EMRFD Message Archive 283

Message Date From Subject
283 2006-12-31 06:52:43 Hari G Wide VCO for SA
Hi All,
 
 Iam looking for a wide VCO for the SA project, there is mention of using discrete VCO for initial testing.Any references or circuits for the VCO is appreciated.
I got hold of SRA-1 mixers  think its ok to use that instead of TUF. 
 
Happy New Year
 
Best Regards
 Hari
284 2006-12-31 07:08:12 Lasse Re: Wide VCO for SA
Har,
how wide is "wide"?? And what freq.?
To roll your own is perfectly possible, but it would be a lot easier if you have access to RF instruments... if you are more of a beginner why not try one of MiniCircuits ready-made VCO's? Not too expensive and allows you to get the instrument going, and you can then concentrate to roll your own VCO. There was a design in VHF Communication ten years ago regarding wide band VCO's. Sorry but do not have the articles available, maybe someone else??

/Lasse


On Sun, 31 Dec 2006 20:03:24 +0530
"Hari G" wrote:
> Hi All,
>
> Iam looking for a wide VCO for the SA project, there is
>mention of using
> discrete VCO for initial testing.Any references or
>circuits for the VCO is
> appreciated.
> I got hold of SRA-1 mixers think its ok to use that
>instead of TUF.
>
> Happy New Year
>
> Best Regards
>
Hari

285 2006-12-31 08:04:47 Hari G Re: Wide VCO for SA
Lasse,
 
          Iam looking for the same spec of POS200 for the ZOI SA,  iam in VU and i wanted this to test till i get hold of POS-200 which iam trying locally but no luck so far. 
            
Many thanks
Hari(VU2GHB)

 
On 12/31/06, Lasse <lasse.moell@swipnet.se> wrote:

Har,
how wide is "wide"?? And what freq.?
To roll your own is perfectly possible, but it would be a lot easier if you have access to RF instruments... if you are more of a beginner why not try one of MiniCircuits ready-made VCO's? Not too expensive and allows you to get the instrument going, and you can then concentrate to roll your own VCO. There was a design in VHF Communication ten years ago regarding wide band VCO's. Sorry but do not have the articles available, maybe someone else??

/Lasse



On Sun, 31 Dec 2006 20:03:24 +0530
"Hari G" wrote:
> Hi All,
>
> Iam looking for a wide VCO for the SA project, there is
>mention of using
> discrete VCO for initial testing.Any references or
>circuits for the VCO is
> appreciated.
> I got hold of SRA-1 mixers think its ok to use that
>instead of TUF.
>
> Happy New Year
>
> Best Regards
> Hari




--
De Hari
VU2GHB
286 2006-12-31 15:00:01 jr_dakota Re: Wide VCO for SA
You could easily take this circuit <
http://www.hanssummers.com/electronics/equipment/spectrumanalyser/mixer1/index.htm
> and modify the range and then use this setup for the 602/612 <
http://www.pan-tex.net/usr/r/receivers/svfo.htm#ne602 > to bring the
LO signal to the output (IF) port of the 602 which gives you a little
more drive for the diode DBM and buffers the VFO (You'll probably need
some more gain to get your +7 or +17 LO drive for the DBM)

It's a cheap and easy way to make a decent VCO and easy to tweak for
the frequency range you want

JR


287 2006-12-31 18:43:55 Hari G Re: Wide VCO for SA
Jr ,
 
  Thanks ,
 
 I have 612 with me, i will try with a J310 buffer and then followed by a MARx MMIC and check the range i get.
 
Few more questions,  how about the ampliude will that be same for the full range or will it change and need an AGC arrangement ?  
 
What need to done with the mixer inputs and outputs, those pins to be left free or ac  grounded with caps ?.
 
Happy Newyear to All
 
Many thanks
 
Bes Regards
Hari
 
288 2007-01-01 13:07:40 jr_dakota Re: Wide VCO for SA
The 2nd link shows you how to set up the inputs to make the 602's LO
appear at the output, basically one input is tied to a cap to ground
like you would normally for a single ended (unbalanced) input and the
remaining input is tied to ground via a 10k ohm resistor

As far as amplitude over range I can't say as I've never tested for it
at those frequencies ...

JR