New Antenna Coming Soon based on Old Favorite.

[Ubbe]

I’d love to understand more about this, but I don’t see it in this thread (other than some personal attestations to some degree of directional reception). Can you elaborate?

If you put two vertical antennas besides each other they will receive the signal with the same phase.

If you put one antenna behind the other they will receive the signal with different phase.

Lets say that one antenna are 1ft behind the other. At 800Mhz a full radio wavelenght are about 1ft long. The two antennas will receive the signal with the same phase and will add the two signal if the antennas as connected to the same reciever.

At 400Mhz the radiowave are 2ft long and one antenna will receive the signal 180 degree out of phase. When one antenna receivers the signal at full positive value the other antenna will recieve it at full negative value. Adding the signals from the two antennas will cancel it out and nothing is left to receive.

So an antenna are directive if it consists of several elements. If the elements looks like a V the distance between them are different at the ends and at where they joins. Antenna elements are tuned to receive a 1/4 wave or 5/8 wave and so on along it's lenght. So the signal level along the element differs very much. Depending of the distance to the other element it will be an increase or decrese of the signals when they are added.

To summarise, the antenna will be directional and it will also be dependent of the frequency.

The too short distance to a metal pole will also have an impact to directivity but are related to reflection and impedance.

/Ubbe

 

[Firekite]

Ok, but none of that applies to this antenna. Sole claim some degree of directionality, but it’s not clear how much (mast shadow notwithstanding).

 

[digitalanalog]

1st antenna is ready for assembly, radials, tubes, insulators, plates, including mast clamp, rubber radial end caps and mast tube end caps, 300-75 ohm transformer with water proof cap, stickey back mounts for transformer w/ zip ties and not shown is a decent size collection of screws,nuts & washers for complete assembly. Very Very labor intensive just getting everything cut, drilled, machined (groves in insulators), and a lot of deburring All aluminum will be polished prior to assembly. Then partially taken back apart for shipping. Side Note: the transformer shown is an old one, the new waterproof ones have not arrived yet.

An option for an addition 6' in length maybe possible as well for getting below 25Mhz, I think i will try it on my shortwave and see how well it works. currently over all length is just under 102", the additional length will make it 174". The add on element will be a 1/8 aluminum rod in the end of each of the main center radials pointing up and down with 3' out each end and 1' down inside the radial held in place with a couple set screws. We shall see.

Price and availability for this antenna will be listed very soon.

I will be putting the Prototype up at 35' tomorrow for some testing.

 

[sdu219]

Count me in. I have 2 ST's in the box's but I wan to try this one.

 

[Ubbe]

Ok, but none of that applies to this antenna.

???
Everything I wrote applies to this antenna.

/Ubbe

 

[buddrousa]

Have you ever used a ST-2 if would have you would know it is the best antenna for scanners ever sold.

 

[prcguy]

This is true if the feedlines to each antenna are identical lengths or phase matched. Otherwise two antennas next to each other can be anywhere from in phase to 180deg out of phase depending on feedline lengths.

If you put two vertical antennas besides each other they will receive the signal with the same phase.

If you put one antenna behind the other they will receive the signal with different phase.

Lets say that one antenna are 1ft behind the other. At 800Mhz a full radio wavelenght are about 1ft long. The two antennas will receive the signal with the same phase and will add the two signal if the antennas as connected to the same reciever.

At 400Mhz the radiowave are 2ft long and one antenna will receive the signal 180 degree out of phase. When one antenna receivers the signal at full positive value the other antenna will recieve it at full negative value. Adding the signals from the two antennas will cancel it out and nothing is left to receive.

So an antenna are directive if it consists of several elements. If the elements looks like a V the distance between them are different at the ends and at where they joins. Antenna elements are tuned to receive a 1/4 wave or 5/8 wave and so on along it's lenght. So the signal level along the element differs very much. Depending of the distance to the other element it will be an increase or decrese of the signals when they are added.

To summarise, the antenna will be directional and it will also be dependent of the frequency.

The too short distance to a metal pole will also have an impact to directivity but are related to reflection and impedance.

/Ubbe

 

[Ubbe]

Have you ever used a ST-2 if would have you would know it is the best antenna for scanners ever sold.

