[minima] Re: Mixers and Crystal Filters

  • From: farhanbox@xxxxxxxxx
  • To: minima@xxxxxxxxxxxxx
  • Date: Sun, 19 Jan 2014 16:41:07 +0000

That's in line with my readings too. But the oscillator is 3v peak to peak! 
That makes it quite strong compared to the tx signal.
- f
Sent from BlackBerry® on Airtel

-----Original Message-----
From: Mark G0MGX <mark.g0mgx@xxxxxxxxx>
Sender: minima-bounce@xxxxxxxxxxxxx
Date: Sun, 19 Jan 2014 16:24:07 
To: <minima@xxxxxxxxxxxxx>
Reply-To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: Mixers and Crystal Filters

Marker 2 is the LO direct to the SA, marker 1 is post mixer.

I make LO suppression through mixer is 33.4 - 8.4 = 25dB

Mark
G0MGX


On 19/01/2014 16:00, farhanbox@xxxxxxxxx wrote:
> Mark, you probably swapped the z and 14 mhz values in the last sweep.
> Can you tell me how much local oscillator suppression are you getting? 
> I don't know what you ref levels are.
> - f
> Sent from BlackBerry® on Airtel
> ------------------------------------------------------------------------
> *From: * Mark G0MGX <mark.g0mgx@xxxxxxxxx>
> *Sender: * minima-bounce@xxxxxxxxxxxxx
> *Date: *Sun, 19 Jan 2014 15:15:30 +0000
> *To: *<minima@xxxxxxxxxxxxx>
> *ReplyTo: * minima@xxxxxxxxxxxxx
> *Subject: *[minima] Re: Mixers and Crystal Filters
>
> All,
>
> I've added another example with a 7MHz signal to the RF port and 27MHz 
> to the LO port and updated this page appropriately:
>
> http://g0mgx.blogspot.co.uk/2014/01/yet-more-minima.html
>
> I also experimented with the 15MHz low pass filter and made another 
> using T50-6s (13 turns for 0.66u and 14 turns for 0.78u) and the sweep 
> looks almost identical to the previous one using T50-2s so I will have 
> to come back to that filter again as I suspect I have too much 
> attenuation at 14MHz. We will see!
>
> I have just made the BFO and uploaded some info here:
>
> http://g0mgx.blogspot.co.uk/2014/01/minima-bfo.html
>
> Mark
> G0MGX
>
>
> On 19/01/2014 08:23, Ashhar Farhan wrote:
>> mark,
>> the local oscillator has to be at 27 mhz. on the higher side. this 
>> will reduce the local oscillator leakage to the RF port (you can see 
>> that the oscillator suppression isn't any great shakes. It is about 
>> -40dbm. That will be only 20 db below the tx signal level unless the 
>> LPF kicks in.
>> - f
>>
>>
>>
>> On Sun, Jan 19, 2014 at 1:02 PM, Mark G0MGX <mark.g0mgx@xxxxxxxxx 
>> <mailto:mark.g0mgx@xxxxxxxxx>> wrote:
>>
>>     Hi Team
>>
>>     Some more musings of mine on the mixer output, crystal matching
>>     and selection plus a sweep of my crystal filter...
>>
>>     http://g0mgx.blogspot.co.uk/2014/01/yet-more-minima.html
>>
>>     Mark
>>     G0MGX
>>
>>
>


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