2019-05-31

Vaguely 10GHz Related: Leaking Alkaline Batteries.

How is leaking alkaline batteries in any way related to 10GHz?, you may ask.

Here goes :

For my wideband 10GHz experiments I need a portable receiver. For the initial experiments I plan to use a portable scanner capable of receiving the IF from a LNB, and it needs to be wideband FM capable.
My old AOR AR-8200 is such a beast, and it has been lying with old batteries for a while, so the battery casing was full of leaked potassium hydroxide - nasty stuff. What to do? Of course, googling a bit does help, and I found that using vinegar should neutralize and make the residue removable, so I tried. Indeed, that helped, but vinegar is somewhat acidic, so in order to avoid further corrosion it has to be washed. The idea is to start with isopropyl-alcohol, then demineralized water, and then let it dry.

I did test that the radio worked with an external power supply, and it is alive, indeed. The best thing about the AR-8200 is that it also receives SSB, so tests can be made with narrow band reception in the field, too.

Next:
I have an old ICOM R3, only AM-FM-WFM capable with a totally dead battery pack. That one has a different power connector to the other radios I have - and runs on 6V only, so I have not yet tested if it is alive.
I hope so, because then I can set up two receivers on 10GHz, and make a WBFM transmitter or two, testing the range of the HB100 module, and possibly make a two-way QSO on 10GHz with those.

You may say that I could "just" use a standard FM receiver, but that requires a second converter after the LNB, and I want to start the simplest possible way. The other way would be using the HB100 module as down converter, but then the sensitivity will suffer in a significant way, probably about 20 dB worse, maybe more, than the LNB system, thereby reducing the possible range, by a lot.

Well, in any case, with a set-up of a single modulated HB100 transmitter and the LNB receive system, I can, at least, test the range of the HB100 module as it is.

Well here is to getting the AR-8200 cleaned and ready for action, and getting a modulator made for the HB100.

2019-05-28

Idea Box: 24 GHz Spectrum Viewing ?

A few weeks ago I tried the use of a TV LNB for seeing 10GHz signals, see this post.

Now, if I want to see something on 24GHz, what do I do?

I have ordered some 24GHz Doppler radar modules, and they are a bit like the HB100 (10GHz) modules. They have a simple resonator, so very unstable, so probably not very useable, also because they operate too close to (or in the) the 24GHz band.

There may be the possibility of using a frequency doubled 11-12GHz signal source which would be more stable, and then use the 24GHz module as a down converter mixer circuit, followed by a wideband amplifier.
It *should* be possible to take the output of a modified HB100 module, maybe grinding the dielectric resonator a bit for frequency adjustment. This will have to be tested, but it is probably worth trying.

The main purpose is getting an indication of how the spectrum looks like, not a detailed measurement, just like when I was using the TV satellite LNB as down converter.

How to make a frequency doubler for these frequencies - in the most simple way, I will have to look into that.

The 24GHz modules have been ordered from China, so it will take a while to get here. (I am still waiting for some 2.4GHz filters to arrive, they were ordered several weeks ago.

So many ideas, so little time.

2019-05-12

QO100 Frequency Stability.

Today I picked up the RF-Zero GPSDO. I also went to another meeting, so tomorrow I will have to re-program the frequency output to 25MHz, as the reference frequency for the LNB, and later for the synthesized local oscillator for the TX up converter.

I looked up the procedure at their website, and it looks simple enough, using a simple text terminal program with the USB port, and entering a few configuration commands.

Additionally a multi-output splitter needs to be made as several devices I intend to use, use a 25MHz reference frequency.

Moreover, other frequencies need to be synthesized in a simple way, e.g. 10MHz, 30MHz and 40MHz. The other frequencies should probably also have multi-output splitters added.

For reception the drift by the 739MHz RX is now all that is left. Certainly not as much as the drift of the modified LNB, even with the 25MHz reference crystal oscillator mounted indoors.

The 25MHz reference could also be used for an up/down converter from 739MHz to the satellite RX and to a Ham band receiver, e.g. a 144MHz receiver.

2019-05-05

Uses for the HB100 Doppler Radar Module 10GHz Experiments.

The HB100 module is intended for use as a Doppler radar motion sensor, e.g. for door openers. Could be used as a primitive speed meter, like the speeding detectors used by the traffic police.

The price of the module itself is somewhere around $3

After testing that the modules with the tuning screw could be tuned down to about 10300MHz without serious degradation of the signal, I can now see several uses of the module, some already described by others.

Here is preliminary list (other uses may be added):

1) simple 10GHz signal generator, using the module as it is, with its PCB patch antenna, tuned to a specific frequency. See also the previous post on this blog where I tested the usefulness myself.
A signal generator for 10GHz for $3.

