2021-10-15

Idea Box: More Simple HF CW Transceiver(s).

 Here is another one for the idea box.

While I am doing stuff for much higher frequencies I am still thinking of this in connection with my "one QSO per band with home made gear" challenge. I was thinking of using a kit (or two) for a simple HF CW transceiver using a direct conversion receiver.

Some examples of those kits are the Pixie, the Rockmite, the Frog Sound and the 49'er. I have a box with some of those kits, and some of them should be quite easy to convert to HF bands up to 18MHz without too much loss of performance.

For higher frequencies I suspect that the receiver sensitivity will be insufficient for efficient work on those bands (21/24/28MHz). Here it is probably a good idea to use two kits, one for TX and one for RX, adding a preamplifier for improved RX sensitivity, and possibly a PA for higher TX power.

Each transceiver would be modified to use a SI5351 synthesizer board. This board should be controller (programmed) by, e.g. an Arduino, so I will have to learn another skill: Micro-controller programming. There are libraries and some programs in existence, but the programming skill will come in handy if I want to extend functions.

A simple 28MHz model could possibly be used as base transceiver for transverters to higher bands. This would not need RX modifications and could possibly be using just a simple TRX kit. I am well aware of the lack of CW activity, especially on the VHF/UHF/SHF bands, but a single QSO, or a few, should be possible.

I do have two other kits for CW transceivers, the QRP Labs' QCX+, with components for 20m and 60m. Still need to be built, but that is a matter of finding time to add those.

Do I have too many kits and projects? Yes, but I will not have any time to be bored, that is certain ...

Another one of the ideas stacking up ;)

2021-10-10

World Wide Propagation on 10m.

The solar cycle 25 has started in earnest, and seems to be ramping up activity. We have already had a few days with the 2800MHz solar flux exceeding 100. Here is to hoping that it will pass 200 (or more) this cycle. That is not guaranteed, hope is all we have.

The past week or so 10 meters has been a band with world wide propagation.

My FT8 monitoring has shown spots form essentially all continents, every day. The past few days signals have been mounting from North America.

Signals from most of the Eastern United States have been coming in here, from the North West all the way down to Texas. 

Today I went on CW and worked barefoot with my R6000 vertical antenna. 3 US stations and also a single PY was what I could work after coming home late afternoon from a birthday party.

Since 10m is my favourite HF band I am quite happy that it is open with F2 propagation again. I have not heard the band like this in about 6 years.


2021-10-09

Batteries for Portable and Fixed Use.

Today I brought my hand held VX-5 on my walk. Yes, I am trying to work myself up to a daily walk of at least 2km. I thought the battery was well charged, and all was fine just operating in stand-by. Having a local chat with the highest power level ... oops! Battery died. Maybe this is because the battery is fairly old. I am now going to check the state of the battery (Li-Ion type, 7.2V)

I may have to purchase a couple of spares, because it is a nice little radio. The standard battery is rated to 1100mAh.

For now, I am thinking of making a battery pack with 3 18650 Li-Ion cells and a cord/connector, just to be sure to have some spare capacity. This way I have can always have a fully charged battery, and I can change the cells when it goes too low. The cells are used, but tested cells with more than 2000mAh, so even with full power (5W) I should have enough juice for some local chatting. I **could** use lead acid batteries, but I don't want a hole in my pocket or rucksack after all those batteries are heavy as lead ;)

I have a good supply of Li-Ion cells and battery cassettes, so I expect to use those for several portable experiments, including going to local hills with the 10GHz WBFM experiments.

In China I found 2 solar chargers with a 3-cell (18650) battery casing, and including a BMS system, possibly fine for portable work.

At home I am slowly building some battery supply, charged mostly by solar panels, but in winter time it is probably necessary to add some juice from the mains power.

Initially this is intended for very low power equipment, such as a 28200 simple beacon receiver and some other simple monitor receivers that should run 24/7, and preferably also when mains supply fails, even if that does not happen often here.

For some of the computing the plan is to use some Raspberry Pi boards. The idea is using this for both WSPR/FT8 propagation monitoring and QRSS. 

As usual, ideas a-plenty, now it is about making time to do something with them.


2021-10-07

Outdated Computers - Spare Parts?

Over time I have collected a bunch of old laptop computers, all too old to run just about anything remotely modern, even decent Linux distributions.

So what to do with this? 

One of the older laptops has 2GB memory and a Pentium 4 (2.4GHz), I could probably run a Windows XP with some "Windows only" programs that I still want to use, e.g. the control program for the 35 - 4400MHz signal generator, some spectrum analyzer software etc, possibly WSJT or QRSS software.

