 01:54 PM.
Here is a nice CM 9510A Colorotor on eBay.
This ships with the nicer preferable (slightly higher quality) older controller box.
I just sold a Vintage CDE AR-40 New Old Stock (Actually branded as Archer ServoRotor II). Sorry you missed it.
A nice Vintage CDE AR-33 New Old Stock just sold as well.
CDE rotors are pretty common, as are the Channel Master Colorotor and the Radio Shack 1225A/1225B aka Archerotor....on eBay.
The Gemini is kind of uncommon, but not rare. These were sold in Walmart up until the early 2000s....so there are a lot of them out there.
CDE rotors are also sold (uncommonly) as CDR rotors, so you might want to search CDR as well....might luck up and get a good deal.
Also when searching on eBay I use the term "rot*" ... which uses a wild card *, which captures both "rotator" and "rotor" for better more inclusive search results. Example: "CDE rot*" or "Channel Master rot*"
Last edited by EscapeVelocity; 03-08-2010 at 03:45 PM.
There is also the Alliance U-100 and U-110, however these have limitations and annoyances.
1.) They are only adjustable to every 5 degree positions (or so). Meaning they arent infinitely adjustable to the degree or whatever, that isnt so bad really, for television work.
2.) They also make a terrible clunk clunk sound (the controllers do).
Here is a video of the clunk clunk sound on the Alliance U-100 and U-110 rotors.
Otherwise these are heavy duty, very good rotors. I like the Alliance T-45 manual control with heavy duty rocker bar (though the rotor itself is very similar to but not identical to the U-100/U-110), but that is more useful for ham work. You have to hold the bar down to turn the rotor and let go when you want it to stop. It has instant reverse via the rocker bar and is infinitely adjustable, so good for zeroing in on a signal. But, as with most rotors, its 1 rotation/revolution per minute....so for TV work, its much more convenient to have a dial control to spin to the correct heading and walk away.
Last edited by EscapeVelocity; 03-08-2010 at 03:01 PM.
The Alliance T-45 and U-100 and U-110 use worm gear drives, all the others mentioned dont. The worm gear is superior, though its not that critical in turning relatively small, lightweight, and close center of gravity television antennas.
Last edited by EscapeVelocity; 03-08-2010 at 03:02 PM.
The Alliance U-100 and U-110 are available at Norm's Rotor Service, New Old Stock. A reputable business that bought up all the stock of the Alliance rotors, when they went out of business.
The Alliance U-100 and U-110 are 4 wires, the Alliance T-45 is 5 wire.
Chief Content Editor
Those Alliance rotors have seperate thrust bearings available for heavy antennas and I think Norm's still has them. These are designed to be mounted below the rotor and cannot be mounted above it. I have 3 or 4 of those rotors and auxillary thrust bearings but I need to order replacement 'gaitors' for the rotors. By the way, Norm says on his website those are the last 'light-duty' rotors made that do not use plastic gears.
Here's a slick trick I invented using an Alliance Antenna Rotor:
Years ago I took one of my U-100 or U-110 rotors and I machined away the part of the casting that normally 'sits' on top of the supporting main mast. The ridged area of the casting I refer to, can be seen above on the YouTube still shot/link.
Then, I slid the center 'driven' portion of the rotor down the top section of a 40 foot telescopic mast to about the 31 foot level. Next, I bolted a 10 foot mast onto the 'outside' of the rotor, to parallel the top section of the telescopic mast and I reversed the wires on the control box. I used a small Cornell Dublier 'doughnut' thrust bearing (it happens to have the same offset) at the top of the works. Setup this way, the rotor with its ten foot mast orbits the stationary (guy wired at 30 feet) 40 foot telescopic 'supporting mast'.
The advantages are: the parallel tubes at the top support each other and in my case, the setup loaded with antennas stayed in the air 22 years without any servicing, surviving many major storms including the one that sunk the Interstate 90 Lake Washington Floating Bridge and the Clinton Innauguration Day Storm that hit us with 90 mph winds.
A second advantage is it lowers the rotor by about 9 feet, so its not a giant pendulum at the top of the whole works, but is only few inches from the top guy wires. Stationary antennas can be added to the 'support mast' anywhere below the rotating top section and a stationary small Yagi or an omnidirectional antenna (say for a police scanner) can be the cherry on top of the supporting mast.
My setup finally blew over (it buckled in half, right above the guy wires/below the rotor) do to metal fatigue/chrystaline metal of the main mast support tube but, I had twenty two years of service life!
Last edited by Fringe Reception; 03-08-2010 at 07:59 PM.
DTVUSA Jr. Member
I took an old balun apart, and I think I know what is going on here. Basically the twin-lead input is run through a ferrite core with two cavities. each lead is wound about 2.5 winds through it's respective cavity and then comes out the other end. One goes to the center conductor of the coax (signal, and probably your "hot" lead). The other goes to the shield of the coax. There is also a second winding through each cavity of the core along with the main wires connected to the twin-lead.
Originally Posted by gary350
The second winding on the side connected to the coax center goes from coax center to coax shield. Not sure if this just adds impedance, or reinforces signal to coax core.
The second winding on the side connected to the shield goes from the shield to the shield. Not positive what this does, unless it just resists current to the shield.
