One radio application carried by larger aircraft was the "Blind Landing" equipment. This allows an aircraft to approach the runway of the airfield in bad visibility. To do this you have to create a radio beam pointing at the runway. This beam has to be narrow enough to accurately guide the aircraft.
You can direct a radio signal by using reflectors, these create an interference pattern strengthening the signal in certain directions and weakening them in others. The problem was that they could not get the beam narrow enough using this method
In the 1930's the Lorenz company discovered that by using two relatively wide beams, the overlapping area of the two beams could be used. By modulating the left side with "dots" and the right side with "dashes", a narrow area exists where the dots and dashes are of equal strength and a continuous tone can be heard:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=lorenz.gif" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/lorenz.gif" border="0" alt="Photobucket"></a>
The "beam" operated at 30 to 33.3 Mhz so different airports could use a different frequency. The dots and dashes were modulated at 1150 Hz giving a clearly audible tone for the pilot.
While this system gave the direction of the runway, the signal strength would only give a rough and unreliable indication of distance from the runway, so a second signal was introduced so that the pilot could estimate the correct glidepath towards the runway. Two approach beacons were placed -one 3000 meters, the other 300 meters- from the runway. These approach beacons were directed upwards so they were only picked up when almost directly overhead. The approach beacons operated at 38 Mhz and transmitted a continuous tone modulated at 700 Hz, a much lower tone than that of the beam.
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=lorenza.gif" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/lorenza.gif" border="0" alt="Photobucket"></a>
The pilot would approach the runway using a the beam and reduce his height to 200 meters. When the first approach signal was heard, he would initiate a slow decent, calculated to hit the runway. At the second approach signal the aircraft would ideally be about 20 meters from the ground with the runway hopefully coming into view within seconds for a safe landing.
So to receive these signals, two receivers were needed, one operating at 30 -33,3 Mhz to receive the beam, the other at 38 Mhz to receive the approach signal.
The Luftwaffe adopted this system and called it the "FuBl 1" or Funk Blindlandeanlage 1". It consisted of two receivers, the EBl 1 and EBl 2 (Empfaenger Blindlande 1/2). The Ebl1 was for picking up the beam signal and could be tuned between 30 and 33.3 Mhz, the Ebl2 worked on a fixed frequency of 38 Mhz.
Here is a nice boxed Fubl 1 set I photographed at Arthur Bauers museum a while back. The EBl 1 is on the left, the slightly larger Ebl 2 on the right:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00582.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00582.jpg" border="0" alt="Photobucket"></a>
The EBl 1 receiver has two pre-set frequecies, either frequency can be selected by the toggle switch on the front of the receiver. Alternatively a small remote control unit could be used to change the channel.
Two antennas were used for the two receivers; a rod antenna or "Bakenstab" to pick up the 30 - 33,3 Mhz beam. This antenna was often placed inside the antenna mast, as was the case in this Ju 88 antenna:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03504.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03504.jpg" border="0" alt="Photobucket"></a>
The antenna rod, inside the mast is connected to the "Antenne Anpass Geraet", AAG1a.
With the Fubl1, an earlier type of AAG was used, the AAG 1:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03506.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03506.jpg" border="0" alt="Photobucket"></a>
The second antenna for the 38 Mhz EBl 2 was dipole antenna, placed under the fuselage of the plane:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=Ebl2antenna.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/Ebl2antenna.jpg" border="0" alt="Photobucket"></a>
The dipole was connected to the received via the "Dipol Anschluss Geraet" DAG 2.
To make things easier for the pilot, Lorenz develop an instrument that could display the information picked up by the receivers. This became the AFN/1, which we already know from the direction finder receiver:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC02843.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC02843.jpg" border="0" alt="Photobucket"></a>
The AFN/1 translated the dots and dashes signal to a left or right deflection of the instrument. When flying in the dash zone, the instrument would point to the right, meaning that the pilot had to steer left to get back towards the centre of the beam. When flying in the dot zone, the instrument would point left. The second dial in the AFN/1 would show the signal strength of the Ebl 1 receiver. This would give a rough measure of the distance to the airport. When the aircraft flow over the approach beacon, the EBl 2 receiver would cause a indicator lamp (seen on the top of the instrument) to light up for a couple of seconds.
