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Thread: FM antenna help

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    Default FM antenna help

    Hi all, Hope it's ok to post here...I couldn't find a radio section. I'm about to install an FM antenna at my place.

    Has anyone had experience at comparing the results from a 3 element FM antenna such as this one:

    With the less conventional options such as these. A friend has just replaced a 5 element with one of the Fracarro's seen here and swears y it's results which has shocked me given that the gain on a 3 element is about 4db and the Fracarro is about 2db. ANy suggestions or advice greatly received, thanks.






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    Manufacturers specifications vary greatly.

    Some are inaccurate, others use different measuring methods using different values.

    You are also comparing three entirely different antennas in the examples shown. (Eg: comparing apples with oranges)

    Gain is not the only factor which determines performance.

    Location in relation to distance between the receiver and transmitter, the polarisation of the signal, terrain, etc, all play a part.

    Eg: If you are in a strong signal area, an indoor antenna will likely be just as effective as an outdoor type.

    Yes, a directional antenna such as the Hills yagi will have more gain due to it's narrower beamwidth and directional design.

    It also has a single polarity, horizontal or vertical, depending how it's mounted and will be better-suited to receiving signals over a greater distance than the other antennas, providing all transmitters are located in the same direction and all signals are of the same polarisation.

    The Fracarro antenna shown is designed to receive both horizontal and vertical signals and is largely omnidirectional.

    It will have less gain that a yagi type, but is more versatile in that it can receive from all directions and signal polarisations, is physically smaller, stronger and less likely to be used by birds as a perch and looks less obtrusive.

    The third 'horizontal ring' example is omnidirectional, but designed primarily to be mounted for horizontal polarisation.

    I have personally installed the Hills and Fracarro antennas, but have no physical experience with the ring-type.

    It's important to consider what radio stations you may want to receive.

    High-power commercial and ABC FM stations transmit mixed polarisation signals, so that either vertical or horizontal antennas can be used.

    Low-power and community stations mostly transmit vertically polarised signals.

    Where signals are a single polarity, your receiving antenna must match that polarisation because using an antenna that is the opposite polarisation (Eg: 90 deg out) will drastically attenuate the signal and for a low-power station, that may make it unable to be received.

    You show your location as Canberra.... if all your FM signals are coming from Black Mountain, (and of the same polarisation) any of the antennas shown will work well. Even an indoor antenna will probably be sufficient.

    It all comes down to what stations you want to receive, how powerful are the signals, their polarisation, terrain and local interference levels, etc.

    Basically, the same principles of selecting a TV antenna apply.

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    I have a Fracarro 3 Element FM antenna on my roof.
    (i see they no longer make this model now)

    I can not believe how good it is! It turned my FM Stations into CD quality (near enough in my view, compared to what it was)
    I am 200k's from the transmission tower if that helps also.
    I have a post about here somewhere.

    I also have a 5 Element FM in the workshop i fear i will now never use
    Its it HUGE!!!!! 3.6meters boom length, (think ham radio huge)
    And i doubt i'll even find a customer to sell it too.

    The Fracarro FM range has really changed since i last looked

    Last edited by ol' boy; 20-07-17 at 02:02 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

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    Thanks for the advice MTV!

    I'm in North Canberra on a 5th floor apartment and looking to hopefully get Wagga Commercial and S/W Slopes ABC FM (I can currently get decent signal on indoor antenna of the S/W slopes and a semi-reasonable Wagga FM. Would also love to get Young Commercial FM but this is much weaker with the indoor. They are all in relatively the same direction.

    Problem is I'm greedy and want it all which includes Queanbeyan FM in the almost opposite direction.

    Given that I guess the omni-directional would be the best bet given that even Wagga is available on an indoor antenna. Young may struggle with that option but in the grand scheme of things it is likely to give Wagga, QBN and SW Slopes rather than a directional 3 element that would likely be good for everything except QBN (unless it picks up a bit of signal off the side which it might i guess as they are semi-local signals).

    Anyway Thanks for the advice MTV and I'll let you know how I go.

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    austar,

    It would have been helpful if you posted that detailed info in your first post.

    Your ideal setup would be a yagi antenna on a rotator.

    5th floor apartment... can you actually mount an antenna on the building roof and run cabling to your apartment?

    I can't give you an exact figure without knowing your exact location, so these figures are approx for Canberra northern suburbs.

    Wagga TX is approx 145km and 280 deg from your location.

    Young is approx 125km and 325 deg from your location.

    That's 45 deg difference between them... not exactly "relatively the same direction".

    Queanbeyan is only around 15km and would be almost directly behind the signal path to Young (and off the side to Wagga).

    Being so close, it will likely pick-up anyway.... the same for Black Mountain signals.

    There is significant terrain between you and both Wagga and Young, but being in an elevated building will help a bit.

    You haven't said what indoor antenna you are using.

    Young, being the weakest station for you, I would suggest aligning the yagi for that station, or perhaps a compromise between Young and Wagga.

    It's something that can only be determined in practice.

    You may want to try testing the antenna mounted both horizontally and vertically, as all stations mentioned use mixed polarisation.

    Keep in mind too that long cable runs attenuate signal, so sometimes the benefit of a directional antenna is lost compared to an omnidirectional antenna on a shorter cable.

    Lots of things to consider.

    Let's know the outcome.

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