[67drake]

I have the original AM radio in my 71' GTO. I'm thinking about switching it out for an AM/FM. Was there any difference in the antennas in the windshields if a car came with an AM or an AM/FM radio?
I would think not,but I just want to know before I pursue this idea any further.

[marxjunk]

no

just if they have a mast..the mast is usually longer on an FM

[tigergto]

My 71 was an original AM and I put a AM/FM in, no problem.

[1969GiPper]

If you're swapping out a radio or had a repair to the existing radio done, the last step of the installation process is to "trim" the antenna. This is done regardless of whether you have a mast or a windshield antenna. The procedure should be in the service manual where information on radio installation is. In my 69 service manual it's included in a number of the illustrations. It's done by adjusting a small screw and only takes about one minute to do. The purpose of trimming the antenna is to get maximum reception. Note: It probably should also be done any time an antenna mast or windshield (with antenna) or coax cable is replaced.

[67drake]

Thanks guys.
We're having a heat wave here,it was 40 degrees out yesterday,so I started the install of my new aftermarket gauges. While under the dash I was thinking I should pull the radio and test it,wires,and speaker as only the back speaker works,and not the front. Then started thinking about how much I miss having a few tunes sometimes while driving,so I'm just kicking the FM idea around.

[tigergto]

Originally Posted by 1969GiPper

If you're swapping out a radio or had a repair to the existing radio done, the last step of the installation process is to "trim" the antenna. This is done regardless of whether you have a mast or a windshield antenna. The procedure should be in the service manual where information on radio installation is. In my 69 service manual it's included in a number of the illustrations. It's done by adjusting a small screw and only takes about one minute to do. The purpose of trimming the antenna is to get maximum reception. Note: It probably should also be done any time an antenna mast or windshield (with antenna) or coax cable is replaced.

Interesting. I'll check my 71 service manual and if it's in there I'll tinker with it when my car comes out of storage in the spring. I don't recall ever doing it. Thanks.

[67drake]

Originally Posted by 1969GiPper

If you're swapping out a radio or had a repair to the existing radio done, the last step of the installation process is to "trim" the antenna. This is done regardless of whether you have a mast or a windshield antenna. The procedure should be in the service manual where information on radio installation is. In my 69 service manual it's included in a number of the illustrations. It's done by adjusting a small screw and only takes about one minute to do. The purpose of trimming the antenna is to get maximum reception. Note: It probably should also be done any time an antenna mast or windshield (with antenna) or coax cable is replaced.

That does make sense. I used to be into CB's and amateur radio years ago and this was SOP on an antenna install. I never knew about the adjustment on the GM car radios though.

[Txbobcat]

I need to adjust mine. When I turn the corner at my house it flips over to a salsa music station and the within a block it switches back to the oldies station.

[Jerry H.]

Originally Posted by marxjunk

no

just if they have a mast..the mast is usually longer on an FM

I believe you might have that backwards. The optimum length for and FM antenna is 31" FIXED, IIRC.

As has been posted, for AM, you follow the directions to 'trim' the antenna by extending it to the length shown in the manual and the adjusting the 'trimming' screw until you get the best reception.

[tigergto]

Originally Posted by tigergto

Interesting. I'll check my 71 service manual and if it's in there I'll tinker with it when my car comes out of storage in the spring. I don't recall ever doing it. Thanks.

After checking my manual I do recall doing the trimming when I inserted new radio. Since this is for AM only it doesn't help my FM reception which I'm not happy with. This spring I will be putting a modern radio into the glove box. I've checked into having the original converted to modern technology but I'm not willing to pay the price.