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Scanner / Receiver Antennas For discussion of any type of receiving antenna used by a scanner or receiver base, mobile or handheld.

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Old 08-28-2014, 7:44 AM
bep bep is offline
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Default ST2 and yagi on same mast

Currently I have a ST2 in the roof "pointed" to one site of a multi site system. Reception is better than it has been. The down side is that I am now loosing good reception of all the other systems I want to listen to.
Considering a yagi dedicated to the multi-site system.
Questions:
Can I mount this above/under the scantenna and if so how much separation do I need between the two?
Would a cell booster yagi antenna work for a system in the range of 856-860Mhz?
If I invest in a high dB gain yagi any ideas about performance if I place in the attic (I know many variables)

Any other ideas gladly accepted.

BEP
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Old 08-28-2014, 8:40 AM
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The ST-2 antenna is omnidirectional, how do you point it at one site?

A good rule of thumb on mounting 2 antennas on the same mast is that they should be mounted with a minimum of 1/4 wave length separation. That 1/4 wave length will be the spacing between the top of the bottom antenna and the bottom of the top antenna. It would also be 1/4 wave length at the lowest operating frequency.

A cell booster yagi antenna would work but it is most likely cut for the wrong frequency which would limit its performance.

Your last question can't be answered with a lot more information like what is your roofing material, what kind of framing was used in your house, etc. All metallic materials will act as a shield and reduce reduce the effectiveness of the antenna.
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Old 08-28-2014, 12:19 PM
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Here's one thing I would ask the op. Are you wanting to rotate both? Or just leave them fixed?


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Old 08-28-2014, 12:58 PM
bep bep is offline
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There are many posts that do state that the ST2 is somewhat directional. Trying to solve my multi-path issue, I have rotated the antenna, pointing to one site, and have had some good results. I know it states it is omnidirectional.

My plan, W5PKY, is to aim the yagi to the one site fixed. The ST2 will be "aimed" toward the populated area. I am physically located at the ocean so I need to aim toward town, and additionally it is only up from here.
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Old 08-29-2014, 6:51 AM
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The ST-2 is only directional to the extent the mast it's mounted on blocks reception of transmitters on the other side. If you use fiberglass or other non-conductive mast mount that effect is minimal.
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Old 08-29-2014, 7:50 AM
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Not really. If the feedline follows the same path as the fiberglass mast there is really no difference in the distorted pattern to using a metal mast.
prcguy

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Originally Posted by jonwienke View Post
The ST-2 is only directional to the extent the mast it's mounted on blocks reception of transmitters on the other side. If you use fiberglass or other non-conductive mast mount that effect is minimal.
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Old 08-29-2014, 11:59 AM
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Hello, I had wondered the same thing a while back and did some research. I found that for receive only the spacing of two or more antennae on the same mast is not critical, problems do arise if the antennae are for transmitting. Some will disagree but I found convincing scientific documentation which even showed that when the elements were interspersed with each other reception was not negatively impacted. I actually have a mast with two yagis one UHF and one 800-900 mhz seperated by about an inch, they work beautifully.
By the way, if you are interested in a nice 800-900 yagi, I picked up one of these and I see they are still on sale.
LAIRD YA9-11 11dBi 900MHz 8 Element Yagi - 900MHz Antennas - Antennas - Wireless - Products
Sturdy construction and really pulls in the signals. I get good results down into the 700 mhz band with it.
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Old 08-29-2014, 12:25 PM
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Quote:
Originally Posted by prcguy View Post
Not really. If the feedline follows the same path as the fiberglass mast there is really no difference in the distorted pattern to using a metal mast.
prcguy
Depends on if the metal mast extends above the midpoint of the ST-2. If it does, then the mast will have a greater effect than the feedline by itself.

You can also reduce the effect of the mast/feedline by extending the mount so the antenna is farther away from the mast.
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Old 08-29-2014, 12:51 PM
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Antennas are reciprocal, whatever they do or whatever pattern they have on receive is the same on transmit. Running a mast up through the elements of a Yagi or Log Periodic with affect TX and RX the same.
prcguy

Quote:
Originally Posted by rrbum View Post
Hello, I had wondered the same thing a while back and did some research. I found that for receive only the spacing of two or more antennae on the same mast is not critical, problems do arise if the antennae are for transmitting. Some will disagree but I found convincing scientific documentation which even showed that when the elements were interspersed with each other reception was not negatively impacted. I actually have a mast with two yagis one UHF and one 800-900 mhz seperated by about an inch, they work beautifully.
By the way, if you are interested in a nice 800-900 yagi, I picked up one of these and I see they are still on sale.
LAIRD YA9-11 11dBi 900MHz 8 Element Yagi - 900MHz Antennas - Antennas - Wireless - Products
Sturdy construction and really pulls in the signals. I get good results down into the 700 mhz band with it.
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