The power for the FuBl 1 installation was supplied by the U8 rotary transformer also used for the EZ 2 receiver. The EZ 2 and FuBl 1 "shared" the same power supply, switched between them using the "Schaltkasten" Sk 13 of the FuG 10 installation. At the same time as switching the power supply, the Sk 13 would switch the AFN/1 indicator between the FuBl1 and EZ 2 direction finder:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03509.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03509.jpg" border="0" alt="Photobucket"></a>
The two yellow switches on the left select either "ZFF" or "LFF", the top switch for the Funker, the bottem one for the pilot (the two switches are interlocked so that they can not select two different modes at the same time). "ZFF" stands for "Ziel Funk Feuer" while "LFF" stands for "Lande Funk Feuer", so ZFF selects the direction finder, while LFF selects the blind landing receivers.
In the run up to the second world war, the Germans discovered that they could use the Lorenz beam technology over much larger distances. Provided that you flight high enough (over 6500 meters) and you use a large enough transmitting antenna the beam could be kept narrow enough to be useful at a distance of 500 km! In fact the antennas were rather large (30 m high and 90 meters wide) and were build on rail turntables so that the direction could be varied. This system was known as the "Knickebein" navigation system:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=knick1.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/knick1.jpg" border="0" alt="Photobucket"></a>
The above picture shows a "small" Knickebein antenna (only 16m high and 45 wide....) often used in occupied territories closer to the targets in England.
The "Knickebein" beam could be pointed at a target in England, a second cross beam could indicate the exact position over the target. This became one of the earliest "blind bombing" system of the war.
Drawbacks of the Ebl 1 receiver were that it had only two pre-set frequencies and was rather insensitive. In 1940 a more sensitive and more widely tunable receiver was developed, the EBl 3. It operated on the same 30 - 33.3 Mhz band, but now it was hand tunable over the full range.
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00521.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00521.jpg" border="0" alt="DSC00521"></a>
Still the same size and still using the now outdated cable connectors, the Ebl 3h could be simply plugged in to replace the old Ebl 1. In some aircraft such as the Ju 88 this caused a problem as the old Ebl 1 receiver was mounted on the back of the radio panel, out of reach of the operator. As an expedient solution the Ebl 3 was strapped on top of the EL receiver so that the Funker could operate the frequency controls of the new Ebl 3.
This shortcoming was solved by the introduction of the EBl 3 f, the "f" standing for "fernbedient" or remotely operated. A motorized tuning mechanism was added to the receiver with a remote control for 33 channels. With this Ebl 3 receiver, the Blind landing installation became known as the FuBl 2:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00523.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00523.jpg" border="0" alt="Photobucket"></a>
The above picture shows most components of the FuBl2 installation. Both the EBl 3h and Ebl 3 f are shown, the hand operated version being on the far right of the picture. On the top is the U8 power supply. A smaller "Antenne Anpass Geraet" AAG 1a was introduced (already shown on the picture with the antenna). The exposed dipole antenna (which often got damaged with debris from the runway) was now faired in, sitting flush with the fuselage under a plexiglass cover. The smaller AFN/2 instrument would replace the AFN/1.
Apart from the AFN/2, all that would be visible of the installation in the cockpit would be the remote control unit:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00522.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00522.jpg" border="0" alt="Photobucket"></a>
When a channel is selected, a motor in the receiver turns to the required setting and feeds back the position to the dial in the remote control, giving feedback that the channel corresponds correctly with the selected one.
A final twist to the story comes in 1944, when a simple navigation system for single seater fighter airplanes was required. A rotating beacon called the "Hermes" was introduced. The Ebl 3 f receiver was incorporated in a new aircraft navigation system called the FuG 125 "Hermine". An V3a amplifier with volume control was added (the EBl receivers did not have volume control). Since part of the electronics needed to operate the AFN/2 instrument were located in the EBl2 receiver, a "Zusatzgeraet" ZuG 125 was needed to complete the FuG 125 installation.
To avoid having to use a separate receiver for the approach beacons, the approach beacon frequency was changed to that of the beam transmitters and the distance of these beacons from the airstrip was increased to 20 and 3 km so that a longer, more gradual approach could be taken. This was done to help the relatively inexperience pilots of 1944/45.