The processors of those old laptops simply don't run fast enough, and the RAM is too low to run any modern applications, so that is really useless. 

What else can be used of such old laptops? 

Batteries can always be disassembled, and the cells used for rechargeable battery packs, providing that the cells have not died. Some testing of their capacity will be needed.

Old hard disks should be checked for usable information on them, and backed up. Really old ones, i.e. used PATA disks should probably be discarded and disassembled for parts. (Stepper motors and magnets come to mind, maybe a few more items.)

From the main boards a few components could be of interest as spare parts. Switch transistors, possibly some capacitors or inductors for the switch mode circuits.

A few modules, such as WiFi modules could possibly be used elsewhere

I would save some small speakers from laptops.

One thing seems quite useful: The laptop screens. With an interface they should be useful for some Raspberry Pi projects. I have a few from old netbook PCs with only 1024x600, a 800x480, and one 1366x768 screen from a recently disassembled defective machine.

With all the propagation monitoring I want to do those screens should prove useful in the shack, and in the lab.

Right now I have two dead Asus machines (one with dual core i5 and one with quad core i7). absolutely nothing happens when the (19V) power supply is connected, and the PS is working. From the description of other faulty laptops etc I suspect one or two defective switch transistors, as I have have had some power cuts with possible transient voltages. Here the disassembled old laptop main boards might provide spare parts. If not I should try to get some replacements.

Fault finding and repair is something I have not done a lot of, but learning something new is always of interest, especially if I can get some useful equipment up and running again. Yes, I have had the tendency to just buy new (or good used) stuff, but the stock is quite high now, so I should get to use more of what I have.

Additionally, I have some very old - and very large/heavy - test equipment. I have got some new and smaller equipment, so the really old/heavy stuff, like an ancient 1.7 - 4GHz signal generator with a **klystron** is not too useful. Very heavy and bulky, and unstable. The new ADF4351 based generator is much better and takes up a fraction of the space. Any useful parts from the generator, like the attenuator(s), will, of course, be salvaged, as they are useful in the lab. 

So this is an effort combining tidying the lab, making space and improving my test equipment, all while I am building some ham radio projects. Absolutely no time to be bored (what is "bored?)

Especially the lab is in an attic with essentially no useful vertical walls, so space is at a premium. Also, while the newer/smaller test equipment is not of professional standard, it will work nicely for my amateur use.

2021-10-06

Slow Progress on the 10HGz WFM Project.

 The past few weeks I have been working a bit on the modulator for the 10GHz HB100 module. The modulator worked, but I needed to build it up on some prototype PCBs and that is almost there. A CW (audio) generator is under way, and then it needs to go into a box, so it can be operated portable.

I may also make myself a test TX ("beacon") with the HB100 and just a CW audio generator. I think I have found some directions where I can test the TX on top of a 12m telescopic fibreglass mast and then walk on road and path to test the path for (near) line-of-sight propagation. First tests will be in the garden, of course, with a max range of about 35m ;)

Then I will have to take some walks, I suspect that I have found a possible distance of about 600m, and maybe one of about 1.6km. 

This will all be using the HB100 with the built-in dual patch antenna on the PCB, and the LNB just with the integrated feed horn. Not a lot of gain, but some people have claimed the range of such a simple arrangement to be 8, maybe 15km. The distance to a fellow amateur who is interested in participating is less than 10km, and we suspect that we could possibly make a line-of-sight contact from garden to garden.

Initially I just build a single TX and RX, but having made one set it is not too difficult to make another.

For longer distances some improved antennas or higher power is needed for WFM contacts.

I hope to be able to make the first one-way tests in my garden this week end, and hope for some decent weather to make the tests on longer distances.

I will need the weather to be dry and not too windy for these experiments, as the HB100 module(s) need to be in the open air, or at least with very low loss material in front of the patch antennas.

Now we start the idea box:

Improved antennas can be the following:

- mounting the HB100 and the LNB (or just the LNB) on a dish. Not easily portable if I need to up a steep road to a hilltop, or up a narrow staircase to a watch tower or the like. Also, for the dish a tripod is needed, and it should not be too flimsy.

- The second option involves more work: Horn antennas. In this case both the HB100 and the LNB need to be "connected" to horn antennas. For this some coax-to-waveguide transitions are needed. I have one.

It may be possible to "glue" a horn antenna in front of the LNB. I will have to test how efficient that will be.

The HB100 *could* be mounted inside a "horn". I do not know how efficient that will be, so modifying a HB100 with a connector/coax to the coax/WG transition.

