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#1
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Antenna Replacement Experiment
Is it feasable to remove the ferrite antenna from an am radio & replace it
with an external multi-turn box loop with the same primary/secondary inductance? |
#2
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Antenna Replacement Experiment
"Spin" wrote in message ... Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? Hi Spin I cant offer any information about removing the ferrite antenna and replacing it with an external loop. But, I can tell you that a few turns of wire from the loop, wrapped aroung the radio, with the original ferrite antenna connected as normal, can be made to couple the external loop to the receiver to greatly improve reception. Jerry |
#3
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Antenna Replacement Experiment
Jerry;
I know how to couple an external loop to the internal ferrite antenna of the radio. I believe that i would get better nulls & gain by removing the internal antenna & directly connecting a box loop in it's place. Please correct me if i am in error. "Jerry" wrote in message news "Spin" wrote in message ... Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? Hi Spin I cant offer any information about removing the ferrite antenna and replacing it with an external loop. But, I can tell you that a few turns of wire from the loop, wrapped aroung the radio, with the original ferrite antenna connected as normal, can be made to couple the external loop to the receiver to greatly improve reception. Jerry |
#4
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Antenna Replacement Experiment
Spin wrote:
Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? Most of those internal ferrite antennas that I have seen are transformers or autotransformers for impedance matching. It would be hard to couple an external air core transformer as efficiently as is possible with ferrite. -- 73, Cecil http://www.w5dxp.com |
#5
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Antenna Replacement Experiment
On Jan 29, 12:41*am, "Spin" wrote:
Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? I wouldnt say its imposssible but it certainly would be a royal pain getting the tuning to track right. I have coupled big antennas to loopstick radios just by wrapping a few turns of wire around the radio and connecting it to an external antenna. I have also wound a few turns around the loopstick and brought it out to a jack for this purpose. At least one commercial SW rx I owned was built this way. Jimmie |
#6
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Antenna Replacement Experiment
JIMMIE wrote:
On Jan 29, 12:41Â*am, "Spin" wrote: Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? I wouldnt say its imposssible but it certainly would be a royal pain getting the tuning to track right. I have coupled big antennas to loopstick radios just by wrapping a few turns of wire around the radio and connecting it to an external antenna. I have also wound a few turns around the loopstick and brought it out to a jack for this purpose. At least one commercial SW rx I owned was built this way. Jimmie If you get the same inductances, coupling and can compensate for any difference in stray capacitance, it should work. Ferrite antennas are used for their small size. Older tube radios used larger loop antennas. Keep in mind there may be some DC voltages present on the ferrite antenna you may not want to take outside the radio. (In other words, while you could make the external loop work, there may be other reasons for not doing so.) |
#7
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Antenna Replacement Experiment
Spin wrote:
Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? It's hard to beat the SelectAtenna. http://www.universal-radio.com/catalog/mwant/4316.html |
#8
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Antenna Replacement Experiment
dave wrote:
It's hard to beat the SelectAtenna. http://www.universal-radio.com/catalog/mwant/4316.html Wow, "+30 dB signal gain" from a passive tank circuit. -- 73, Cecil http://www.w5dxp.com |
#9
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Antenna Replacement Experiment
Hi Spin There may be different rules for connecting external antennas depending on if the objective is to get max gain or to get strongest null response. An external, capacitor tuned loop is a high Q device and appreciates loose coupling when used to receive weak signals. If the objective of the loop is to null out a specific frequency, I suspect the direct connection of the external loop will result in very effective nulling. I hope you try this antenna modification and report the results Jerry KD6JDJ "Spin" wrote in message ... Jerry; I know how to couple an external loop to the internal ferrite antenna of the radio. I believe that i would get better nulls & gain by removing the internal antenna & directly connecting a box loop in it's place. Please correct me if i am in error. "Jerry" wrote in message news "Spin" wrote in message ... Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? Hi Spin I cant offer any information about removing the ferrite antenna and replacing it with an external loop. But, I can tell you that a few turns of wire from the loop, wrapped aroung the radio, with the original ferrite antenna connected as normal, can be made to couple the external loop to the receiver to greatly improve reception. Jerry |
#10
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Antenna Replacement Experiment
On Thu, 29 Jan 2009 06:41:17 GMT, "Spin"
wrote: Is it feasable to remove the ferrite antenna from an am radio & replace it with an external multi-turn box loop with the same primary/secondary inductance? Those with more than one coil (almost all) are not primary to secondary relationships. One coil is the RF/Mixer stage, and the other is the Oscillator stage and the ferrite provides the mixing path as well as the signal pickup path. If you closely examine the variable capacitor, you should see that it is also two independent sections on the same frame (or inside the same enclosure). There should also be a trimmer for each, one for peaking the RF, the other for tracking the Oscillator. If there is a TRF stage, it will probably have another coil/cap combo and probably with that coil as a separate item. It would help if you identify the "am radio." 73's Richard Clark, KB7QHC |
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