BCT15 Overloaded Front End

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yeg_scan

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Aug 7, 2017
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Well installed my BCT15 in my car yesterday and only one issue. The front end is overloaded. That is pretty big issue as it does not work well.

I am mostly listening to a 800 MHz system. With some trial and error .. I determined that is the issue as I made one quick key normal and one I turned on attenuation for the system. I am posting this .. so that it may help someone in a similar situation in the future.

I am using a Larsen Tri band antenna on a Diamond mount. Those work well, though likely going to change to a 1/4 wave VHF antenna as it is a bit more discreet. I know .. crime issues around here and want to make it not stand out.

I determined that the system where it is attenuated worked better. The only issue .. 20 dB attenuation is a bit much and in some places the signal gets a bit weak. So my solution is below but I am very open to suggestions, so please post thoughts below if you like.

I decided that several things were going on .. the 800 MHz system was being overloaded (due to cell phone towers). The answer .. put the antenna inside the car not outside. However .. I did not want to attenuate the VHF / UHF bands just 800 MHz.

What I decided on .. is using a MFJ diplexer and splitting 2 antennas to the scanner. I did test it on 868 MHz on my R7000 and I was losing less than 1 s-unit by adding the diplexer. I know it is only rated to 500+ MHz. ;-)

I was ok with that as the radio was overloaded and sometimes it is about not having to strong signals.

I am using a Maxrad 800 MHz antenna on the one connection and the Larsen on the other. The maxrad inside .. the larsen outside the vehicle. I found that the signals are about 2 bars stronger than on the attenuated system. With this setup .. I can use the normal un-attenuated version.

Moving the antenna, just enough to solve the issue and not have the too weak signal problem. I am just guessing but probably at least 10 dB weaker (maybe more) than outside but enough to make the scanner linear and not be hit with a RF hammer.

Btw, for the record .. I tried a Whistler 1095 in the vehicle a while ago and it did not work at all. Totally overloaded and any amount of attenuation, putting the antenna inside the car, filters, or antenna changes did not fix the issue. I was forced to remove it.

Hope this helps someone in a similar situation.
Kevin
 
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woodpecker

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Aug 7, 2005
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Most scanners have poor filtering, the best thing to do is fit notch filters to block the interfering signals, if the signals are close spaced it does get more diificult as you need high Q filters to avoid blocking what you want to hear.
 

ka3jjz

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Jul 22, 2002
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Bowie, Md.
yeg, It would be helpful to know where you are (county/state is fine) and what system you are trying to receive...Mike
 
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