# Blocking a few radio stations.

#### DeCaff2007

Joined Jan 13, 2017
3
.... but just for MY vehicle.

I've been looking into notch filters and they seem easy enough to build, but I can't find any definite way to determine the values for the components.

Isn't there one straight up formula if I know the frequency?

Thanks.

#### Papabravo

Joined Feb 24, 2006
16,173
Notch filters come in all shapes and sizes. Their performance depends on other things besides frequency. In particular the required attenuation in the stopband and how wide the transition bands are. Why don't you tell us an example frequency, a required stopband attenuation, and the bandwidth of the notch.

https://www.amazon.com/Analog-Filte...84402889&sr=8-1&keywords=Analog+filter+Design

I'm curious about why you want to block a couple of radio stations. That is what the tuning dial is for.

#### DeCaff2007

Joined Jan 13, 2017
3
Fair enough. I keep my vehicle radio on the "SCAN" function because no one single station interests me. That said, I'm forced to hear one particular station every so often that highly offends me. Since I cannot do anything about the source, I can at least block it from my radio. The frequency is 99.1FM.

About your link, looks like a good read. As for the required attenuation? Well, -90dB sounds good. That should make SURE nothing gets through. Transitions bands? Aren't radio stations spaced 200Mhz apart?

Ok thanks.

#### Dodgydave

Joined Jun 22, 2012
9,956
If your radio has a Loc/Dx option use it, or use the store facility on the radio, and save your favourite music stations.

#### Papabravo

Joined Feb 24, 2006
16,173
90 dB might be a tall order with a simple circuit. My initial guess is that you will need 10 poles or more. FM stations are spaced 200 kHz apart, so let us start with 99.1 MHz ±100 kHz.

Here is an online calculator for a 10 pole filter because 6 is not enough
http://www.wa4dsy.net/filter/filterdesign.html

The problem is that they require physically unrealizable capacitances of fractions of a picofarad. You might be able to do this with microstripline techniques using CAD software that costs more than your car and the radio, but my guess is that you will find it more trouble than it is worth.

You could also try being less easily offended. High BP is really really bad for you. You might shave 10-15 years off your life.

#### SLK001

Joined Nov 29, 2011
1,548
Sorry, but you are just wasting your time. If you could build a notch filter narrow enough to get rid of your station (and only your station), you would need equipment probably 3 or 4 times the cost of your vehicle NEW just to properly tune it.

Here are some other options for you:

1) Quit scanning - therefore you won't hear the offending station.
2) When your scanning stops on your station, push the SCAN button to move it on.
3) When your scanning stops on your station, start humming a catchy tune until scanning continues.
5) Man up and quit whinning.

#### Kermit2

Joined Feb 5, 2010
4,162
I used to love finding weird music and strange viewpoints on the radio dial. (AM at night)
Now we must protect Virgin thought patterns from even the mere chance encounter of contradictory opinions?

I know a doctor who could write you a prescription for a couple of testicles.
Not a bad troll effort overall. You got several of us going for a bit.

I give it a 7.

#### Papabravo

Joined Feb 24, 2006
16,173
Just because you want a filter does not mean you can actually build it.
I thought the TS found the music offensive. I never considered the possibility of talk radio. I was taken in so give him an 8.

#12

#### RichardO

Joined May 4, 2013
2,271
A coax cable stub will act as a notch filter. It is easy to do but it will not work as well a filter made using a bunch of inductors and capacitors.
Here is some background:
http://www.arcticpeak.com/antennapages/quaterwavestub.htm

Do a search for this to get more information: coax cable stub notch block filter

#### SLK001

Joined Nov 29, 2011
1,548
A coax cable stub will act as a notch filter. It is easy to do but it will not work as well a filter made using a bunch of inductors and capacitors.

Do a search for this to get more information: coax cable stub notch block filter
Actually, a coax cable stub will make a better notch filter than discrete inductors and caps - has to do with the "Q" of the parts. However, the equipment needed to properly construct the stub is again, very costly.

