Factory tuned from the factory. And I don't even have a signal generator / counter good for RF. We got one hamtronics board, and won't buy another until we get this one working.
On Wed, Mar 30, 2016 at 10:08 AM, Joe Leikhim <rhyolite@leikhim.com> wrote:
Were these receivers factory built and tuned or did individual club members build them? Either way, you might try others from the lot. If you have only a rudimentary signal generator and / or frequency counter, perhaps I can walk you through some "field expedient" steps over the phone.
On 3/30/2016 12:01 PM, Skyler F wrote:
I don't have the test equipment to go through all of the dirty Local Oscilator, SINAD, etc., so I will have to wait on that a few weeks before the president of the club gets back in town.
WHEN I bypassed the capacitor and resistor ( 1k and .03µ) , the RTCM was able to calibrate squelch. The LED flashed several times and then was steady. Maybe the capacitor is the wrong value. There was no code on it, but based on the resistor code, the value was correct.
73Skyler
On Mon, Mar 28, 2016 at 4:08 PM, Joe Leikhim <rhyolite@leikhim.com> wrote:
If you are using an external reference, you cannot make up for the 2nd LO error if it is wildly off. There is an easy SINAD related test in EIA-603 that is called Offset Acceptance Bandwidth that would indicate if the IF were off center. Things that could go wrong apart from simple misalignment of the Quad Detector coil could include the LO crystal being way off frequency, the IF filters being wrong BW or off spec pass frequency.
Given the symptoms, I am putting my money on a misadjusted quad coil.
Joe
On 3/28/2016 5:06 PM, Bryan Fields wrote:
On 3/28/16 2:51 PM, Joe Leikhim wrote:
1) Make sure the receiver First Local Oscillator is adjusted correctlyThese are both very good points i didn't consider. I normally don't check my
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.
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.
--
Joe Leikhim
Leikhim and Associates
Communications Consultants
Oviedo, Florida
JLeikhim@Leikhim.com
407-982-0446
WWW.LEIKHIM.COM
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-- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida JLeikhim@Leikhim.com 407-982-0446 WWW.LEIKHIM.COM
--
-- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida JLeikhim@Leikhim.com 407-982-0446 WWW.LEIKHIM.COM