R/T

R/T

Joined: July 21st, 2008, 7:16 pm

March 29th, 2009, 3:57 pm #1


Hi all. Please could someone tell me how the pilots used the R/T? I am wondering because in previous aviation books that I have read, the pilots simply talk over the R/T. However, in both Piece of Cake and First Light it says that they had to hit a transmission switch. Piece of  Cake almost contradicts itself, because later in the book Hornet Squadron recieve a complaint for swearing over 'the tannoy'. But surely, if they had to hit a transmission switch, they can't be accused of swearing or 'chatting' because for each transmission they would have to hit a switch...?

Sorry if this doesn't make sense. Oh, and in the film the BoB-the pilots just simply chat away.

Cheers

Ben
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Joined: August 23rd, 2003, 10:11 pm

March 29th, 2009, 6:48 pm #2

Hi Ben,

Although I don't know the ins and outs of RAF R/T techniques, I do know there are two ways of operating the R/T.

First of all is the R/T switch which needed (and still needs) to be pressed to be able to send your message to another station, be it earthbound or airborne. Usually this switch is located at a ready to reach position. If you don't see the senders hands, you won't see he's operating the switch. This is assuming your microphone is active.

Next, the RAF had switches on their microphones to operate the mic. I believe these were used when an intercom system was on board; bomber stuff.
In the movie Dambusters, you can see the actors clicking this switch on and off constantly.

I'm not sure if this was a possibility in the early years for sending to other stations. It seem to remember it was possible back then to open the R/T switch to transmit (permanently), which really didn't start sending until the microphone switch was operated.
In the heat of the fight, one sometimes forgot to put the microphone switch back to 'off'.

If the R/T switch is very easily accessible, say on the throttle or yoke, it is conceivable someone kept pressing the button after speaking, again in the heat of the fight of course.

So there would be several scenario's were pilots could swear into an open line, without them consciously doing so.

I would like to hear if anyone can shed more light on the transmission switch / microphone switch situation early on in the war.

Cheers, Toine
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Joined: July 21st, 2008, 7:16 pm

March 29th, 2009, 8:10 pm #3

Thanks for the info Toine-that makes a bit of sense, I understand now how they would have 'talked'.
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Joined: November 16th, 2003, 5:40 pm

March 30th, 2009, 6:36 pm #4

I have a mint 1943 4-channel R/T control box that was used in many types like the Spitfire, Mustang, etc. I'm not an expert, and have never used one before but here's my educated guesses on how it works. Here are some pics, quarter is there to show scale:

[/IMG]

Red buttons select OFF or one of four preset frequencies. Solid feel to the button action. Push in to select. Pushing another button in will pop the previous one to the out (deselected) position (like using the radio station presets on an old 70's car stereo).

To the right of the buttons are lights to indicate which button is active (day use). When in the down position (as pictured), the metal slider switch at the top of the windows moves an opaque blue dimmer screen for night use. If you look closely, you can see a letter on each window that matches the push button beside it. At night you wouldn't be able to see the raised letters beside the buttons so the back lit shade would indicate the active freq.

At the bottom of the face there is a large black 3-position toggle switch (T, R and REM.), probably Transmit, Receive, and well, I don't know what REM. means... Moving the slider just above the toggle switch to the down position locks out the REM. selection and spring returns the toggle switch to R. This is probably the normal operation - hold the switch to Transmit, say your message, and it returns to Receive after you release it. With the slider in the up position the switch will stay in any of the three selections. This would probably result in an open mic ('hot mic') on the freq if toggled to 'T'. There is also a light next to the toggle switch which I figure comes on when the unit it transmitting.

[/IMG]


Anybody know what the 'REM.' position is for?







Cheers!
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Joined: February 8th, 2007, 5:19 pm

March 30th, 2009, 6:38 pm #5

REMOTE!
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Joined: November 16th, 2003, 5:40 pm

March 30th, 2009, 6:52 pm #6

I have a mint 1943 4-channel R/T control box that was used in many types like the Spitfire, Mustang, etc. I'm not an expert, and have never used one before but here's my educated guesses on how it works. Here are some pics, quarter is there to show scale:

[/IMG]

Red buttons select OFF or one of four preset frequencies. Solid feel to the button action. Push in to select. Pushing another button in will pop the previous one to the out (deselected) position (like using the radio station presets on an old 70's car stereo).

