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HRD 780 v5.24 BPSK Modulation and ALC

Discussion in 'Ham Radio Deluxe - HRD' started by AI4RA, Apr 4, 2017.

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  1. AI4RA

    AI4RA XML Subscriber QRZ Page

    I use an Icom 7200 coupled with a Toshiba laptop, both of which seem to play very well together on digital modes. I use the USB port on the rig plugged into a USB port on the laptop for digimode transmissions.

    I am a quite active PSK operator (mostly PSK31 but use PSK63 and PSK125 also), and have noticed quite a few overdriven PSK signals on the HF bands, some from ops using HRD 780. As most of you probably know, these show up on the waterfall trace as rather ugly sideband streaks on both sides of the main waterfall transmission for a given PSK signal. While I have received many compliments from other PSK operators about putting a clean signal on PSK, I must admit that I simply set up HRD to work on my ICOM 7200 and never paid much attention to the modulation level. After recently having a QSO with a ham who had such modulation problems and got criticized by a volunteer monitor for it, I started thinking about how I can make sure my own signal is consistently good on all bands on which I use PSK, preferably without always having to ask other operators how my signal looks to them.

    I've heard that one should not see any ALC indication on the rig while using PSK (or other digital mode, for that matter), and so when I checked mine, I noted that it showed one or two ticks on it while transmitting. I tried to adjust the USB level on the rig as well as the TX slider bar in HRD, and neither seemed to affect the ALC reading on my rig in any way. What am I missing? Is there some other control on the 7200 or on HRD that I'm not aware of that could be causing this? Or is it normal on these Icoms to see one or two ticks on the ALC reading?

    Any help here is greatly appreciated and this might be helpful to a lot of hams who are inadvertently overdriving their rigs on PSK. I've even seen folks with new IC-7300 rigs who have splashy, overdriven PSK signals.

    Thanks and 73 to all,
    Raf
     
  2. KF2M

    KF2M Ham Member QRZ Page

    Raf I too see a good number of operators who overdrive their radios as well. Tuning your radio for digital isn't rocket science but it is a dance between power settings, and modulation levels between the computer and radio. But to answer your question the speaker output from your laptop is the missing piece. If the laptops speaker output is already overdriven into the radio adjusting the USB Level is not going to help. Think garbage in/garbage out. With the ALC you should not be seeing any ALC registration at all. I tune until I see that there is registration on the ALC then backoff until there is no ALC indication. Also pushing more than 20-25W is not going to help either.
     
  3. AI4RA

    AI4RA XML Subscriber QRZ Page

    KF2M: Yes, you are correct! My computer has two audio outputs it generates: one for the speakers and one audio CODEC for output. For digital software such as HRD, I use the audio CODEC output. What I didn't realize was that the speaker control on the computer controls the output for both the computer speakers AND the audio CODEC output. So adjusting the speaker control on the computer is what did the trick to control the ALC level on the rig. As you said, I adjusted it to get one tick on the ALC, and then backed off slightly to get no ticks showing up on the ALC. It also helps with other digimodes besides PSK, such as JT65.

    That said, perhaps the developers of digimode software could program such that the TX level control also controls the speaker output of the computer. That would make it a bit easier for newbies to put out a good signal. Then again, I am using an older version of HRD, so maybe newer versions of that software are doing that.

    I hope this is helpful to all hams using digital modes. We should all do everything we can to transmit clean signals.

    Thanks and best 73,
    Raf
     

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