The FuG 125 only became operational in a handful of aircraft at the end of the war.
regards,
Funksammler
You can direct a radio signal by using reflectors, these create an interference pattern strengthening the signal in certain directions and weakening them in others. The problem was that they could not get the beam narrow enough using this method
In the 1930's the Lorenz company discovered that by using two relatively wide beams, the overlapping area of the two beams could be used. By modulating the left side with "dots" and the right side with "dashes", a narrow area exists where the dots and dashes are of equal strength and a continuous tone can be heard:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=lorenz.gif" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/lorenz.gif" border="0" alt="Photobucket"></a>
The "beam" operated at 30 to 33.3 Mhz so different airports could use a different frequency. The dots and dashes were modulated at 1150 Hz giving a clearly audible tone for the pilot.
While this system gave the direction of the runway, the signal strength would only give a rough and unreliable indication of distance from the runway, so a second signal was introduced so that the pilot could estimate the correct glidepath towards the runway. Two approach beacons were placed -one 3000 meters, the other 300 meters- from the runway. These approach beacons were directed upwards so they were only picked up when almost directly overhead. The approach beacons operated at 38 Mhz and transmitted a continuous tone modulated at 700 Hz, a much lower tone than that of the beam.
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=lorenza.gif" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/lorenza.gif" border="0" alt="Photobucket"></a>
The pilot would approach the runway using a the beam and reduce his height to 200 meters. When the first approach signal was heard, he would initiate a slow decent, calculated to hit the runway. At the second approach signal the aircraft would ideally be about 20 meters from the ground with the runway hopefully coming into view within seconds for a safe landing.
So to receive these signals, two receivers were needed, one operating at 30 -33,3 Mhz to receive the beam, the other at 38 Mhz to receive the approach signal.
The Luftwaffe adopted this system and called it the "FuBl 1" or Funk Blindlandeanlage 1". It consisted of two receivers, the EBl 1 and EBl 2 (Empfaenger Blindlande 1/2). The Ebl1 was for picking up the beam signal and could be tuned between 30 and 33.3 Mhz, the Ebl2 worked on a fixed frequency of 38 Mhz.
Here is a nice boxed Fubl 1 set I photographed at Arthur Bauers museum a while back. The EBl 1 is on the left, the slightly larger Ebl 2 on the right:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00582.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00582.jpg" border="0" alt="Photobucket"></a>
The EBl 1 receiver has two pre-set frequecies, either frequency can be selected by the toggle switch on the front of the receiver. Alternatively a small remote control unit could be used to change the channel.
Two antennas were used for the two receivers; a rod antenna or "Bakenstab" to pick up the 30 - 33,3 Mhz beam. This antenna was often placed inside the antenna mast, as was the case in this Ju 88 antenna:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03504.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03504.jpg" border="0" alt="Photobucket"></a>
The antenna rod, inside the mast is connected to the "Antenne Anpass Geraet", AAG1a.
With the Fubl1, an earlier type of AAG was used, the AAG 1:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03506.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03506.jpg" border="0" alt="Photobucket"></a>
The second antenna for the 38 Mhz EBl 2 was dipole antenna, placed under the fuselage of the plane:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=Ebl2antenna.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/Ebl2antenna.jpg" border="0" alt="Photobucket"></a>
The dipole was connected to the received via the "Dipol Anschluss Geraet" DAG 2.
To make things easier for the pilot, Lorenz develop an instrument that could display the information picked up by the receivers. This became the AFN/1, which we already know from the direction finder receiver:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC02843.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC02843.jpg" border="0" alt="Photobucket"></a>
The AFN/1 translated the dots and dashes signal to a left or right deflection of the instrument. When flying in the dash zone, the instrument would point to the right, meaning that the pilot had to steer left to get back towards the centre of the beam. When flying in the dot zone, the instrument would point left. The second dial in the AFN/1 would show the signal strength of the Ebl 1 receiver. This would give a rough measure of the distance to the airport. When the aircraft flow over the approach beacon, the EBl 2 receiver would cause a indicator lamp (seen on the top of the instrument) to light up for a couple of seconds.
