QO-100 Analogue Ground Station

Yes, it can be done. One can use a fully analogue ground station for QO-100 operations.

My first attempt included a Yaesu FT-290R2 for reception, along a Yeasu FT-817 for transmission on 70cm. Once a TX frequency has been established, following the drift of the LNB was an OK-ish task during QSOs. Changing frequencies was an unpleasant juggle of setting the receive frequency and trying to find the transmit frequency without annoying everybody else of the transponder. This ballet is performed with VFO controls of two different radios.

Second attempt: Yaesu FT-736R, the satellite machine from the past. It was doing great, in particular when changing frequencies, using the satellite mode. However, my cheap LNB kept drifting in sunlight, while the up-link converter stayed rock-solid. Hence, using the FT-736R was a constant switching between SAT-mode and RX-QRG. Once a frequency was established, TX-QRG needed to be adjusted. I am not sure how many actuations the little SAT-switch can take. What I am concerned, it took a lot of focusing in order to not adjust the VFO in the wrong setting, thereby messing up the RX/TX-offset.
With a stabilized LNB, this might be a different story.
I liked the possibility to use the VFO-knob to scan up and down over the band, knowing that, whenever I pushed the PTT, the frequency would be at least close.

The FT-736R is back in its box for now. In terms of having contacts, the SDR-option seems a lot more convenient, in particular when locking the reception to the satellite's beacon. Transmission is stable enough, in my experience, so nothing to be bothered about.
As an added bonus of the SDR solution of the analogue way, there is signal processing available when using a computer for reception. 

Further, I tried to use a Yaesu FT-790R2 as baseband up-link transmitter. It did work. However, there are two observations to share: 1) some weird spurious transmission were visible in A1A, 2) the audio in J3E was OK but not punchy at all.

Consequently, I will be using the Yaesu FT-817 as a baseband TX and the SDR receive setup, for the time being.

QO-100 A1A up-link idea

This is something I had in mind for quite some time by now. What about an A1A only up-link for QO-100?

This is an old idea. At the time, this idea was to create a CW transmitter for 70cm based of a 2m signal. I have seen similar attempts to get something transmitting on 3cm. So, why not on 13cm?

Having done some "maths", I came up with a carrier of 96MHz, which is available as a regular crystal.

With a factor of 25, this will result in a 2.4GHz frequency.

Now, why is that interesting? The multiplication of 25 can be achieved with 5 x 5 .... dahhhh. Yes, sounds simple enough. Here is the interesting thing, it should be easy with a square-wave oscillator to generate 480MHz. At this frequency, it is pretty easy to build a strip-line filter or cavity resonator to clean the signal. Now, we just have to multiply the signal again. So, we might want to use a non-linear amplifier again, in order to create all the wonderful harmonics. Again, a 2.4GHz resonator should not be to hard to build.
And here is the idea. What if we used a rather high powered amplifier at 480MHz, which is easy to build, and a non-linear element to generate all those harmonics at decent power.

With a VTCXO of 96MHz, slightly pulled by a few kHz, one should be easily creating a signal in the CW band of QO-100, using the above mentioned method.

QO-100 Up-link update

 The last few days have seen a little bit of modification and optimization to my setup. Mainly, the shortening of the helix feed. While I was monitoring my A1A signal on the downlink, I gradually cut windings of the the uplink helix. I was not sure if I could see any difference in signal strength, to be honest. Anyway, I ended up with this:

Downlink (left) and Uplink (right)

The dishes are ducked down for a reason. This is my roof deck, we often experience heavy winds in the Netherlands. With the dishes sitting low, weighted down, the positions will be stable over the course of the year.

Presently, the UL uses 10m of RG-6 cable, the original one with the hollow dielectric. This length is certainly not ideal. In the near future, I will build an outdoor unit, sitting next to the UL feed, housing the converter and the PA. This should improve my signal by some dB.

For the time being, all I heard was that my signal could be stronger, but was fine to copy... what more do you want?

73!

SDR and the DJ-Tech DJ-Mouse

Here is what you have missed, if you are not in the world of DJs.
The DJ-Tech Mouse, which employs a super-nice big wheel in the center. Have a look:
https://djtechtools.com/2009/08/20/the-dj-mouse/

Guess what this wheel can be used for in any random SDR software.... a VFO.

QO-100 ground station update

My previous post show tons of opportunities for improvement. The more I was thinking about those, the closer I came to my initial gut feel, i.e. using a helix as a feed for the up-link dish.
In fact, the helix was sitting on my desk for quite some time by now. I had doubts how to mount the helix in the first place, also matching appeared to be a big deal, without the help of any decent GHz-capable measurement equipment.

