[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Bryan Fields bryan at bryanfields.net
Wed Mar 30 12:34:45 EDT 2016


Sadly you cannot buy harmonics and expect it to work with out a full alignment.  It's not the same quality it once was.

I've seen many shortcuts and issues with their designs.  The ceramic caps in most of the exciter are crap and must be replaced with mica to clear up their server microphonics.

You would be best served by getting a basic service monitor.  There is simply no good way you'll be able to run a repeater well with out one. :(

73s



On March 30, 2016 12:11:06 PM EDT, Skyler F <electricity440 at gmail.com> wrote:
>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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--
Bryan Fields
727-409-1194
http://bryanfields.net
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