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Thread: best antenna

  1. #1481
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    I'd not do (1) the down lead will pick up noise in competition to the signal before both are amplified - in fact I'd only use (1) with no amplifier.

    I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).

    (2) wins - maybe slip a sleeve over the copper and smother the bottom and end of sleeve in silicon chalk (bathtub stuff) - that will come off again with determination - there' s 1001 ways to do this.

  2. #1482
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    I'd not do (1) the down lead will pick up noise in competition to the signal before both are amplified - in fact I'd only use (1) with no amplifier.

    I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).

    (2) wins - maybe slip a sleeve over the copper and smother the bottom and end of sleeve in silicon chalk (bathtub stuff) - that will come off again with determination - there' s 1001 ways to do this.

    Quote Originally Posted by lanzarote View Post
    After seeing the results, the best way to get the best coverage is the cable. The 5 meters long "only" has increased my coverage in an incredible way. I always used (at home) a 20 meters cable with an amplifier. I have just changed the 20 meters and amplifier into a 5 meters long cable only (without amplifier) (the receiver now is installed at the base of the pole with a long Ethernet and power cables) and im really happy. Im so impressed that i wanted to write a post. ;-) (329nm)
    just curious - was the amplifier at the antenna end or the receiver end?

    (wondering if we can get a raspberry pi + dongle in a coke can - nope it's too long)

  3. #1483
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    Quote Originally Posted by peterhr View Post
    I'd not do (1) the down lead will pick up noise in competition to the signal before both are amplified - in fact I'd only use (1) with no amplifier.

    I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).

    (2) wins - maybe slip a sleeve over the copper and smother the bottom and end of sleeve in silicon chalk (bathtub stuff) - that will come off again with determination - there' s 1001 ways to do this.



    just curious - was the amplifier at the antenna end or the receiver end?

    (wondering if we can get a raspberry pi + dongle in a coke can - nope it's too long)
    One piece was next to the antenna, and the other piece (with power supply) was next to the receiver...
    Covering the Canary Islands, Madeira & North West Africa
    F-GCRR1: 565 meters high. F-GCRR2: 614 meters high. F-GCRR3: 604 meters high.
    F-GCRR5: next to the airport. Improving Canary Islands and Western Sahara MLAT.
    F-GCRR6 (Ex-FGCRR4): 358 meters high. F-GCRR7 : 300 meters high.

    Rafa - Lanzarote, Canary Islands, NW Africa - EA8APP

  4. #1484
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    Quote Originally Posted by peterhr View Post
    I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).
    Peter, here's a discussion on insertion loss at another forum. Executive summary: If you would like to use a connector, use a connector; you will not notice the loss.

  5. #1485
    Captain abcd567's Avatar
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    Maybe something like this spray will help in water proofing

  6. #1486
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    Quote Originally Posted by 747-8F View Post
    I want to put it on top of the roof. I got an Amplifier, DC 15v and I made a DC power inserter same like the one you abcd567 made and you use it, but I am confused I don't know what to do what works or what's the best to use Amplifier.
    Here take and look at the picture see what I got and what I know so far, but I can't do anything I want to be sure.
    Attachment 4605

    What do you guys think? Any idea ?

    Thanks
    Quote Originally Posted by peterhr View Post
    I'd not do (1) the down lead will pick up noise in competition to the signal before both are amplified - in fact I'd only use (1) with no amplifier.

    I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).

    (2) wins - maybe slip a sleeve over the copper and smother the bottom and end of sleeve in silicon chalk (bathtub stuff) - that will come off again with determination - there' s 1001 ways to do this.
    If the Cantenna is not in an enclosure or not waterproofed, another option is to install the Amplifier inside the building, very close to the point where cable enters the building.

    Please see option 1A in revised drawing below.



  7. #1487
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    I have received an email on my email address "abcd567@hotmail.com", which has valuable information about CoCos. I am copying it below:
    Captain ABCD567,

    I tried adding a comment to the fr24 forum "best antenna" thread, but it seems my message was lost in moderation. I thought you might find some of this interesting:

    LENGTH AND PHASING.—Although the 1/2 wavelength is the basis for the collinear element, you will find that greater lengths are often used. Effective arrays of this type have been constructed in which the elements are 0.7 and even 0.8 wavelength long. This type of array provides efficient operation at more than one frequency or over a wider frequency range. Whatever length is decided upon, all of the elements in a particular array should closely adhere to that length. If elements of different lengths are combined, current phasing and distribution are changed, throwing the system out of balance and seriously affecting the radiation pattern.
    SPACING.—The lower relative efficiency of collinear arrays of many elements, compared with other multi-element arrays, relates directly to spacing and mutual impedance effects. Mutual impedance is an important factor to be considered when any two elements are parallel and are spaced so that considerable coupling is between them. There is very little mutual impedance between collinear sections.
    Where impedance does exist, it is caused by the coupling between the ends of adjacent elements. Placing the ends of elements close together is frequently necessary because of construction problems, especially where long lengths of wire are involved.

    The effects of spacing and the advantages of proper spacing can be demonstrated by some practical examples. A collinear array consisting of two half-wave elements with 1/4-wavelength spacing between centers has a gain of 1.8 dB. If the ends of these same dipoles are separated so that the distance from center to center is 3/4 wavelengths and they are driven from the same source, the gain increases to approximately 2.9 dB.

    A three-dipole array with negligible spacing between elements gives a gain of 3.3 dB. In other words, when two elements are used with wider spacing, the gain obtained is approximately equal to the gain obtainable from three elements with close spacing. The spacing of this array permits simpler construction, since only two dipoles are used. It also allows the antenna to occupy less space. Construction problems usually dictate small-array spacing.
    The above from:
    http://www.navymars.org/national/tra.../14182_ch4.pdf
    More on element spacing at:
    http://www.w8ji.com/stacking_broadside_collinear.htm

    It seems most people agree that a "free-space" tuned CoCo will be detuned by placing it inside a plastic tube. However, if this detuning makes the antenna "appear" too long, the detuning might not be disastrous, because longer-than-λ/2 elements are not necessarily that bad? And with a "too long" antenna, the apparent element spacing would also be longer, which might actually be beneficial. All in all, to PVC or not to PVC might be a moot point?

    Also, simulating insulated wires is supposed to be possible in 4NEC2, see this post:
    http://kk7s.net/2012/07/12/modeling-...ks-in-4nec2-4/

    It's a bit disheartening to see how much trouble people have getting these coco designs to work, but I'm going to give it a shot anyway. Or actually three shots; I would like to try 1) classic cable coco, 2) rod/pipe air dielectric vf 1.0 coco, 3) 0.75λ; element spacing coco. It might be a month until I have time to actually do this.


    Cheers from Norway,

    XXXXX
    .
    EDIT: Email sender's name removed as per sender's request
    Last edited by abcd567; 2014-08-17 at 02:22.

  8. #1488
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    One of the 1001 ways of water proofing the Cantenna

    Last edited by abcd567; 2014-08-16 at 22:23.

  9. #1489
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    How about using this sealant for Cantenna?


    .

  10. #1490
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    I chose the name "Cantenna" because:
    Cantenna = Can Antenna
    Cantenna = Canadian Antenna

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