Replacing the Power Antenna in the First Generation RX-7

Installing an Aftermarket Power Antenna

This page last updated December 4, 2005.
When I first developed this web page, I wrote it to describe installation of an inexpensive Radio Shack antenna that was available at the time. That part has since been discontinued, but I've had a few people write to tell me that the instructions below work just fine with any number of other replacement power antennas on the market. "Metra" is one of the brands that is most frequently cited, and they make a series of antennas that are commonly available through suppliers such as Circuit City and other nationwide electronics retailers. One person was good enough to suggest that Metra part number 44-PW22 or AW-PW22, marketed through the Metra subsidiaries “RoadWorks” and “AntennaWorks,” will be a very close match to the Radio Shack unit. The basic design and wiring are nearly identical. The most significant difference between this model and the Radio Shack antenna is that the RS unit is 39 inches in length when fully extended, versus the Metra antenna’s 31 inch height. I did a little further investigation online and found that many other Metra antennas have the same characteristics of design and wiring, but antenna height is the most frequent variable. My expectation is that the tallest antenna will yield the best reception, but will also be most prone to breaking or bending. So my advice to you is to try to find a similar antenna, but don’t get too bogged down with trying to find an exact match for the Radio Shack unit. Many different antennas will do the job just fine. When you get yours installed, drop me a line and let me know what worked for you.

After a quick Google search, I found the Metra 44-PW22 for $33 at Audio Outfitter. As an added bonus, the Metra 44-PW22 has a replacement antenna mast available for only $18.

Note that Audio Outfitter suggests using the less expensive 44PW12B when the 44PW22 is out of stock, but I have no information that the 12B will or will not fit in a first gen RX-7. Somebody let me know!

If you ever want to replace a broken power antenna in one of these cars, Radio Shack sells a power antenna for a whopping $39.95 that seems to do the job just right. (Part number 12-1330 – note that this part is now officially discontinued, so in-store stock will be sparse. You can still order one from Radio Shack at 817-415-2829. Best of all, the clearance price is only $19.95, plus $5 for shipping and handling!) What's more, I've come up with some easy instructions for wiring this new antenna so that it works the way a power antenna should: when you turn the key off, the antenna goes down automatically. (The stock antenna must be lowered by turning off the radio before the car is powered off. I always hated that about the stock antenna.)

Another factor that should motivate you to dump Mazda's OEM antenna, if it should every break, is that Mazda wants $80 just for a replacement mast, which still has to be installed in the stock power antenna assembly. That installation job is a chore and a half, as the antenna motor has to be disassembled, including a clockwork-like spiral spring that's just dying for an opportunity to eject antenna parts all over your work area. Don't bother! A complete replacement antenna, as of this writing, will cost you $240 from MazdaTrix, and it still won't retract at shutdown the way a power antenna should.

The Radio Shack antenna looks much like the stock antenna when it's down. Height, when fully extended, is about the same as the stock antenna too. The motor noise is virtually identical to Mazda's -- that is, it's noisy. I'd expect that Radio Shack gets these antennas from a reliable manufacturer, so I don't hesitate to recommend them. I've had one in my '84 for about three years before I sold it, and I installed one into my '85 when I bought that. Both are still working flawlessly. Lastly, if I should ever manage to bend another antenna mast and I can’t find any more of the Radio Shack units, these same instructions can likely be used for other aftermarket antennas. (Tip: READ THOSE SIGNS AT THE ENTRANCES TO AUTOMATED CAR WASHES!)  :)

Removal of the OEM antenna, and installation of the Radio Shack unit

Remove the right taillight assembly, then the antenna will easily come out the back of the body. With a little bending and cutting, you can get the OEM antenna mounting bracket to bolt right up to the stock bolt holes of the Radio Shack power antenna. The way I refabricated the mounting bracket, the antenna leans slightly backward when extended, as opposed to the OEM antenna which used to extend straight up. An electrical engineer could argue that this slight angle could compromise radio reception very slightly, but I've never experienced any reception differences from between stock antennas and the Radio Shack replacements.

