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Loosing distance

 
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Loosing distance
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stylzmovement
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Joined: 11 Oct 2003
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Post Loosing distance Reply with quote
What causes a transmitter to loose radiated power ,for example this transmitter is putting out 400watts with a good reception at 20 miles away, then all of a sudden the reception gets cut to 10 miles, what causes that?
Thu Sep 18, 2008 8:35 pm View user's profile Send private message
intertech
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Joined: 15 Mar 2006
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Location: Chicago USA

Post Reply with quote
Check the power level of the transmitter, may be someone "turned" down the output

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Fri Sep 19, 2008 12:43 am View user's profile Send private message Visit poster's website
intertech
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Just kidding, sounds like you are having some kind of atmospheric inversion/anomaly. Another possible cause is timing, as you know there are many frequencies only used at certain times of the day, it could be that you propagated 20 miles because the "other station" was off the air at that time, when they began to broadcast your signal was cut in half.

Suggest you take some readings at various times throughout the day/night, also try searching www.radio-locator.com to see what other stations are on your frequency.

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Fri Sep 19, 2008 12:51 am View user's profile Send private message Visit poster's website
rickv152
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Post Re: Loosing distance Reply with quote
your problem could be a # of things.
you need some sort of reference other than "you heard it so far away"; obviously something has changed, but like the other comment says, you need to check things starting with the output forward power vs reflected power. So many things could have changed:
1) your antenna feed line has water or ?? in it or is damaged.
2) your antenna became detuned (if it's tunable).
3) your antenna ground changed (yep this can affect it).
but mainly a check of forward and reflected power will show up something.
A handy unit to have (we use it in new york to tune hi power FM antennas) is a MFJ 259B. it does almost everything except brush your teeth and is low priced. Hooking one up to your feedline going to antenna, disconnected from transmitter will tell you what's going on: SWR and Impedance of antenna system.


stylzmovement wrote:
What causes a transmitter to loose radiated power ,for example this transmitter is putting out 400watts with a good reception at 20 miles away, then all of a sudden the reception gets cut to 10 miles, what causes that?

Tue Oct 07, 2008 11:08 pm View user's profile Send private message
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