vhf/uhf receive issues

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bkspear

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I recently raised my Diamond vhf/uhf antenna that is mounted on the eave of my roof about 6 feet higher than it was originally. My receive signal has seem to have gotten worse than were it was at before. I am hearing alot more noise and some stations do not come in at all. I thought "the higher, the better", but apparently thats not the case. Anyone have any ideas why my signal would be worse? Or any suggestions for an improved receive signal ? Thanks.
 

mmckenna

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Did the coaxial cable change? Did you add an extension? Did the cable get pulled on while it was moved?

Easy to damage the coax if it's not properly secured. I'd check that first. SWR meter could tell you a lot. If you don't have one, disconnect the coax and test end to end.

Other issues could be:
Now it's higher, it's hearing some interference it didn't before.
Probably a few others, but that'll give you a place to start.
 

bkspear

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Thanks for the response Mmckenna. I did not change the cable, did not add or remove extensions. The cable might have gotten pulled a little or tugged on, but probably not that much. Unfortunately I don't have a SWR meter. Thanks again.
 

wyShack

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What are you using as a receiver? Quite often we fail to realize that the issue is not signal strength but signal to noise ratio. As antenna height increases, so does the noise level and number of noise sources. Especially if you are using a radio with a 'wide' front end (like a HT with a 118-174 Mhz receive range), this 'extra' noise swamps the receiver. You may also have raised your antenna to a point where it can 'see' a strong signal (that just has to be in the 'passband for the AGC) which will have the effect of your receiver 'backing down' on its gain. Most base/mobiles have a 'tighter' front end (actually better filtering in the IF stages ) and can handle things better. Just one more example of needing to know what goes on 'under the hood'. or in other terms sometimes more isn't better.

Hope this helps
 

bkspear

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wyShack,
Thanks for your reply. I am using the same two radios I was using before I raised the antenna. I can notice the noise on both radios. One is an HT and the other is a mobile being used as a base. Thanks.
 

FKimble

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What model is your antenna? What type coax? If an end was not on real good, it would not take much to damage the connection.
 

mmckenna

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Thanks for the response Mmckenna. I did not change the cable, did not add or remove extensions. The cable might have gotten pulled a little or tugged on, but probably not that much. Unfortunately I don't have a SWR meter. Thanks again.
I'd recommend checking the coaxial cable before you do much else. Can you find someone with an SWR meter locally, or do you have a multimeter?

I suspect that the coaxial cable connector on the antenna end might have taken a bit too much strain. Also, if it's not waterproofed, even getting a bit of moisture from condensation in the connection will quickly destroy the connection. At minimum I'd recommend taking it down and checking everything end to end.
 

Cognomen

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Or any suggestions for an improved receive signal ? Thanks.
Put it back on the eave. :)

Is this a base or mobile antenna? If mobile, maybe you have a ground plane issue that wasn't present when it was mounted on the eave.
 

bkspear

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It is a Diamond D50 antenna I believe and the coax is 50ft of RG8X. I do not have a SWR meter, but I do have a multimeter. Thanks for the suggestions everyone.
 

FKimble

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Per one of the online coax loss calculators, if your radio puts out 50 watts of power, your 50ft of 8x coax will cost you a loss of 18.x watts. Switching toLMR400/RG-8 type coax(of a good brand) will produce a 50ft loss of about 8 watts. This works both ways, transmit and receive. A coax upgrade should produce about a 2 db gain in both directions. I assume you mean a Diamond x-50. A very good antenna for the money. That is what I run in my attic. Mine works very well at about 25 feet above ground level.
 
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