hi i recapped this set changed all out of tolerance res. and still no fm then i hooked a dipole ant. i made out of 300 ohm wire to the existing ant. and it works fine my ques. is do these older sets need a external ant. for fm? i have an old crosley which acts in the same manner. this set has the fm hooked to both sides of the loop ant. the crosley just has a wire to a metal clip on the power cord i live about 40 miles from the nearest fm station. i'm just wondering if i'm trying to fix something that is already working as it should. thanks butch

Some sets do use the line cord as an antenna. You'll see some sort of coil arrangement that links the cord to the antenna circuit via inductance. Sometimes condensers are used as well. With your arrangement, whatever is in the loop will serve nicely as a local antenna. FM does not travel as far as AM because it travels in straight lines, and so it hits the horizon and then disappears. It can also run into mountains or hills. AM, on the other hand, bounces up and down, bouncing off of the ionosphere in the atmosphere, and can travel around the Earth.

40 miles really isn't too far away for FM, as all of suburbia here in Milwaukee picks up stations located in downtown Milwaukee just fine. Most of the suburbs are about 35 to 40 miles away. Reception can be weak at times. If you have some objects blocking the signal, though, or if the signal is weak, then it could be quite a distance to travel. If you have all of the components in that radio working as they should (precisely), you can try going over the different adjustments on the radio with a signal generator. You're really supposed to go over the IF cans with a sweep generator that puts out a wide bandwidth signal. This maintains the high fidelity of the set. However, if no such instrument is available, a regular signal generator can do a fair job for you. Most FM IFs are aligned at 10.7 MC. It could be that you just live in a funky area, it could be that your circuits are out of tune, or it could be that there is a faulty component somewhere in the radio. Be very careful when adjusting an FM radio. Unless you know exactly what you're doing, you can sometimes mess things up a bit. RF in the megacycle region is very sensitive. Keep track of what you do and undo.

T.

:Some sets do use the line cord as an antenna. You'll see some sort of coil arrangement that links the cord to the antenna circuit via inductance. Sometimes condensers are used as well. With your arrangement, whatever is in the loop will serve nicely as a local antenna. FM does not travel as far as AM because it travels in straight lines, and so it hits the horizon and then disappears. It can also run into mountains or hills. AM, on the other hand, bounces up and down, bouncing off of the ionosphere in the atmosphere, and can travel around the Earth.
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:40 miles really isn't too far away for FM, as all of suburbia here in Milwaukee picks up stations located in downtown Milwaukee just fine. Most of the suburbs are about 35 to 40 miles away. Reception can be weak at times. If you have some objects blocking the signal, though, or if the signal is weak, then it could be quite a distance to travel. If you have all of the components in that radio working as they should (precisely), you can try going over the different adjustments on the radio with a signal generator. You're really supposed to go over the IF cans with a sweep generator that puts out a wide bandwidth signal. This maintains the high fidelity of the set. However, if no such instrument is available, a regular signal generator can do a fair job for you. Most FM IFs are aligned at 10.7 MC. It could be that you just live in a funky area, it could be that your circuits are out of tune, or it could be that there is a faulty component somewhere in the radio. Be very careful when adjusting an FM radio. Unless you know exactly what you're doing, you can sometimes mess things up a bit. RF in the megacycle region is very sensitive. Keep track of what you do and undo.
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:T. thanks thomas i don't have a sweep generater but i did align it with a signal gen. and a fluke dvm it works but not without a short lenth of wire on the fm ant. i may go through it again when i adjusted the fm discriminater i kept getting gain until one screw was all the way in so i'm sure something is still not right. butch

If you have to keep turning the screw down to get a loud station, then something else is likely out of alignment. Be sure to use a GOOD signal generator that is properly aligned. Adjust the IF transformers to the exact frequency designated for that radio. At first this may throw things off and make things quieter. Then adjust the antenna and oscillator circuits appropriately. Adjusting the IF transformers simply so that the radio is louder is not a good idea because you may be peaking them on the wrong frequency. A good indication of whether things are okay or not is whether the stations synchronize or not. They will not synchronize unless all circuits are aligned properly. In a superheterodyne radio, frequencies are mixed to create a new frequency that is passed through transformers that are tuned only to that frequency. Unless the oscillator, which creates the second frequency to be combined with the first frequency (radio signal), is adjusted to create the right frequency for the right station, the frequency created by the two combining will not be correct. If the IF transformers are not peaked on the proper frequency, instead of seeing the station that should be tuned in (which is combined with the oscillator frequency), they will see stray stations that also pass through the front end, and will pass one of these stray stations instead. Remember that each stage tunes in a narrow band of frequencies. It is only by passing the station through stage after stage that all unwanted ones are rejected. This should give you an idea why the front end does not perfectly tune in one station.

Anyway, don't want to confuse you or something, but be accurate when tuning the radio, especially when working with FM. Since you say that the radio had critical components missing from it, then it was likely tampered with, and it is probable that the circuits have been tampered with as well.

Just so that you know, the high fidelity of an FM receiver is achieved by passing a wider band of freqencies than AM radios do. A typical AM radio passes like 10 KC of information through its circuits. When this is rectified by the detector, you only get about 5 kc of information, which is why the music sounds kind of crappy. FM uses circuits that pass about 19 MC of information, so almost all of the frequencies which we hear pass through. With a sweep generator and an oscilloscope you are able to tune the IF transformers of an FM radio to pass this more broad band of frequencies. Instead of simply producing the 10.7 MC IF signal, the sweep generator produces a signal that deviates about 9.5 MC either way of this signal (sweeps back and forth), allowing you to tune the circuits until all of this signal can be passed. Using a conventional signal generator will cause you to peak the transformers on a much narrower bandwidth. If you run into distortion or the music lacks the high end, you can try staggering the primary and secondary of each transformer just a tiny bit one way and the other (alternate).

Thomas

::T. thanks thomas i don't have a sweep generater but i did align it with a signal gen. and a fluke dvm it works but not without a short lenth of wire on the fm ant. i may go through it again when i adjusted the fm discriminater i kept getting gain until one screw was all the way in so i'm sure something is still not right. butch