The BN-V12U is a NiMh battery used in JVC video camera / recorders in the 1990s. It was used in a lot of competitors products, and found its way into other applications. In my case, it is used in a Leica T107 theodolite.
This article documents initial tests on two new after market Chinese made batteries purchased on Aliexpress 12/2023 for about $34 for two, incl shipping. These have a label rating them at 2.1Ah. Continue reading Battery testing – BN-V12U
Some radiosonde signals are successfully decoded at distances well in excess of the specified range for the radiosonde.
Experience reported here relates to Vaisala RS41-SGM radiosondes which are specified at 60mW max transmitter output and range up to 350km.
Whilst the path is over land, the radio path at high altitudes approaches a free space path, albeit with some ground reflection effects at the receiver.
The transmit antenna is probably close to a vertical dipole in performance, lets assume that it has a gain of 2.13dBi in the path direction.
Receive antennas will commonly be omni directional, and fairly low directivity, so lets just assume rx antenna system gain 0dBi.
If the path was free space, the rx field strength would be 13.8dBµV/m, tx power -115.5dBm. This model ignores ground reflection gain and losses, but it is in the ball park. Continue reading Radiosonde propagation – is aircraft enhancement significant?
Voltage baluns are making a comeback for HF antennas discussed the application of a common Ruthroff 1:4 (voltage) balun design to a slightly unbalanced theoretical scenario.
This article applies the same analysis to two reported measured dipole cases at 3.6MHz.
(Hunt 2015) reported measurements of his dipole antenna system at 3.6MHz. Continue reading Voltage baluns are making a comeback for HF antennas – some real antenna measurements
I planned this article to be a Youtube video, but recent behaviors of Google / Youtube give me pause to consider whether or how I use Youtube in the future. So, this article is a simpler presentation of the underlying concepts.
For most purposes, users of HF antennas would like the feed line to perform that function alone, ie to not participate as radiating or pickup conductors.
For that end, we want the common mode component of feed line current to be very very low.
Discussion of antennas tends to represent them as two terminal devices in free space, ie ignoring the presence of ground in close proximity. This applies whether the feed line is coax or two wire line.
A more complete representation (or model) is a three terminal network that includes a terminal to permit current to flow to ground. Above is a Wye or Delta equivalent circuit, and that can be transformed to an equivalent Tee circuit. Continue reading Voltage baluns are making a comeback for HF antennas?
I have a GPSmap 76 which has not been used for perhaps 12 years, stored without batteries.
The GPSmap 76 appears to use an internal battery for non-volatile memory and clock, likely to be a MC621 rechargeable LiIon (MnO2) button cell of about 3mAh capacity. Continue reading Reviving a Garmin GPSmap 76 (GPSmap76)
What’s that… the centre to centre distance is less than the round wire diameter… a physical impossibility… never mind, Google Bard can solve it!
Not only solve it, but warm you with a bit of humanistic chat to lend credibility to its answer.
This is worse than your average online expert on social media! A high tech automaton that is not fit for this purpose?
PS: I hope my doctor does not use Google Bard to recommend my treatments!
Having seen an online expert speaking very positively of Google Bard in solving ferrite cored inductor problems… so I tried it out.
Well, that is encouraging, seems a lift from datasheets and it seems ok at a glance.
Now lets go deeper. Continue reading Google Bard on ferrite cored RF inductor challenge
I find it convenient to capture the screen from my tiny devices directly to a computer over the USB connection.
I use a script derived from Ho-Ro’s nanovna-tools.
The script emits a png of the screen, and a png of the screen with the colours inverted (for presentation and printing).
Above is a screen shot from a tinysaultra.
The script is published on github: https://github.com/owenduffy/tinydevicecapture .
I have been asked about compatibility of the RFPM2 current probe with the TinySA and variants.
The current probe was intended for use with a broadband 50Ω RF power meter, but could also be used with a Spectrum Analyser with 50Ω input or an oscilloscope with 50Ω input.
RFPM2 – current probe described a current probe for use with a power meter calibrated in dBm (eg RFPM1 and RFPM2). RFPM2 – current probe – #2 exposed some of the build details. RFPM2 – current probe – #3 showed the implementation.
Above the current probe with RFPM2. Whilst this is not of a clamp-on design, the aperture in the core is sufficient to pass a DIN 7/16 connector through. Continue reading RFPM2 – current probe – #4 – TinySA Ultra
I purchased two of these Irwin folding utility knives, they seemed like a clever design that addressed the failures of every other folding ‘Stanley blade’ knife I have owned.
Above is the Irwin knife, the blade is secured by a dog on the button shown at top, and the button is blocked from being depressed except when the knife is folded at 45° as shown. Continue reading Unjamming your Irwin folding utility knife