However, seen that no matter what I did, I could not really improve the performance of the up-link. Essentially, I spent two entire night to find the best position of the dish. (Night-time, so nobody is on the satellite, avoiding to disturb more senior users)

When listening to traffic on Es'hail 2, I often heard that operators switched from patch feeds to helical feeds for their up-links and reported better results with those. Was my gut feeling correct?!

So, today, I returned to trusting my gut feeling. So I removed the patch from the weird reflector / holder shown in the last post. I used a small piece of PCB to form a base, essentially a mount, for the helix. Yes, I could pretend that this was a carefully calculated matching strip for matching my 75Ohm SatTV cable to the helix, but it wasn't. I dimensioned and adjusted the PCB just such that the helix would be - more or less - in the center of the reflector.

note the remainders of glue where the patch was

Feel free to count the turns, which would result in a little of 6. My idea was, that I could always cut some off. It is much harder to cut wire on ;-)

The photo shows, it is night-time again. So, why not firing up the station and do some test transmissions?
And how right was my gut?!

lower beacon at 69dBuV

What a difference! My signal is now just 9dB weaker than the lower beacon!
Of course I had to do some side-band test. And yes, now I think I am QSO worthy.

The present setup still employs the "attenuator" made of about 10m of 70Ohm SatTV cable. So, as long as I still have not yet figured out how to build an outdoor unit (PSU,TX-converter and PA in a weather-proof box), I still will be able to do one or the other QSO.

QO-100 Es'hail-2 ground station

It has been a while since I was busy with a ground station for the geosynchronous (geostationary) satellite Es'hail-2 also known as Qatar Oscar 100 or QO-100.

The major delay in the beginning of the project was to receive an assortment of coax adapters. Finally, those were in, now, the down-link was sorted rather quickly. There was a disused 35cm dish, which I used to analog ASTRA reception. When ASTRA satellites turned digital, I lost interest in watching those, so I never upgraded the equipment. Although, I never dumped any of that stuff either.

So, here was my down-link receiver, PLL-LNB with the old 35cm dish in a FUNcube SDR dongle. That worked perfectly. I later replaced the FUNcube dingle with an SDRplay RSP1A, so that I could receive the entire bandwidth of QO-100's narrow band transponder, allowing for locking on the mid-beacon for frequency stabilization.

Concerning the up-link, I decided to go for a DXpatrol converter. I like the possibility to select the baseband, although, I will probably stick with 432MHz.
To amplify the 2.4GHz signal, I went for the omni-present chinese 8W WiFi-PA.

Then came a long struggle of what to do about the up-link hardware.
Initially, I considered an RHCP helical antenna, something in the realm of 15 to 20 turns.
Then I found a 60cm offset dish in the trash. So, what about a 4 to 6 turn LHCP feeding helix? And yes, I wound that thing. But, the mechanical details of holding the thing in place put me off again.
Finally, I decided on a K3TX LHCP patch feed for the 60cm dish. 
I know, 60cm is rather small for a 13cm wavelengnth... 10 lambda upwards make the deal... I know. However, 60cm is what I got.

The dish I got had not LNB/feed mounting hardware, so this is what I came up with.

K3TZ LHCP patch, PCB over Al

You may wonder what the strange structure to the left is, this will be the mount to the dish.
Something not obvious from the above picture, I am using a F-connector for this feed.
Please note that this picture was taken before I filed down the edges to of the reflector to the circle seen scratched into the aluminium sheet.

The patch feed added to the up-link dish

Winds can be pretty strong over here, so I mounted the dish to a concrete parasol stand.

Up-link (grey) and down-link (white)

Note that both channels are using 75Ohms satellite cable. While for the down-link this is fine, the up-link will experience this as an attenuator, in particular over the length I am using for this experimental setup (about 20m).

Having done some experiments, I could hear my signals in both CW and SSB (USB). While CW was easy, single side band was somewhat challenging. I would not count for any SSB QSO with the attenuator in place.
However, CW should be just fine. Have a look how the signal compares to the lower beacon:

Lower beacon and pa1gsj carrier

This was my first day of bouncing signals from QO-100. I know what I need to do now, i.e. building an outdoors cabinet next to the up-link dish.

I hope to be QRV as an audible station on Es'hail-2 soon.

Update

After further improvements, I can now provide relative signal strengths from my receive setup:

• transponder noise about 32 dBuV
• CW beacon 58 dBuV
• my own signal 41 dBuV

I can also report that I made two CW contacts by now, the lower report was 589. 

Boom boom pafffff

Something totally off topic today, OK, it's audio, no electronics involved however.

