[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [linrad] Mistake: frontend LO frequency stability

Leif and all.

I suppose  now that I don't build my GPS disciplined frequency standard
 for a home made Linrad's DC front end, maybe later WSE... ) for no
purpose....hear hear....

Maybe a LO of better than long term 10^-10 ( at 144 MHz )  is a bit overkill
( though one's interests keep one going '.... ), but as I understand now,
still useful ( required ) for filtering at FFT bins < 0.1 Hz at 144 MHz
 possible ) QRSS.

Leif, I presume obviously that  your correction underneath does not only
concern your WSE 144 c.s., but any 144 MHz converting frontend ?
Be it DC ( to be home built ) or not ( as your WSE chain ) ?
Right ?


73, Peter.

From: "Leif Åsbrink" <leif.asbrink@xxxxxxxxxxxxxxxx>

> Hi Peter and All,
> In a previous posting I wrote:
> > The low noise local oscillators in the WSE high level converters that I
> > currently work with are stable enough if they are kept at
> > constant temperature.
> > An FFT that spans 40 seconds with a bin bandwidth of about 0.05Hz
> > (50% interleaved transforms with a sine squared window) will have
> > a bandwidth
> > below 0.1Hz most of the times when averaged over 2 minutes. It may go up
> > to 0.15 Hz occasionally but as I have them, lying on a table
> > indoors, there is nothing to gain with a better LO for 144 MHz QRSS
> > except for absolute frequency accuracy.
> The above is NOT correct. My brains slipped, the scale was in Hz and not
> in 0.1Hz per division. I was just careless......
> When I discovered this mistake I decided to have a closer look.
> The conclusion is that the WSE converters have to locked to a
> frequency reference if bin widths below about 0.5 Hz are used.
> Provision is made to allow this, all LO frequencies are multiples
> of 100kHz. It is nothing I will give priority, but may be some day....

> 73

> Leif / SM5BSZ