Too close to cell tower

[donv911]

I have a BC796D Scanner. My location is a problem - I can't move the tower.... nor the best option would be to move away from the tower.

However with that said - I am trying to monitor the State of Michigan APCO25 system, with a next door neighbor being that of a couple very tall towers my scanner is being overloaded on the front end with 800Mhz signals from the "shadow of the tower.

Does anyone have any suggestions to such a problem.

Thanks!

Don

 

[N_Jay]

I have a BC796D Scanner. My location is a problem - I can't move the tower.... nor the best option would be to move away from the tower.

However with that said - I am trying to monitor the State of Michigan APCO25 system, with a next door neighbor being that of a couple very tall towers my scanner is being overloaded on the front end with 800Mhz signals from the "shadow of the tower.

Does anyone have any suggestions to such a problem.

Thanks!

Don

Buy a good filter that coveres just teh band you want.

 

[Al42]

Michigan system - 850 MHz
Cellphone towers - possibly 850 MHz

It'll take a few sharp cavities to suck out any signal at all, and scanners aren't very well shielded.

Unless all the cellphone activity on that tower is 1.9 GHz.

 

[wa8pyr]

However with that said - I am trying to monitor the State of Michigan APCO25 system, with a next door neighbor being that of a couple very tall towers my scanner is being overloaded on the front end with 800Mhz signals from the "shadow of the tower.

Does anyone have any suggestions to such a problem.

Try setting the attenuator ON for each trunked frequency. It will reduce your reception range on the 796, but will also reduce the interference.

I have the same problem with the 2096 in the truck from time to time (when close to a cell tower) and the attenuator cuts the interference out completely; since my local system is a 6-site simulcast I have experienced little difficulty with reduced reception range.

Tom WA8PYR

 

[N_Jay]

Michigan system - 850 MHz
Cellphone towers - possibly 850 MHz

It'll take a few sharp cavities to suck out any signal at all, and scanners aren't very well shielded.

Unless all the cellphone activity on that tower is 1.9 GHz.

Cellular 869 and and up.

Most 800 MHz is 866 and below,

NPSPAC is 866 to 869 (But will be moving down after rebanding)

Nextel towers are the exception, they are currently 854 to 866, but will be 862 to 869 after rebanding.

 

[LarrySC]

I have a towing service customer with a cell tower across the street from his shop. He always had lots of scanner problems with 800. I put up an 800 yagi and pointed it appx 62 deg away from the tower. This factor, 62deg, is the the side lobe null for yage ant's. The antenna was NOT pointed in the direction of the Hwy Patrol tower, but, rather than use the antenna for gain, we used it to null. Also dropped down to RG-59 with a little higher loss at 800. Scanner had to use ATT feature, BUT, IT WORKED.

 

[donv911]

Will see what happens...

The cell tower is NEXTEL...

I will try and get a pic of the two towers and post them.


Thanks

 

[Al42]

Cellular 869 and and up.

Most 800 MHz is 866 and below,

NPSPAC is 866 to 869 (But will be moving down after rebanding)

Nextel towers are the exception, they are currently 854 to 866, but will be 862 to 869 after rebanding.

Scanners make barn doors look like narrow filters. It wouldn't surprise me if a top of the line scanner listening on 900 MHz was desensed by a close 815 MHz signal. Or even a close 150 MHz signal. (My 396 is totally desensed by my 5 watt, 146 MHz signal from about a foot away from the scanner, when I'm scanning a trunked system on 866 MHz.)

 

[N_Jay]

Scanners make barn doors look like narrow filters. It wouldn't surprise me if a top of the line scanner listening on 900 MHz was desensed by a close 815 MHz signal. Or even a close 150 MHz signal. (My 396 is totally desensed by my 5 watt, 146 MHz signal from about a foot away from the scanner, when I'm scanning a trunked system on 866 MHz.)

You are probably getting in somewhere other than the front end.

Remember 5 watts at a few feet is VERY strong signal.

 

[Thayne]

Front End is the proper place to get in--right??

 

[Al42]

You are probably getting in somewhere other than the front end.

On a scanner? I doubt there's any part of the circuitry I'm not getting into. And I doubt that the cell tower next door isn't getting into any part of the circuitry either. After all, scanners are so well shielded ...

 

[N_Jay]

On a scanner? I doubt there's any part of the circuitry I'm not getting into. And I doubt that the cell tower next door isn't getting into any part of the circuitry either. After all, scanners are so well shielded ...

Yes, but the cell tower across the street is probably only getting into the front end.
It is a strong signal by receiver standards, but probably not strong enough to affect anything beyond the front end.

The portable at 5 feet could easily overwhelm some internal signal between stages.

Just because the end result seems similar, does not mean the actual cause is the same.

People here use "overload" way to generally.

5W ERP at 5ft has the same effect as
25W ERP at 10 ft,
625W ERP at 20 ft
390,625W ERP at 40 ft

 

[Al42]

People here use "overload" way to generally.

If it causes intermod, or even nonlinearity, in the front end, it's overload.

 

[mmartinfan]

Cut the tower down!!!!!!!!!!!!!!!!

 

[N_Jay]

If it causes intermod, or even nonlinearity, in the front end, it's overload.

TRUE!

But that is NOT what you said in the post I was answering!