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
Last of the trial recipes was a small batch of marmalade using 50% Australian Lime and 50% Eureka Lemon.
The marmalade is light coloured, sweet and tangy, but a hint of the bitter lemon aspect of the Eureka. Continue reading Australian Lime & Lemon Marmalade
I mentioned that NBN is coming….
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
We had a small excess of Tahitian Limes ripen, so I tried a test batch of Tahitian Lime Marmalade.
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.
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.
The Red Dot 2016A is a digital HF+ VSWR meter.
The frequency range is specified as 1.6-60MHz. Continue reading InsertionVSWR of Red Dot 2016A
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.
Lets drill down on Gebenkember’s article, specifically the coupler design.
Continue reading InsertionVSWR of Grebenkemper’s Tandem Match
Arduino thermistor thermometer – a tutorial gave a method for designing a thermometer based on a formula predicting the behaviour of the sensor. This article explains a different approach where that is not possible.
Above is a characteristic from the manufacturer’s data.
The curves to no lend themselves to simple curve fits, so a cubic spine interpolation will be made based on key points from the curve.
Four our purposes, the mean curve (green) is sufficient for design.
Above, the mean curve was digitised to capture the shape of the curve, 17 points were used.
Continue reading Fan controlled by humidity sensor – design technique
The Revex W560 is a dual range VSWR meter that was also sold under other brand names.
The low frequency range is specified as 1.8-160MHz. Continue reading InsertionVSWR of Revex W560 on HF
The KG-UV920P is infamous for failure of the driver FET, they run excessively hot and clearly outside of safe operating limits.
I repaired one for a friend some years ago, and the dealings with Wouxun were enlightening. If I had little confidence in them before that experience, after it I would not give consideration to purchase of any Wouxun radio.
My repair / modification notes have been copied literally from the old VK1OD.net webside, and may contain stale links etc, but if it is of use to hams with a broken radio, see KG-UV920P – a repair / support story.
I have seen lots of articles on this problem over the years since, including ones that try to add a heatsink on top of the driver FET. The driver FET is meant to lose its heat through the bottom metal pad, and heatsinking the plastic encapsulation will not be very effective. Bottom line is to reduce the operating voltage on the driver (as per the factory advice), and keep the radio cool.
Don’t operate the radio sitting on the desk or the like, the bottom is the heatsink.
Wouxun are not alone in manufacturing radios that run red hot, see my notes on supplementary cooling for an IC-220H: http://owenduffy.net/blog/?s=IC2200H+cooling.
I have a problem with machine tools getting condensation on them when conditions in the shed read dew point.
A possible solution being explored is to circulate air with a fan, possible inducting outside air, when humidity approaches condensing conditions.
A quick search reveals the HDS10 resistive humidity sensor for a dollar or so on eBay.
Above is the HDS10 humidity sensor.
Most low cost humidity sensors use a humidity dependent capacitive element, the HDS10 is different in being a humidity dependent capacitive element and is therefore simpler to use with microcontrollers with ADC input.
The above graph is from the datasheet. It is intended primarily for sensing high humidity (dew point, condensing conditions) which suits this application.
Continue reading Fan controlled by humidity sensor