I don't critisize the antenna. I only explain why it is directional to the guy who wanted to know the reason.

/Ubbe

 

[Ubbe]

This is true if the feedlines to each antenna are identical lengthsngths.....

I left out the coax as it is not part of my explaination of the antennas physics.

/Ubbe

 

[buddrousa]

Ubbe it is surprising how omni it really is I will test out how directional it is when I get the HAM III and tower up.
I still want one of the new ones to test.

 

[Firekite]

???
Everything I wrote applies to this antenna.

/Ubbe

I’m sure you’re right, as I have only shallow antenna theory understanding, but you talked about having multiple vertical antennas beside or behind the other. This is a single antenna with elements on a single vertical plane. I guess if each half of the V counts as a separate antenna, then waves approaching against the “edge” of the V would reach each side at a slightly different time, compared to hitting them broadside. Is that what’s going on here? How much effect is there? Considering they’re arranged in a V, does it matter that a wave approaching along the edge would encounter more element material as goes, approaching the point of the V?

I only explain why it is directional to the guy who wanted to know the reason.

I always like to know the reasons for things, but in this case I was more interested in the result. How directional is it?

 

[digitalanalog]

I have just set up Professional Testing for this antenna.
It will be sent out and Fully tested and compaired to other known brand antennas as well as a side by side comparison to the ST2.

I need this very valuable information before selling can take place. I was going to NOT have it tested but decided the best way to know what it is capable of receiving and how well it stacks up against others. So It Needs Tested.

Availabilty will be delayed until testing is complete. which could take up to 2-3 weeks or longer.

I should have set this up sooner but as I mentioned I was not going to have it done at all.
The results Good or Bad will be shared when they become available.

The price is all ready set for this antenna, and the test results may or may not affect that price.
Stay tuned...............

 

[Ubbe]

I always like to know the reasons for things,

Me too!

but in this case I was more interested in the result. How directional is it?

One guy mentioned 6dB, that's one S unit on a signal strenght meter. If you have one vertical element and then one in front of it, tilting forward, and one element behind that tilts backwards in the exact same angle, at one frequency the front element could then be at a 1/2 wave distance and the back elements as well, so 6dB loss, 1/4 of the signal are left, are possible.

A symetrical antenna have no directivity, like a discone that are symetrical. An antenna that are unsymetrical will always be directional and the level of directivity depends of several parameters and are best to evaluate in practice. A SDS scanner has a signal strenght meter graded in dBm that can be connected to the antenna. A portable radio that can transmit at the frequencies you want to test for can be used, set at it lowest output power, something like 100mW, and the scanner set to attenuate, and a program like ProScan or Butel ARC can be used to record the signal which will include the signal strenght. Transmit with the radio, at unused frequencies, and walk around the antenna while talking in the radio mentioning what direction you are in, which should ideally be done at ground level in an open space. I would probably connect my signal generator to the antenna and walk around with a scanner that can display the signal strenght in S values or finer graded. I beleive a cheap VNA antenna analyzer can work as a signal generator for this kind of test of directivity and comparisons between different antennas gain. I would test not only for omni direction but also hight, if the directivity goes up too much in the sky.

/Ubbe

 

[prcguy]

I don't think you are looking at the ST2 antenna correctly. The vertical and tilted elements are connected to the same feedpoint and do not act the same as two different antennas spatially separated with feedlines feeding a common point. On the ST2, at different frequencies the RF currents will favor one element or the other or maybe divide between them. Any phase difference between elements connected to the same feedpoint is minimal and should not cause phase cancellation.

Also, the radiation pattern or directivity of a symmetrically fed or asymmetrical (offset fed) antenna can be virtually the same. Take a 1/2 wave center fed dipole and compare to an offset center fed or end fed of the same size. The radiation pattern will be nearly identical, you are simply choosing a different place to feed it and adjusting the impedance at the various feedpoints to obtain a good match. Except for a little pattern degradation from the coax exiting the antenna at different points, the lobes are the same.

Me too!
One guy mentioned 6dB, that's one S unit on a signal strenght meter. If you have one vertical element and then one in front of it, tilting forward, and one element behind that tilts backwards in the exact same angle, at one frequency the front element could then be at a 1/2 wave distance and the back elements as well, so 6dB loss, 1/4 of the signal are left, are possible.

