Radio cable length from rear aerial

The rear screen heater is a pure resistance being fed with direct current and normally will cause no radio interference as it does not vibrate or oscillate, though a loose or dirty connection or dirty switch could produce interference.

Some cars use the rear screen as a radio aerial and these are prone to producing radio interference, especially when trying to receive vertically polarised signals.
I tried this myself using a bi-fi rear screen aerial adaptor and was very disappointed with the results, the signal-to-noise ratio was appalling.

If your car uses the rear screen as an aerial there is likely to be a box of electrickery physically somewhere near the rear screen where the aerial cable originates. This box contains stuff to decouple the radio signals from the HRW circuit and will probably contain a signal amplifier.

The static you hear might just be a drastic reduction in signal strength rather than actual generated interference. You can do little else but to check the connections to and from the unit particularly the ground connections and check the voltages present on the related wiring. If no external faults are found it is likely the box of electrickery has failed.

Spending a while looking at dedicated forums might help further.

Check the aerial earth at the carbody make sure its clean and tight ,check the aerial cable is pressed all the way into the radio socket.

It is usually best to check an aerial from the radio end with an ohmmeter or continuity checker. The aerial cable is a coaxial cable with a centre core that carries the signal and an outer braid that when properly grounded keeps interference to a minimum.

Measuring between the centre and the outer there should be an infinity reading on an ohmmeter, indicating no short circuits in the cable or aerial base. Measuring between the outer and a good ground the reading should be very low, no more than a few ohms indicating a good ground connection to the aerial base and of the aerial base to the bodywork.
The next test is simple and tricky at the same time as one lead of the meter will need extending. Remove the aerial mast and test for a very low reading of just 2 or 3 ohms between the cable centre and the stud or socket where the mast mounts. If all tests are fine it indicates the mast has an internal fault. If the tests aren't fine the cause is fairly intuitive.

To some extent you can perform the tests at the aerial base but the results will be limited due to the physical connection between the cable and aerial base won't be part of the test.

You need to be aware some installations are fitted with an aerial amplifier which can confuse matters and make checking more difficult.

This may not be very easy. Presuming that the aerial cable was already there and there was a standard plug on the cable that fitted into your standard socket on the radio, and presuming that you are confident that it all fitted OK, then the problem is with a faulty cable or aerial.

Just before you start, can I suggest that you DO test the radio and check that there is no fault in it. Particularly if you have removed an old radio with perfectly good reception. You might want to take it back to the shop and ask them to hook it up and test it for you. If the radio is clearly good, then my thoughts are as follows:

Typically the fault will eventially trace down to a portion of the outer copper brading in the cable being in contact with the inner core that carries the radio signal. This is usually right at the end in the plug and it's worth cutting off the plug and refitting a new one as a first step (You might even be able to carefully bare the inner core of the cable and push it into the cernre hole in the socket of the radio and test it before the new plug is fitted).

The second area of failure is typically the point at which the cable reaches the car aerial. It's not uncommon for water to get into a seal wher it is attached to the body and affect the performance of the aerial. Once again, you MAY be able to snip the cable at this end and re-make a nice clean dro connection. I have to be honest and say I don't know how the fitting go in this vehicle, so I'm shooting in the dark a little here. Obviously, if the vehicle has a built in aerial in the windscreen or back window somewhere, then my last suggestion is pretty redundant.

Finally, having tried to re-make connections at both ends of the cable, it's potentially time to buy a new aerial and cable and re-fit the whole thing from end to end. This is not a very fun job!

Assuming its broken outside the unit: most aerials are very similar to fit, serving the exact same function and not worth the cost of locating the exact same one used for your model due to time, and purchase costs.
Find an old transitor radio with similar sized aerial, ie length and diameter to fit your radio. Measure it and the replacement from an old radio you or a friend does not need.
Purchase a small screwdriver to remove and refit aerial to your grundig. Small sets of screwdrivers can be bought cheaply from discount stores, ebay etc.

Hi, the wires have odd shaped pieces of metal attached to the ends, these are the wireless aerials. They fit in the top of the screen. If you lay the cables in the screen casing as they naturally fit by length around the outer edges of the LCD panel you will find the aerial ends are just about correctly placed and you will need to figure out the angle the aerials fit in the plastic casing. Once done refit the screen front cover.
From Steve at Olive Country Computers in Spain.

Usually when water corrodes the base of the antenna housing, it can cause the resistance in the cable between the aerial and radio can increase. Sometimes just a clean and greasing can resolve, or depending on how badly the aerila base is corroded, an aerial replacement may be required.

Hi Fiona
Somewhere along the line from the aerial there must be a signal splitter that feeds the upstair and downstair terminals.
Try to find that splitter and switch the output to see if the problem goes from up to downstair.
If it does switch then you know the problem is with the splitter block, and if it stays the same then the problem is with the cable and/or the connectors that run downstairs.
Also the reason you get a pixellated(snowy) picture is because of signal loss during the length of the cable you ran downstair.
If running a cable downstair becomes the best option to fix your problem , then you could buy a cheap 10db signal booster/r.f amplifier to correct the signal loss and a cable splitter to feed both tv`s
That booster would be installed upstair in your case(near the source of the signal to be amplified).
I could send you a small diagram if need be. Hope this will help and Merry Chrismas

did the aerial rise up when you turned the radio on??

YOU'LL HAVE TO REPLACE THE AERIAL BASE & AERIAL MAST UNFORTUNAETLY FOR THIS NOT TO BAD OF A JOB TO DO YOURSELF & PARTS ARE NOT TO EXPENSIVE TO PURCHASE.