Anyway to boost signal? - AVS Forum
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post #1 of 9 Old 09-06-2010, 11:17 PM - Thread Starter
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I have a Clarion head unit and a kenwood HD module in my car. I live outside of Pittsburgh and there really isn't anything to listen to on the radio except on HD (unless you like country music.. wtf) Anyways, the HD channels seem to drop a bit too frequently while I am driving, and I've seen quite a few posts mentioning that they should be solid signals for approx. 40 miles from transmission.

I've read through several potential solutions and none of them really state if there is a decent way to increase signal quality beyond checking grounding of the antenna etc. The antenna boosters seem to be nominal if not useless from reviews, so what could I do to improve signal in my car? I considered building a better antenna but don't see anyone who talks much about it other than to recreate the stock antennas. Regular FM reception is quite good, but the HD is spotty.

I'm out of ideas on what I could really do. looked through (http://ham-radio.com/k6sti/index.html) and (http://www.avsforum.com/avs-vb/showthread.php?t=1208016). Any suggestions would be welcome.
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post #2 of 9 Old 09-07-2010, 04:36 AM
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This was my great project once:

http://www.avsforum.com/avs-vb/showthread.php?t=849634

I eventually took it off as the trunk mount was starting to chip the rear windshield, and it was just weird driving through parking garages. But it was a significant improvement over the on-glass antenna that came with my car.


Signal amps are... they can work, and I've had some success with them. It depends on exactly where you are. If there's interference, it'll boost the interference and make it worse. If you're too close to the transmitter towers, it'll overload your receiver and make it worse. But they have on/off switches you can toggle when that happens. I'd be using one now, if I could figure out a good place to mount the thing.
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post #3 of 9 Old 09-07-2010, 10:17 AM
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Pittsburgh and its hills are incompatible with driving, whether it be snow on the roads or bad FM reception -- one of the reasons I got the 'ell out of there 30 years ago. No signal amp is going to help multipath interference. The rejection is built into the receiver itself.
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post #4 of 9 Old 09-07-2010, 04:25 PM
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Pittsburgh has the most unruly hills in the world. They must have be designed by a committee that wouldn't talk to each other.

Kevin
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post #5 of 9 Old 09-09-2010, 05:44 PM
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I'm the Chief Engineer for 2 Radio stations in Pittsburgh, what stations are you trying to listen to?
The strongest HD signals in Pittsburgh are WLTJ, WDSY, WDVE, WWSW, WRRK & WQED
Since you are a non radio employee I'm very interested in seeing why your having reception issues, trust me I had the same problems and I had to mount a old style 31" antenna on the fender of my Honda to receive a decent HD signal
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post #6 of 9 Old 10-28-2010, 02:25 PM
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Quote:
Originally Posted by radioagogo View Post

I'm the Chief Engineer for 2 Radio stations in Pittsburgh, what stations are you trying to listen to?
The strongest HD signals in Pittsburgh are WLTJ, WDSY, WDVE, WWSW, WRRK & WQED
Since you are a non radio employee I'm very interested in seeing why your having reception issues, trust me I had the same problems and I had to mount a old style 31" antenna on the fender of my Honda to receive a decent HD signal

2 brief questions please........

1. I learned that radio stations use (some, but maybe not all ) use audio cables that cost 1k a piece. Are they really that much more effective than the ones you could buy from Monoprice or off the shelf ? The only reason I can think of is that you might need a better cable because you have so many in close proximity to each other and they need to be well insulated.

Is that true ?


2. I know I will get flamed for this one. But you said you have a 31 inch antennae on your car. Mine is in the windshield but I have had cars with rod antennae just like everyone else. How come the auto manufacurers can't figure out a way to mount the antennae inside the engine compartment or to the side of the car ?

It seems like with all the metal in a car, that they could figure out how to use it to receive radio signals instead of having to have a separate mast on the hood. I know I am not the first to think of this. I am sure there is a good reason they don't do it, but I am confident that a smart person in Detroit could figure it out.


Thanks.
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post #7 of 9 Old 10-31-2010, 11:30 PM
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Quote:
Originally Posted by Raymond42262 View Post

1. I learned that radio stations use (some, but maybe not all ) use audio cables that cost 1k a piece. Are they really that much more effective than the ones you could buy from Monoprice or off the shelf ? The only reason I can think of is that you might need a better cable because you have so many in close proximity to each other and they need to be well insulated.