#### RichardO

Joined May 4, 2013
2,271
Actually, a coax cable stub will make a better notch filter than discrete inductors and caps - has to do with the "Q" of the parts. However, the equipment needed to properly construct the stub is again, very costly.
I think that the standard technique is to start trimming a coax that is too long and keep trimming until the station goes away.

#### wayneh

Joined Sep 9, 2010
17,152
Depending upon the signal strength of the 99.1 station that you don't want to hear, you might get relief from an FM transmitter set to that frequency and carried in your car. e.g., http://www.ebay.com/itm/Bluetooth-C...348550?hash=item4d3e28e246:g:OHYAAOSwKtlWmYJK
I agree this is probably the easiest solution, other than manning up. They make those little dongles to send your iPod music onto FM so you can listen in a car. Get one and set it to the offending frequency. It won't completely obliterate the other station but it will likely make it unintelligible.

Then seek mental help. You will never be happy in life if a few seconds of unpleasantness cause you this much anxiety.

#### ClassOfZero

Joined Dec 28, 2016
114
One could demand a safe space from the local university, failing that contact your local SJW and collude to create a movement that demands a trigger warning announced every 10 - 30 seconds or so, failing that a smear campaign to have the station taken off the air may be used.

One could stop driving, thereby taking one away from the influences of the straight white male patriarchy.

From about 3:40 regarding being offended.

Steve Hughes is a great comedian.

#### tcmtech

Joined Nov 4, 2013
2,867
I solved the crappy OTA music problem years ago.
I just put in head units that have CD and USB MP3 players and make my own play lists of crappy music I don't mind hearing. 16 gig of music on a USB stick gets me the better side of a month of driving around playtime without hearing a song twice.

As for the OP, I think som Ritalin for ADD might solve the scanning size plus likely make him a more focused driver as well as a second gainful side effect. Two wins for society in one little pill.

#### DeCaff2007

Joined Jan 13, 2017
3
I used to love finding weird music and strange viewpoints on the radio dial. (AM at night)
Now we must protect Virgin thought patterns from even the mere chance encounter of contradictory opinions?

I know a doctor who could write you a prescription for a couple of testicles.
Not a bad troll effort overall. You got several of us going for a bit.

I give it a 7.
Mkay... not where I was going with this. Definitely not trolling. For those of you that have researched 99.1FM, it's a SPANISH radio station. I'm not apologizing for being offended by a non English speaking broadcast in America.

Maybe not the only one in the country, but it's only one I receive in my area. This is why I was leaning toward a notch filter.
As for the MP3 player idea, ALL music sucks, which is why I keep my radio on SCAN.

Next solution would be RADIO OFF. If I do that, I can hear the guy next to me in traffic blasting his BS (in spanish).

So excuse me if I didn't think that blocking ONE radio station was such a big deal.

#### nsaspook

Joined Aug 27, 2009
8,392
So excuse me if I didn't think that blocking ONE radio station was such a big deal.

#### BR-549

Joined Sep 22, 2013
4,938
DeCaff.......I understand your frustration and I sympathize. You only got two options. Recheck your auto manual and make sure you can not exclude channels from a scan. Or perhaps scan only favorite channels.

Or replace the radio with features you require. This is your best solution.

Forget about blocking it. In a ham shack there is room for proper filters and can easily be re-tuned. Not in a car.

You need a digital solution.

#### Kermit2

Joined Feb 5, 2010
4,162
Bluetooth and a Samsung phone.
Any thing I can find and play on the phone will play on my car radio.
If you do it this way you can play anything (music or commentary)
your little heart desires and no longer be at the mercy of a free market offering a multitude of choices to a multitude of different peoples.

#### tcmtech

Joined Nov 4, 2013
2,867
As for the MP3 player idea, ALL music sucks, which is why I keep my radio on SCAN.
Then what are you scanning for?

If you looking for talk radio either you have to download and play your own on MP3 or spend the money for an XM radio unit and go to full sattelite all talk all the time stations.

And if you aren't looking for talk radio either then maybe it time to either shut the thing off or maybe start seeing a psychologist about social anxiety and possible OCD and or ADD issues.