Time to get some experience with 32bit microcontrollers – some progress

At Time to get some experience with 32bit microcontrollers I wrote that after almost 50 years working with 8bit microcomputers and microcontrollers, I thought it about time to get my hands dirty on some 32bit microcontrollers.

This article reports some work in the STM stream.

I abondoned the ST Discovery board in favour of a low cost basic ST32F103 development board costing about $4 on eBay. The chip is a 32bit microcontroller clocked at 72MHz.

As a learning vehicle, I decided to implement the functionality contained in Arduino thermistor thermometer – a tutorial.

The development environment is Eclipse with the GNU ARM toolchain, a debugger probe, the basic development board, and a 1602 LCD display with I2C backpack and an inexpensive CP2102 USB RS232-TTL interface.

ST32F103-d01

Above is the working trial. The GDB debugger allows On Chip Debugging (OCD).
Continue reading Time to get some experience with 32bit microcontrollers – some progress

Exploiting your antenna analyser #23

Seeing recent discussion by online experts insisting that power relays are not suitable to RF prompts an interesting and relevant application of a good antenna analyser.

Screenshot - 03_08_16 , 14_12_56

Above is a sweep of an A/B changeover relay intended for HF application at up to 100W and lowish VSWR. The sweep is actually from 1 to 61MHz to be confident that there is not poor behaviour just outside of the HF range that might present on another implementation of the same design. Continue reading Exploiting your antenna analyser #23

End fed half wave – NEC models for 20m

Introduction

End Fed Half Wave antennas are again very fashionable with hams, accompanied by extraordinary claims and somewhat sparse understanding (the way of modern ham radio).

To add some light I have created a set of NEC 4.2 models of a half wave antenna on 20m to give some insight into the behaviour of a bottom fed vertical half wave over real ground.

This analysis does not consider harmonic operation, antennas are a half wave at 14.2MHz.

Four models are used:

  1. 20mHW-VEP – bottom fed vertical above perfect ground;
  2. 20mHW-VEA – bottom fed vertical above real ground;
  3. 20mHW-VCA – centre fed vertical above real ground (ie ground independent feed);
  4. 20mHW-HCA – centre fed horizontal at 5m height above ground;

NEC 4.2 model description:

  • 14.2MHz;
  • no conductor loss;
  • real ground assumed to have conductivity=0.005S, εr=13, of course results are dependent on these values;
  • conductors are ~10m long, 20mm diameter;
  • bottom fed vertical half wave uses a 10m x 20mm vertical driven ground electrode;
  • centre fed vertical is raised 200mm above ground;
  • feed line and feed line common mode current are excluded;
  • the centre of all antennas is ~5m above ground (real or perfect).

clip-230

Above are the patterns from the models for discussion. Continue reading End fed half wave – NEC models for 20m

Mandarin & Lime Marmalade

I couldn’t help myself, Mandarins are falling and I had to try a marmalade of Mandarins and Limes. I made a small batch of marmalade using 50% Tahitian Lime and 50% Imperial Mandarin. Raw sugar was one third the added sugar to impart a darker colour.

MandarinLimeMarmalade

The marmalade is light coloured, sweet and tangy. Continue reading Mandarin & Lime Marmalade

Accuracy of AIMuhf system – AIM910B vs several recent versions on a ferrite cored inductor

AIMuhf

At Accuracy of AIMuhf system – AIM910A vs several recent versions on a ferrite cored inductor I reported significant problems reconciling several recent versions of AIM software measuring the same inductor. Continue reading Accuracy of AIMuhf system – AIM910B vs several recent versions on a ferrite cored inductor

Another chapter in the NBN debacle – Jul 2016

I mentioned that NBN is coming….

NBN201607-01

This NBN cabinet has been in place for about eight months, no electronics in it… but an important showpiece in the government’s desire to show that Malcolm Turnbull’s copper based NBN was on track. Empty cabinets probably persuaded some naive voters at the federal election earlier this month.

The deception worked, Malcolm was returned, albeit with barely the majority to allow majority coalition government.

NBN is a wholly government owned ‘enterprise’ operating on a ‘commercial’ basis. Who else could afford to spend capital on infrastructure that delivers no service.
Continue reading Another chapter in the NBN debacle – Jul 2016

Tahitian Lime Marmalade

We had a small excess of Tahitian Limes ripen, so I tried a test batch of Tahitian Lime Marmalade.

TahitianLimeMarmalade

The marmalade is light coloured, sweet and tangy.

The downside is that the fruit is full of seeds, not just in the equatorial plane but distributed right through it, so scooping seeds out is quite a task.

Screenshot - 26_07_16 , 10_37_42

 

It is the first time I have made jam from these, and essentially I used the 40:60 mix from FAO’s Generic Jam Recipe, though being limes no acid was needed, in fact about 6g of Sodium Bicarbonate per kg of fruit to achieve the ideal pH of 3.2-3.3. The limes were cooked to release some Pectin, but a little Pectin 10g/kg) was added as the cooked fruit gave a slightly weak reaction in Methylated Spirits.

Endpoint was assessed by measuring Brix using a refractometer, confirmed by setting a drop of jam on a cold plate.

InsertionVSWR of Grebenkemper’s Tandem Match

The findings at InsertionVSWR of Revex W560 on HF and the suggestion that the low frequency problem is characteristic of poorly designed Sontheimer couplers (Sontheimer, C & Frederick 1966).

These couplers were popularised by (Grebenkemper 1987)  in his Tandem Match – An Accurate Directional Wattmeter and have appeared in ARRL handbooks over the decades, and may have inspired the many commercial implementations of the coupler.

Grebenkemper claims his meter is ‘good’ down to 1.8MHz, but does not clearly claim any particular InsertionVSWR. There is limited value in an instrument that can measure down to 1.05 when it causes significantly higher VSWR itself.

Screenshot - 24_07_16 , 15_31_41

Lets drill down on Gebenkember’s article, specifically the coupler design.
Continue reading InsertionVSWR of Grebenkemper’s Tandem Match