RTTY

[Relax]

After last years appalling and wind swept cruise on the west coast I have decided to expand my sources of weather data on board.

Firstly I have invested in a Navtex - the PC type (Nasa) - and this currently appears to be connecting OK although I'm not getting a signal where I am (several miles inland).

My second option was RTTY - radio teletype. I had a shortwave receiver anyway (a Roberts) and now have it connected to the lappy and feeding through the sound card to a SEATTY programe. This all appears to be functioning OK - but its not receiving anything. I do have a long extending wire aerial and its outside - is this enough?

Any comms experts out there with experience in this department?

How sensitive does the antenna need to be?

Is there something I need to do to get the data out? It appears to function - responds to changes in input but nothing comes out.

Is it just poor reception where I am?

 

[whipper_snapper]

I am using seatty for RTTY and can receive German transmissions here in Nairobi!! So I suspect you have a setting wrong. Are you getting sound into the PC ? ie can you see the display change as you change volume or frequency ? Can you hear the appropriate warbling noise from the radio ? What radio frequency are you using ?

 

[Relax]

Hi,

I am getting a feed through the sound card into the lappy - you can see the response through the programme when you disconnect or adjust the frequency.

What I'm not getting is any 'warbling' - I have tried all programme 1 frequencies including the 10100.9 kHz. Reception of other shortwave programmes (spoken) is OK.

I have a lot of difficulty in making any sense of the 'help' bit (which you could predict really) - its written (to me anyway) in impenetrable geekspeak.

 

[Pye_End]

When you say a Roberts receiver do you mean SSB or with a BFO?

I have used a Roberts reciever in the past to get Navtex, reasonably successfully, but did find that the 'tuning' via the BFO was pretty critical. It is possible that more modern software is better so may not be such an issue.

What frequencies are you using and what times?

 

[Bilgediver]

I don t know which Roberts radio you have however if it has a bfo you might need to learn to fiddle...You should here the result through the speaker.

Try frequencies 4608 and 8038 which are weatherfax frequencies. also around 516 is navtex which I believe Seatty resolves.

I will have to run seatty to see what problems it might be giving but yes it could be you have some settings wrong

John

 

[Relax]

Its an ordinary multiband reciever - and the tuning is digital so I do not have the fine adjustment you have with a dedicated set - it can only discriminate down to 1 kHz.

Maybe this is not good enough?

I have tried all the programme 1 frequencies - but only in the evening - does this make a big difference?

 

[whipper_snapper]

1KHz should be enough; you can compensate in seatty, I will have a play to confirm that. But if you can't hear the station warbling away then you have no chance of decoding it. I will check the frequencies that come through most strongly, I know they were booming in the UK, but are still very strong here. There are a range of frequencies, you should be able to hear at least one at almost any time. It is pretty much continuous broadcast from Hamburg.

 

[Relax]

I'll have another fiddle tonight with the headphones on and see what I can get.

After last years experience I wanted as many means to forecasting as I could and RTTY seems a pretty reasonable option - though perhaps not as good as GRIB files by email - but this was a much bigger step.

As you may have guessed I'm a bit of a technoprole.

 

[Bilgediver]

A good place to start is navtex which is on a frequency of 518 . You might have to tune down to 516 to peak it and for navtex set your Seatty to mode amtor fec.

You might have to fiddle the reverse normal if you are on the wrong side band.

For RTTY nav warnings you need to set to RTTY at 45 baud and 170 hz the window at the bottom should show 1473 hz and 170 hz.

You should hear the signal from the speaker. a sort of chirruping sound.

 

[Deleted member 478]

Download this WEATHER FAX SCHEDULE (once it's open, you can then save it), read para 3 on page 6 and note the difference between the carrier frequency and the published frequency.

Some where in the schedule, you'll find the correct frequencies for the different RTTY broadcasters and the times that they are broadcast.

Hope this helps.

 

[saltwater_gypsy]

Here is a useful site for all the worldwide SSB schedules plus a lot more.
http://www.bonito.net

then click technical services at the right hand side----bingo!

 

[Relax]

A lot of stuff here!!

