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Post by acbaker123 on Fri Sep 25, 2020 4:36 pm

I have a 1930 echophone S-3 AM radio that i need to find an antenna for, on the schematic it says primary 250 turns no 36 wire one turn, secondary 120 turns no 29 wire dead end. also when i put my hand near the tuner the signal gets much stronger, assumingly because my body is acting as the antenna, but when i touch the tuning wheel it makes the signal go away altogether, i have tried several different antennas including a little am high turn ferrite core antenna. is there anything wrong with the radio or do i not have the right antenna.

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Post by acbaker123 on Fri Sep 25, 2020 4:37 pm

there are just two lugs on the back, one says ant the other is ground to the chassis

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Post by Chas on Fri Sep 25, 2020 10:18 pm

acbaker123 wrote:I have a 1930 echophone S-3 AM radio that i need to find an antenna for, on the schematic it says primary 250 turns no 36 wire one turn, secondary 120 turns no 29 wire dead end. also when i put my hand near the tuner the signal gets much stronger, assumingly because my body is acting as the antenna, but when i touch the tuning wheel it makes the signal go away altogether, i have tried several different antennas including a little am high turn ferrite core antenna. is there anything wrong with the radio or do i not have the right antenna.
Antenna Search Echoph10
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Is L1 present in the radio? Without L1 (called the antenna coil) a direct connection of antenna and ground will result is broad tuning signals and possible hand capacity effects.

Is this coil assembly missing? The side notes include all the specifications for winding the antenna except the diameter and length of the coil form. On a guess the antenna coil is the same length and diameter as the RF stage coils... Most likely a brown phenolic mounted on an angle bracket.

When one does not have the instruments to measure the uh of the coil created, then only a near exact duplication will create results that will work properly.

The primary winding is untuned, it is the secondary winding that is most important, the uh must be enough so the tuned circuit created is the same as the tuned circuits in the RF stages.  Chas
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Post by acbaker123 on Sat Sep 26, 2020 2:31 pm

my radio is the original one not the "improved" S-3, on the schematic for both L1 is an RF transformer. my radio has all the coil sets in it

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Post by Chas on Sat Sep 26, 2020 4:23 pm

acbaker123 wrote:my radio is the original one not the "improved" S-3, on the schematic for both L1 is an RF transformer. my radio has all the coil sets in it
Sounds like its all O.K. from your report... Chas
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Post by acbaker123 on Sat Sep 26, 2020 5:43 pm

does it just want a single long loop i wonder, and why would touching the metal tuning knob cancel it out?

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Post by Resistance is Futile on Tue Oct 06, 2020 4:36 pm

That radio didn't have a loop antenna.
Most of the old radios just had a long wire antenna. The windings are for the R.F. coil primary and secondary as was stated at the beginning.
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Post by acbaker123 on Wed Oct 07, 2020 10:10 am

is the ground not used? and how long, can it be coiled up?

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Post by Chas on Wed Oct 07, 2020 1:57 pm

acbaker123 wrote:is the ground not used? and how long, can it be coiled up?
The aperiodic (untuned) receiving antenna needs to be some 25 to 75' long up and away from the receiver. It can be run around the room near the ceiling if practical or up in the attic. If run outdoors some sort of lightning protection is required. It must be reasonably away from metal objects. An indoor antenna may be useless or at least perform poorly if the home has metal siding, built of poured concrete or stone. Then, an outdoor antenna would be suggested.

The ground or better said an earth connection. For the tuner not to have sensitivity to hand contact or other strange responses. the ground wire must be short and as direct as possible to earth. Coiling the excess wire will result in creating an accidental inductance that can make the receiver sensitive to this anomaly...

If a ground cannot be found it is possible to create a counterpoise. That is a circuit of wire run under the antenna wire for its entire length yet insulated from ground and the antenna. It must be at least as long as thee antenna. If this is outdoors then it maus also have lightning protection, even if the chassis of the radio is part of the circuit... The counterpoise can be difficult to crate and have it work properly, it is not often used...

Do not consider coax wire as a means to shield the incoming radio signal for an aperodic antenna. Since a full resonant BD receiving antenna is not practical. An aperiodic antenna will have different impedance's for what ever broadcast signal is desired to be received. That, translates to an un-matchable situation to a coax which must be matched for impedance for proper signal transfer.. If coax is not matched it simply becomes a linear series capacitor "shorting" desired signals...  GL  Chas
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Post by acbaker123 on Wed Oct 07, 2020 4:57 pm


For a simple little AM radio from the 1930s?!

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Post by acbaker123 on Wed Oct 07, 2020 4:59 pm

i dont really understand what i need to do with the ground lug on the chassis, go to earth?

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Post by Chas on Wed Oct 07, 2020 5:19 pm

acbaker123 wrote:
For a simple little AM radio from the 1930s?!

acbaker123 wrote:i dont really understand what i need to do with the ground lug on the chassis, go to earth?

Yes, the radio is known as a TRF "Tuned Radio Frequency" although it has moderate sensitivity it is not as sensitive or selective as a common 5 tube radio of the late 40's-50's and early 60's. That is why there are external connections for the antenna and ground.

The TRF radio is known for more of a high fidelity response to the program material because of its broader selectivity than a superhetrodyne...

If there is a ground connection factory marked on the chassis, that, is connected to earth via a wire to a cold water pipe, a ground rod. Do not connect it to the cover screw on a duplex electrical outlet or the "U" ground on the outlet. The shorter the path to Earth ground the less likely there will be electrical noises induced into the wire.

You seem to be very unsure about all this. You can find identical information using WIKI for antennas and ground connections. If you are still questioning, several photos of the back of the radio, the proposed antenna location and ground will help in a response that will give you confidence. GL  Chas
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Post by acbaker123 on Wed Oct 07, 2020 6:59 pm

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I have no idea where i would put the antenna, i dont want it to be permanent

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