- The other option for keeping the size/bulk of the equipment low also involves more work: Going narrow band. This could be NBFM as we use it on 2m and 70cm, or it could be a CW transmitter, to keep it as simple as possible. Both would likely involve generating a much lower frequency, and using frequency multipliers to get to 10GHz. Much more complex electronically, but still relatively simple mechanical construction.

We shall see what we will do, but first some short range tests will be done, likely this autumn.

10 Meters Is Opening, Slowly, But Surely.

 For the last few weeks I have been monitoring 10m FT8, and lately the beacons on 28.200.

A few weeks ago the band started opening to South America from here. There has not been a day within the last 3 -4 weeks without receiving SA stations, mostly from Brazil, and often stations were also coming in from Southern Africa. I suspect that some of this propagation was trans-equatorial propagation (TEP). This fits well into the pattern of TEP being strongest around the Equinox times.

Then stations started coming in from the Far East and Oceania, and the South American stations started coming in during day time, and several stations from Australia. 

The past week the propagation has moved closer to the North American continent, Northern part of South America, and Caribbean stations coming in, and the past few days South Eastern and also North Eastern United states have come through, as well as regular propagation to the Middle East and Atlantic islands like the Canaries and the Azores. These are clearly single hop F2 propagation  

The past week or so I have re-started monitoring 28.200, and  daytime propagation has been detected on this frequency. Almost daily signals from CS3B and ZS6DN, and occasionally very strong signals from the 4X6TU beacon.

To me this means that the F2 propagation on 10m has returned after the deep solar minimum, and I am happy that my favourite HF band is coming to life again.

I suspect that we will see more North Atlantic propagation in the next few months, unless the sun goes very quiet again. That may happen in short periods, but I suspect that we will have good, maybe excellent 10m propagation the next 3 - 5 years or so. Who knows, with the new weak signal digital modes we may even see weak F2 propagation on 6m. That would be exciting. 

The most general predictions for the next solar maximum (cycle 25) is much like the previous cycle, but we can always hope that it will be larger. As a Danish poet said about 100 years ago: "Prediction is difficult, especially about the future" ;)

2021-09-21

Spectrum Analyzer Extender Using the HB100 Module as Down Converter.

Tonight I made a test of using the HB100 module as a down converter, so I should be able to "see" 10GHz band signals on my (low-cost) Tiny SA spectrum analyzer.

I have a few of the modules, so here goes:

With a previous test I had used a LNB with a more expensive spectrum analyzer I had access to. I tuned some HB100 modules to different frequencies, so I had some simple signal sources on frequencies from 10300 up to 10500MHz in 25MHz steps. I also made one for 10368MHz (narrow band) and for 10489MHz (QO100 segment).

Today I wanted to test how the HB100 module did as a simple dowm converter. Because it has been used with (broadcast) FM band receivers I am aware that it can be used as a general down converter, and sure enough, using a 10450MHz HB100 and a 10375MHz module, connecting the spectrum analyzer to the IF output of the module produced a 75MHz IF output. It does work as I expected.

However, I do not know the RF or IF) bandwidth of the module, so I have not checked that.

The base bandwidth of the Tiny SA is 350MHz, so I tested with a 10300 module and a 10600 module, and got a nice 300MHz signal. Using the modules is a bit tricky because the apparent output varies a lot when tuning.

Using a 10600MHz module should make "seeing" 10300 - 10900MHz with a small gap around 10600 (zero IF). Not too bad for a $5 module. For the putpose I also made a 10500MHz module (10200 - 10800MHz coverage) a 10300MHz module can be added for coverage all the way down to the 10000MHz band edge (10000 - 10600MHz)

I am well aware that I do not have any image rejection, but as long as I can calculate expected frequencies I should be able to estimate the spectrum of an oscillator or a transmitter.

The Tiny SA has a base bandwidth of 350MHz (LOW input), but also has an extended coverage up to 960MHz, so it should be possible to see more than 1800MHz with a single module. The question is how much IF bandwidth the module can provide. 

SM6WHY estimates on his blog that the IF bandwidth of the HB100 might be up to 2GHz. I have my doubts, but if that is the case I might try using my Chinese 35 - 4400MHz (primitive) spectrum analyzer which uses direct conversion to sweep the band. If I recall correctly, only 350MHz can be displayed at a time, but the 10500MHz version then might be able to cover 8500 - 12500MHz with a small gap around 10500.

Even if this is far from calibrated, it is much better than not being able to see anything.

For the initial test I just used the modules lying on the desk, with the antennas there. I do think that removing/disconnecting the antenna(s) and adding connectors, and put the module in a stable casing will improve the set-up considerably, both with respect to stability and reliability.

What do you think? a spectrum analyzer extender to the 10GHz band for about $5? Not bad.