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Re: SHARI programming error
#programing
The entry format for frequency requires 3 digits to the left of the decimal point and four to the right (as in XXX.XXXX).? You used 446.025 instead of 446.0250.
Steve - N8AR |
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SHARI programming error
#programing
Paul B
I am getting the following error. After multiple attempts at loading the 818 I tried the same number as in the loading instructions. See image.?
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Re: Antennas
As I am sure you are aware, the impedance of this type of antenna is highly dependent on the ground plane used with the antenna,? When I measured the antennas using my HP8753C VNA, I found they were only resonant as specified when mounted over a large copper ground plane.? As used in SHARI (and HT 's in general), where the ground plane consists of the case and the shield of the SA818 and the antenna can be adjacent to numerous other conductive surfaces, it is not possible to maintain a low VSWR.??
The SA818 module was designed by niceRF for use as the RF module in an HT using a rubber duck antenna.? They call it the " NiceRF SA818 1W Embedded walkie talkie module" so we know that it has been designed for use with a rubber ducky antenna with an uncontrolled impedance.? For a greater safety margin, SHARI is wired to operate at the low power setting of 1/2 watt. Steve - N8AR |
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Re: Shari Harmonic Suppression Question
Hi Vince,
Of the over 30 SHARI UHF kits I have built, I have found the 2nd harmonic is in the range of 44 to 52 dB below the carrier (dBc).? Most are in the 46 to 50 dBc range.? The third harmonic is greater than 60 dBc.? For SHARI's 1/2 watt max output, the requirement is more than 40 dBc.? I use an HP8568B to make my measurements. As used in SHARI, measured with an HP8753C VNA from the RF output pad of the SA818U through FL1 to the output connector terminated in 50 ohms, I? measured an attenuation of? -1.23 db at 450 MHz, -36 dB at 880 MHz and -40 dB at 1320 MHz. Steve - N8AR |
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Re: Two SHARI's, one Pi
The USB power controller in a Pi3/4 is a DIODES AP255X Precision Adjustable Current-Limited Power Switch???The USB Pi wiring is not included in the official Raspberry Pi schematic but the datasheet shows how the circuit is likely wired on the RPi.?The chip is configured for 1.2A max current for the USB 5V rail.??The USB 5V is common to all 4 ports. So the 1.2A is shared.? The AP255X provides reverse current and voltage protection.? It also asserts a FAULT condition to the processor.? I can find no information on the web about what happens for this situation.
As I stated in my previous post, I suspect that the Pi will be able to power two SHARI's simultaneously.? If not then the easiest solution is to use a powered USB hub.? The split cable powering approach should work if the USB power connectors are connected to the SHARI USB jack closest to the center and USB cables providing data only connection are connected between the PI and the outer USB connector on SHARI.? However, be aware that there is no overcurrent protection (i.e. fuse or current limiter) built into SHARI as that function is normally provided by the Pi USB port. |
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Re: Two SHARI's, one Pi
Mike and Steve,
I have an application for two SHARI's and one Pi for a split UHF transceiver (one in monitor only), allowing semi-duplex from an HT.? Interesting about the current problem, how about powering the Pi and SHARI's from a "2 male one female" usb cable".? Some on Ebay for $2.79? shipped from LA (not China) says good for 10A.? Would there be any problem back-powering the Pi that way from a high power usb source. |
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Re: 2M Shari Kit
#programing
It appears that the Pi is in communication with the CH340 USB to UART converter in SHARI but the CH340G is not in communication with the SA818.? Look carefully at your solder joints at terminals 16 and 17 of the SA818 (terminal 1 is at the bottom left corner of the SA818 when you can read the silksreen on the board).? Make sure there is a good connection from the pad on the board to the wall of the castellated hole of the SA818.? Also be sure the solder joint is not bridged to the shield of the SA818,? Use an ohmmeter to check for a short to ground from these terminals..
Also check the solder joints at pins 8 (VBAT) and 9,10 (GND) Steve - N8AR |
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Re: Two SHARI's, one Pi
Hi Mike,
According to the hamVOIP website, there should be no issue as far as the software. But we need to consider a potential hardware issue.? The Pi3 and Pi4 are rated to supply 1.2 amps +/- 10%? total current to the USB ports.? On the devices I measured, SHARI required about 500 mA when in transmit.? But this could vary quite a bit depending on the actual voltage delivered to SHARI which is dependent on the Pi power supply and the IR losses in any cable used to connect SHARI to the Pi.? Also individual characteristics of the final power amplifier transistor will cause the TX current to vary, unit to unit.? ?The current is not an issue for one SHARI but for two that are transmitting at the same time (they will do this for sure on the hour unless the cron job is modified) the current could approach the 1.2 amp current limit.? Moreover, as we discovered while testing some BRIAN devices, there is probably a higher startup current transient on TX which would be enough to trigger the USB current limit in the Pi. The bottom line as I see it is two SHARI devices on one Pi will probably work but no guarantees. Steve - N8AR |
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Re: Removing "Squelch Crash" when using SHARI
#CTCSS_reverse_burst
#programing
The frequency has to be entered as 439.0500.? Four numbers after the decimal point.??Enter Tx Frequency (xxx.xxxx):
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Removing "Squelch Crash" when using SHARI
#CTCSS_reverse_burst
#programing
There is a discussion on the HamVOIP ARM-allstar list about how to remove the 'squelch crash' when using SHARI.? This is typically done using CTCSS with reverse burst.? For this to work, the radio you are using to talk to your SHARI must support reverse burst.? The SA818 used in SHARI can be programmed to send/not send reverse burst but that command is not included in the 818-prog program that we have been using to program SHARI.
It turns out that the default setting for the SA818 in SHARI is reverse burst turned on.? I use a Kenwood TH-F6A and hear no squelch tail with it turned on. I have modified the 818-prog program to include the capability to set reverse burst to off/on.? When using the program '0' means no CTCSS reverse burst and '1' means send CTCSS reverse burst.? The new program is called shari-pixx-prog and has been uploaded to the File section of this group.? If you want to experiment with reverse burst, you can upload it to the /usr/local/sbin folder of your Pi using WinSCP.? After you upload it be sure to make it executable by right clicking on it from within WinSCP and checking the three executable boxes (boxes labeled X).? You run the program the same way you run 818-prog. Steve - N8AR |
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Re: File updated in [email protected]
Steve,
I have run the DRA818's as low as 3.0V but have not gone the other way..They run fine at 3.0...Or at least the one I did run there did. |
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Re: File updated in [email protected]
Hi Lawrence,
Thanks for the suggestion.? I have not investigated the Dorji DRA818 transceiver modules because the specified input voltage is 3.3 - 4.5 volts while the NiceRF SA818 is rated for 3.3-5.5 volts.? SHARI would require a circuit to lower the input voltage of up to 5.2 VDC from the Pi.? In BRIAN I use a series diode to drop the voltage about 0.9 VDC since the BF888S is normally powered by a 3.7 VDC battery. My examination of the SA818 revealed that there is an internal 3.3 VDC regulator which powers the RDA1846 transceiver IC and the CPU which controls it.? The driver and PA are powered directly from the input voltage.? I am wondering if the Dorji module does not employ a regulator and thus the 4.5 VDC limit because the RDA1846 is specified for 3.3 to 4.8 VDC.? Have you powered the Dorji module from as much as 5.2 VDC (the official Pi 4 power supply output) and/or have additional information as to the Dorji circuitry and input voltage specification? Steve - N8AR |
Steve-N8AR
Pete Bickerdike
Larry Macionski