IKEA is known for some interesting projects here and there, beyond the famous bookshelf. Lately, they introduced a product range which appears to be a collection of random stuff, the collection being "FREKVENS". There are even products that could be interesting for a blog concerned with electronics. No worries, I wont be writing about a silver rain coat or a silver cushion cover either.
Let's have a closer look at the only real IKEA flat pack product in the collections, the FREKVENS Cajón (drum).
No, this is not a drum, this is a cajón, and instrument well known in Spanish and Afro-Cuban music. A cajón can create sounds similar to various parts of a drum kit, which is a matter of great skill, which I don't have.
There are a few more things wrong in the product listing, at least what the images are concerned. The side with the big whole is the back-side (or reverse, depending on your style of English). Hence, the guy in the photo sits on it the wrong way. Also, he appears to be slapping the sides of the instrument, which are made of much thicker material and not supposed to be the main playing surface.

Anyways, I bought one of those flat-pack instrument kits and build it according to the provided instructions. BIG mistake! The more I learn about the instrument, the more obvious this should have been.
The assembly instructions take a similar order to something like a nightstand. Which, seen from IKEA's perspective, does make sense. However, when following the leaflet, it is almost inevitable to create a misaligned box  that does not sound right.

Step 1
The instructions start with mounting the snares to the (front of the) bottom-plate, so far so good.

Step 2
The side-walls are screwed to the bottom-plate. This is the first instance where things can go wrong. The alignment of the outer edges of bottom-plate and side-walls needs to be precise. This might not be that important on the bottom-plate, desirable however.

Steps 3 and 4
According to the instructions, the top-plate is now mounted to the side walls, very similar to bookshelves, nightstands,  etc. I cannot emphasize enough, don't do this yet. I did it and I ended up with a slightly misaligned top-plate. This misalignment kills the instrument!

Step 5
In this step, the playing surface, i.e. the front, is mounted. Remember, the front is where the snares are. This is very important for the functioning of the instrument and not clear from the instructions.
This step should be done after step 2, if not before...
If you followed up to now, you will understand that it is important to not tie down any of those screws yet.

Step 6
Here, the back-plate of the cajón is screwed to what we assembled so far. Please note, we skipped steps 3 and 4, so there wont be any (I should have written about that in step 5, sorry!).

Final assembly according to me
If you followed my advice, you skipped steps 3 and 4. What you should have by now should be a square wobbly bucket with no lid.
At this stage, carefully work the top-plate into its position. This might be a bit tricky, therefore, we did not tighten those screws. Once the top-plate is in place, we want to first tighten the screws of the front-plate including the ones we skipped. This will auto-align the top-plate to the side-walls. This alignment is most important to the good functioning of the instrument.
Once this alignment is established, screw down and tighten the 2 front screws on the top and the side-walls.
Now apply all the remaining screws. And tighten all screws on the back and the lower half of the screws on the front.

Tune up
In case of all screws being tight, you will have to hit the cajón very hard to get the snare effect. This will result in an imbalance between the snare and the bass drum sounds.
Therefore, what you are looking for is a small gap between the top-plate and the front-plate. To realize a somewhat even gap to your liking, you have 5 screws in the top half of the front-plate to play with, i.e. loosen and tighten. Every little bit of tension here and there will change the tone and snare sound created by the cajón. It took me a while to balance the right and left corners of the upper playing surface.

Conclusion
IKEA is good in creating wooden flap-pack products. The FREKVENS Cajón is no exception, when built and aligned correctly.
There are competing products available from musical instruments suppliers, here is an example. This example supposedly requires additional materials for assembly, although at a lower price.
What I am concerned, after having aligned my cajón, I am pretty happy with the sounds it can create and look forward to learning this instrument.

60m Region 1 Crystal Combination

Sorry for having been silent for so long. There was a lot going on over the last few years.

Anyway, the present situation brought me back to Ham Radio and thinking of building stuff. However, I have to mention that this post should be considered more as a note to myself or inspiration of fellow RF designers, rather than a fully worked out recipe.

The topic of one of my next projects will be building some QRP rig for 60m. Over here in the Netherlands and in Region 1, we got a very small slot from 5351.5kHz to 5366.5kHz assigned as secondary service with a maximum EIRP of 15W. This is a range which appears to me to be almost ideal for building some QRP gear.
In modern times, we could use DDS systems to get us anywhere with anything, I must admit. In the older days, using combinations of readily available inexpensive crystals was the #1 choice for QRP.
Whilst having CW in mind, some of my thoughts my actually be useful for a side-band superhet design.

Here is what I found:

• 15.360 MHz crystals for use in a VXO (or superVXO)
• 10.000 MHz crystals and oscillators for BFO and filter stages.

To be honest, I just cooked up the idea and have not thought is through entirely. But here is what my mind came up right away.

As a side remark, subtractively mixing of crystal oscillators is a well known method of eliminating temperature drifts. So, effectively, this could lead to very stable designs, when done properly.

