This article describes a solution for robust and reliable ‘production’ programming of Silabs based BLHeli ESCs.
The intention is to test and tune the BLHeli configuration, save the configuration in some form, and a scripted solution to programming multiple ESCs now and later replacements with high confidence that they are exactly matching configurations.
There does not appear to be any batch facility for writing flash using the BLHeli bootloader, nor does it appear that BLHeliSuite can save the relevant hex files for later use, so excluding use of the BLHeli bootloader.
The configuration data is held in a block of flash memory labelled EEPROM in the source code. It is not actually EEPROM, the MCU does not have EEPROM, but for consistency the block will be referred to as EEPROM in this article.
Having tested and tuned the configuration using BLHeliSuite, the EEPROM block from the test ESC is read back using Silabs Flash Programming Utility (FPU) and a toolstick attached to the ESC’s C2 interface.
I bought a remote speaker-microphone (RSM) for a MD-390 DMR portable from 409shop.com, a 41-80K.
They assured me it was compatible with the radio in digital mode, but it turned out to be lousy with ‘motorboat noise’ on tx audio due to RF ingress tot he electret capsule.
Since the RSM was otherwise a good rugged and economical product, it was worth trying to rectify the RF ingress problem.
Above is a pic of the electret. Two fine tracks can be seen bonding the metal can of the electret to the -ve pin, so that is good… the can showed low resistance to the -ve pin. The +ve line is bypassed to the -ve line about 12mm from the electret with an unknown capacitor, but it was clearly not effective at 440MHz. Continue reading Another RFI mod of a speaker mic (41-80K) for DMR use
In a recent long running thread on impedance matching on one of the online fora, one poster offered the Ten-tec 540 manual as a reference for clarity on the subject (which of course got murkier with every posting as contributors added their version to the discussion).
The Ten-tec 540 was made in the late 1970s, one of the early radios with a solid state PA, and their manual give the Technical facts of life to guide new owners to successful exploitation of this new technology.
Amongst the technical facts of life is this little gem:
The standing wave ratio is a direct measure of the ratio between two impedances, ie an SWR of 3 to 1 tells us that one impedance is three times the other. Therefore the unknown impedance can be three times as large or three times as small as the known one. If the desired impedance that the transceiver wants to see is 50 ohms, and SWR of 3 to 1 on the line may mean a load impedance of either 150 or 17 ohms. …
I purchased a Retevis SM that was advertised as original equipment for the MD-380, but turned out to be lousy with RF interference in the form of the ‘motorboat noise’ on transmit audio.
Dismantling the SM (fighting the way through TORX with PIN screws, what are they trying to protect) I found there is precious little RF filtering, just a single SMD cap at the end of a long (wrt 500MHz) branch track.
I have an IC-7410 with R1 of the firmware installed.
I have attempted to use its PTT tuner start feature (triggers ATU tune on PTT if frequency changed a significant amount) with an MFJ-993B ATU, but it fails.
The symptoms are that the IC-7410 does not transmit its tune carrier, it remains in the mode active when PTT was pressed.
Tuner operations initiated from the IC-7410 TUNE switch appear to all work as expected.
Above is a logic trace of the ATU control wires on PTT tune. everything looks good, when the /START signal is recognised as valid, the ATU asserts KEY and the IC-7410 should put tune carrier out… but it doesn’t and the ATU aborts after about 0.5s without tuning. Continue reading Icom IC-7410 – PTT tuner start doesn’t work
The humble ‘F barrel’ as it is known, the F81 adapter, is specified by IEC 61169-24:2009. That specification includes an extended performance type good to 3GHz.
It seems that every seller on eBay has worked out that they cannot sell F81 adapters unless they state that they are 3GHz rated… and they almost all lie.
Above is the internals of an F81 purchased as 3GHz rated on eBay. The construction is simply the popular construction used since the 1970s and good to almost 1GHz, good enough for VHF/UHF TV. Continue reading Anatomy of an F barrel (F81)