Johnson's Techworld

 In a response to my post in the HamSCI (Ham Radio Science Citizen Investigation) Google Group, N8SBE mentioned that 700-800 MHz is quite useful for first responders as it penetrates structures well. Within building coverage is of vital importance to firefighters. According to him, building owner is required to place repeaters inside to assist coverage as well. Skimmed through our National Frequency Allocation Plan 2022 and found that 614-890 MHz has been allocated for fixed, mobile and broadcasting services. 806-811 MHz frequency and 851-856 MHz paired frequency has been allocated to Public Protection and Disaster Relief (PPDR). There are also other frequency bands mentioned for PPDR applications. I presume that it will correspond to the first responder use mentioned by N8SBE. In the introduction of NFAP 2022, it has been mentioned that before any part of the spectrum is put to use in India, a licence is required to be obtained from the Wireless Planning and Coordination Win...

 When I started using computers long back, mouse had only two buttons, a left and a right button. Then came three button mouse with an extra scroll button. I have read that there was also a single button mouse, but I have not seen one. Now here is a six button mouse, that too a wireless mouse with a USB-A Nano Dongle and 2.4 Ghz wireless connection. In the earlier era, mouse had a rolling ball which would gather dirt and sometimes stop functioning well. Now we have optimal mouse which uses a red light source and an optical sensor instead of the rolling ball. The wireless mouse works on a single 1.5 V, AA battery with a projected battery life of one year!

 Yesterday I came across a piece of PVC pipe brought by the plumber who told me that it is ASTM. That prompted a Google search as usual and I could find a bit about ASTM International. ASTM International was formerly known as American Society for Testing and Materials, till they changed their name officially in 2001. That PVC pipe actually showed ASTM D-1785, which is a specification for pressure pipes used in plumbing. Another abbreviation noted on the same piece of pipe was PVC-U which stands for Poly Vinyl Chloride - Un-plasticised.

  The meter in FT-710 radio has several functions. On receive mode it functions as signal strength meter or S meter. On transmit it can have different functions like SWR (Standing Wave Ratio), Power, ALC (Automatic Level Control), VDD (Final amplifier drain voltage), ID (Final amplifier drain current) and COMP (compression level during speech processor operation). These functions can be selected by touching the meter display and choosing the options. Alternatively an external mouse can also be used to make the selections.

 Radio amateurs are very fond of getting signal reports from whichever station they work. When I started off in 1985, I did not have any S meter in the Philips Prestige home radio which I used as a receiver for my ham radio activities along with a homebrew QRP transmitter. I used to give reports 'by the ear' like many other operators in those times. Those with commercial transceivers used to give S meter readings from their radios. Looking back, even that may not have been very accurate as many analog radios did not have a well calibrated S meter. Analogue S meter or signal strength meter was a sensitive microammeter with a full scale deflection of 50-100 microamperes. In 1930s, S9 corresponded to 50 microvolts at the input terminals of the receiver. International Amateur Radio Union (IARU) Region 1 had brought out technical specifications for S meter readings in 1981. According to that, S9 on HF bands corresponded to -73 dBm. That would be 50 microvolts at the receiver's a...

Transequatorial Propagation Transequatorial VHF propagation was first noted by radio amateurs in August 1947 when Mexican stations could work Argentine stations regularly across the equator in the late afternoon and early evening on 50 MHz. This occurred for few more years during the maximum of Solar Cycle 18. Transequatorial Propagation came down during the period of sunspot minimum and reappeared in 1955 and continued through the maximum years of Solar Cycle 19. We can expect similar conditions as we are heading for the maximum of Solar Cycle 25 in 2025. Two types of transequatorial propagation has been described. One occurring during late afternoon and early evening with maximum distance of about 6000 km in low VHF band of 6 m. Second one was between 7 pm to 11 pm local time with contacts on 2 m and sometimes on 70 cm band. Mechanism by which transequatorial propagation occurs is the presence of equatorial anomaly, which is a high concentration of electrons on either side of the equ...

 Here is a recording of a visible pass of International Space Station in my region at 7.15 pm IST, which was a spectacular sight, in spite of a cloudy sky with city haze. Space Station can be seen as a tiny white dot moving across the sky. Sideways movements are because I tried to adjust the position of the phone to capture a better view. You can make that out form the movement of the faintly seen nearby building outline. Reverse movement occurred again due to readjustment of mobile phone position when the Space Station was going beyond the view of the camera. Visible passes occur either soon after sunset or some time before the sunrise.