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Re: Offset dish focal point
Mansueto Grech <mansueto.grech@...>
Hay Doug. Thanks for the reply and info. Very helpful indeed. 73's Mans 9h1gb
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Re: Offset dish focal point
Mansueto Grech <mansueto.grech@...>
toggle quoted messageShow quoted text
On 12 Dec 2016 14:21, "Doug Parker doug.parker@... [ukmicrowaves]" < ukmicrowaves@...> wrote:
Hi,
Try
Or
73s Doug
Hi all, Does anyone have the formula/workings to find the focal point of offset dishes. The one I found was for prime focus. Focal length = F Depth = c Diameter = D f = ( D * D ) / ( 16 * c )
Thank you in advance 73's Mans 9h1gb
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Re: 1296.328MHz MSK144 Test Transmission
Mark
toggle quoted messageShow quoted text
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 13:33
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission It might be worth raising the Ftol setting. You are set to 50Hz, and the tone measured by your decoder software is showing as 1450, so right on the edge of that Ftol setting I've just checked my frequency, and its currently 5 +/-1 Hz low The source is one of those little 'Micro Crystal' Swiss OCXOs that were mentioned here a while ago. I assume it's still bedding in, as the frequency has changed by about 10 to 15Hz since I started this morning - once it had had enough time to warm up. On 12 December 2016 at 13:25, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote:
Andy I received two transmissions from you at 12.51, with signals at -4 and -5dB. Other than that there is nothing – hardly surprising as you are beaming north ! John G4ZTR, in darkest Essex, JO01KW. I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
GORDONJ REASON <gordonj.reason@...>
Locs , have never moved me , never had a maidenhead map ...... easings and northings I can handle , to a point but only if you have a map ????? I do wish people would simply give real locations more ............ Merry Christmus to all microwavers !!!!!
toggle quoted messageShow quoted text
On 12 December 2016 at 13:00 "Andy Talbot andy.g4jnt@... [ukmicrowaves]" <ukmicrowaves@...> wrote:
Really, Gordon.... Don't you know your LOCs like the back of your hand :-)
Lat 50.909635N Long 1.291497W Or if you want to know a town / city
Hedge End, near Southampton, S Coast (of the UK, that is)
Andy G4JNT (QTHR)
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Re: 1296.328MHz MSK144 Test Transmission
Andy G4JNT
It might be worth raising the Ftol setting. You are set to 50Hz, and the tone measured by your decoder software is showing as 1450, so right on the edge of that Ftol setting
I've just checked my frequency, and its currently 5 +/-1 Hz low
The source is one of those little 'Micro Crystal' Swiss OCXOs that were mentioned here a while ago. I assume it's still bedding in, as the frequency has changed by about 10 to 15Hz since I started this morning - once it had had enough time to warm up.
'jnt
On 12 December 2016 at 13:25, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote:
Andy I received two transmissions from you at 12.51, with signals at -4 and -5dB. Other than that there is nothing – hardly surprising as you are beaming north ! John G4ZTR, in darkest Essex, JO01KW. I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Mark
toggle quoted messageShow quoted text
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 12:59
To: ukmicrowaves@...
Subject: RE: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission Andy I received two transmissions from you at 12.51, with signals at -4 and -5dB. Other than that there is nothing – hardly surprising as you are beaming north ! John G4ZTR, in darkest Essex, JO01KW. I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: Offset dish focal point
toggle quoted messageShow quoted text
On 12 Dec 2016, at 12:09, Mansueto Grech mansueto.grech@... [ukmicrowaves] < ukmicrowaves@...> wrote:
Hi all, Does anyone have the formula/workings to find the focal point of offset dishes. The one I found was for prime focus. Focal length = F Depth = c Diameter = D f = ( D * D ) / ( 16 * c )
Thank you in advance 73's Mans 9h1gb
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Re: 1296.328MHz MSK144 Test Transmission
Andy G4JNT
Interesting. Only thing I can think of that might give the sloping lines is that SpecJT, dating from the old suite, uses 11025Hz sampling rate, so there could be some interaction going on. Perhaps...
Andy 'jnt
(all in line images and old text trimmed)
On 12 December 2016 at 12:17, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote:
Quite strong and clearly audible at times here now, still looks like this though J:
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Re: 1296.328MHz MSK144 Test Transmission [1 Attachment]
Andy G4JNT
Really, Gordon.... Don't you know your LOCs like the back of your hand :-)
Lat 50.909635N Long 1.291497W Or if you want to know a town / city
Hedge End, near Southampton, S Coast (of the UK, that is)
Andy G4JNT (QTHR)
On 12 December 2016 at 12:55, GORDONJ REASON gordonj.reason@... [ukmicrowaves] <ukmicrowaves@...> wrote:
[Attachment(s) from GORDONJ REASON included below]
Can we get back to basic's .... Where is IO 90 +++++++++ , in reality ? On 12 December 2016 at 10:48 "'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves]" <ukmicrowaves@...> wrote:
I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Andy I received two transmissions from you at 12.51, with signals at -4 and -5dB. Other than that there is nothing – hardly surprising as you are beaming north ! John G4ZTR, in darkest Essex, JO01KW.
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: Monday, December 12, 2016 09:57
To: ukmicrowaves@...
