[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Sun Apr 3 02:49:31 UTC 2016

Just FYI, the RTCM input has 47 PF to ground and is about a 60k ohm load
without JP1 and about a 33k ohm load with JP1.
The detector chip in the r303 receiver has an output impedance of about 450
ohms and needs to feed the RTCM as directly off pin 9 as possible without
any series resistance or any capacitance to ground that might attenuate the
high frequency noise that the squelch needs. Don't forget to have a series
capacitor to block DC, around 5 or 10 microfarad should be good.
Chuck

On Sat, Apr 2, 2016 at 4:06 PM, Chuck Henderson <
rpt2 at chuck.midlandsnetworking.com> wrote:

> "Once you have verified that the firmware is running, place a jumper shunt
> on JP8 and JP10. Be sure to
> do this at a reasonable human room temperature (like 60-80 deg. F). This
> is necessary because this
> procedure initializes the operating parameters in the EEPROM and also does
> a *temperature compensation*
> *diode calibration* which needs to happen at room temperature. Once the
> jumper shunts
> have been installed, power-cycle the board and wait for the system
> activity light to come on steady
> (about 4 seconds or so after the 5 second initial wait time). Then remove
> the jumper shunts."
>
> From https://allstarlink.org/votersystem.pdf page 20
> Chuck
>
>
> On Sat, Apr 2, 2016 at 3:23 PM, Skyler F <electricity440 at gmail.com> wrote:
>
>> Well stupid me for not listening to you guys. I guess the hamtronics is
>> really sensitive to low impedance outputs, and the highs get cut off if you
>> have any sort of load at all. When I turned on the internal amplifier, the
>> RTCM was happy with calibrating squelch.
>>
>> Can anybody explain to me what "Diode calibration" means?
>>
>> 73,
>> Skyler
>>
>> On Wed, Mar 30, 2016 at 5:42 PM, Joe Leikhim <rhyolite at leikhim.com>
>> wrote:
>>
>>> Skyler;
>>>
>>> Here is a wideband VHF 136-156 MHz radio that will solve your ham club
>>> problems for $35 each. If these were UHF I would be buying a bushel full.
>>> You will need to get the programming software from Ritron. I think it is
>>> free.
>>>
>>> There are similar models with an enclosure, but for much more $$.
>>>
>>> See the auction below on E-Bay:
>>>
>>> Seller dale575
>>>
>>> Ritron VHF Transceiver PCA, 136-156MHZ, 5 Watt, Model DTX-142-GCWD-I
>>>
>>>
>>> http://www.ebay.com/itm/Ritron-VHF-Transceiver-PCA-136-156MHZ-5-Watt-Model-DTX-142-GCWD-I/191557457767?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35389%26meid%3D4bbbffc700cc4aefba654c3ce0d394f8%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D401085025343
>>>
>>>
>>>
>>> On 3/30/2016 12:11 PM, Skyler F 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>
>>>> 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
>>>>>
>>>>> _______________________________________________
>>>>> App_rpt-users mailing list
>>>>> App_rpt-users at ohnosec.org
>>>>> http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users
>>>>>
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>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Skyler Fennell
>>>> amsatnet.info
>>>> KDØWHB
>>>> 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>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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>
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