[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Bryan Fields Bryan at bryanfields.net
Mon Mar 28 17:06:50 EDT 2016


On 3/28/16 2:51 PM, Joe Leikhim wrote:
> 1) Make sure the receiver First Local Oscillator is adjusted correctly 
> on frequency. (Fo -10.700 MHz) Likewise the second LO should be at 
> around 10.2450 MHz. The second LO is not adjustable, so any minor error 
> would have to be made up with the TCXO U3. After this second step:
> 
> Then :
> 
> 2) Make sure the general alignment is set properly, especially the 
> discriminator coil T2 which responds to 10.7000 MHz from a signal 
> generator, has an S curve response.  In my experience with these sort of 
> Quadrature  Detector chips, you can get a false sense of IF centering 
> where the noise component is suppressed. You might try adjusting for 
> maximum noise first without the 10.7000 MHz signal. Be careful you don't 
> jam the coil slug.

These are both very good points i didn't consider.  I normally don't check my
reference oscillators in the hamtronics as they are using an external 10MHz
source.

You will want to check SINAD on it as well, if it's not making spec (and those
hamtronics are very sensitive), something else is wrong with it.

-- 
Bryan Fields

727-409-1194 - Voice
727-214-2508 - Fax
http://bryanfields.net



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