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
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Today’s Topics:
- Re: Hamtronics receiver issue with AllStar RTCM (Chuck Henderson)
- 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,
SkylerOn 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
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
SkylerOn 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:
- 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 :
- 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 LeikhimLeikhim and Associates
Communications Consultants
Oviedo, Florida
407-982-0446
App_rpt-users mailing list
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You do not need a password to unsubscribe, you can do it via email
confirmation. If you have trouble unsubscribing, please send a message to
the list detailing the problem.–
Skyler Fennell
amsatnet.info
KD?WHB
electricity440@gmail.com–
Joe LeikhimLeikhim and Associates
Communications Consultants
Oviedo, Florida
JLeikhim@Leikhim.com
407-982-0446
WWW.LEIKHIM.COM–
Skyler Fennell
amsatnet.info
KD?WHB
electricity440@gmail.comelectricity440@gmail.com–
Joe LeikhimLeikhim 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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Message: 2
Date: Sat, 02 Apr 2016 21:07:42 -0400
From: “Michael J. Wolthuis” wolthuis@gmail.com
To: “app_rpt-users@ohnosec.org” app_rpt-users@ohnosec.org
Subject: [App_rpt-users] How to add chan_rtpdir.c to DIAL
Message-ID: 0426FF03-B422-471B-A684-7F9BF8307E2B@gmail.com
Content-Type: text/plain; charset=“utf-8”
I am finally replacing a very old install of ACID at a HUB site with DIAL.
This site does have some ties though to rtpDir_tm which is older, but still fun and working?
I can?t seem to get chan_rtpdir.c to compile into Asterisk. I put it in the channels folder and recompiled, but it acts like it didn?t add it / compile it in.
[Apr 2 21:02:37] NOTICE[1305] app_rpt.c: Normal Repeater Init 2363
[Apr 2 21:02:37] NOTICE[1305] app_rpt.c: Normal Repeater Init 1000
[Apr 2 21:02:37] WARNING[1318] channel.c: No channel type registered for ‘rtpdir’
[Apr 2 21:02:38] WARNING[1305] app_rpt.c: rpt_thread restarted on node 2363
[Apr 2 21:02:38] WARNING[1305] app_rpt.c: rpt_thread restarted on node 1000
[Apr 2 21:02:38] WARNING[1322] channel.c: No channel type registered for ‘rtpdir’
[Apr 2 21:02:40] NOTICE[1305] app_rpt.c: RPT thread restarted on 2363
[Apr 2 21:02:40] WARNING[1305] app_rpt.c: rpt_thread restarted on node 2363
[Apr 2 21:02:40] NOTICE[1305] app_rpt.c: RPT thread restarted on 1000
[Apr 2 21:02:40] WARNING[1305] app_rpt.c: rpt_thread restarted on node 1000
Anyone have any suggestions?
Mike
kb8zgl
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