To the right of the buttons are lights to indicate which button is active (day use). When in the down position (as pictured), the metal slider switch at the top of the windows moves an opaque blue dimmer screen for night use. If you look closely, you can see a letter on each window that matches the push button beside it. At night you wouldn't be able to see the raised letters beside the buttons so the back lit shade would indicate the active freq.

At the bottom of the face there is a large black 3-position toggle switch (T, R and REM.), probably Transmit, Receive, and well, I don't know what REM. means... Moving the slider just above the toggle switch to the down position locks out the REM. selection and spring returns the toggle switch to R. This is probably the normal operation - hold the switch to Transmit, say your message, and it returns to Receive after you release it. With the slider in the up position the switch will stay in any of the three selections. This would probably result in an open mic ('hot mic') on the freq if toggled to 'T'. There is also a light next to the toggle switch which I figure comes on when the unit it transmitting.

[/IMG]


Anybody know what the 'REM.' position is for?







Cheers!
Here's the unit installed in a Mustang cockpit (right side wall):

[/IMG]

Spitfire cockpit diagram (top left):

[/IMG]


I believe the earlier TR9 radios had a flip switch in the cockpit that had to be placed in one position to transmit and another to receive, so I'm sure it was possible to forget and leave it in the transmit position.

Cheers!
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Joined: November 16th, 2003, 5:40 pm

March 30th, 2009, 6:54 pm #7

REMOTE!
What purpose did that serve? Anything to do with Huff Duff?

Cheers!
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Joined: February 28th, 2004, 3:00 pm

March 30th, 2009, 7:05 pm #8

Here's the unit installed in a Mustang cockpit (right side wall):

[/IMG]

Spitfire cockpit diagram (top left):

[/IMG]


I believe the earlier TR9 radios had a flip switch in the cockpit that had to be placed in one position to transmit and another to receive, so I'm sure it was possible to forget and leave it in the transmit position.

Cheers!
The control box you featured Joel was the type used on many single seat aircraft where the pilot might need to keep hands free. It was also used on the TR1196 radio sets as originally fitted to the Dambuster aircraft in place of the combined TR1154/55 set. The TR1196 was then replaced by the TR1143. Im not a radio expert, but I believe it allowed for an open channel so that crews could direct and advise on attacks in a 'hands free' mode.

A nice clear description and photos Joel, many thanks.
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Joined: September 7th, 2008, 5:53 am

March 30th, 2009, 7:19 pm #9

I wrote out a long answer to this but it vapourised!

Anyway, for a bomber pilot....there is a three position switch on left (right for copilot) top of yoke. push it forward, it stays there. This is intercom talking position. Middle position it is null so no intercom talking or radio talking. Pull it aft against a spring and now you are talking on the radio.

Sunderland had this. Concorde had this. H-P products postwar had this. Quite nice to use too.

Leave it on intercom, somebody will say "your bacon is done" because the static resembles the sound of frying bacon....so you will promptly flip it back to the null.

Fighters only had 5 or 6 freqs that could be used at a time. The box photo just posted is teo select the freq desired. Usually termed button this or button that in the US although Chris could elaborate. The crystals could be changed out to suit the mission. Other units might have completely different crystals except for the common guard emergency freq.

The mic switch on the oxy mask merely selcts or deselects that mic. The REAL mic switch has two functions. One is to connect the mic to the radio and the other is to cause the radio to transmit. Therefore, it must have two independent sets of contacts actuated by a common throw. This is done by the yoke/stick switch.

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Joined: September 7th, 2008, 5:53 am

March 30th, 2009, 7:23 pm #10

Here's the unit installed in a Mustang cockpit (right side wall):

[/IMG]

Spitfire cockpit diagram (top left):

[/IMG]


I believe the earlier TR9 radios had a flip switch in the cockpit that had to be placed in one position to transmit and another to receive, so I'm sure it was possible to forget and leave it in the transmit position.

Cheers!
It is always in receive. The REAL mic switch I referred to in my other post forces the movement of a relay switch which unpowers the reciever and powers the transmitter. The radio can only receive or transmit at any given time. To do both would blow it up as the tranmitter's power would fry the receiver in a nanosecond.
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