Propaganda found after sinking!

[andylegate]

We found this allied propagranda after sinking a merchant!

http://img.photobucket.com/albums/v160/andylegate/receivers.jpg http://img.photobucket.com/albums/v160/andylegate/torpedoyester.jpg

[Brag]

The smiling faces show that German torpedoes bring happiness to merchie crews:rotfl: :rotfl: :rotfl: .

[SteamWake]

Hrm.... :hmm:

How on earth can a broadcast RECIEVER help the enemy locate you ?

Unless your turning them up like a ghetto blaster.

Maybe they meant transmitters ?

[SleazeyWombat]

Nope, it really was the receivers.

The old tube receivers, and the tuning circuits they used (super-heterodyne) actually had a radio frequency oscillator as part of the circuitry. It helped the sensitivity and selectivity of the receiver.

However, a sufficiently sensitive U-boat radio receiver, tuned to the target ship's superhet intermediate frequency (IF), could pick up the superhet's inadvertent transmissions. A skilled U-boat radio operator could then home in on the merchant ship.

The IF frequency was constant; it didn't depend on what station the sailors were currently listening to. I do not know if all brands and models of superhet receivers used the same IF. The IF used was an engineering decision, not an FCC standard, so it probably differed from brand to brand, or model to model. Obviously, this made the U-boat operator's task of searching for stray IF emissions somewhat easier, since as long as a radio was on, it was transmitting on the same parasitic IF.

Update: The IF chosen was somewhat standardized within a country or continent. The U.S.A. and Australia(!) used the same IF's, which varied over the years as circuitry improved. European manufacturers had a different set of IFs that they used. I haven't found any time line that shows when different IFs were active. Nowadays, for broadcast receivers in the US, it's 455kHz. Ham and military radios use different IFs for different frequency bands.

Later, special receivers were built for use on the high seas, that were either shielded, or used a different tuning method to avoid emitting a parasitic radio signal like the superhets.

[BulSoldier]

Well if you send signals you can be found by triangulating (not sure about spelling) though if you only listen there cant be a way to find anyone this way (may be secret german wonder weapon ????):hmm:

[bookworm_020]

THey guy that's been rescued looks like Tony Bullimore!:huh: Thow him back into the water, he's a Jonah!



http://en.wikipedia.org/wiki/Tony_Bullimore

[andylegate]

Good explination SleazeyWombat.


In order to transmit radio waves any significate amount of distance, you need two things:
Power and High Frequency.

In order to send out a radio signal (such as reporting a contact to BdU, etc), you have to take the information (IE Voice / telegraph) and modulate it with another frequency that is higher than the information known as a carrier wave(our voices go from about 20 Hz to 14 Khz and a telegraph is only so many pulses per second). So a transmitter will have an oscillator and a mixer, the mixer mixing the two together. This is nomally called modulation, and you can modulate something either in Amplitude (AM radio) or in Frequency (FM radio).
Once you have your modulated signal, you can now amplify it to give it power and out the antenna it goes (I realize this is a GREATLY simplification of the process, but enough to make one understand what is happening).
You will have a receiver so that you can hear what is being sent back. The way a receiver works is backwards from the the transmitter: receive and amplify the signal. Mix the signal with another signal that is 180 degrees out of phase with the incomming signal. This basically strips the carrier away and leaves you with the information (IE Voice or telegraph) which is then sent to amplifiers and speakers.

Now. Even if you don't transmit anything, if your radio set is left on, you have two problems:
Transmitter's oscillator and the Receiver's oscillator. They are still oscillating and generating energy that can be detected.
Radio silence is just that: silence. Means you must power down your radio equipment.
Any decent detector can see these oscillators, and a radio operator can be trained to sit there and adjust a detector's tuning capabilities to detect any radio energy.

Unless, of course your radio equipment is shielded! :arrgh!:

The radar systems I worked on in the Navy, when we went to Radar Silence, it simply meant to redirect the radars RF energy into what we called a Dummy Load (this was a device that absorbed the RF energy instead of letting it out the antenna). All our cabinets had RF shielding around the cabinet doors to keep the RF from leaking out (this is a good thing. Constant exposure to RF energy can lead to ....... health problems!), and can help keep any electronic "ears" from hearing your ship.
Why not just shut our radars down?
Because of warm up time. My radar system, the AN/SPS-48C radar takes up to 15 minutes to be ready to transmit when powered up. It didn't mater if I had just shut it down 5 seconds before. The interlocks on on timing relays that have to time out to 15 minutes before you can bring the transmitter up.
(actually, that's a mis-statement there. The AN/SPS-48C has 4 parts to the transmitter: first stage, second stage, Driver stage, and Final stage. First stage would be ready in 5 minutes, but you'll only see out to 70 NM with it. Second stage would be ready in 10 minutes, but again, you'll not see to far with just it and First stage going. The last two stages, Driver and Final time out at 15 minutes, and you can see over 220 NM with them.).

Whoops.....looks like I'm prattling on again! :ping:

[bigboywooly]

Interesting thread
You just keep learning new stuff on here

[Jimbuna]

THey guy that's been rescued looks like Tony Bullimore!:huh: Thow him back into the water, he's a Jonah!



http://en.wikipedia.org/wiki/Tony_Bullimore

LMAO :rotfl: