Menu
▾
▴
Re: [wsjt-devel] FT4 & FT8 and ALC
|
From: David T. <dt...@ca...> - 2019-06-13 23:50:18
|
All, I've seen a lot of theoretical discussion re: signal purity and many conflicting opinions on ALC and lots of assertions that "My signal is clean!!!". Let's put our money where out mouths are. Let's set up a time and frequency where we can each transmit at various signal levels and have the other group members capture screenshots of their SNR and signal on their waterfall. A frank exchange of actual data would help everyone. I see too many 2nd and 3rd harmonics of signals to believe that ALC doesn't matter. DSP gurus out there - can we have a version of WSJT-X that _only_ responds to 2nd and higher harmonics please??? I try to help out people that are generating bad signals, but I can't always decode the fundamental to see who they are. I don't have the DSP chops to pull that off, although I suspect changing the tone spacing (and filter bandwidth) would be a first step. Here's a 7th harmonic, just for proof (I made sure it wasn't in my receiver): [cid:688BB27E-17B0-40D1-B664-FCFCDB4E05F3] -- David Tiller Sr. Architect/Lead Consultant | CapTech dt...@ca...<mailto:dt...@ca...> On Jun 13, 2019, at 2:55 PM, Topher Petty <ai...@gm...<mailto:ai...@gm...>> wrote: I've never seen the need for an ALC meter in digital modes... Put the power output on the rig to max, hit the tune button in the app, turn the audio drive up until you just barely reach your desired power output on the watt meter, click the tune button again to turn the signal off, and start making contacts. The only meter I've ever needed is my Watt meter. For what it's worth, at 100 Watts out on my IC-718, the ALC meter shows zero. It's only when I overdrive the audio at 100 watts out that ALC starts to show. Your rig may behave differently. Tune your power output with your Watt meter, and stop turning up the audio when you JUST BARELY reach your desired power output, and you won't be overmodulating your digital signal. Just my two cents. 73 de AI8W, Chris On Thu, Jun 13, 2019 at 2:28 PM Maurizio Brameri <mau...@fa...<mailto:mau...@fa...>> wrote: Not completely true. I am using a 7610 with power set to 100% and with ALC to 0 I have 95 W out. I have done more than 150 countries in 9 months with ALC set to 0 and 95 W. ;) Bye, Maurizio Il 13/06/2019 19:34, Ron WV4P ha scritto: Amazing how people can believe that all radios handle ALC the same. Again.. Contrary to people's Opinions, don't be afraid of ALC, Especially if you have an IC 7300 or 7610, if you manage to get it to zero, have fun not making contacts. About 50% works very well.. Ron On Thu, Jun 13, 2019, 12:11 PM Steven Greer <km...@gm...<mailto:km...@gm...>> wrote: I have to agree with Mike on this one. If you are showing any alc your are over-driving and putting out a crappy signal. I see it all the time. These poorly setup stations with an extra wide signal that no one can operate next to because they are causing distortion that is outside the bandwidth for ft8. I run an OLD radio a Kenwood ts-520 with a home made interface. I can run my rig all the way up to about 120 watts before showing ANY alc and then I back it down to show NONE. This is not SSB Phone so ignore everything about alc when it come to ssb phone operation that you have learned. If you are showing alc your putting out a crappy signal and you should stop. If you don't have a clue what you are doing stop transmitting and find someone to help you that knows something about digital operations. Those who are running crappy signals are just ruining operations for everyone else. Regards, Steven Greer K3SRG OMISS #10630 OMISS 80M Band Coordinator NOTE: This e-mail was made with 100% recycled electrons. No electrons were harmed, No trees were destroyed, No animals were killed, and No political correctness was observed in making or sending this message. On 6/13/19 12:39 PM, Black Michael via wsjt-devel wrote: Nobody is saying that ALC is the cause of the problem. There's lots of things feed into the ALC. It's simply an indication that SOMETHING is over driving the rig when the ALC indicates more then 0dB of attenuation. I think you'll find if you reduce the USB Mod Level you'll find the ALC can be reduced to 0 on the scale and still get 90W out if WSJT-X is at full power and you have 0dB on the Playback device. I've done that on about 5 IC-7300's and they all end up at either 6 or 7 on the USB Mod Level. de Mike W9MDB On Thursday, June 13, 2019, 11:27:43 AM CDT, Roy Gould <roy...@gm...><mailto:roy...@gm...