Mobile antenna

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gerald123
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Mobile antenna

Post by gerald123 »

Hi, I have put a scanning antenna on roof of my car..works great when car is parked with engine running.......but as soon as I drive of I get a lit of inter fearance like the wind is catching the antenna ....if I stop and keep engine running audio is clear ...very frustrating can someone help.
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radiosification
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Re: Mobile antenna

Post by radiosification »

That just happens, and it happens more on higher frequencies, so UHF and 800MHz is affected much more than CB for example. As you move about, the signal varies which causes this. It is commonly called flutter. Here is a link to some more information on flutter: https://en.wikipedia.org/wiki/Flutter_( ... unication)

The only other possibility I can think of is that there is a loose connection, but you could probably rule that out by wiggling the cable around a bit while still to see if the same effect is produced.
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gerald123
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Re: Mobile antenna

Post by gerald123 »

thanks for replying, radiosification it also happens on the ameture bands eg 145.7500
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Re: Mobile antenna

Post by paulears »

You sure something is not loose, and it's being caused by intermittent contact? Flutter is normally only an issue when the path is marginal, and the antenna passes through zones of high/low/high/low signal. If you are listening to a very weak signal and moving at more than 20mph or so, the effect can be annoying - especially on AM, FM far less so. If it does it on string signals, it's usually a fault caused by vibration, if it does it on weak ones - perfectly normal.
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Re: Mobile antenna

Post by gerald123 »

http://www.ebay.co.uk/itm/391500161348? ... EBIDX%3AIT just waiting for this antenna from ebay just to try it.
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Re: Mobile antenna

Post by WeatherWatcher »

gerald123 what frequencies are you most interested in, because looking at that mag mount you have shown I personally think you will still get some flutter due to the open spring coil. If 100Mhz upwards maybe a better solution would have been a dual band ham whip with an enclosed coil.
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Re: Mobile antenna

Post by gerald123 »

Mostly ameture 2 metre band and marine band......what you suggested sounds like what I should have ,never thought about a closed coil ....so which one do you suggest ..thanks.
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Re: Mobile antenna

Post by WeatherWatcher »

currently using one of these, does not flex and handles the TX power I use.
http://www.ebay.co.uk/itm/NL-NR-770S-UH ... 569177d4bd
Bought mine over 6 months ago from Hong Kong for less - I already had the SO239 mount
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Re: Mobile antenna

Post by gerald123 »

What is the audio like when you are driving on motorway eg using that antenna any flutter ,,or interference.. It looks like it will do the job pretty stiff ..like you say does not flex.
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Re: Mobile antenna

Post by WeatherWatcher »

Tend not to use the radio much on motorways, the car is quite noisy at those speeds anyway - Subaru :D , I like to concentrate on my driving especially at speed. Mine is mounted on a boot lip mount but when not used at high speed around the legal limit have had no problems at all.
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Re: Mobile antenna

Post by gerald123 »

i only monitor the frequencies ..........I do not transmit. so it is like listening to a normal car radio so I can concentrate on my driving the same time.lol..........I will try the one I am getting of ebay ,if that does not work . I will order the same one you use . thanks
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