[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Skyler F electricity440 at gmail.com
Wed Mar 30 12:11:06 EDT 2016


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 at 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.
>
> 73
> Skyler
>
> On Mon, Mar 28, 2016 at 4:08 PM, Joe Leikhim <rhyolite at 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 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.
>>>
>>>
>> --
>> Joe Leikhim
>>
>>
>> Leikhim and Associates
>>
>> Communications Consultants
>>
>> Oviedo, Florida
>>
>> JLeikhim at Leikhim.com
>>
>> 407-982-0446
>>
>> WWW.LEIKHIM.COM
>>
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>
>
>
> --
> Skyler Fennell
> amsatnet.info
> KDØWHB
> <electricity440 at gmail.com>electricity440 at gmail.com
>
>
> --
> Joe Leikhim
>
>
> Leikhim and Associates
>
> Communications Consultants
>
> Oviedo, Florida
> JLeikhim at Leikhim.com
> 407-982-0446
> WWW.LEIKHIM.COM
>
>


-- 
Skyler Fennell
amsatnet.info
KDØWHB
electricity440 at gmail.com
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