[Elecraft] TX/RX Discrepancy

Wed Jan 22 12:53:01 2003

I did try that earlier Gregg without success, but I will be doing the 
filters again shortly (having done a factory reset) so I'll let you 
know.
Thanks
Trev

In message <001b01c2c23c$6029be90$46322543@DESK>, Gregg Lengling 
<[email protected]> writes
>The more I think about your problem...more I think you have the Filters
>incorrectly calibrated.  I'm sure once you re-calibrate the filters (per
>the list you created in SSB manual) you'll be fine.
>
>
>Gregg R. Lengling, W9DHI
>Camel Communications, Inc.
>http://www.camelcomm.com
>Politics is the art of appearing candid and completely open, while
>concealing as much as possible.   -States: The Bene Gesserit View
>
>
>
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Trevor Day
>Sent: Wednesday, January 22, 2003 11:12 AM
>To: [email protected]
>Subject: Re: [Elecraft] TX/RX Discrepancy
>
>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