A symetrical antenna have no directivity, like a discone that are symetrical. An antenna that are unsymetrical will always be directional and the level of directivity depends of several parameters and are best to evaluate in practice. A SDS scanner has a signal strenght meter graded in dBm that can be connected to the antenna. A portable radio that can transmit at the frequencies you want to test for can be used, set at it lowest output power, something like 100mW, and the scanner set to attenuate, and a program like ProScan or Butel ARC can be used to record the signal which will include the signal strenght. Transmit with the radio, at unused frequencies, and walk around the antenna while talking in the radio mentioning what direction you are in, which should ideally be done at ground level in an open space. I would probably connect my signal generator to the antenna and walk around with a scanner that can display the signal strenght in S values or finer graded. I beleive a cheap VNA antenna analyzer can work as a signal generator for this kind of test of directivity and comparisons between different antennas gain. I would test not only for omni direction but also hight, if the directivity goes up too much in the sky.

/Ubbe

 

[emt_531]

I recall I paid very close to $25 in the area right around 2010 for an ST-2 at Radio Shack. I remember this, because I was pricing antennas at the time.

Got two more when RS was closing, you don't want to know what I paid for those! Wish they had 50 of them, I'd 'a bought every one

Same here!!!!

 

[N9JIG]

When RadioShack was closing them out I found several at local stores for $5.00 each that I snapped up. I kept some and gave a couple others away. One store had a dozen or so according to a friend who worked at a different store but by the time I got there someone else snapped them up.

 

[wa8pyr]

When RadioShack was closing them out I found several at local stores for $5.00 each that I snapped up. I kept some and gave a couple others away. One store had a dozen or so according to a friend who worked at a different store but by the time I got there someone else snapped them up.

Ditto! I grabbed three at $5 each, gave one away; the other two are living happily in my attic. . .

 

[Ubbe]

On the ST2, at different frequencies the RF currents will favor one element or the other or maybe divide between them.

It will for sure divide between them, and not favor one element and totally isolate the others, that's impossible, and will cause a phase difference problem.

Also, the radiation pattern or directivity of a symmetrically fed or asymmetrical (offset fed) antenna can be virtually the same.

I explain badly. I do not mean an offset antenna. If you have two vertical elements pointing up like a V, you will have a directional signal strenght phenomen depending of if you have the broadside to the signal or if the elements are in line with a space between them that will receive the signal at different phases.

/Ubbe

 

[prcguy]

Its common to use resonant stubs to add bands to an antenna element and when you have an antenna element with multiple resonant sections tuned for different frequencies, the signal will not simply divide between those elements, the current will flow most in the element which produces a good match to the feedpoint and little current will flow on frequencies where its not resonant and the match is bad. For example take a vertical element tuned for 7MHz in parallel with an element tuned for 14MHz and in a V configuration. When transmitting or receiving a signal at 14MHz, the 7MHz element will have a really high impedance compared to the 14MHz element because its a half wavelength and most if not all the current will flow on the 14MHz element, ignoring the 7MHz element, and that element is essentially out of the circuit.

The V shaped things on the ST2 antenna could also be capacity hats, which generally don't radiate much and only add electrical length. I don't believe an antenna like the ST2 has any problems with phase cancellation due to the V shaped elements and it may or may not be slightly directional comparing broadside to inline of the elements. I think the lower section of the antenna running parallel with the mast and coax will have more of a directional effect than the V shape of the antenna.

It will for sure divide between them, and not favor one element and totally isolate the others, that's impossible, and will cause a phase difference problem.

I explain badly. I do not mean an offset antenna. If you have two vertical elements pointing up like a V, you will have a directional signal strenght phenomen depending of if you have the broadside to the signal or if the elements are in line with a space between them that will receive the signal at different phases.

/Ubbe

 

[RRR]

An option for an addition 6' in length maybe possible as well for getting below 25Mhz, I think i will try it on my shortwave and see how well it works. currently over all length is just under 102", the additional length will make it 174". The add on element will be a 1/8 aluminum rod in the end of each of the main center radials pointing up and down with 3' out each end and 1' down inside the radial held in place with a couple set screws. We shall see.

Vertically polarized for SW?