Hi all was just woundering if any body here has played around makeing a ferrite antenna for the old tube radio. And if so any tips, also Im just finding out about ferrite, anybody know what it is?

:Hi all was just woundering if any body here has played around makeing a ferrite antenna for the old tube radio. And if so any tips, also Im just finding out about ferrite, anybody know what it is?
:

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
Rod antennas are easy to make. Try Google for more info.
Ferrite is a powdered iron (or other magnetic material) which is pressed into rods and other shapes.
http://www.amidoncorp.com/r61-025-400/

Rich
>>>>>>>>>>>>>>>>>>>>>>>>

Ferrite is powdered iron, compressed into a permanent (if brittle) solid mass using a binding agent. In rod antenna form, it basically acts as a magnetic field "concentrator", allowing a small coil of wire wound around it to pick up a level of signal equivalent to that produced by a physically much larger coreless wire loop.

Small antenna size first became important in portable radios, especially transistor sets. However, ferrite antennas were sometimes used in later tabletop or console tube sets because of their additional unique properties of being highly directional and (if fitted with a grounded aluminum "tent" ) able to reject noise that is borne on the e-field component of the radio wave. German radio manufacturers of the 50s and 60s usually used internal ferrite-rod antennas on the standard broadcast and longwave AM bands. Some were rotatable by a knob on the front panel to allow the radio user to maximize reception by adjusting the rod's direction without needing to move the entire set.

Small size, however, is the principal reason for ferrite antennas becoming popular in the tiny AM BC radios that flourished starting in the late 50's. Ferrite rod antennas don't have much of an advantage over standard wire-loop or long-wire antennas in a typical large tube-style AM radio, and they are pretty much useless at the much higher frequencies of shortwave and FM.

:Ferrite is powdered iron, compressed into a permanent (if brittle) solid mass using a binding agent. In rod antenna form, it basically acts as a magnetic field "concentrator", allowing a small coil of wire wound around it to pick up a level of signal equivalent to that produced by a physically much larger coreless wire loop.
:
:Small antenna size first became important in portable radios, especially transistor sets. However, ferrite antennas were sometimes used in later tabletop or console tube sets because of their additional unique properties of being highly directional and (if fitted with a grounded aluminum "tent" ) able to reject noise that is borne on the e-field component of the radio wave. German radio manufacturers of the 50s and 60s usually used internal ferrite-rod antennas on the standard broadcast and longwave AM bands. Some were rotatable by a knob on the front panel to allow the radio user to maximize reception by adjusting the rod's direction without needing to move the entire set.
:
:Small size, however, is the principal reason for ferrite antennas becoming popular in the tiny AM BC radios that flourished starting in the late 50's. Ferrite rod antennas don't have much of an advantage over standard wire-loop or long-wire antennas in a typical large tube-style AM radio, and they are pretty much useless at the much higher frequencies of shortwave and FM.
:
:
:Thanks thats interesting info, I made a coil on my lathe and put it on a wood dowel, works really well with short wave not much diff on am, was thinking about makeing a longer coil this one is 17ft.
:

::Ferrite is powdered iron, compressed into a permanent (if brittle) solid mass using a binding agent. In rod antenna form, it basically acts as a magnetic field "concentrator", allowing a small coil of wire wound around it to pick up a level of signal equivalent to that produced by a physically much larger coreless wire loop.
::
::Small antenna size first became important in portable radios, especially transistor sets. However, ferrite antennas were sometimes used in later tabletop or console tube sets because of their additional unique properties of being highly directional and (if fitted with a grounded aluminum "tent" ) able to reject noise that is borne on the e-field component of the radio wave. German radio manufacturers of the 50s and 60s usually used internal ferrite-rod antennas on the standard broadcast and longwave AM bands. Some were rotatable by a knob on the front panel to allow the radio user to maximize reception by adjusting the rod's direction without needing to move the entire set.
::
::Small size, however, is the principal reason for ferrite antennas becoming popular in the tiny AM BC radios that flourished starting in the late 50's. Ferrite rod antennas don't have much of an advantage over standard wire-loop or long-wire antennas in a typical large tube-style AM radio, and they are pretty much useless at the much higher frequencies of shortwave and FM.
::
::
::Thanks thats interesting info, I made a coil on my lathe and put it on a wood dowel, works really well with short wave not much diff on am, was thinking about makeing a longer coil this one is 17ft.
::
:
:
The first thing you have to remember is that the coil, be it ferrite or air, has to resonate with the tuning capacitor at the incoming RF signal, in order to pass the maximum signal to the converter stage.
Lewis

:The first thing you have to remember is that the coil, be it ferrite or air, has to resonate with the tuning capacitor at the incoming RF signal, in order to pass the maximum signal to the converter stage.

... this depends on the radio. If the antenna is direct-coupled like many tabletop sets of the 40s-60s with "built in" wire loop (or ferrite rod) antennas, then the antenna does indeed form part of a tuned circuit and its inductance value must be within a fairly narrow range in order to be tunable to the desired frequency. Otherwise sensitivity will be poor. However, most AM broadcast-band radios built before around 1940 were designed to be used with an untuned "long wire" type antenna and used an antenna coupler transformer, with only the secondary circuit being tuned.

