[Elecraft] Using CAL FIL and Spectrogram to set up the K2 filters

[M5KVK - Gareth]

Good points, Don.
Last night, I experimented using DM780 (the datamodes program in the HRD suite) to visualise the audio rather than using Spectogram. I found that the waterfall made it much easier to see the "shape" of the filters. I don't have a noise generator so I'm using band noise. The randomness makes it quite difficult to see the shape in Spectogram; particularly at low audio; whereas a waterfall is more defined.

I'll return to the setting up of the filters at the weekend and report back.

Incidentally, using the waterfall exposed that I hadn't actually set the VCO calibration as I originally thought. As I said earlier, I actually tuned off WWV by 600Hz. Now I'm using a waterfall I can see that I was actually tuning the 100Hz timecode subcarrier.

Gareth, M5KVK

Sent from my iPad

> On 26 Feb 2015, at 14:01, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> 
> Gareth,
> 
> Good work.  May I offer a couple suggestions:
> 1) On SSB filters other than the FL1 OP1 filter, look carefully at the actual filter width.  On many K2s, the actual width is far wider than that indicated by the K2 display.  You ideally want to have each filter progression about 200 to 300 Hz more narrow then the prior filter.  The easiest way to set that up is to first do LSB - the low frequency slope of the passband will not move substantially as you adjust the width.  The set the BFOs for the filters after adjusting00 the width.
> 
> 2) Rather than using SSB FL4 for PSK and other data modes, turn on RTTY in the secondary menu.  That gives you another set of filters and an independent compression setting from SSB and you don't have to remember to turn compression off when using data modes.  I normally set RTTY FL1 the same as SSB FL1 (including the BFO settings - RTTY is LSB and RTTY rev is USB) and then set the FL2 to 1000 Hz, FL3 to 700 Hz and FL4 to 400 Hz widths.  I center those 3 filters on 1000 Hz.  If you are not able to properly center the 400 Hz wide filter, you will have to pad the BFO with a small value capacitor (try 15 to 22pF) between pins 6 and 3 of RF board U11 - then recheck the BFO range.  If you do have to make that change, you will need to re-do all the BFO alignments.
> 
> 73,
> Don W3FPR
> 
>> On 2/26/2015 8:29 AM, Gareth - M5KVK wrote:
>> Having finally got my KSB2 board working (it was a hi-resistance solder joint: enough to depress performance but not stop all signals), and calibrated the dial, I turned to setting up the filters.
>> 
>> I started with the filter widths and BFO settings in the KSB2 manual, but it didn't sound right. So I decided to use WWV and Spectrogram.
>> 
>> Now that I knew that the VFO was OK, I set it to 10000.00. No audio on LSB or USB, which is good.
>> I then tuned off by 600Hz to create a steady signal at 10000.60kHz (9999.40kHz on the other sideband) and displayed the audio on spectrogram with a 600Hz marker set.
>> I then went through CAL FIL, adjusting the BFO so that the audio tone was exactly 600Hz.
>> 
>> I did this on all modes and filter widths: except FL4 on LSB and USB, which I adjusted for a 1000Hz centre (so I can use them for PSK31).
>> 
>> I was surprised how far off the displayed spectrum was with the factory settings. On USB FL4, the centre was at 400Hz with the manual’s suggested BFO setting.
>> 
>> 73, Gareth M5KVK
>