The power for the FuBl 1 installation was supplied by the U8 rotary transformer also used for the EZ 2 receiver. The EZ 2 and FuBl 1 "shared" the same power supply, switched between them using the "Schaltkasten" Sk 13 of the FuG 10 installation. At the same time as switching the power supply, the Sk 13 would switch the AFN/1 indicator between the FuBl1 and EZ 2 direction finder:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC03509.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC03509.jpg" border="0" alt="Photobucket"></a>
The two yellow switches on the left select either "ZFF" or "LFF", the top switch for the Funker, the bottem one for the pilot (the two switches are interlocked so that they can not select two different modes at the same time). "ZFF" stands for "Ziel Funk Feuer" while "LFF" stands for "Lande Funk Feuer", so ZFF selects the direction finder, while LFF selects the blind landing receivers.
In the run up to the second world war, the Germans discovered that they could use the Lorenz beam technology over much larger distances. Provided that you flight high enough (over 6500 meters) and you use a large enough transmitting antenna the beam could be kept narrow enough to be useful at a distance of 500 km! In fact the antennas were rather large (30 m high and 90 meters wide) and were build on rail turntables so that the direction could be varied. This system was known as the "Knickebein" navigation system:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=knick1.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/knick1.jpg" border="0" alt="Photobucket"></a>
The above picture shows a "small" Knickebein antenna (only 16m high and 45 wide....) often used in occupied territories closer to the targets in England.
The "Knickebein" beam could be pointed at a target in England, a second cross beam could indicate the exact position over the target. This became one of the earliest "blind bombing" system of the war.
Drawbacks of the Ebl 1 receiver were that it had only two pre-set frequencies and was rather insensitive. In 1940 a more sensitive and more widely tunable receiver was developed, the EBl 3. It operated on the same 30 - 33.3 Mhz band, but now it was hand tunable over the full range.
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00521.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00521.jpg" border="0" alt="DSC00521"></a>
Still the same size and still using the now outdated cable connectors, the Ebl 3h could be simply plugged in to replace the old Ebl 1. In some aircraft such as the Ju 88 this caused a problem as the old Ebl 1 receiver was mounted on the back of the radio panel, out of reach of the operator. As an expedient solution the Ebl 3 was strapped on top of the EL receiver so that the Funker could operate the frequency controls of the new Ebl 3.
This shortcoming was solved by the introduction of the EBl 3 f, the "f" standing for "fernbedient" or remotely operated. A motorized tuning mechanism was added to the receiver with a remote control for 33 channels. With this Ebl 3 receiver, the Blind landing installation became known as the FuBl 2:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00523.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00523.jpg" border="0" alt="Photobucket"></a>
The above picture shows most components of the FuBl2 installation. Both the EBl 3h and Ebl 3 f are shown, the hand operated version being on the far right of the picture. On the top is the U8 power supply. A smaller "Antenne Anpass Geraet" AAG 1a was introduced (already shown on the picture with the antenna). The exposed dipole antenna (which often got damaged with debris from the runway) was now faired in, sitting flush with the fuselage under a plexiglass cover. The smaller AFN/2 instrument would replace the AFN/1.
Apart from the AFN/2, all that would be visible of the installation in the cockpit would be the remote control unit:
<a href="http://s672.photobucket.com/albums/vv86/Funksammler/?action=view&current=DSC00522.jpg" target="_blank"><img src="http://i672.photobucket.com/albums/vv86/Funksammler/DSC00522.jpg" border="0" alt="Photobucket"></a>
When a channel is selected, a motor in the receiver turns to the required setting and feeds back the position to the dial in the remote control, giving feedback that the channel corresponds correctly with the selected one.
A final twist to the story comes in 1944, when a simple navigation system for single seater fighter airplanes was required. A rotating beacon called the "Hermes" was introduced. The Ebl 3 f receiver was incorporated in a new aircraft navigation system called the FuG 125 "Hermine". An V3a amplifier with volume control was added (the EBl receivers did not have volume control). Since part of the electronics needed to operate the AFN/2 instrument were located in the EBl2 receiver, a "Zusatzgeraet" ZuG 125 was needed to complete the FuG 125 installation.
To avoid having to use a separate receiver for the approach beacons, the approach beacon frequency was changed to that of the beam transmitters and the distance of these beacons from the airstrip was increased to 20 and 3 km so that a longer, more gradual approach could be taken. This was done to help the relatively inexperience pilots of 1944/45.
The FuG 125 only became operational in a handful of aircraft at the end of the war.
regards,
Funksammler
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