I understand that the knob labeled RF doesn't really control RF gain, but since Elecraft labeled it that way, I think it's better to reference it that way.
I have an XG2, and had done the RF gain calibration using it. Dale recommended doing it using the factory defaults. I'm waiting to hear back from him why. It's a kit, just a tad over a year old, with all available mods. The mechanism by which the tables may get hosed is the same principle which makes them work. HPFM. (HocusPocusFreakyMagic) :-D . 73, Mike NF4L On 10/21/2010 7:42 AM, Guy Olinger K2AV wrote: > The thing to note here, this ain't your daddy's analog radio, the only > actual "stage gain" adjustments you have are ATT and PRE. The rest is > all in the numbers, as the front panel knobs are just numerical advice > to the firmware. They don't directly control anything. > > What needs to happen is a calibration of what voltage sent to the > variable 8 MHz stage produces a specific number out of the 15 kHz > analog-to-digital converter, etc, and exactly what stage gain change > occurs when PRE enabled, ATT enabled. > > Also note here that the PRE and ATT button is also just advice to the > firmware. The button does not directly control a circuit, as opposed > to a DPDT switch carrying RF on its terminals that literally removes a > PRE from the circuit. The in and out is done by a one or zero bit > state from the MCU, converted to a switching voltage which biases > various diodes which change the signal path in the RX. > > All of this stuff gets tabled up in the firmware, which constantly > consults it to set levels in the output and optimize IF gain into the > 15 kHz ADC. If the numbers in the table are goofy, so will the > behavior be goofy. > > Better to calibrate the K3 on a signal source (over the years, the > XG-2 will pay for itself, over and over) and have it right. > > If you bought the radio assembled, this was done for you when you got > it. If you assembled it, needs doing. > > Personally, sometimes I think the tables get hosed by ??? and needs > redoing. Done it a couple of times to restore normal function and have > no clue what happened to make it that way. > > 73, Guy. > > On Thu, Oct 21, 2010 at 6:41 AM, Mike<[email protected]> wrote: >> Thanks, Vic. >> >> Per Dale's suggestion I did a calibration using factory defaults, and the >> dead spot >> is gone, and the S-meter is back to rising with a decrease of RF gain. >> Dagnab it..... >> >> 73, Mike NF4L >> >> On 10/20/2010 11:50 PM, Vic K2VCO wrote: >>> My guess is that you need to do the RF Gain Calibration procedure with the >>> K3 utility. If >>> you have an XG1 or XG2 you can use it as a calibrated source, or if not you >>> can tell the >>> utility to use the factory default settings. >>> >>> On 10/20/2010 8:13 PM, Mike wrote: >>>> Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the >>>> receiver >>>> goes dead. It's not dependent on the THR or SLP settings which I adjusted >>>> to match >>>> some advice given here short time past. >>>> >>>> I also realized my S-meter doesn't rise as the RF gain is reduced. I like >>>> that, but I >>>> don't know how it got that way. :-P >>>> >>>> I have the latest firmware. >>>> >>>> It's not really a big deal, but is is puzzling. >>>> >>>> 73, Mike NF4L >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