Transmitter

Option A is a canned 10.000MHz oscillator and push the signal through a 10MHz crystal in order to produce a sine wave.

Option B would be a regular crystal controlled discrete beat oscillator.

Mix any of option A or B with a 15.360MHz VXO to generate a 5.360MHz output signal. Should the pull be insufficient (not very likely at 15MHz) one could still use a superVXO.

Receiver

Here is where the concept presently struggles. 

Of course you would think building a crystal filter with inexpensive 10MHz crystals. However, this would probably exclude option A for the TX. Here is where the struggle lies, would it be possible to create a filter design with 10.000MHz crystals that pulls 600 or 800Hz away?

When using option B for the TX, of course, one would add a simple RIT design.

CW

You have seen me writing about two different options. Why bother, you might ask yourself. Well, to me, it is all about simplicity. 

For a mere transmitter, in option A, I might just use a canned 10.000MHz high precision oscillator and key just said oscillator, rather than a buffer stage for CW operations.  Experimentation will have to show how that sounds. In terms of simplicity, this would be pretty neat. Such a TX could be combined with some sort of SDR receiver or maybe a Polyakov direct conversion RX based on a 2.68MHz VFO.

Option B would allow for a fairly regular QRP CW transceiver. Nothing to write home about, however, this will certainly be a more complex design.

SSB

Obviously, option A is no longer available here. However, seen that it is recommended to use USB on the Region 1 assigned 30m band, it would be an obvious measure to use a pulled 10MHz BFO for both RX and TX. However, mind the mirror, we are subtractively mixing here.

Having in mind the upper portion of the 60m band, i.e. the weak signal band from 5366.0 to 5366.5kHz, option A might just come into play again. Mind you, QRSS & Co, don't mind about the sideband too much, as long as the operator knows what she/he is doing.

Over the upcoming days, I will work on a concept/prototype and hopefully will be able to report on some progress soon.

 

Portable Stereo Stage

This channel has been silent for some time by now, sorry for that! Will be getting more active in the near future.
While this blog started as a RF only outlet, slowly I drifted to all sort of electronics, including speaker enclosure designs using PVC piping material. Yes, those pipes are still in my living room, connected to a class A tube amplifier and fed by some CD players. While sounding pretty good, this is not really portable per se, although, seen against cement speaker enclosure, this is probably relatively portable.
Travelling back and forth nowadays, I was searching for an alternative.

Lately, I found said alternative. Got a couple of JBL Flip 4 BT speakers. Those are connected to my phone using BT.

Those JBL Flip 4 BT speakers can be used as a pair of stereo speakers. Not having read any instructions, I took me some to to figure out how to actually create that stereo stage. Having tested the setup with different kind of listening, from Vivaldi over Herbie Hancock to Dream Theater, I am deeply impressed!
Seen that the setup is that small and inexpensive that fact that I could not find any flaw in the sound experience tells me that I found my next stereo system.
Although in comparison to my tube class A amplifier, some additional noise is evident.

For aesthetic reasons, I chose both Flip 4s to be black. Of course this makes them a little bit more difficult to setup in the right way. A small sticker indicating which is left and which is right should not be a bit deal however.

If you can live with a little bit of pink noise, a setup of dual JBL Flip 4 speakers is highly recommended.

PVC Tubes Driven by Tubes

Dear reader,

please accept my apologies for keeping you in suspense over my latest projects for so long. 2017 was a very intense year for me. During said year, I changed my day-jobs twice, so, the radio hobby and the audio hobby had to take a break. Concerning jobs, I believe to have finally found the position of my dreams with a lot a really nice people in the company... I believe I have never been happier before!
Anyway, this is not about life, this is about driving tubes, PVC that is, with tubes, such as in vacuum.

My pipe dreams, as you know, are employing 3W (8Ohms) broadband drivers, which came with a super-cheap set. By now, I am convinced that those drivers were the most valuable part in the entire kit.

In search for a 2 x 3W class A amplifier, I came across a Chinese kit supplier (Douk Audio, cf. ebay), who sells single-ended class A amp kits based on 6N1 and 6P1 tubes. Said kits are comparably inexpensive and, while provide good quality parts, come without a mains-transformer.

My choice of mains transformer fell on a 100W transformer offered by a supplier in the UK, search for "big.daddy!" on ebay.

The combo works as a charm! The amplifier kit seems to be made for my pipe dreams.

As an audio source, I am presently using a professional grade table top DJ CD player by Numark.
In the future I consider to add a passive equalizer / tone control circuit to the setup in order to allow for compensating deficits from compressed digital audio formats. For now, I am pretty pleased with the raw performance from CDs.