[App_rpt-users] Hamtronics receiver issue with AllStar RTCM

Joe Leikhim rhyolite at leikhim.com
Wed Mar 30 19:42:35 EDT 2016


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 
> <mailto: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 <mailto: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 <mailto:JLeikhim at Leikhim.com>
>>
>>         407-982-0446 <tel:407-982-0446>
>>
>>         WWW.LEIKHIM.COM <http://WWW.LEIKHIM.COM>
>>
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>>
>>
>>
>>     -- 
>>     Skyler Fennell
>>     amsatnet.info <http://amsatnet.info>
>>     KDØWHB
>>     electricity440 at gmail.com <mailto:electricity440 at gmail.com>
>
>     -- 
>     Joe Leikhim
>
>
>     Leikhim and Associates
>
>     Communications Consultants
>
>     Oviedo, Florida
>
>     JLeikhim at Leikhim.com <mailto:JLeikhim at Leikhim.com>
>
>     407-982-0446 <tel:407-982-0446>
>
>     WWW.LEIKHIM.COM <http://WWW.LEIKHIM.COM>
>
>
>
>
> -- 
> Skyler Fennell
> amsatnet.info <http://amsatnet.info>
> KDØWHB
> electricity440 at gmail.com <mailto:electricity440 at gmail.com>

-- 
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

JLeikhim at Leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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