[Elecraft] TX/RX Discrepancy

Wed Jan 22 12:15:00 2003

Thanks Don,
I'm just going through a full alignment; once I have finished I'll do as 
you suggest and let you know here.
Trev

In message <[email protected]>, Don Brown 
<[email protected]> writes
>Hi
>
>I went out to the lab and tried it on my K2. The reference control voltage
>and the VFO control voltage do not change from receive to transmit on USB or
>LSB when keying the transmitter. You will see a shift in CW mode because the
>side tone is added in on receive. If the control voltages are changing on
>your K2 then you need to track down why. The +8 volt supply is regulated on
>the control board so a control board swap may help isolate a problem on the
>supplies if that is what is causing the frequency shift. Note you must key
>the transmitter, not use tune for this to work. Pressing tune in USB or LSB
>is the same as CW and you will get a shift in voltage.
>
>Hope some of this helps you locate your problem
>
>Don Brown
>KD5NDB
>
>
>----- Original Message -----
>From: "Don Brown" <[email protected]>
>To: <[email protected]>; <[email protected]>
>Sent: Wednesday, January 22, 2003 9:02 AM
>Subject: Re: [Elecraft] TX/RX Discrepancy
>
>
>> Hi
>>
>> When set to usb or lsb the transmit and receive frequency should be the
>same
>> so if you measure the reference oscillator control voltage at pin 1 of U6A
>> it should be the same for transmit or receive as well as the VFO control
>> voltage at pin 7 of U6B should not change from transmit to receive. If
>these
>> voltages are changing check the +8 volt supply (8B) and the 5 volt supply
>> (5B) if these voltages are stable then the problem is most likely firmware
>> related or a bad DAC or synthesizer chip (not likely). I would swap out
>the
>> firmware from the other radio first (just swap the control boards). I have
>> not actually tried the above tests on my K2 so I am not sure of the method
>> but I will go out and do it and let you know what I get. If the transmit
>and
>> receive frequencies are different something must be telling the VFO to
>> change or a power supply is changing somewhere That should be reflected in
>> the VFO control voltages.
>>
>> Don Brown
>> KD5NDB
>>
>>
>> ----- Original Message -----
>> From: "Trevor Day" <[email protected]>
>> To: <[email protected]>
>> Sent: Wednesday, January 22, 2003 7:34 AM
>> Subject: Re: [Elecraft] TX/RX Discrepancy
>>
>>
>> > Hi All,
>> > Continuing from yesterday, I have carried out Cal PLL on all bands.
>> > When carrying out the Rx Mode SSB Filter test from p15/16 of the KSB2
>> > manual, to get the LSB BFO freq of 4913.5, the BFO parameter is 160 ie.
>> > BF1t160L (This seems too high?)  When I try to set the USB frequency of
>> > 4916.30, I can only reach 4916.24 equating to a BFO parameter of 255
>> > (the upper limit).
>> >
>> > Looking at spectrogram, when I have Cal Fil enabled, the passband of the
>> > filter is centred around 800 Hz, tailing off at around 300 with a
>> > gradual drop off on the high side to 2500 Hz.  When I disable Cal Fil
>> > (revert to freq display) the passband shifts left and changes shape
>> > becoming almost a CW response centred on 500Hz, dropping low to 0Hz and
>> > high to 1kHz.  I have checked that this is the same filter (Op1)
>> > selected in both cases.
>> >
>> > Just to remove one variable, I have exchanged the KSB2 with my own after
>> > doing the checks below, but before doing the checks above, and found no
>> > difference. In other words, I still saw a frequency discrepancy between
>> > tx and rx. The KSB2s are now back with their respective units.
>> >
>> > I remain somewhat puzzled.....help!
>> >
>> > Thanks,
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-- 
Trevor Day