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1979-1993 & 94 Conv [Subscribe to Daily Digest] |
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Hey Folks, I just did a thorough R&R on my antenna and thought I would post the results. My AM reception has been poor since I bought my '92 three years ago; normally it would "pop" when I went under power lines, then I would get serious alternator noise for the next 10-15 minuites, just enough to rule-out AM on my drive home from work. That, and I had the standard, run of the mill poor distance reception.
Anyway, I had originally started by reinforcing a poor ground at the alternator, which helped a bit, but didn't really fix the problem. So... I decided go at it from the antenna end, after reading that the antenna ground is crucial to AM reception and that the 900 doesn't exactly have the best ground there. In the end, I had my reservations about that second part, but the good news is it's basically fixed and it didn't cost me anything. The single most important step was simply bending two little tabs.
There are some good technical documents on the Saabmaster website which suggests taking two resistance readings with a multimeter. I had no problems with the first reading for proper antenna grounding, which didn't surprise me as the antenna is thoroughly grounded to it's bracket, and it's bracket is bolted to the body, which is, effectively, "the ground". But just to be overly thorough, I bolted a heavy grounding cable to the bracket, and attached that directly to the frame grounding point in the back by the brake lights.
The test that my antenna had problems passing was the second test "for play in the antenna rod". The test is to check that there are no more than 30 ohms resistance between the top of the antenna and the center pin on the antenna's signal-cable connector. My first test reading was over 100 ohms, but the rod did seem rigid, so I didn't see how that could account for everything.
Now... in between the antenna rod and the sleeve that it sits inside, there is another small, shiny sleeve or shim. You can see this 2" long shiny sleeve on your standard replacement mast assembly. The purpose of this additional sleeve is to allow the last section of the antenna to extend and stop, and--more importantly, to facilitate contact between the antennna rod and the sleeve it sits inside. This is accomplished by two little tabs, one that pushes into the rod, and one that pushes against the outer sleeve (the clean shiny surface helps as well). Anyway, by simply bending these tabs to provide firmer contact, I got my resistance reading down to just about 30 ohms.
After throwing everything back together and making sure all of my connections were tight, I was pleasantly surprised to find that I had near-perfect reception. Occasionally I still get the same "pop" while going under power lines and the my volume will drop, but since there is no longer any noise, I can just turn up the volume to compensate for this. Anybody know if that pop can be negated completely? I might actually spring for a whole new mast assembly one of these days.
I did also take out the whole antenna assembly (not so hard: just remove the nut at the top, two screws on the bracket, and fold-up the drain tube and hold it tight against the unit as you pull it out). I opened it up (also easier than it looks, just unscrew the nut in the middle of the spool section at the bottom, pry it apart and then keep track of what little part goes where) and found several 1/4" - 3" sections of the nylon cable that pushes up the mast. I cleaned these out along with all the other crud in there, and re-lubed everything with white lithium grease and vasoline, which should make it much easier to put a replacement mast in there next time.
Pep Boys sells a universal replacement assembly for $65 that is nearly identical, but it also needs some modifications to the attachment points to make it work. Honestly, the old antenna is built well and I don't see any reason to put in a replacement unit if the motor in the old one still works. Take the time to clean it out, or just try to put in a new mast and see what happens. You can buy a replacement mast for $10-20 at a dealer or online. Masts come in different sizes, so make sure it is the right one!
Final note: when putting everything back in, keep the two screws inside loose until you are finished. You want the button on the top of the antenna to come just slightly above the finishing nut (when the antenna is retracted) so keep tightening the nut on top until the button gets that high (you may need to push the unit up from inside) then tighten the screws inside.
--Norm
posted by 67.163.18...
Link to SAABMASTER AM/FM Troubleshooting Doc
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