Is that true ?

Not sure where you heard that one from, but it sure is a doozy!
Most radio stations i've been in (and i've been quite a few) just use standard Belden or Gepco cables, like what you can buy from Ramtronix or Markertek for change per foot. And they are very effective at shielding. I work in a TV station which uses AES audio, and we just use standard Belden cables for that.

The real expensive "cables" are typically the AM sample cables, which are usually high end RF cables. But even they aren't $1000, unless you have a massive run.

So chalk that one up with that solid gold outlet and the air infused cable conspiracy theories.

--Mike Fitzpatrick
Broadcast Engineer

Put your boots on folks, it's getting pretty deep in here!
Note: opinions and advice given here are mine and mine only.
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post #8 of 9 Old 11-02-2010, 04:47 PM
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Quote:
Originally Posted by Raymond42262 View Post

2 brief questions please........

2. I know I will get flamed for this one. But you said you have a 31 inch antennae on your car. Mine is in the windshield but I have had cars with rod antennae just like everyone else. How come the auto manufacurers can't figure out a way to mount the antennae inside the engine compartment or to the side of the car ?

It seems like with all the metal in a car, that they could figure out how to use it to receive radio signals instead of having to have a separate mast on the hood. I know I am not the first to think of this. I am sure there is a good reason they don't do it, but I am confident that a smart person in Detroit could figure it out.


Thanks.


I asked this question in a car forum and received the following 2 replies.

They are very thorough and explains why it is not practical.

I just thought that others might be interested.



Quote:
Originally Posted by Arty View Post

First you need to understand just how small the signal your FM reciever can detect is. When you are at the edge of reception, you are competing with background radiation left over from The Big Bang. Swap that for the electrical noise from the ignition that's so loud you can often hear it with the human ear.

Next the filter will introduce loss. You'll need a good one. Let's say you use a SAW and it only has a 3dB insertion loss. That's half your signal gone, and your reception area drops by 1/2.

Next you've put it in a biscuit tin surrounded by the hood and wings. Let's say that's 40dB. That's a further 10000 times reduction in your reception area.

So for a longer antenna you need a +47dB gain antenna. 1/4 Wavelength (for use with a practical dipole) for 100MHz is 0.75m, so you'd need a 35m antenna just to break even. You'd probably want a little more as the proximity of the vehicle chasssis ground will absorb signal.

Next you are looking at in band noise. That's between 97-104MHz and you can't filter that because it's on the same frequency as the wanted signal and the filter can't tell the two apart.
Subtract another 20dB (100 times), which you can never recover.

So they put it in the rear windscreen, in the element for the heater that is already there. They just change the length to 0.75m, they don't need a filter, and they can have three independant antennas and it is possible to add 6dB to the wanted signal by means of antenna diversity.



Quote:
Originally Posted by Arty View Post

The antenna needs to be
1) as high as possible
2) to work with signals received from all sides of the vehicle
3) to be separated for the vehicle chassis ground


The best radio solution is a ~1 meter antenna mounted dead centre of the roof

The best looking solution is an antenna mouted in the glasswork

There is already metal in the rear screen for the demister, and by careful tuning, it can also serve as an antenna. The E46 has 3 antennas in the rear screen and the best signal is selected from the three.

The worst solution would be to use the entire vehicle chassis as it is not tuned to the FM frequencies, or inside the engine bay, where it is boxed in by the hood and wings, and close to sources of electrical noise from the ignition.

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post #9 of 9 Old 11-20-2010, 09:25 PM
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Quote:
Originally Posted by TydalForce View Post

This was my great project once:

I eventually took it off as the trunk mount was starting to chip the rear windshield, and it was just weird driving through parking garages. But it was a significant improvement over the on-glass antenna that came with my car.


Signal amps are... they can work, and I've had some success with them. It depends on exactly where you are. If there's interference, it'll boost the interference and make it worse. If you're too close to the transmitter towers, it'll overload your receiver and make it worse. But they have on/off switches you can toggle when that happens. I'd be using one now, if I could figure out a good place to mount the thing.

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