Will need a lot of sifting to get what I need but on the first pass the frequencies shown for DWD Hamburg are different to those I am tuning to - this might be the problem?

I lifted the ones I am using from Frank Singleton's page.

 

[Bilgediver]

Please note Stingos frequencies were mostly FAx which might be a problem with Seatty......below are som RTTY frequencies to play with.
Tables

As Stingo has said there might be a difference between the frequency in the table and the one indicated on your radio.

This is because in commercial practice they give the true frequency of the signal which is the radio frequency plus the radio frequency however hams and others just give the carrier frequency. The difference is around 1500 HZ. up or down dependng which sideband you are using.

find a strony RTTY signal and play. 10.100 is strong here today but needs to be tuned at 10.0985.

You will also find RTTY in the ham band at around 14.070 however remember hams like to be different and use 50 baud.

If you can find a strong signal you will soon find how to do this and yes you will be able to tun the same signal on forward and reverse however you will note the frequency is slightly different and what you are doing is tuning either the upper or lower side band and seatty will resolve either if the settings are right however get in the habit of using upper side band USB.

 

[Danny]

[ QUOTE ]
Its an ordinary multiband reciever.....

[/ QUOTE ]You've not actually said which one. Does it have a function or switch called SSB (or possibly USB / LSB) or CW or BFO? You'll need this to produce an audible output for the PC sound card to use.

 

[Relax]

Currently I have the headphone socket of the radio plugged into the microphone switch of the PC and the sound card is certainly picking up something.

I have no idea about a switch - I will look though - there is a switch of some kind adjacent the phono socket --- oops? /forums/images/graemlins/tongue.gif

 

[Oldhand]

[ QUOTE ]
[ QUOTE ]
Its an ordinary multiband reciever.....

[/ QUOTE ]You've not actually said which one. Does it have a function or switch called SSB (or possibly USB / LSB) or CW or BFO? You'll need this to produce an audible output for the PC sound card to use.

[/ QUOTE ]

Your receiver needs to be set to USB (Upper Side Band) mode, if it doesn't have such a facility you will have great difficulty decoding RTTY or Navtex.

 

[Danny]

It's a long time since I delved into this sort of thing but I think that RTTY is normally delivered with a modulation technique called "frequency shift keying" (FSK). To make this properly 'audible' the receiver needs to have an oscillator providing another frequency close to the one(s) used by the transmitter. Together they produce a "beat" frequency, or heterodyne, in the audible range.

This local oscillator in the receiver is called a BFO (beat frequency oscillator) or a carrier insertion oscillator if the receiver has SSB capabilities.

A receiver designed for normal AM transmissions from broadcast radio stations might not have this facility. It would always be available in a "communications receiver".

If you know the model of the radio I'm sure someone here will be able to reassure you (or not) as to whether the radio has the required feature.

 

[Relax]

Its........... a Roberts R876.

and no I can't see any BFO button - only the 'Mono/sterio' one

I did try the 4.584 Mhz frequency tonight and its recieving something ......warbling away quite strongly. The 10.100 frequency is there but much weaker.

Does this mean I need to spend more money on more kit??

 

[Danny]

[ QUOTE ]
Its........... a Roberts R876.

and no I can't see any BFO button - only the 'Mono/sterio' one

I did try the 4.584 Mhz frequency tonight and its recieving something ......warbling away quite strongly. The 10.100 frequency is there but much weaker.

Does this mean I need to spend more money on more kit??

[/ QUOTE ]Sorry to be the bearer of bad news but the answer is: "yes."

I've had a look at the user manual and it would appear that this receiver will only receive AM and FM broadcasts. It has no facility for SSB or CW so therefore it won't provide a controllable audio output from an RTTY signal.

Hopefully someone else can review this and confirm my conclusion (or not, of course).

 

[Bilgediver]

As far as I can see this radio R876 is not suitable. Roberts do a similar radio which does have SSB . See the 861.

Another small radio that does the job is the old Sony IC 7600 also the sony SW 55 which I use but these do swallow up dry batteries and so need to run from an exterior supply.

There are a few cheap SSB receivers like the NASA but I have no experience of them.


John