Weak FM radio reception in 2010 Prius?

Jeremy, based on your circuit description, it looks to me as low-pass filter instead of high-pass one, which has L-C swapped in a pi layout (Ls are in paralel and C in seriel).

 

No, it's definitely a high pass T filter. I got the capacitor values wrong in that first post (I didn't write the values down at the time, but tried to remember what they were). The values on the diagram I gave are ones I calculated for a 75 ohm high pass filter with an 80MHz cut-off frequency.

There is an example of this high pass T filter configuration on this Wiki page: [ame=http://en.wikipedia.org/wiki/Electronic_filter]Electronic filter - Wikipedia, the free encyclopedia[/ame]

Jeremy

 

Yes, but you mentioned the Pi filter in the post I quoted. T is correct.

 

Sorry, PaJa, my mistake, I meant to write T but wrote Pi in error!

Jeremy

 

Like the original poster, I get poor reception with my gen 3/IV. If there are trees anywhere near, no signal. I had satellite radio installed in my husband's car and he gets great reception. What's the concensus on how to remedy this problem? Does getting a shark fin help?

 

If you search this thread you'll see that just about everything has been tried, from changing antennas, changing head units to fitting screening and filters.

The problem is primarily with the design of the car, it emits a lot of radio frequency noise that gives the radio a tough time when the signal is a bit low. Some radios work a bit better than others and the consensus is that the stock Toyota fit radio is generally poor so reception can be improved a little with a radio change. However, changing the radio isn't a complete fix for many, although it can improve things a bit in some cases.

Toyota don't want to know about the problem, if you read this thread you'll find many have had battles with dealers and Toyota in-country HQs to no avail.

Some of us have tested our cars, as I have, and confirmed that it emits a fair bit of radio frequency noise from the power electronics. The easy test to see if this is causing your radio problem is to park up in an area where the radio reception isn't great and turn the car to "accessory" mode (press the power button without putting your foot on the brake). If your radio reception is better in accessory mode than it is in ready mode then it's primarily interfering noise from the car that's causing the problem, not the radio or antenna itself.

The filter I've just added to the antenna lead makes a pretty big difference, but isn't a straightforward mod and also means that the radio can no longer receive AM broadcasts.

FWIW, fitting a shark fin antenna would almost certainly make the radio reception poorer. The standard Prius antenna has a pre-amplifier built in to the base to try and give it better performance, an after market antenna most probably won't have this. Anyway, shark fin antennas are a fashion statement, not an efficient antenna design. It's hard to get a better antenna than a near vertical rod, at least for a car.

Jeremy

 

I posted the first time here about 2 years ago, about 50 pages back...and a few times after that.
After several emails, calls, dealer help, etc. I finally had Toyota Germany to refund the defective radio (since they cannot change it with anything that works, and offered me to replace it with a navi equipped unit for 500€ extra....) in the form of free services, in particular the 30.000km and the 45.000km ones. That is close to about 400€ cash.
The solution came from me, since it appeared that Toyota Customer service could only come up with the nonsense solution above...

So the radio still does not work, but at least I am getting in a way or another my money back. They put in 5w-30 oil instead of the more expensive 0w-20, but unless I changed the oil myself, which I cannot do to void the warranty (and I would not know where to do it and then I would have to pay to dispose of the old oil) I would never really know what they used even if they charged me the more expensive one... The 5w-30 is not perfect, but I am getting very good mileages in any case and it will not destroy my engine.

I hope the solution with the filter works (I don't care about AM) so that I can add it after the warranty expires. In the meantime I enjoy my iPod...

 

OK, So I have some 27pF ceramics and working on getting the 75nH coil.
Is that all I need for compnents.

I also have a antenna wire with ends that are for an old FM I-pod connector to radio, non-aux connection.

I don't need AM so I hope this helps.
Has anyone located or identified if it is low frequency or high frequency noise?

EDIT:
I am going in a new route. I am adding a Low Pass filter that has SMA connections wired to the antenna leads. The low pass will block everything over 108Mhz.

So if the interference is high frequency than it will work by blocking everything over FM.
The AM signal should also stay intact.

I will tackle the radio dis-assembly this weekend.

RESULTS of LOW Pass Filter:

I added the low pass filter, everything below 108Mhz was passed.
Everything above that was blocked.
The filter helped a little bit.

my2cents.

 

Where can I get a 75nH inductor in the UK?
Can I check that your diagram does show 75 nano and not 75 micro?

 

The value is nano, not micro. You can buy the filter ready made, from here: Radio Society of Great Britain EMC Filters Go for Filter 2, the FM band one. It has the wrong connectors, but it's easy to take the thing apart and just solder it inline with the antenna lead.

 

duplicate reply deleted

 

They look like the garex ones.
SPECTRUM COMMUNICATIONS

They are just down the road(ish) and offer different connectors. They might be able to ship me one stripped down already.

 

You're right, they do look to be the same.

 

Have been in touch with Spectrum and they are currently designing a filter for in car FM. They are not sure whether to go nominal 72 ohm or 150 ohm (typical car aerial). Do we have a preference?

 

AFAIK, most newer car systems are 75 (72) ohm. The older 150 ohm capacitive low frequency antenna system has pretty much been phased out, I believe.

 

Spectrum have produced a filter for me to try. It only allows the FM band through and has car aerial connectors. Fingers crossed.

 

It's a little off topic but I just installed the Flyaudio $499 Nav and the FM is improved now. The local channels lock and no static. This is from 2 days of use.

I will need to test it more on my 40mile daily commute next week.

Thx.

 

Does the weak FM reception issue also apply to the Base non-JBL system too?

 

yes!!

 

and I can add YES! YES!! and YES!!!