2) Simple 10GHz WBFM (wideband FM) or FM-ATV TX, using the module as it is, but modulating the power supply. A relatively simple modulator/power supply on PCB (or experimental board) is needed. Some people have already tried this, and a Google search will reveal several ways to generate the modulation.
The modulator could probably be made for $5-10.

3) Simple RX down converter for WBFM and FM-ATV, using the module as it is, and adding a receiver at the IF port. Poor sensitivity, so very short range as the module is.
If used as receive converter only, the TX signal should be terminated in 50 ohm or similar in place of being connected to the TX patch antennas.
$3 and a bit of work.

4) Simple down converter for spectrum analyzer/frequency counter. Using the module as in (3), with the IF port connected to Analyzer/Counter.
$3

5) Very simple WBFM transceiver for *very short range* communication, using the module as is, with a modulator and an inexpensive 80-108MHz FM receiver, Chinese module, can be purchased as a simple kit for around $3, and a cheap audio amplifier, also an inexpensive Chinese module.
I estimate that the complete transceiver could be made for about $25, depending on the  external circuits used

5a) The very simple transceiver can, most likely, be enhanced by a low gain "preamplifier" between the IF output of the module and the FM receiver.

5b) Some experimentation with mounting the HB100 inside a "horn antenna", using the module's patch antennas as "illuminators".

5c) The simple TRX can, of course, be mounted in or near the focal plane of a dish antenna.

6) I have a defective HB100 (No oscillation, and high power consumption, most probably due to reversed polarity of the power supply). Experimentation should be done to see, if it can be used as an up converter with a local oscillator suited for narrow band transverters.
A simple test would be trying to insert a low level RF signal at the IF port of a functioning HB100, and check the resulting spectrum radiated from the RX patch.

6a) The mixer could also be used as an RX down converter mixer, in the receive chain of a NB transverter

It should be noted that  the very simple WBFM TRX, or the module used as a simple down converter, has poor RX sensitivity, due to the loss in the passive mixer.
However, some people have made QSOs up to 200km LOS (line of sight) when using parabolic dish antennas, interesting what can be done with just a few mW. True QRP with extremely simple and inexpensive equipment.
Some experimentation with a TV-LNB followed by a WBFM RX, would probably result in enhancing the sensitivity by 10dB or more.

I can see that the is room for experimentation, and I need to try out some of the above ideas.

If you can think of other uses for the HB100, feel free to comment.

2019-05-04

10GHz Testing, HB100 and LNB.

Today I got my first test gear for 10GHz up and running.

I have a spectrum analyzer (SA) covering up to 1.5 or 1.7GHz. Not much to see on 10GHz with that one. So, as a test I fed the SA with the down converted signal from a PLL LNB.
I chose the cheapest one I have, a Goobay that I discarded for use with OSCAR 100, because it has more local oscillator phase noise/jitter than I like. For this purpose, and for experiments with wide band FM (WBFN) it was expected to work nicely. It certainly does for the test equipment.

So how to test the system. I have a pile of HB100, cheap ($5 or so) Doppler radar modules. Some with a tuning screw, some without. 5V to the HB100, and a nice signal appears on the screen with the LNB about a meter or two away. The system clearly works. Increasing gain of the spectrum analyzer (well, reducing attenuation) shows the noise floor of the LNB, and some spurious outputs of the DRO, some 40 - 50dB under the main carrier.
A thought: This spurious response could be due to the PLL local oscillator of the LNB, and probably not from the DRO of the HB100 module. I consider this the most likely explanation. Maybe I should try with another PLL LNB, or maybe with an older DRO controlled LNB. More to try out.

Next step was creating some signal sources. What to use? HB100 modules, of course. I tested the tuning range of the modules, and found that some of them went down to 10275MHz without any problems. So, now I have some wideband signal generators covering 10275MHz - 10500MHz in 25MHz steps. Further i tuned one for 10368 (narrow band segment) and one for 10489MHz (The transponder downlink for QO-100.

What are the limitations of this, you may ask. The stability of the DRO and the rather critical setting of the tuning screw makes it difficult to adjust within less than +/- 2MHz of the wanted frequency. This makes the test system more suited to wideband system tests,  but a crude spectrum analysis of narrow band equipment is feasible.
All this with some low cost accessories for the existing test equipment that I have.
The LNB should also be useable as a converter for a frequency counter, this will have to be tested later

This does not mean that I do not want a bit more 10GHz test equipment. I am thinking of making a narrow band signal generator for somewhere around 10368MHz, either with a 24MHz crystal oscillator and a series of multipliers, or with a ADF4350/4351 synthesizer and a tripler. This will have to be later.

I think that the next step in test equipment should be a MMDS down converter with the bandpass filter removed, so I can see signals around 2400MHz. Using the LNB for 10GHz provided me with a proof of concept for the idea.