Subject: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
GORDONJ REASON <gordonj.reason@...>
Can we get back to basic's .... Where is IO 90 +++++++++ , in reality ?
toggle quoted messageShow quoted text
On 12 December 2016 at 10:48 "'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves]" <ukmicrowaves@...> wrote:
I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 10:30
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Andy, Almost continual, strong, reflections. No decodes, however. I'm off out shortly, so unable to try again until later this afternoon. WSJT1.7 RC2
73 de Sam, G4DDK
Sent tomorrow from my time machine
On 12 Dec 2016, at 12:33, Andy Talbot andy.g4jnt@... [ukmicrowaves] < ukmicrowaves@...> wrote:
Here are two audio files. One is recorded from the Tx drive audio generated by the WSJT-X software The other is my transmitted beacon signal, demodulated via the SDR-IQ . The file names show which is which:
Play back the audio into WSJT-X to prove your decoder works with a correctly tuned signals. Use an audio spectrum analyser to see what it looks like
Andy G4JNT
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Re: 1296.328MHz MSK144 Test Transmission
Andy G4JNT
Here are two audio files. One is recorded from the Tx drive audio generated by the WSJT-X software The other is my transmitted beacon signal, demodulated via the SDR-IQ . The file names show which is which:
Play back the audio into WSJT-X to prove your decoder works with a correctly tuned signals. Use an audio spectrum analyser to see what it looks like
Andy G4JNT
On 12 December 2016 at 11:41, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote:
I’m only using SpecJT as a means of generating a waterfall; I am monitoring using WSJT-X v1.7.0-devel r7005 Have you got an audio file I can use to test the decoder? Mark On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !) On 12 December 2016 at 10:48, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Mark
Quite strong and clearly audible at times here now, still looks like this though J:
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 12:12
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission Excellent stuff. Still only a few faint AS smears so far here Andy, just raised the antenna bit, still monitoring Neil G4DBN ... and apart from ultra strong local copy, the first proof this PIC based DDS and Direct Upconverter approach works I'll put an audio file out shortly... On 12 December 2016 at 11:44, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: And finally….. I suspect that is your signal just full of AS:
On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !) On 12 December 2016 at 10:48, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Excellent stuff. Still only a few faint AS smears so far here
Andy, just raised the antenna bit, still monitoring
Neil G4DBN
Congrats!!
... and apart from ultra strong local copy, the first
proof this PIC based DDS and Direct Upconverter approach
works
I'll put an audio file out shortly...
Andy G4JKNT
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Mansueto Grech <mansueto.grech@...>
Hi all, Does anyone have the formula/workings to find the focal point of offset dishes. The one I found was for prime focus. Focal length = F Depth = c Diameter = D f = ( D * D ) / ( 16 * c )
Thank you in advance 73's Mans 9h1gb
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Re: 1296.328MHz MSK144 Test Transmission
Andy G4JNT
Congrats!!
... and apart from ultra strong local copy, the first proof this PIC based DDS and Direct Upconverter approach works
I'll put an audio file out shortly...
Andy G4JKNT
On 12 December 2016 at 11:44, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote:
And finally….. I suspect that is your signal just full of AS:
On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !) On 12 December 2016 at 10:48, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Mark
And finally….. I suspect that is your signal just full of AS:
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 11:15
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !) On 12 December 2016 at 10:48, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Mark
I’m only using SpecJT as a means of generating a waterfall; I am monitoring using WSJT-X v1.7.0-devel r7005 Have you got an audio file I can use to test the decoder? Mark
From: ukmicrowaves@... [mailto:ukmicrowaves@...]
Sent: 12 December 2016 11:15
To: ukmicrowaves@...
Subject: Re: [ukmicrowaves] 1296.328MHz MSK144 Test Transmission On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !) On 12 December 2016 at 10:48, 'Mark, G0MGX' mark.g0mgx@... [ukmicrowaves] <ukmicrowaves@...> wrote: I’m seeing something that could be MSK144 in the waterfall, but I can’t decode anything using WSJT-X. Not convinced that the time sync is correct. Is this what it should look like? Seem to be 5s on 5s off…. Mark G0MGX
Nothing so far, I'll leave it monitoring Neil G4DBN I'm transmitting an MSK144 test transmission using the direct upconversion approach described yesterday. 5 seconds on 5 seconds off. (*) Centre frequency 1296.328MHz (SSB tuning ref 1296.3265) Currently beaming north from IO90IV58. Which is into various aircraft holding patterns up and down the country. Antenna is a QLoop with probably something like 15 - 20 degree beamwidth (and a lot of sidelobes) The transmission decodes locally, but I haven't been able to get it weak enough to see what the threshold is - that's an experiment for another day when the source is boxed up properly and 100dB or more of screening becomes feasible. So don't know just how well my modulated waveform generation is. The spectrum looks right; when down converted, the same as the WSJT generated audio waveform, and it decodes OK so if it looks like and quacks like.... Please send requests to turn the beam as and when . I'll announce here when there are any changes. (*) The on period is synchronised manually with the 10s UTC marker, but MSK144 is not a true time synced mode so timing isn't at all critical - the code generator just free runs with a crystal timing it..
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Re: 1296.328MHz MSK144 Test Transmission
Andy G4JNT
toggle quoted messageShow quoted text
On 12 December 2016 at 11:13, Andy Talbot <andy.g4jnt@...> wrote: That doesn't look convincing, Neil. You seem to be using a very old SpecJT view? It's not centred, and there are too many discrete spectral lines that are sloping. That looks more like QRM
The tone should be centred on 1500Hz and roll off gently towards the edges of the SSB filter . This is what the signal looks like in a 5kHz bandwidth (when very strong !)
Andy
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