From: "Adam Farson" To: Subject: RE: [Icom] SM-20 and PRO Date sent: Fri, 10 Nov 2000 09:53:08 -0800 Send reply to: icom@qth.net From: "Adam Farson" Steve, The use of "low cut-off' is a matter of personal taste and room acoustics. By listening to your own transmitted audio using [MONITOR] and a good pair of headphones, you can determine which sounds best - IN or OUT. OUT probably works best with the [WIDE] Tx occupied-bandwidth setting ([COMP ON/OFF WIDE/MID/NAR] key). Start with the gain control in the base of the mike 1/4 to 1/3 open and the [MIC GAIN] control on the radio at 9 o'clock. Adjust [MIC GAIN] for 40% to 50% deflection on the ALC meter scale on voice peaks. There should be no evidence of flat-topping on the transmit "Spectrum Scope" display (set "Scope during Tx" = ON in SET menu). If using compression, set [COMP] for no more than 5 to 10 dB compression on voice peaks. Best 73, Adam, VA7OJ/AB4OJ http://www.qsl.net/ab4oj/ > -----Original Message----- > From: owner-icom@qth.net [mailto:owner-icom@qth.net]On Behalf Of Steven > Olson Sent: Friday, November 10, 2000 8:46 AM To: icom@qth.net Subject: > [Icom] SM-20 and PRO > > > From: Steven Olson > > Just received an SM-20 which I am using, among other mikes, with the > 756 PRO. Am wondering what most folks do with the "low cutoff" setting: > ON? or OFF? Also the gain settings both on the rig and the base of the > mike. Thanks, > > Steve, W2WX ============================================================================== Date sent: Fri, 10 Nov 2000 13:24:47 -0600 From: "George, W5YR" To: icom@qth.net Subject: Re: [Icom] SM-20 and PRO Send reply to: icom@qth.net From: "George, W5YR" Adam, I need some instruction on the ALC function and metering in the PRO. First, I find virtually no mention of ALC in the manual. Second, on non-voice modes, the ALC indicator goes to the end of the red line. Even with rather low settings of the mic input gain, the ALC indication is much higher than I would expect. I have been setting up the mic gain such that I talk up the power metering to about 50-60 watts on peaks and set the compression for occasional ventures to near 10 db, but mostly around the 5 db level. The ALC runs up to near max with those settings. The r-f output envelope is clean as can be with those settings, with no clipping, etc. BTW, in your comment re the Spectrum Scope in the quotation below, are you looking for the existence of additional sideband frequencies as an indication of overdriving? I have not paid a great deal of attention to the transmit spectrum indications since I usually use the "soft" metering screen while operating. I have found that the spectrum is extremely useful for setting up AM operation where you can clearly see the sidebands. I set the carrier output to 25 watts with the sidebands hitting peaks 6 db down from the carrier and I have been getting outstanding audio quality reports, especially with the GoldLine and W2IHY equalizer. Words of wisdom, I pray, oh guru . . . 72/73, George W5YR - the Yellow Rose of Texas NETXQRP 6 Fairview, TX 30 mi NE Dallas in Collin county QRP-L 1373 Amateur Radio W5YR, in the 55th year and it just keeps getting better! Icom IC-756 PRO #02121 (9/00) Kachina #91900556 (12/99) IC-765 (6/90) Adam Farson wrote: > > Start with the gain control in the base of the mike 1/4 to 1/3 open and > the [MIC GAIN] control on the radio at 9 o'clock. Adjust [MIC GAIN] for > 40% to 50% deflection on the ALC meter scale on voice peaks. There > should be no evidence of flat-topping on the transmit "Spectrum Scope" > display (set "Scope during Tx" = ON in SET menu). > > If using compression, set [COMP] for no more than 5 to 10 dB compression > on voice peaks. ========================================================================= From: "Adam Farson" To: Subject: RE: [Icom] SM-20 and PRO Date sent: Fri, 10 Nov 2000 19:43:38 -0800 Send reply to: icom@qth.net From: "Adam Farson" Hi George, The usage of the ALC scale and Compression control/meter scale are described (albeit rather briefly) on pp. 36 - 37 of the IC-756Pro user manual. The [MIC GAIN] control should be set such that the meter remains in the red (analogue scale) or green above the red line (bar-graph scale) on voice peaks. [COMP] should be set for 5 to 10 dB of compression on voice peaks. On transmit as well as receive, the scope samples the 64.455 MHz high IF. In the event of gross overdrive, you should see some broadening-out due to IP's, as well as flat-topping. The spectrum scope is the best possible way to adjust the carrier and modulation levels for AM. You can also use it to check received signals - especially if the other station can put up a 1 kHz test tone. Best 73, Adam, VA7OJ/AB4OJ http://www.qsl.net/ab4oj/ > -----Original Message----- > From: owner-icom@qth.net [mailto:owner-icom@qth.net]On Behalf Of George, > W5YR Sent: Friday, November 10, 2000 11:25 AM To: icom@qth.net Subject: > Re: [Icom] SM-20 and PRO > > > From: "George, W5YR" > > Adam, I need some instruction on the ALC function and metering in the > PRO. > > First, I find virtually no mention of ALC in the manual. > > Second, on non-voice modes, the ALC indicator goes to the end of the red > line. > > Even with rather low settings of the mic input gain, the ALC indication > is much higher than I would expect. > > I have been setting up the mic gain such that I talk up the power > metering to about 50-60 watts on peaks and set the compression for > occasional ventures to near 10 db, but mostly around the 5 db level. The > ALC runs up to near max with those settings. The r-f output envelope is > clean as can be with those settings, with no clipping, etc. > > BTW, in your comment re the Spectrum Scope in the quotation below, are > you looking for the existence of additional sideband frequencies as an > indication of overdriving? I have not paid a great deal of attention to > the transmit spectrum indications since I usually use the "soft" > metering screen while operating. > > I have found that the spectrum is extremely useful for setting up AM > operation where you can clearly see the sidebands. I set the carrier > output to 25 watts with the sidebands hitting peaks 6 db down from the > carrier and I have been getting outstanding audio quality reports, > especially with the GoldLine and W2IHY equalizer. > > Words of wisdom, I pray, oh guru . . . > > 72/73, George W5YR - the Yellow Rose of Texas NETXQRP 6 > > Fairview, TX 30 mi NE Dallas in Collin county QRP-L 1373 > Amateur Radio W5YR, in the 55th year and it just keeps getting better! > Icom IC-756 PRO #02121 (9/00) Kachina #91900556 (12/99) IC-765 (6/90) > > > Adam Farson wrote: > > > > Start with the gain control in the base of the mike 1/4 to 1/3 > open and the > > [MIC GAIN] control on the radio at 9 o'clock. Adjust [MIC GAIN] > for 40% to > > 50% deflection on the ALC meter scale on voice peaks. There should be > > no evidence of flat-topping on the transmit "Spectrum Scope" display > > (set "Scope during Tx" = ON in SET menu). > > > > If using compression, set [COMP] for no more than 5 to 10 dB > compression on > > voice peaks. > ----