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Thread: FM Frequency Selection

  1. #1
    Rebuilding for 2017 :-) kidcole's Avatar
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    Default FM Frequency Selection

    I have noticed that the medium powered FM stations keep a gap of .4 MHz between their transmit frequencies. And a few of them command .6Mhz gaps. It was very hard in my area of Cary to find gaps like this but I did find the 87.7 has a .4MHz gap to the next station up. And 104.7 has a .4MHz gap up and down.

    I have not consulted any of the FM sites about which of these two frequencies is more desirable. Frankly I like 87.7 because I am making a lighted sign and there's one less character to deal with. But I thought this might be a good discussion if anyone knows.

    Does anyone know if the upper frequencies are better than the lower ?

    btw - my antenna showed up today and I made a small portable mount for it using a folding microphone stand. Kinda neat. I hope to just use that on my front porch and should get plenty of distance for cars driving by .. I will report on my FM progress later.
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Moving to Xlights for 2017 !

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  2. #2
    Trying to behave here-NOT John's Avatar
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    Default Re: FM Frequency Selection

    In an ideal world, it would be nice to have the .4 Mhz open on each side of your low power transmitter freg, but in most metro areas, that's almost impossible to find anymore with all the regular stations, plus translators, boosters and repeaters that are in use.

    A low or high freq should not make any difference to your transmitter, if your antenna is also "tuned"

    As to your choice between the two freq, the 87.7 is not a valid frequency in the US or Canada. WKNC in Raleigh is on 88.1 and runs 25,000 watts ERP. Make sure your radio transmitter and receivers will go that low, if you decide to use it.

    The other freq, 104.7 has WFXK on 104.3 running 100K watts ERP and WDCG on 105.1 at 73,000 watts. With .4 spacing on each side, you should be OK with that freq also, but that is a lot of power on each side of it.

    You might also consider 90.3, each side is 89.7 WCPE 97K watts and 90.7 WNCU 50K watts

    92.9 has 92.5 WYFL 100k AND 93.9 WKSL 100K

    or 102.3 has 101.5 WRAL 96k Watts and 102.9 WWMY at only 1700 watts.

    The above info is from www.radio-locator.com and could be dated. Sometimes the FCC issues construction permits for new stations, boosters, translators and such but I've seen the FCC data base that radio-locator uses to be a year or more behind after the CP expires and the station is up and running.

    My suggestion is to park in front of your house and just tune the band looking for "holes", then drive several blocks around your area tuned to each of the "holes" to be sure they really are clear and open. (I do this in the day then again at night) New boosters and translators keep jumping in to fill the "hole" freq I used the year before. And the radio data bases don't even show that they are there. Getting harder to find an open freq around here.

    I know it doesn't need to be said, (since I'm not talking to Al, and you are a smart man, Denny) but do this before making your sign

    Just my opinions.

    BTW - great idea for your antenna mount!
    John (The Mascot)
    www.tennholidays.com

    480 LOR Channels + 2 CCR + 8 Mighty Minis + 10 Rainbow Floods+ 1 vdrive and vflood, Lynx Express and over 40,000 LEDs

  3. #3
    Rebuilding for 2017 :-) kidcole's Avatar
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    Default Re: FM Frequency Selection

    Wow ! Awesome information John. I actually got the 87.7 and 104.7 from sitting in my driveway with my Jeep radio. Sounds like I better not use it in case some radios can't tune that low. I am glad we have some radio buffs here.

    I bought the fmdx quarter wave adjustable antenna and plan to try a few frequencies tomorrow. Here's the link I was given, in case anyone else wants to look into this one. I am finding a lot more people who like this style rather than the dipole, so I think it'll work out great.

    http://www.fmdxantenna.com/products.php?cat=7

    Over time the group will very much appreciate your post John. A very good reference for location a good neighborhood frequency.
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Moving to Xlights for 2017 !

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  4. #4
    Registered User Don Williams's Avatar
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    Default Re: FM Frequency Selection

    Denny, we use 100.1 here, so while in your jeep check it out. Last time I checked there was only 2 stations using it , 1 on the coast and 1 in the foothills.

    Let me know how the Ant. works !! I am interested.

    John gave you some great info. which I have used.

    Don

  5. #5
    This space for rent. Al in Raleigh's Avatar
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    Default Re: FM Frequency Selection

    Denny, use the radio locator link that John gave you. If no "assigned" frequencies exist and nobody else with a display is using that frequency then your transmitter and antenna will overwhelm overwhelm anything locally. Good lord the antenna that you are using will go further than you should be transmitting. Find a blank on the website and give it a shot.

    John plagiarized the information from his post. As soon as I started reading it, I knew he copied it from a smart person.

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