This article is a review of the Baofeng GT-3TP MkIII, a hand held 2m/70cm FM transceiver.
The radio is supplied with a bunch of useful accessories (even if the power supply lacks the necessary Australian approval) and a brief and inadequate manual.
Above, the Baofeng GT-3TP purchased for about A$85 delivered overnight from Sydney. Continue reading Baofeng GT-3TP MkIII review
Correspondents have asked about application of the technique used in Antenna span spring tensioner using Antenna wire catenary calculator to a span tensioned with a counterweighted halyard.
The scenarios bear a lot of similarity, the main difference being that the tension from the counterweight is constant up to the point that the counterweight travel reaches its limit.
The tension applied is the weight force of the counterweight with a little increase to allow for friction in the sheave block.
So, lets say the scenario is a 42m wire plus halyard that adds 1m to the span under no wind conditions and can pay out a further 1m at which it reaches its limit. Lets say the counterweight is 5kg weight so 49.0N tension. Continue reading Antenna span tensioner using a counterweighted halyard
After almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers.
The plan is to investigate two streams, one ST Microcontoller based and one ATMEL based, both ARM architecture. Continue reading Time to get some experience with 32bit microcontrollers
A correspondent asked about application of the Antenna wire catenary calculator to a scenario with a spring tensioner in a simple span.
His proposed tensioner has a maximum length of 2.6m at a tension of 445N, and the intention is to tension the span with no wind loading to 178N at which the tensioner is 1.92m long. Minimum GBS of the tensioner is 1560N, WLL=456N (ie the tensioner is specified that with safety factor 3.5, it reaches its working load limit at full extension).
The following is a simple analysis that assumes the fixed supports are equal height, the tensioner has the same m/l as the wire, and 2mm (#12) 30% Copperweld is used for the wire which is 42m long, so the distance between supports is taken to be 45m. Continue reading Antenna span spring tensioner
There are applications where you might want to make the tuning of a wire dipole adjustable.
Adjusting the length is often not convenient, especially in-service tuning which might be triggered by changing vegetation, ground moisture etc.
This article shows some simple means of attachment of a small capacitive load to deploy near the high charge points, and to adjust their effect by moving them to or fro on the main dipole wire. Continue reading Capacitive loading device for fine tuning wire dipoles
One often sees enquiries by people trying to save the hex file made during the Arduino build process.
It is not trivial, as in their wisdom, Arduino hides these details, and builds the hex file in a randomly named temporary directory for each IDE which it deletes when the IDE is closed.
There are times when you may want to save the hex file, perhaps to load it without a bootloader or using a non-supported bootloader, Flashing LED driver using an ESC was just such a project. Continue reading Capturing the AVR hex file built by Arduino on Windows
This is a review of an inexpensive 8010F Chinese bang-bang thermostat that was purchased on eBay for around A$13 complete with thermistor sensor and postage.
Above is the front view of the thermostat. There are many thermostats on the market with similar front panels, but they differ in internals and most importantly, performance and quality.
Above, the rating label is clear and informational. It is rated at 10A for resistive loads (AC-1), but it is doubtful that AC-3 motor loads of more than 20-30% of that should be used. Continue reading Review of inexpensive Chinese thermostat – 8010F
I have described a solution an overheating problem with my IC2200H at Cooling an IC2200H.
Another solution for control of the fan to minimise nuisance draft and noise is one of the inexpensive digital thermostats on eBay.
I reviewed one of these things at Review of inexpensive Chinese thermostat – MH-1210. It had its issues, but as modified for 12VDC operation, I tested it for control of the fan in the above pic.
Above is the thermostat, though modified, purchased for about A$12 including post and the sensor thermistor. Don’t buy the MH-1210 as some at least are shipped with incorrect calibration. Continue reading Cooling an IC2200H – update #2
David, VK3IL, describes a small transmitting loop (STL) at Portable magnetic loop antenna.
At VK3IL’s 3m circumference LDF4-50B loop on 40m. I reviewed his loop behaviour on 40m, and its efficiency was quite low… though typical of a loop of that size at that frequency.
Radiation resistance of a STL is proportional to the fourth power of frequency, and since it is often dwarfed by loss resistance, we should expect that doubling frequency will dramatically improve performance.
As far as I can glean from the article, it is made from a 3m length of LDF4-50B Heliax, and uses a Patterson match to tune it.
David offered measurement of VSWR around centre frequency for the loop approximately matched (VSWR=1.24) on 20m. He has measured the VSWR=2.86 bandwidth shown between markers 2 and 3 to be 45kHz. Continue reading VK3IL’s 3m circumference LDF4-50B loop on 20m
At Efficiency and gain of Small Transmitting Loops (STL) I explained an approach to assessing the gain the efficiency of STL, and provided a link to a calculator to perform the calcs.
This expands on application of the concepts and introduces an enhanced calculator to perform the calculations.
Firstly, this technique applies to antennas where the VSWR characteristic is consistent with a feed point or virtual feed point where around the frequency of minimum VSWR, X varies with frequency much more than R. The simplified analysis assumes that R is constant, and change in X is the reason for the VSWR characteristic. See VSWR curve of a simple series resonant antenna for more information. Continue reading Enhancement of Calculate small transmitting loop gain from bandwidth measurement