Re: [App_rpt-users] Hamtronics receiver issue with AllStar RTCM (Chuck Henderson) Re: App_rpt-users Digest, Vol 86, Issue 5
Impedance matters. That the output/source circuit and/or the input/load circuit mis-match alters frequency response is sloppy implementation. Unless you have complete control over system components design and implementation, it is prudent for audio-take-off/recipients/input circuits to not terminate at whatever unknown source impedance, but instead bridge-tap at 10k ohms. The outputs you have design/implementation control over can be whatever you want, but convention is typically 600 ohms, 0 dB max standard level from 300-3000 Hz. Squelch noise detection from an Rx detector may begin at 4 KHz (marginally low) or typically 6 KHz for white noise. The Motorola Micor SQ chips and not so obvious app notes indicate/allow a higher frequency detection limit at the base/repeater (6KHz) than the mobile (more subject to flutter) of 4KHz. All that yadda aside... folks need to learn that audio connections between unknown gear might best be bridging (10k ohms) to get audio, and should provide/tolerate 600 Ohms to give audio. If even bridging affects the frequency response the source audio point is questionably engineered/implemented. Impedance matters. From: "app_rpt-users-request@ohnosec.org" <app_rpt-users-request@ohnosec.org> To: app_rpt-users@ohnosec.org Sent: Saturday, April 2, 2016 6:07 PM Subject: App_rpt-users Digest, Vol 86, Issue 5 Send App_rpt-users mailing list submissions to app_rpt-users@ohnosec.org To subscribe or unsubscribe via the World Wide Web, visit http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users or, via email, send a message with subject or body 'help' to app_rpt-users-request@ohnosec.org You can reach the person managing the list at app_rpt-users-owner@ohnosec.org When replying, please edit your Subject line so it is more specific than "Re: Contents of App_rpt-users digest..." Today's Topics: 1. Re: Hamtronics receiver issue with AllStar RTCM (Chuck Henderson) 2. How to add chan_rtpdir.c to DIAL (Michael J. Wolthuis) ---------------------------------------------------------------------- Message: 1 Date: Sat, 2 Apr 2016 16:06:16 -0500 From: Chuck Henderson <rpt2@chuck.midlandsnetworking.com> To: Skyler F <electricity440@gmail.com> Cc: "app_rpt-users@ohnosec.org" <app_rpt-users@ohnosec.org> Subject: Re: [App_rpt-users] Hamtronics receiver issue with AllStar RTCM Message-ID: <CADEYVwhCSq8vx+g58i8tZVHGM5P6CvKsAiq2QeHqPmXzefFLKw@mail.gmail.com> Content-Type: text/plain; charset="utf-8" "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@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@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-D...
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@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 .03?) , 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@leikhim.com> 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 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@Leikhim.com
407-982-0446
WWW.LEIKHIM.COM
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-- Skyler Fennell amsatnet.info KD?WHB electricity440@gmail.com
-- Joe Leikhim
Leikhim and Associates
Communications Consultants
Oviedo, Florida JLeikhim@Leikhim.com 407-982-0446 WWW.LEIKHIM.COM
-- Skyler Fennell amsatnet.info KD?WHB <electricity440@gmail.com>electricity440@gmail.com
-- Joe Leikhim
Leikhim and Associates
Communications Consultants
Oviedo, Florida JLeikhim@Leikhim.com 407-982-0446 WWW.LEIKHIM.COM
-- Skyler Fennell amsatnet.info KD?WHB electricity440@gmail.com
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Jim Aspinwall