Nope, nothing visible. I'm going to order the capacitor and see if it helps.

It must be some sort of feedback loop between the LEDs and the pressure switches/master cylinder/radio antenna.  It's possible that brake pressure changes the resistance/impedance of the switches which leads to the frequency change. I'd need an oscilloscope to sort that out. Maybe someone can come up with a better idea.

Stuart

-----Original Message-----
From: Alistair Bell <albell@shaw.ca> 
Sent: Friday, March 16, 2018 11:53 AM
To: stuartmacm@gmail.com
Cc: vanagon@GERRY.VANAGON.COM
Subject: Re: Thought problem for Friday

Ok, ok. 

Have a look at the brake lights when someone presses pedal. See if flickers.

Yeah, I’m going down a blind rabbit hole.

Ab

> On Mar 16, 2018, at 11:29 AM, <stuartmacm@gmail.com> <stuartmacm@gmail.com> wrote:
> 
> Nothing explains the frequency change with pressure. I can play a tune while coming to a stop, and then it stops. Static electricity from the brake pads interacting with the LED's? Piezo electric effect? Cosmic rays? Gasoline bacteria? Trolls & gremlins?
> 
> Stuart
> 
> -----Original Message-----
> From: Vanagon Mailing List <vanagon@gerry.vanagon.com> On Behalf Of 
> Alistair Bell
> Sent: Friday, March 16, 2018 10:02 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Thought problem for Friday
> 
> It’s the led lights.
> 
> I bet there is a PWM or some circuit in there somewhere on the led . The light bar perhaps.
> 
> I notice radio interference when my led back up lights engaged. Also had issue of severe interference with my first go round of H4 led bulb experiment.
> 
> Strangely though, the offending h4 bulbs produced no interference in friends van. So seems some radio installs more sensitive than others.
> 
> Alistair
> 
>> On Mar 16, 2018, at 9:40 AM, OlRivrRat <OlRivrRat@COMCAST.NET> wrote:
>> 
>>       Since the Brake Light Circuit is a simple On/Off Circuit I 
>> would doubt that it is the
>> 
>> the Lights that are the cause ~
>> 
>>       My guess is that somehow the Brakes Themselves are Generating 
>> an RF Noise Signal ~
>> 
>> Hopefully 1 of our Resident Electronics Gurus will have the answer ~
>> 
>>                                               ORR ~ DeanB
>> 
>>> On 16 Mar , 2018, at 10:25 AM, Stuart MacMillan wrote:
>>> 
>>> Figure this one out:
>>> 
>>> 
>>> 
>>> When I depress the brake pedal I hear a faint high pitched "whine" 
>>> from the radio. It's pitch (frequency) changes with pedal pressure 
>>> (higher with more pressure), and only happens on AM stations.
>>> Unfortunately, my favorite sports radio stations are AM so I hear it often.
>>> 
>>> 
>>> 
>>> It didn't change with a new radio last year, and I do have LED brake 
>>> lights and the GW high mounted LED brake light. Brake light switches 
>>> have not been replaced.  Whine was there with the 1.9 engine and is 
>>> unchanged with my '93 Subaru 2.2 engine conversion. I have not 
>>> switched the bulbs back yet, but I'll give that a try and see if it goes away.
>>> 
>>> 
>>> 
>>> It's just a nuisance, but I'm stumped, particularly by the change in 
>>> frequency with pedal pressure. Any ideas why LED brake lights might 
>>> cause this? Maybe install a capacitor on the radio like this?
>>> https://www.amazon.com/PAC-CSS12-Passive-Filter-Capacitor/dp/B000CED
>>> Z
>>> BA
>>> 
>>> 
>>> 
>>> Stuart
>>> 
>>> '85 Westy
>