Question on car antenna (in-glass, rear windshield)

Archived from groups: rec.audio.car,rec.audio.tech,rec.radio.amateur.antenna (More info?)

Hi all

Let me preamble this by saying I am new at this, and need your
help. But I am a quick learner!

I have a few specific questions and perhaps you can help. I am
trying to troubleshoot a Fm static problem

1) Is the car coax cable lead one or two wires? I am quite sure
it is two (one outer (the ground) and one inner wire) but I'll
ask to confirm

2) Should a "in-glass" rear winshield antenna be grounded to the
car's body? If so, from which end of the coax cable? (see Q 3)

3) Does the expression "grounding the antena" (in the case of a
glass mounted antenna) be as simple as soldering a grounding wire
from the outside coax lead end that plugs into the HU to a metal
ground of the car? Or should it be done closer to the actual
antena? SUch as at the junction of the end of the coax and where
the antenna starts...

Here is more detail on my problem if this helps: inconsistent FM
reception (re: static) with in-glass antenna where I use to get
crystal clear reception with old car. However, there is a twist
to my problem: I noticed that the coax cable (inner cable) from
the HU is not truly connected to the antenna even if it looks
like it is. I tested it with a continuity tester and it is not.
When I try to connect the inner coax wire directly to the antenna
(using a wire and soldering), then I can test it and it is well
connected. In other words, the inner wire of the coax makes a
continuous circuit from the HU's to the end of the antenna. Yet,
I still get some static on some FM station (which is not induced
by the engine or the car's electrical systems).

Any suggestion? It is an RSX 2004 (Acura). I changed the HU twice
(two models) and the problem persists (same issue with the OEM)

TIA

Archived from groups: rec.audio.car,rec.audio.tech,rec.radio.amateur.antenna (More info?)

HU is head unit, or radio


"Richard Crowley" <rcrowley@xpr7t.net> wrote in message
news:11hr8r78l0cf670@corp.supernews.com...
> Frank wrote:
>> 2) Should a "in-glass" rear winshield antenna be grounded to the car's
>> body? If so, from which end of the coax cable? (see Q 3)
>
> Grounding an antenna completely defeats its purpose.
> Is this also part of a defrosting heating element or such?
>
>> 3) Does the expression "grounding the antena" (in the case of a glass
>> mounted antenna) be as simple as soldering a grounding wire from the
>> outside coax lead end that plugs into the HU to a metal ground of the
>> car? Or should it be done closer to the actual antena? SUch as at the
>> junction of the end of the coax and where the antenna starts...
>
> The expression "grounding the antenna" is nonsense
> in the absense of better colatteral information. If it is
> just an antenna (and not part of a heater or something)
> then "grounding the antenna" sounds stupid.
>
> What/who/why is "HU"? If this is a part of the circuit
> you are working on, you need to reveal the entire situation.
> Otherwise, you will get misleading responses based on
> guessing from thousands of miles away.
>
>> Here is more detail on my problem if this helps: inconsistent
>> FM reception (re: static) with in-glass antenna where I use to get
>> crystal clear reception with old car.
>
> In-glass antennas have never been noted for their good
> performance. They are only popular because they are
> easier for the auto manufacturers (and car washes). Many
> people add a proper antenna after-market when they are
> stuck with these things.
>
>> However, there is a twist to my problem: I noticed that the coax cable
>> (inner cable) from the HU is not truly connected to the antenna even if
>> it looks like it is. I tested it with a continuity tester and it is not.
>
> If "HU" means Heating Unit or something, it seems likely
> that the antenna lead is connected via a capacitor. The cap
> would conduct RF voltage while appearing to be an open
> circuit at DC (which is what your meter is using.)

Archived from groups: rec.audio.car,rec.audio.tech,rec.radio.amateur.antenna (More info?)

Sounds like a loose connection - possibly in the power supply (DC voltage).
Does the static also happen on the AM band ?
If so, the loose connection may be in the power supplying the radio.
If positive side checks out ok - don't forget to check out the ground side -
all the way back to the battery.
I had a similar problem with an old buick once, and fixed it (after much
troubleshooting with a multimeter) by running a wire from the negative side
of the battery to a screw on the body - The lights stopped blinking - the
radio static cleared up - and all was well in the world.

Archived from groups: rec.audio.car,rec.audio.tech,rec.radio.amateur.antenna (More info?)

Frank wrote:
> Hi all
>
> Let me preamble this by saying I am new at this, and need your
> help. But I am a quick learner!
>
> I have a few specific questions and perhaps you can help. I am
> trying to troubleshoot a Fm static problem
>
> 1) Is the car coax cable lead one or two wires? I am quite sure
> it is two (one outer (the ground) and one inner wire) but I'll
> ask to confirm
>
> 2) Should a "in-glass" rear winshield antenna be grounded to the
> car's body? If so, from which end of the coax cable? (see Q 3)
>
> 3) Does the expression "grounding the antena" (in the case of a
> glass mounted antenna) be as simple as soldering a grounding wire
> from the outside coax lead end that plugs into the HU to a metal
> ground of the car? Or should it be done closer to the actual
> antena? SUch as at the junction of the end of the coax and where
> the antenna starts...
>
> Here is more detail on my problem if this helps: inconsistent FM
> reception (re: static) with in-glass antenna where I use to get
> crystal clear reception with old car. However, there is a twist
> to my problem: I noticed that the coax cable (inner cable) from
> the HU is not truly connected to the antenna even if it looks
> like it is. I tested it with a continuity tester and it is not.
> When I try to connect the inner coax wire directly to the antenna
> (using a wire and soldering), then I can test it and it is well
> connected. In other words, the inner wire of the coax makes a
> continuous circuit from the HU's to the end of the antenna. Yet,
> I still get some static on some FM station (which is not induced
> by the engine or the car's electrical systems).
>
> Any suggestion? It is an RSX 2004 (Acura). I changed the HU twice
> (two models) and the problem persists (same issue with the OEM)
>
> TIA
>
>

Have you deffinantly got the antenna power line connected to the head
unit. On an ISO radio connector this is a blue wire which provides
power to an antenna amplifier found on some cars.

Make sure you've fitted the earth (ground?) bar from your radio to
the car's body (for example the bolt that holds the radio cage in).

Try using a different antenna to see if the problem re-occurs.

--
Regards,
Aaron.