PSK newbie with a question
I'm just starting in this mode. I am using a 706G with a MFJ-1275 and an older Dell desktop. I know this is a low power mode so I'm trying to understand how to set up my adjustments on the 706. I can go into a menu and set the rf output on a scale of 1 to 10. My head tells me to set the output to 2 or 3 and then set the mic gain so there is little or none alc deflection on the 706. Is this right?
Ok, I'm amending this with a 2nd question. My MFJ is hooked up using audio cables to sound card and the mic cable with the attached modular plug goes to the rear mic jack on rig. It all seems to work as it should (not withstanding my first ? above) but the red transmit led on the MFJ is lit all the time even though everything is clearly in the rx mode. I set all the internal jumpers on the MFJ as per their chart for the Icom radios. Any ideas?
Last edited by N4EYZ; 11-30-2011 at 04:55 PM.
I'm not up on Icom models, but on the Yaesu models you have to set them for DIG or DATA versus USB mode to get the TX to work with the rear port. See your manual for details.
As far as the power, most tutorials suggest you leave the radio set to full power, and starting with the TX audio set to zero, transmit (many software packages have a tune button which works better) and adjust the audio to get 25-30% of the rated output at the peaks. You might find a tutorial specific to your radio that recommends different methods or adjustments according to the ALC indicator.
Obviously you want to use a dummy load until you get things sorted out and keep your transmissions very brief until things are set correctly. Digital modes are very hard on the radio when you try to crank the power too high -- which is why you start at zero audio.
I'm not familiar with the equipment you are using but the previous posting explained the principles. Do you have an ACC1 socket, if you have I suggest you use that. I also suggest you have an SWR/power meter to keep a check on what power you are using.
The RF out on the rig should be at maximum and you adjust so that there is no ALC visible, none at all. The power to your antenna is adjusted using the VOL and wave sliders on the computer. The mode requires low power, 15 to 25 watts on the meter. Something to consider, a PSK idle signal is twice the average power, so if you are showing 25 watts on a power meter you will actually be transmitting 50 watts. Keep the power at 25% or 33% of the tranceiver rated PEP.
I use a simple opto coupler so the signal from ACC1 connects to the opto coupler and the connections to the computer are using the Line In and Line out and the 9 pin connection on the PC
Ok you guys have answered my biggest question. I had been told to use the max rf setting (in the 706 menu) and reduce the drive by the audio input but I thought I could reduce output the same way (menu setting). But I will defer to you guys with far more knowledge and experience than I. And yes I do have an ACC socket on the rear of the 706 and plan to use the audio line out from that line. Currently using the external speaker line to the mfj and have an extension spkr from that, but I realize the advantage of the fixed audio from the radio. The acc socket also has a modulator input pin, is this where the audio out from the sound card (thru the MFJ) would go? The MFJ is configured for my Icom and there is a modular plug(cable) that goes from the MFJ to the rig and I can plug my mic into the MFJ so there is no connecting or disconnecting of the mic. Thanks again for the willingness to answer questions from an old fart!
I'm not familiar with the MFJ unit, but I hope you do have a way of using the ACC plug for the audio from the radio. This all sounds similar to the way my older RigBlaster hooks up - the audio from the radio comes off the ACC plug, but the transmit audio and PTT are fed in through the mike connector on my IC746. I use a RigBlaster Plug n' Play on the IC7000, which uses the ACC plug for everything. The downside of this is that the mike for the IC7000 stays hot and I need to remember to disconnect it when I work digi modes.
Yes, definitely set the power output to 100% and use the audio level control on the computer and the mic gain control on the radio to reduce the power until there is very little or no ALC showing on the meter. If adjusted correctly, you should still see about 30-50% power displayed when transmitting.
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<<< newb question: If I understand correctly, the concern about managing ALC level is related to the use of an amplifier. Is that correct, or is ALC management as described imortant to manage always?
Still important to manage your rig's internal alc for PSK31, the advice to run your transceiver at max rf setting and adjust your audio input level to about 30% output (or less) is correct. A few watts output more or less will not matter much but showing any ALC on most radios will degrade your IMD when using BPSKx modes.
Originally Posted by KC9TZT