I was working recently on an antenna and a visitor was intrigued by a device I was using.
Above, the device is for tensioning a wire span, commonly called a come-along though that term gets applied to all manner for appliances for broadly similar purpose. A significant difference is that this was designed for smooth hard drawn copper wires, and has smooth flat jaws (70x6mm) and does not put a kink in the wire (as do most wire grips for more general fencing and FSWR use). This one has had the strap replaced, it came with a 1.25″ canvas reinforced rubber transmission belt which became hard over time. Continue reading Come-along from the past
Last update: 3rd August, 2017, 5:58 PM
On 5/10/2016 we cut over to a new broadband Internet access service, switching from Telstra 8Mb/s ADSL to iiNet NBN 12Mb/s.
Over some years, I have run an automated file transfer to measure the speed of our access service. The tests are done between 6:00 and 22:00, I am interested in performance during the times I want to use the service, and less interested in times when I would usually be sleeping.
One of the performance measures is speed, it seems simple enough especially when it is talked about by politicians and promoted by RSPs and NBN’s advertisements.
So, how does one characterise the speed. People like to think of simple concepts like ‘average’, but let us look at the distribution of speeds.
Above is a chart of the frequency distribution of speed observations for a week in March 2017. It is not in the form of the Normal Distribution, the classic bell-shaped curve for which common parametric statistics like Mean (average) and Standard Distribution are meaningful, but it is a skewed distribution. Without knowing the characteristics of the distribution, it is a misuse of parametric statistics to apply parametric statistics like Mean (average) and Standard Distribution. Continue reading Review of 10 months of iiNet broadband Internet access
Last update: 25th December, 2017, 11:14 AM
On the back of failure to buy decent BN-V11U batteries for my theodolite (Chinese BN-V11U NiMH replacement battery), A fall back was to fabricate a battery that would fit in the battery compartment.
Above is a battery pack made from 5 x 2/3A 1.6Ah NiMH cells. Continue reading Chinese batteries – 5 x 2/3A 1.6Ah NiMH cells
Last update: 30th July, 2017, 10:40 AM
My theodolite uses the once common BN-V11U NiMH camcorder battery.
I purchased a replacement on eBay, they are getting harder to find since changes to regulations about transport of batteries, but there are still quite a few sellers. Continue reading Chinese BN-V11U NiMH replacement battery
Last update: 30th July, 2017, 10:08 AM
This article is a brief review of some issues that were found with initial testing of a Hantek DSO8102E two channel 100MHz hand held oscilloscope.
The DSO8102E is a member of the DSO8000 series (DSO8060, DSO8070E, DSO8100E, DSO8150E, DSO8200E), and shares most specifications across the series.
The specifications are very impressive, and price at just under $1000 for a Chinese brand seemed reasonable (hand held oscilloscopes are expensive compared to bench oscilloscopes).
The test scenario was a practical application, observation of the data traffic to/from a DHT22 temperature and humidity sensor in the project ESP8266 IoT DHT22 temperature and humidity – evolution 2. Continue reading Review of Hantek DSO8102E hand held oscilloscope
Last update: 18th October, 2018, 8:07 AM
This article documents a first project with the Espressif ESP8266 in its third evolution (based on ESP8266 IoT DHT22 temperature and humidity – evolution 2).
The objective is a module that will take periodic temperature and humidity measurements, and in this evolution publish them using a RESTful API.
The example platform used in this article is a Wemos D1Pro. In this case, the D1Pro is configured for an external antenna, and a modification is made to the board to add a 1N34A diode for the deep sleep reset circuit (NodeMCU devkit V1 deep sleep). A three pin right angle header to the top of the board (as seen) and another on the underside on the opposite edge to get GND, +5, +3, and D4 for the DHT22 data wire. There is less than $20 in parts in the pic above. Continue reading ESP8266 IoT DHT22 temperature and humidity – evolution 3
Last update: 18th October, 2018, 8:07 AM
This article continues on from Implementation of G5RV inverted V using high strength aluminium MIG wire documenting impedance measurements and voltage calculations.
Impedance was measured with an AA-600 looking into 500mm of RG400 then the Guanella 1:1 balun, then 9m of fabricated transmission line as described in earlier articles in the series. The balun is located at the antenna entrance panel and the coax shield is grounded via that panel (ie the normal operating common mode current path exists).
Above is the impedance measurement plotted on a Smith chart. This is more useful and very meaningful as an interactive display in Antscope where are you move the cursor, the frequency and key data are displayed. Continue reading Implementation of G5RV inverted V using high strength aluminium MIG wire – impedance measurements
Last update: 6th April, 2018, 6:33 AM
A correspondent wrote about trying to reconcile by G/T worksheet with EME Calc.
Many times I have tried to validate it and run into problems. At one time I reported them to the author, but they were never acknowledged, much less fixed.
The specific problem on this occasion relates to the receiver performance tab.
Above is a screenshot (with my annotations) where I have basically stripped the configuration down to a receiver attached to a noiseless antenna with lossless line. Continue reading EME Calc v11.11 reconciliation issues
Last update: 22nd July, 2017, 8:13 AM
This article continues on from Workup of G5RV inverted V using high strength aluminium MIG wire and describes the implementation.
Above is a view of the steel mast with the Inverted V G5RV rigged from the top of the 11m mast using a halyard though a purchase on a small gibbet to offset the antenna and feed line from the mast. There are lateral guys at 7m height, and the left hand one is non-conductive synthetic fibre rope. Atop the mast is a 2m/70cm vertical. Continue reading Implementation of G5RV inverted V using high strength aluminium MIG wire
Last update: 22nd July, 2017, 11:57 AM
Richard (G3CWI) published an interesting blog article Comparison of groundwave performance of Small Transmitting Loop and Quarterwave GP summarising a recent WSPR test on 40m over 20km distance.
This article is a walk through of the expected WSPR receive S/N for the case of the 20mW tx on a quarter wave vertical.
100% efficient tx and rx antenna systems
Ground wave suffers attenuation due to two key components:
- dispersion of energy as the wave spreads out from the source; and
- absorption of energy in heating the soil.
Item (1) is simply inverse square law effect, and Norton provides us with several approximations for estimating (2) from Sommerfields work.
Calculate efficiency of vertically polarised antenna from far field strength uses Norton’s f5 approximation for ground wave attenuation.
Above is a calculation for a 100% efficient transmitter. (The trick to getting this is to leave the measured field strength field empty and the calculator will insert the value that gives 100% efficiency.)
So the next question is what ambient noise level might we expect in a rural setting on 40m. Continue reading G3CWI’s ground wave tests Jul 2017 using WSPRlite
Last update: 17th July, 2017, 8:01 AM