Here we go, I put the Micromite into a plastic box and put it to work.

Naturally i'm using it not for the main intended purpose as an IF alinement device, but, to look at the response of the coil set in the TRF receiver I will get around to finishing one of these days.

The MM does exactly what it says it does, provides a sweep signal between 2 set points, or, a single signal with the option of modulation. When I drive the TRF set you can SEE visually (I know) the effect of twiddling coil cores, gang trimmers and the strange things the AGC loop can do to the tuned circuits, however I did not go into that aspect in this essay.

Cheers, Fred.

Micromite TRF

Document uploaded.

Another excellent article Fred
I built one of those SC alignment boxes too. Havent had a chance to use it on a radio yet.

Ben

Hi Ben, looks like a very handy bit of kit and saves me trying to make my valve wobulator work at RF signal frequency.
How it works is a bit beyond me being firmly stuck in valve technology.
Maybe someone with a bit more talent could figure out a way of looping the general sweep output through the internal display as it does when in the IF test mode. Probably some programming thing but that's way beyond me. Odd that the designer did not do this anyway or maybe he did and I cant see it?
I cant be bothered asking SC and getting a non answer.
Fred.

Looks like a useful device, I'd like to get one. Hopefully I could order one over the internet, so I'd need a link to it. Google didn't have a clue...

I know your comment is three years old, but I recently finished building one of these. I found their website hard to follow as to exactly what parts to buy. I wrote an email to this effect, to which I received the following reply:

"I agree it's confusing.

I suggest you purchase:

1) Micromite LCD BackPack V2 kit - select the "Radio IF Alignment with DDS" programming option along with whichever lid colour you want.

https://www.siliconchip.com.au/Shop/20/4237

2) AD9833 DDS module with programmable attenuator:

https://www.siliconchip.com.au/Shop/7/4205

That covers the first two items in the parts list. You can get the remainder from Jaycar."

It would be handy if you also have the articles in SI, Apr, May and Sept 2017 as no instructions come with the parts, but the construction is straightforward.

I presently have it hooked up to my old frequency counter and it says it is 33 Hz high when set to 1MHz. This probably means it is my counter that is inaccurate since I bought it at a HRSA auction many years ago and it has three stickers on it:
RES 10, WORKS OK and RS.

I also set it to 1404kHz modulated with 1000Hz and got a nice tone at 1404kHz on a Samsung PLL radio, a better test perhaps. So all in all, encouraging so far.

STC good going so far.
Re the accuracy, I don't even worry about that.
These modern devices are inherently far more accurate that valve era domestic test equipment.
Valve radios talk in terms of frequencies of 455kHz not 455.000098!
You are only looking for accuracy of 1 part in 100 or 1 part in 1000 at the best.
It matters not one jot if the IF is set to 455.0 or 455.5 kHz.
Your unit is 33 hz different to your standard. that is 33 in 1 million or 3 in 100,000.
That is far closer than service instruments of 1 in 1000 or lab instruments of 1 in 10,000 OF THE ERA.

Same when I sweep a circuit.
As the sweep response varies dynamically according to signal condition I am only interested in the general shape at the moment.
That tells me if a coil is not resonating as it should.
The width of say an IF response then tells you what the bandwidth and audio frequency response is.
I never use the "IF sweep function doodad thingy "LCD read out mode.
I could not get to grips with what it means.
I just use the unit as a sweep for any circuit from audio to RF and use a CRO as the indicator.

Press on matey.

Fred.

I will press on Fred.

Am not concerned about the level of accuracy, just that they should agree and they do. If they were say 10% different that would be different and would mean that the frequency counter was out considering the RS label on it. I am confident to use that now as I haven't had anything to check it against.

One of the counter's ranges (x100) doesn't work at all but that shouldn't be a problem for old AM radio work. It is a Dick Smith kit which I might write a thread on as there is no model number on the front and no circuit board number visible on the top - would need to take the board out to find that. Once I have a circuit or hopefully an EA or ETI article I might be able to calibrate it and fix the 100x range.

Haven't got into the sweep side of it yet. I am thinking of aligning my two AWA 429MAs to get the hang of it on something that is working normally.

"I never use the "IF sweep function doodad thingy "LCD read out mode.
I could not get to grips with what it means."

To my way of thinking the sweep gives a curve with maximum marked, with -3dB (half) signal strength marked either side. Alignment should make these equidistant from the maximum to give a symmetric curve shape.

They use log scale to accommodate easily a wide range of signal strengths, without fancy scaling software.

Is this the way you see it Fred?

The log curve, being flattened, doesn't give much idea of curve shape, so I suppose that's why you also use the scope so that you have a picture that you are used to looking at.

Bang on, the log curve thingy is meaningless to me.
I don't want to see what some program works the response might be.
I want to see what the coil is actually doing and if I have to change a range on the CRO to measure it so be it.
Of course, when you sweep audio circuits or tuning circuits the inbuilt programmed screen is useless.
The genius of the design is the sweeper and touch screen controls, I don't think much of the rest.

Fred.

I decided to check my frequency calculations from my CRO display by checking them against my Micromite. Spot on, but playing around discovered that triangle wave from the MM gives a sine wave output on the CRO, and square wave gives a triangle wave tending slightly to a sawtooth. The triangle wave also gives a blip wave at whatever time period that the sweep is set at; it does not sweep, just blips.

The sweep function and other features are as advertised.

I am about to write off to Silicon Chip about this but I thought that I would check and see what Forum members experience with the MM is.

STC I'll check mine tomorrow.
Memory tells me it has the advertised wave shapes.
Fred.

I've just had a play around. The behaviour I saw was at 450kHz. But at audio frequencies all is well. Once you get above this things degrade. I'm not sure whether this is failure of the Micromite to produce the waveform, or inability of the CRO to respond to, or both. Will have another look tomorrow.

Did a double check for dry joints, solder bridges, incorrect connections etc but all seems to be well.

Just checked mine, relax mine is the same.
The waveshapes are approximate and only hold over audio frequencys up to 30k or so.
Above that every thing is "sine wave".
I dont use those functions at all, only the sweep function.
Fred.

Good o. I would have thought that my 20MHz CRO would have had the bandwidth to pick up a square wave at 450kHz. The reason it didn't is because it isn't there.