Below are the Radio Shack antenna, on the left, and the OEM Mazda antenna with the mounting bracket installed, on the right. The OEM bracket has four removable bolts on it. The two riveted screws in the middle will still be used to mount your new RS antenna to the body with this old bracket, but the very bottom of the bracket -- where it makes a u-turn, looping back up -- will have to be bent down 90 degrees to get the bolt holes to line up to the bottom of the RS antenna. (Don't break it, or you'll be heading off to a junk yard to buy a new one for $20 or so.) The top of the OEM bracket can be unbolted with the top two bolts and re-installed on the RS antenna. All images below are clickable, by the way.

The mounting bracket has a 180 degree bend on the bottom. (right) I partially straightened it to a 90 degree bend, and snipped a portion of one of the bolt holes to accommodate the Radio Shack's bottom mounted bolts. (left)

The finished product.

You can see that I had to bend the bottom of the bracket to lean it over in such a way that the antenna mast and studs on the bracket would all line up to the holes in the chassis. Brad Good, from the first generation RX-7 mailing list, recently reminded me of why I chose to do this: I wanted to make sure that both mounting bolts, on the bottom of the antenna, were secured to the bracket. Brad instead chose to use only one mounting bolt, on the left of this picture, and install it through the right mounting hole of the bracket. This is slightly less secure, in my opinion, and may allow a little more flexing of the bracket or vibration that could eventually allow the bolt to back out or the mast nut to come loose; Brad also had to install that single lower bolt after the antenna and bracket were in place in the fender, in order for the whole assembly to clear the tail light hole. But I’ll concede that Brad’s method is certainly easier, and that the bolt or mast nut will probably never come loose. As an added benefit, the backwards leaning antenna on my car is probably more resistant to damage from low branches than a perfectly upright antenna would be.

Wiring it up

Like most aftermarket antennas, the RS unit has three leads -- "accessory on" (the orange lead, usually powered directly by a signal from a tuner), unswitched power (red) and ground (black). These are different from the three Mazda leads, and you cannot merely plug them into the wiring harness for the Mazda antenna. The black wire should be easy enough to wire up -- it's just a chassis ground, and I hooked mine up to one of the OEM-turned-Radio-Shack mounting bracket nuts. The red lead must have full time power regardless of whether or not the ignition key is in the accessory or on position. I found a great source nearby the antenna: the hatchback interior light has a full time power lead going into it. If you remove the rear hatch panel, you'll see two wires connecting into the back of the light. The blue/yellow wire (on the light, not on the OEM antenna harness!) is unswitched power -- the switch is a plunger mechanism on the driver's left side of the hatch latching mechanism. Finally, the "antenna up" signal for the orange wire can be used from the blue wire on the original Mazda antenna wiring harness.

As an aside, that blue wire was the most "interesting" part of this whole project. Mazda's OEM antenna is controlled by a relay under the dash. The relay is activated by a fairly common +12v signal from the tuner, but Mazda chose to send a completely different signal back to the antenna, via this convoluted relay. The three wires on the original Mazda antenna wiring harness play a three way shell game between battery positive and battery negative. When the antenna is going up, the blue wire gets battery positive, and the red wire gets battery negative. When the antenna is going down, the red wire gets battery positive, and the blue/yellow wire gets battery negative. So the red lead alternates between positive and negative, the blue wire only sees positive when the stock antenna is supposed to be up, and the blue/yellow wire only sees negative when the stock antenna is supposed to be down. Got that? :)    The cool thing is that you don't have to, because most aftermarket antennas have the relay mounted on the antenna, making the wiring logic a helluva lot easier to follow for you and I.

Another little tip: I used tap-in squeeze connectors (Radio Shack part number 64-3053) to connect to these wires without any cutting or soldering. A little electrical tape around the OEM antenna wiring harness would also be a smart idea to keep the hot leads from ever accidentally contacting the chassis. These tips should allow you to retain the stock wiring harness, just in case you or some future owner decides he/she wants to restore the car to totally stock parts.

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