Interesting, I had 2 of the ST-2's come in the mail to me, and neither were damaged. None of the DPD antennas I have were damaged.
New Antenna Coming Soon based on Old Favorite.
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Interesting, I had 2 of the ST-2's come in the mail to me, and neither were damaged. None of the DPD antennas I have were damaged.
Do not twist what I said. If a ST2 was bent like this test antenna it would not have made it.
Not twisting anything, it was a direct quote. If you meant something else, ok.
Regardless, if this "Searcher eye" antenna does not have gain, then how could it possibly be any better than anything else out there? No gain would put it even, or below those with gain, no?
Regardless, if this "Searcher eye" antenna does not have gain, then how could it possibly be any better than anything else out there? No gain would put it even, or below those with gain, no?
I am guessing that the balun used was more due to availability than actual impedance. 300-75 baluns are a dime a dozen and any antenna company would have these available as they are commonly used for TV antennas.
Any antenna is a compromise and actual impedance will vary widely due to the large range of frequencies covered by scanner antennas. It is not as critical as transmit antennas. With scanner antennas close enough is usually good enough. That is also why 75 ohm coax is usually just as good as 50 with scanner antennas. The shielding and total loss is much more important than the measured impedance at any given frequency since the impedance is going to change depending on the frequency being measured. Transmit antennas are usually tuned to a specific frequency center and impedance is much more critical.
That a Discone has no gain makes it the ideal baseline. Most gain measurements are based on a quarter wave ground plane being the base standard (or Zero Point), but since one would need several different antennas for the base measurement for a scanner antenna covering a wide range of frequencies the Discone is the next best tool. As long as the measurements are otherwise equal (elevation, coax, obstructions, frequency etc.) the Discone is actually an ideal baseline for a scanner antenna comparison analysis.
For receive only antennas like this "Gain" is just a relative tool for measuring effectiveness. an antenna that displays 5db of gain is better than one that displays no gain, a 10db measurement is even better (but not twice as good, it isn't a linear measurement).
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I think the front small elements are 800/900MHz and probably longer than 1/2 wavelength overall giving the illusion they are 400-500Mhz. I also think the extra angled elements lower the impedance due to more capacitance between opposing elements.
I suspect the placement of the feedpoint is similar to a log periodic where it always connects to the high frequency end of the transmission line that runs the full length of the log antenna.
Ubbe
Member
It is actually only a couple of the elements that are active at a given frequency. It is the wavelenght from where the the coax connects that determine where a frequency will work along the boom. The longer from the coax point the longer the wave are, and a lower frequency, and the elements lenghts increase to match the frequency. The greater the frequency span of an LP antenna the fewer elements are active for a frequency and then it has less gain and less directivity.
One guy made real measurements of a Create LP antenna that advertise 10-12dBi and it had 6-7dBi, 4-5dB more than a single dipole. That's what to expect when 3 elements are active at one frequency in a LP antenna.
/Ubbe
Ubbe
Member
Initally I thought the same but it's measurements match to a 1/2 wave dipole for 420MHz and 500MHz respectivly and there's really no other elements that looks to be made for two bands in high UHF.
That could be the case, but it doesn't explain the nonused transmission line and I beleive it's the reason for having the balun at the front, it didn't work having it at the other end due to the mismatch of wavelenghts. I guess that there where no professor in physics and antenna theory that design the antenna. It's just a bunch of elements for different frequency bands connected together and having as many elements as possible will make it pick up signals at most frequenceis, that are not too far from the levels what a single tuned dipole can generate, or a mistuned offset dipole.
/Ubbe
Are you able to provide a design that would at least match and then exceed the noted coverage and performance of this passive antenna? I would definitely like to see your design. That would be fantastic. I'm not expecting a prototype, just a design with measurements. Start a thread and post the details please. Thank you.
The ST-2 was designed by a TV antenna company who has many patents, so you would think the same engineers would have designed the ST-2.
Ubbe
Member
This is not about me designing a new omni multiband antenna, I have no use of a zero gain antenna where I live. It's about trying to dissect the ST-2 and trying to understand the designers intention with the different elements and how the transmission line are used, and not used.
I read some of Antennacrafts patents and mostly they are about how to be able to manufacture antennas in a most cost effective way, using cheap material but folding sheet metal elements in angles and making dents and other ways to make them more sturdy and equal to more expensive tubular elements. Other patents about using material that reduce corrosion and having systems to fold antennas to make it more easy to distribute in a box and so on. Not much about actual antenna performance. They had one UHF antenna where they added a reflector made for VHF to make it dual band. They had made a standard bow tie antenna but instead of the usual horisontal V at each end they had perforated sheet metal making it "different" and could apply for patent, and so on.
To be able to compete in the antenna business you'll need to have a lower cost than the competition and use less expensive material and have a minimal manufacturing cost to be able to sell the product at an attractive price.
/Ubbe
I read some of Antennacrafts patents and mostly they are about how to be able to manufacture antennas in a most cost effective way, using cheap material but folding sheet metal elements in angles and making dents and other ways to make them more sturdy and equal to more expensive tubular elements. Other patents about using material that reduce corrosion and having systems to fold antennas to make it more easy to distribute in a box and so on. Not much about actual antenna performance. They had one UHF antenna where they added a reflector made for VHF to make it dual band. They had made a standard bow tie antenna but instead of the usual horisontal V at each end they had perforated sheet metal making it "different" and could apply for patent, and so on.
To be able to compete in the antenna business you'll need to have a lower cost than the competition and use less expensive material and have a minimal manufacturing cost to be able to sell the product at an attractive price.
/Ubbe
UBBE Is that why Lincoln Cadillac and Lexus are very profitable car dealers?
techman210
Member
Expecting gain out of a multiple-octave antenna is an unreasonable expectation.
If it were possible, the military contractors would have done this a very long time ago.
I’m thinking that the original designers came up with something that looked different and then later were surprised how well it worked.
After all, it’s “marketing first and engineering second”
If it were possible, the military contractors would have done this a very long time ago.
I’m thinking that the original designers came up with something that looked different and then later were surprised how well it worked.
After all, it’s “marketing first and engineering second”
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Being an Omni X owner and having owned the ST2 I can tell you the Omni X is far superior in the 700/800 Mhz range and on digital traffic. I will also mention that the Omni X is built like a tank compared to the original ST2. Your version looks great and built to last which is a HUGE plus. The Omni X is also much more wide banded than he advertises, It can easily RX HF traffic and does.
It's too bad the ST2 didn't have the Professor. I guess some of us will continue to enjoy the design by Gilligan...once again. Seriously though, it is a different tool in the toolbox and it has its place.
Regarding competition, racing to the bottom is an odd business model. Would I like a $100 discone made by Kreco, sure. For $100 it is made by Diamond instead.
Regarding competition, racing to the bottom is an odd business model. Would I like a $100 discone made by Kreco, sure. For $100 it is made by Diamond instead.
So if gain is not expected, then what would possibly make this expensive antenna desirable? A wire coat hanger in the air will "pick up" radio traffic. Gain is how you measure the performance of the antenna.
So, let's see the tests. Where is the gain at?
So, let's see the tests. Where is the gain at?
digitalanalog
Active Member
If you are not going to buy it then STOP THE BEAT DOWN. Give it a chance to be tested.
Actually, no. Antennas only care about frequency, not how the frequency is modulated or data is encoded.
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