Re: [Elecraft] [K3] K3 FSK power transients
I'm surprised I can see a difference between the two tones through the flatter filter 8-pole filter. It's just enough to see on the 200W scale of an old (pretty much uncalibrated) Daiwa CN-520. With the 8 pole filter I see 2 watts difference on the N8LP LP-100 wattmeter. However, in AFSK A or DATA A modes for PSK I see as much as 15 watts (0.7 dB) difference (maximum to minimum) as the tone frequency varies from 200 Hz to 2800 Hz in DATA A (FC=1500 Hz) or 1000 Hz to 3500 Hz in AFSK (FC=2210 Hz). 73, ... Joe, W4TV -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Randy Farmer Sent: Sunday, September 27, 2009 7:57 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] [K3] K3 FSK power transients The roofing filter IS offset to put the RTTY tones (Data | Pitch) in the center of the filter. Good to know. That's how I would have done it I were the designer. I'm surprised I can see a difference between the two tones through the flatter filter 8-pole filter. It's just enough to see on the 200W scale of an old (pretty much uncalibrated) Daiwa CN-520. 73... Randy, W8FN __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
Dave - I experience the same issue and Elecraft indicated that the FSK mark/space power fluctuations are caused by the transmit filter's passband ripple and where the transmit signal falls within the filter's passband. I'm using the standard 5 pole 2.7khz filter. They indicated the 8 pole filter should be flatter. 73 Phil NA4M Dave Hachadorian wrote: I'm getting my K3's set up for the CQWW DX RTTY, and notice that there is a significant variation in power output whenever the FSK goes from mark to space or space to mark. One of these K3's is driving a high gain tetrode amp, and the amp's screen current is jumping all over the place. The power transient is only at the time of transition. The steady-state power of the mark and space are equal. I've complained about this before, but it seems to be even worse now. I'm using FW rev 3.30. This amplitude modulation has got to be producing some illegal sidebands. Dave Hachadorian, K6LL Yuma, AZ . __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html -- View this message in context: http://n2.nabble.com/K3-FSK-power-transients-tp3712691p3716185.html Sent from the [K3] mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
Joe Subich, W4TV-4 wrote: With the 8 pole filter I see 2 watts difference on the N8LP LP-100 wattmeter. However, in AFSK A or DATA A modes for PSK I see as much as 15 watts (0.7 dB) difference (maximum to minimum) as the tone frequency varies from 200 Hz to 2800 Hz in DATA A (FC=1500 Hz) or 1000 Hz to 3500 Hz in AFSK (FC=2210 Hz). If the fall-off is only at the edges I wouldn't be unhappy with this. Last time I checked, a few months ago when the power control in data mode was finally made to work properly, I found that the power output was pretty well flat between about 400 to 2400Hz, once the audio level has been adjusted for 4 bars of ALC as instructed. Personally I wouldn't operate with a sound card program outside of that range, anyway. If you are transmitting some sort of wide FSK mode then I suppose you will see differences because the ALC can only keep the power level average. I guess this is where having the option to set TX EQ in data mode could come in useful, though whether the adjustment currently permitted is fine enough to cancel out filter ripple is another matter. I wouldn't have thought any other radio would do any better, though. With many radios you have to keep the drive below the ALC threshold so you are completely at the mercy of the sound card frequency response and the TX filter ripple. - Julian, G4ILO. K2 #392 K3 #222. * G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html -- View this message in context: http://n2.nabble.com/K3-FSK-power-transients-tp3712691p3732143.html Sent from the [K3] mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
Dave - I experience the same issue and Elecraft indicated that the FSK mark/space power fluctuations are caused by the transmit filter's passband ripple and where the transmit signal falls within the filter's passband. I'm using the standard 5 pole 2.7khz filter. They indicated the 8 pole filter should be flatter. 73 Phil NA4M Dave Hachadorian wrote: I'm getting my K3's set up for the CQWW DX RTTY, and notice that there is a significant variation in power output whenever the FSK goes from mark to space or space to mark. One of these K3's is driving a high gain tetrode amp, and the amp's screen current is jumping all over the place. The power transient is only at the time of transition. The steady-state power of the mark and space are equal. I've complained about this before, but it seems to be even worse now. I'm using FW rev 3.30. This amplitude modulation has got to be producing some illegal sidebands. Dave Hachadorian, K6LL Yuma, AZ . __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html -- View this message in context: http://n2.nabble.com/K3-FSK-power-transients-tp3712691p3721951.html Sent from the [K3] mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
I experience the same issue and Elecraft indicated that the FSK mark/space power fluctuations are caused by the transmit filter's passband ripple and where the transmit signal falls within the filter's passband. I'm using the standard 5 pole 2.7khz filter. They indicated the 8 pole filter should be flatter. I'm using a 2.8kHz 8-pole as the main transmit filter and at nominal 100W output I can see a perceptible wobble on the wattmeter as the signal shifts between mark and space. It's hard to believe the ripples in the filter would be so steep that a 170 Hz difference in frequency of the two tones would make much difference. If you use the standard 2125 Hz / 2295 Hz mark/space convention, this would make the signal appear fairly close to the filter's transition band, assuming there's no center frequency offset applied in the transmit path. This amplitude mismatch will introduce an unintentional AM at the baud rate, but it's probably not enough to appreciably broaden the transmitted signal. I don't have access to a spectrum analyzer or I would examine this further. Maybe someone with a well-instrumented bench can have a look and report back. 73... Randy, W8FN __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
If you use the standard 2125 Hz / 2295 Hz mark/space convention, this would make the signal appear fairly close to the filter's transition band, assuming there's no center frequency offset applied in the transmit path. The roofing filter IS offset to put the RTTY tones (Data | Pitch) in the center of the filter. However, since the 5 pole filter has +/- 1 dB of ripple in the passband and the ALC is applied in DSP (not based on power output), it is possible to see 20 or 30 watts difference between the tones. 73, ... Joe, W4TV -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Randy Farmer Sent: Sunday, September 27, 2009 4:33 PM To: Phil NA4M; elecraft@mailman.qth.net Subject: Re: [Elecraft] [K3] K3 FSK power transients I experience the same issue and Elecraft indicated that the FSK mark/space power fluctuations are caused by the transmit filter's passband ripple and where the transmit signal falls within the filter's passband. I'm using the standard 5 pole 2.7khz filter. They indicated the 8 pole filter should be flatter. I'm using a 2.8kHz 8-pole as the main transmit filter and at nominal 100W output I can see a perceptible wobble on the wattmeter as the signal shifts between mark and space. It's hard to believe the ripples in the filter would be so steep that a 170 Hz difference in frequency of the two tones would make much difference. If you use the standard 2125 Hz / 2295 Hz mark/space convention, this would make the signal appear fairly close to the filter's transition band, assuming there's no center frequency offset applied in the transmit path. This amplitude mismatch will introduce an unintentional AM at the baud rate, but it's probably not enough to appreciably broaden the transmitted signal. I don't have access to a spectrum analyzer or I would examine this further. Maybe someone with a well-instrumented bench can have a look and report back. 73... Randy, W8FN __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] K3 FSK power transients
The roofing filter IS offset to put the RTTY tones (Data | Pitch) in the center of the filter. Good to know. That's how I would have done it I were the designer. I'm surprised I can see a difference between the two tones through the flatter filter 8-pole filter. It's just enough to see on the 200W scale of an old (pretty much uncalibrated) Daiwa CN-520. 73... Randy, W8FN __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