This is not what I pictured for matching 4:1 transformer. I expected two isolated loops through a toroid to transform the balanced differential voltage and current from the antenna halves to the unbalanced voltage and current of the coax with a turns ratio of 4:1.
The way this works, essentially one half of each antenna bay is tied to the shield, and the other half is tied to the center conductors on the coax (with some additional filtering). That said, when you connect the coax to the splitter / combiner, you are shorting together the two coax shields. That is fine if both shields correspond to the same sides.... I.E. Two lefts are good, or two rights, but not a mix of left and right. Mixing left and right essentially combines the signals out of phase, and causes them to destructively interfere with each other, reducing the signal instead of increasing it.
Phase is critical. It is the reason for the crossovers at the top and bottom of the 4 bay setup to begin with. The signal has to travel half a wavelength to reach the same point as the middle bow ties. In order for the current and voltage to be in phase at this point, the signal is taken from the other side (the crossover inverts the signal), and then it travels half a wavelength (inverting the signal back) to produce an in phase signal at the point where the top bow tie combines with the middle bow tie on the way to the feed point.
Without this crossover the top feed wires would need to be a full wavelength long to maintain phase with the middle bow ties. If you just left out the crossover and maintained the half wavelength spacing, you would be subtracting the signal from the top and bottom bow ties from the middle bow ties and get a very weak signal.
The same applies if the wrong phasing is used from the left group of 4 to the right group of four phase mismatching causes signal degradation. You even have to be sure to match up the short coax lengths going from the baluns to the combiner. Mismatches in those lengths can also degrade the signal.
This antenna is essentially a 16 element phased array antenna, with hard wired fixed phasing. By varying the relative phase (not connecting the baluns in phase), you can change your antenna pattern moving nulls and lobes. The intent is to create a simple straight forward frontal lobe design, but mismatching the phase can create side lobes and a null straight forward.
anyway, I hope this makes things clearer as to why it matters which line you hook up on the balun.
I am still not sure a 4:1 balun is appropriate for a 4 bay, since each bow tie is around 300 ohms and connecting 4 in parallel should give closer to 75 ohms (4 times the current, same voltage). I do agree with the comment on your original connecting scheme. You would have to flip that tab around and bring the coax between the feed points, so that the wire from the center conductor was the same length as the tab from the shield. To do that you would have to drill out the center of the middle plastic block.
Each bowtie is about 600 ohms at resonance give or take....and it increases moving up and down frequency away from resonance (oversimplification but a good one none the less).
I am still not sure a 4:1 balun is appropriate for a 4 bay, since each bow tie is around 300 ohms and connecting 4 in parallel should give closer to 75 ohms (4 times the current, same voltage).
But you are right, by the time you get to the feed point on a 4 bay you are at about 150 ohms at resonance, greater off resonance. (There are some other things that effect it as well but lets just keep it simple.)
But the gist of what you were saying is correct.
Hope that helps.
DTVUSA Jr. Member
Originally Posted by EscapeVelocity
Thanks for getting the numbers right.
I should have researched a bit further.
So... If a 4:1 balun isn't ideal for a 4 bay, what is?
And where can it be bought?
Or how can it be built?
After reading a few threads on this, I am wondering if the feedpoint and phasing lines are not the main limitations of these larger array antenna setups. Everything I read seems to convince me that the feed system would be better off being ALL coax from all 16 triangular sections. That would give the best shielding to the feed wires, and the most uniform phase velocity to a central feed, but matching each coax to a triangle could be problematic, and getting the lengths exact could also be an issue.
It almost looks like you would need to use the impedance calculation for a coax (ratio of inner diameter to outer diameter) to do the match, by slowly flaring the shield at the end of the coax until it matches the impedance of the antenna element (or the impedance of free space, not sure which is better), then solder the tip of the cable to the tip of the triangle.
You could then combine the right side triangle signals into one group, the left side triangles into another, and use a transformer to convert from balanced differential signals to a single output feed. Since all the signals would start out single ended on the center conductor of the coax, it would not be an issue to have the shields tied together, but it would be important not to mix right side and left side cables, as that would cause signal cancellation.
Do 4:1 combiners/ 1:4 splitters match the impedance so all the signals stay 75 ohms? and no discontinuity occurs in the combiner / splitter? If they do, that might work out for the combining of all the left and right side segments, but there would still be a need for a transformer for the final feed.
Alternatively, you could use a transformer at each pair of triangles (bow tie), but phasing and impedance match would be problematic. From what EV says, we would need 600 ohm to 75 ohm (8:1) baluns. That could be pricey and hard to find.
If each bow tie is 600 ohms, then would a dual bay be nearly the perfect match at 300 ohms? It has the simplest phase line configuration. That would mean four 4:1 baluns, and a 4:1 combiner would give an 8 bay with good shielding for feeds. It would of course be important to verify the phase of each balun as each two bay section is tied into the combiner to make sure the signal is increasing, not decreasing.
Does anyone have a better concept in mind?
I think that the CM 4221 HD circuit board baluns may be custom matched to a different ratio than 4:1....like say 2.7:1 or some such.
Last edited by EscapeVelocity; 03-15-2010 at 02:40 PM.