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Band pass filter for 11m

Joined
Dec 23, 2004
Messages
230
Location
Honoka'a, HI
#1
Hello all,

I’ve been working on resurrecting my CB base station that I used to use several years ago, and one thing I noticed is that many of the same local stations that I used to hear fairly clearly now seem to be shrouded in static. I know this could be due to many different factors, but one big change since the last time I used my setup is the activation of a local P25 trunked system with a site only about 500 ft from my house. It blasts a constant control channel on 151.4075 MHz. Is it possible that this could be desensitizing the receive on my radio even down on the CB freqs?

I am thinking about getting a 11 meter band pass filter, or will that not really do any good? Do most CB radios have something like that already built in?

The filter I am thinking about trying is this one:

http://www.surgestop.com/filter-products/m-411cb.html

Just curious if getting one of these would be pointless, or if I am way off track.

Thanks.
 
Joined
Dec 22, 2013
Messages
2,824
#2
I think you are way on track. I have considered one myself. The modern receivers are not nearly as bulletproof as the old radios that were made of discrete components by real radio designers. Plus a lot of new stations have popped up that might not have bothered in past.
 

jassing

Member
Premium Subscriber
Joined
Jan 31, 2012
Messages
214
Location
Shelton, WA
#3
They are better used during transmission... To keep a poorly tuned transceiver or amp from splattering nearby bands. They won't help for static. But...
It's possible a high power system could be overloading your receiver; and if so...
If you can prove the trunk is causing interference on 11metets,file a complaint with the FCC. They should be filtering their transmission.
151mhz is a long way from 27mhz.
I'd check power supply, antenna connections, and coax run before tossing more components into your feed line.
 
Joined
Dec 23, 2004
Messages
230
Location
Honoka'a, HI
#4
Thanks for the info... I may give the filter a try just to see.

That strong VHF control channel has been giving my scanners problems too even in the UHF band, so I certainly wouldn’t be surprised if its wreaking havoc on 27 mhz.
 
Joined
Dec 22, 2013
Messages
2,824
#5
If for any reason, someone might use one of those RM Italy or similar amps, especially the ones with the unfiltered preamp, this filter will clean up the transmission (keep "regulatory complaints at a minimum") as well as protect the outboard receiver preamp. Not that I would advocate such... The other reason it might be good is that CB radios are not designed to meet any industry standards like EIA603D, so there could be spurious receiver responses that lower the receiver noise figure. Being that we are in a sunspot minimum, a few dB of improved receiver sensitivity might make the difference of 10 miles or 20 miles reception.
 
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