Alpine Reception

[MHC]

Thanks. I don't know where they mount the FM aerial, but I suspect it is high up, so away from the tub. Just a thought, but I seem to remember that there is some aluminium foil stuck to the inside of the boot (or trunk in the US) of my M100 Elan below where the aerial is. Will have a check, but may be it is there to solve the same problem (the reception in my Elan is far better than in the Evora).

[MikieP]

Precisely why that is there. However, the thickness does have some effect on the gain or lack thereof, of the antenna system and in general, the thicker, the better up to about 1/8", just as is the diameter size (again the larger diameter, the broader the frequency bandwidth) of the tubing in the standard TV antennas we are all familiar with from the old days. Yes, a Ham Radio Operator from age 11 (1959) and have been involved with many varieties of antennas.

[MHC]

Anyone got a service manual or parts diagram showing where the aerial is on a MY11 Evora S, and how to get at it? I think I read somewhere that Lotus have changed the position of the aerial since the first cars came out.

[Bibs]

Here it is, behind the A pillar.

No wonder the reception is so shit, this is just a short length of wire tucked up behind the trim.

In this car, the headlining is going to be removed, a reflector placed on the reverse of it and much longer stretch of aerial wire on top of it.

I read somewhere that 31" lengths are the key to FM reception, make any sense?

[Derek]

While we are on about 2011 Alpine, is there anyway of getting the nav to show GPS speed?

[Bibs]

Press the little icon on the left in the middle that's showing the 3 lines of info to bring up the trip computer, then click 'set info' at the bottom, one of the options is 'current speed' off the top of my head.

I'm sure I used to like current speed, current speed limit and 'potential fine' the compass.

[Derek]

Not sure I understand which icon you mean.

My screen looks like this:

[MikieP]

Bibs,

31" is the accepted length for FM band. 31" for the aerial and at least that or more for the reflector half of the vertical dipole (meaning two parts). There is simply no substitute for the old upright centered on the car's metal roof. For us there is no metal roof, no metal rod. Anything else will be a half measure. Second best is to go back to metal a "olde metal rod" in front of door pillar with foil stuffed down inside the pillar (which is attached to the antenna's shield only) if possible or middle of trunk with metal reflector pasted underneath the plastic body part you mount your antenna on top of. Other measures are wishful thinking. Marine antennas were designed just for plastic boats but they are not going to fit on a Lotus. One other useful possibility is to locate an older rod style antenna that has most of its wire length coiled around making it shorter than the rod type and they were called Rubber Duckies for FM, but their capabilities are only 1/4 of the "olde rod" due to its 1/4 length.

Note that the position of the reflector should be as close to directly underneath the director (olde metal rod's replacement) as possible or your reception azimuth will be skewed and not a good round circle surrounding the car.

Alternatively, isn't there Sirius or XM or equivalent over there? Either way, proper antenna is vital to any radio working well.

[MHC]

May be an expensive solution as it probably means replacing the headset, but anyone used a DAB aerial in a car?

[MHC]

Here it is, behind the A pillar.

No wonder the reception is so shit, this is just a short length of wire tucked up behind the trim.

In this car, the headlining is going to be removed, a reflector placed on the reverse of it and much longer stretch of aerial wire on top of it.

I read somewhere that 31" lengths are the key to FM reception, make any sense?

Useful pictures, thanks. Is there room to get a helical whip aerial in there either behind the A-pillar trim or lower down next to the dash? Ideally with the bottom fixed to some metal to act as the reflector (alternatively enough space to put some foil in to act as the reflector). I am sure that won't be perfect, but can hardly be worse than the current set up.

Something like one of these:

http://www.bluespot.co.uk/car-audio.aspx/7617495224-aerial

Pretty much what the M100 uses (with a sheet of aluminium under the glass fibre wing to act as the reflector.

Or has anyone tried one of these:

http://www.bluespot.co.uk/car-audio.aspx/7617495142-aerial

Bit ugly though.

[MikieP]

I do have one other alternative for you now that I know what the Evora does have for the FM/AM antenna. This does not apply to XM/Sirius or SAT/NAV, only FM and AM. Do any of you remember the days when there was a dipole wire actually glued the your windshield - looked similar to the rear window defrost resistive elements glued to it. It is horizontally polarized unlike the vertical polarization of most FM and AM transmitters world-wide so there will be losses due to the incorrect polarization of the transmitted energies but it will be in the open and does NOT require the base plate, reflective element to function and it is not esthetically pleasing, but it will work much better than the wire in the A pillar. However, there is nothing better than the old vertical whip fastened to the center of a car's metal roof. It gave uniform reception patterns, and maximum gain without going to more advanced designs which for cars, is not usually possible at all. As to SAT/NAV/XM/Sirius, just lay it in the trunk atop of everything else and all will be fine. I am assuming cars other than my Esprit use Glass for lids too. It does not need a reflector at all as they are actually already part of the antenna unit.

To answer your BlueSPot questions:

The ...224 antenna is the good 'ole whip with a Pre-amplifier (booster) in line while the ...142 is probably a simple loop or quad antenna with Pre-amplifier in line. Loops have a wide bandwidth but a negative gain without reflectors available for the Director element (the primary loop). Whips generally have 0 gain. However, the loop will not require a ground plane (the other half of the 1/2 wave dipole antenna) such as a metal roof, foil underneath, etc, while the whip does require one to perform its best. Without the other half, you now have a 1/4 wave whip which has a negative gain comparatively speaking. In addition, in-line Pre-amplifiers will amplify signal and noise levels together as they can not differentiate between the two signals. The best Pre-amplifiers are designed to have a very narrow pass band and this limits the amount of noise they amplify. Hope this helps.

Edited July 29, 2012 by MikieP

[Bibs]

We're going to try a duplicate antenna in the other a pillar, just looking for a y-lead to join them up

[MikieP]

Bibs,

Not altogether a bad idea! But here is something to think about when you add the other element to the other pillar: Before using a Y per se, since I think you will find the original wire is probably tied to the center conductor of the coax feed line (and it is an assumption that Lotus used coax for the feed line), try tying the new lead to the outer conductor (shield) before trying the Y connection. In antenna theory, you would be adding the other half of the half wave dipole element and might perform better than just a longer element when Y'ed together, although the separation between the two might be its undoing as well. Never have thought about it before but give it a try. Either way, it will not hurt anything and should be some improvement.

How is the antenna wired to the radio in the Evora? Coax, just a single wire into a plug?

Edited July 29, 2012 by MikieP