> wrote: For what it's worth, I have a different view of how ALC works. First of all, I don't think that properly implemented ALC causes more than a trivial amount of distortion in the signal. Audio processors in studio sound boards and in commercial radio stations use it routinely. It has the benefit of stabilizing the audio level. The FT8 signal has constant amplitude so ALC does not have to work hard at all. It just sits there maintaining constant transmitter output power. I checked to see what the ALC was doing in my ICOM IC-7300 and saw that it was about 55%, which is perhaps a little too high. So I reduced the Speakers (USB Audio CODEC) from 20% to 15% and the ALC dropped to 45%. I am using the built in soundcard in the IC-7300. I am not having any problems in making contacts and I think that my signal is clean. To prove otherwise would require using laboratory instruments to test the signal... 73, Roy, W7IDM On Thu, Jun 13, 2019 at 8:47 AM Ryan Tourge <rya...@gm...<mailto:rya...@gm...>> wrote: I have used the following method regardless of radio used... Use an external power meter (after the transmitter). Adjust audio gain/drive until the point where power meter stops rising. At this point, the radios ALC meter will start to show some deflection. Back the audio back slightly. The power output will stay about the same and ALC will be "0" on the radio's meter. Make contacts :) On Thu, Jun 13, 2019 at 7:42 AM Black Michael via wsjt-devel <wsj...@li...<mailto:wsj...@li...>> wrote: Only when the manual is correct. Most are wholly inadequate in this respect. Mainly due to not addressing digital modes at all. Even Kenwood's own TS-890S multi-lingual manual doesn't mention this. I just worked with a user yesterday with in IC-7000 and RigBlaster Advantage in the ACC socket and had to have the MIC level set at 1 and we could crank up the RigBlaster TX to get 90W without any ALC action on the rig. If we cranked up the MIC gain and turned down the RigBlaster TX we could get ALC action at 10W (note that the rig was always set at 100W). Any manual that talks about SSB Phone mode needs to be ignored as it has nothing to do with digital operations. My main point is that if you can get 90W without ALC indication you are pretty well guaranteed your signal is as clean as it can get. And I've been able to get 90W/No ALC on 99% of the rigs I've dealt with. de Mike W9MDB On Thursday, June 13, 2019, 01:06:46 AM CDT, Roeland Jansen <roe...@gm...<mailto:roe...@gm...>> wrote: so we agree that we should follow the manuals of the manufacturers? On Wed, Jun 12, 2019 at 4:56 PM Black Michael via wsjt-devel <wsj...@li...<mailto:wsj...@li...>> wrote: I finally got a reply from Kenwood for the TS-990S -- this quite likely applies to all the Kenwood's with the red ALC zone. The bottom of the meter is 0dB ALC. I would maintain once you see the "beings to swing" you back off a bit for no swing. You won't find the PSK31 words in the multi-lingual manual...it's in the English manual (and perhaps the other individual languages). It tells you to set the rig for almost no ALC indication. de Mike W9MDB Regarding the ALC 0dB and +6dB, refer to the picture below. [X] In the TS-990S instruction manual, it is mentioned as follows. --------------------------------------------- In the case of operation in the digital mode such as PSK31 using a PC, you must adjust the audio output level from PC until the ALC meter of the transceiver begins to swing. --------------------------------------------- The level "begins to swing" is not zone max (+6dB) but threshold 0dB. On Thursday, June 6, 2019, 01:09:07 AM CDT, Wolfgang <oe...@gm...<mailto:oe...@gm...>> wrote: There is a common belief that became an internalized misentrepretation: "NO ALC", or even "ALC is bad", this can not be applied to all rigs. On a Kenwood rig the manual says, you should not go (drive) the rig beyond the red bar. For example, the Kenwood TS990 audio input setting to "no ALC" will result in an Power output that goes down to indeterminable value, compared to the Po setting on the front panel knob & meter. So please consult your rigs manual, the designers gave you the right info. 73 de Wolfgang OE1MWW ---------- Amateur radio is the most expensive type of free-of-charge communication! Amateurfunk ist die teuerste Art der kostenlosen Kommunikation! _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel _______________________________________________ wsjt-devel mailing list wsj...@li...<mailto:wsj...@li...> https://lists.sourceforge.net/lists/listinfo/wsjt-devel |