:
::The first thing you have to remember is that the coil, be it ferrite or air, has to resonate with the tuning capacitor at the incoming RF signal, in order to pass the maximum signal to the converter stage.
:
:... this depends on the radio. If the antenna is direct-coupled like many tabletop sets of the 40s-60s with "built in" wire loop (or ferrite rod) antennas, then the antenna does indeed form part of a tuned circuit and its inductance value must be within a fairly narrow range in order to be tunable to the desired frequency. Otherwise sensitivity will be poor. However, most AM broadcast-band radios built before around 1940 were designed to be used with an untuned "long wire" type antenna and used an antenna coupler transformer, with only the secondary circuit being tuned.
:
So must be you guys are comparing inductive vs non the radios im using have built in loops does that mean an inductive antenna wont work? And one other thing if I understand correctly is a tunning condenser would be use to get an inductive antenna to be intune with a narrow frequency?

.... all loop antennas are inductive; for simple AM sets with internal wire loop antennas, the inductance of the antenna is designed to match the range of the tuning cap in order to select any desired frequency in the band.

Therefore, if you want to replace a wire loop (factory) antenna with a ferrite rod antenna, you will need to match the inductance of the original antenna in order to avoid loss of sensitivity. This inductance value can be computed from the loop wire diameter, the number of turns, and the loop dimensions. With this info in hand you can compute the necessary characteristics of an equivalent ferrite antenna (wire diameter, ferrite core diameter, # of coil turns) in order to match the factory unit's inductance.

:
:.... all loop antennas are inductive; for simple AM sets with internal wire loop antennas, the inductance of the antenna is designed to match the range of the tuning cap in order to select any desired frequency in the band.
:
: Therefore, if you want to replace a wire loop (factory) antenna with a ferrite rod antenna, you will need to match the inductance of the original antenna in order to avoid loss of sensitivity. This inductance value can be computed from the loop wire diameter, the number of turns, and the loop dimensions. With this info in hand you can compute the necessary characteristics of an equivalent ferrite antenna (wire diameter, ferrite core diameter, # of coil turns) in order to match the factory unit's inductance.
:
So if thats the case nothing would work better than the factory loop?

You won't get an amazing improvement in reception by replacing a factory wire loop antenna with a ferrite rod unit. You will generally get a marked improvement in reception by using an external (i.e., located outside your dwelling) antenna. Most radios, even inexpensive AA5 units, have a provision for connecting an external antenna to the set.

There's an old adage in radio which is, "If you want better reception, put up more metal."

::
::.... all loop antennas are inductive; for simple AM sets with internal wire loop antennas, the inductance of the antenna is designed to match the range of the tuning cap in order to select any desired frequency in the band.
::
:: Therefore, if you want to replace a wire loop (factory) antenna with a ferrite rod antenna, you will need to match the inductance of the original antenna in order to avoid loss of sensitivity. This inductance value can be computed from the loop wire diameter, the number of turns, and the loop dimensions. With this info in hand you can compute the necessary characteristics of an equivalent ferrite antenna (wire diameter, ferrite core diameter, # of coil turns) in order to match the factory unit's inductance.
::
:So if thats the case nothing would work better than the factory loop?

Ray:
I would say that as long as the inductance of the loop can resonate with the tuning capacitor, and all of them are 365 pF at the low end of the band, then whatever you put into the radio should be about the same. There is a trimmer cap on the main cap to peak the radio for max performance. You are not going to burn the house down by expermenting with loops, so I avise that you experiment.
Lewis
:

:Ferrite is powdered iron, compressed into a permanent (if brittle) solid mass using a binding agent. In rod antenna form, it basically acts as a magnetic field "concentrator", allowing a small coil of wire wound around it to pick up a level of signal equivalent to that produced by a physically much larger coreless wire loop.
:
:Small antenna size first became important in portable radios, especially transistor sets. However, ferrite antennas were sometimes used in later tabletop or console tube sets because of their additional unique properties of being highly directional and (if fitted with a grounded aluminum "tent" ) able to reject noise that is borne on the e-field component of the radio wave. German radio manufacturers of the 50s and 60s usually used internal ferrite-rod antennas on the standard broadcast and longwave AM bands. Some were rotatable by a knob on the front panel to allow the radio user to maximize reception by adjusting the rod's direction without needing to move the entire set.
:
:Small size, however, is the principal reason for ferrite antennas becoming popular in the tiny AM BC radios that flourished starting in the late 50's. Ferrite rod antennas don't have much of an advantage over standard wire-loop or long-wire antennas in a typical large tube-style AM radio, and they are pretty much useless at the much higher frequencies of shortwave and FM.
:
:
:
:
************************************

Building MW ferrite antennas:

https://googledrive.com/host/0B4azXCQ9cxMZbmppcjBVc25aLVk/ARADARCHIVE/comp&data/mwcoildata0564pw/page1.jpg

Rich

**********************************