Posted on July 16, 2017
As expected, even though the variable capacitor was a massive Palstar model, a roller inductor has more friction, hence requires more torque.
When I spun it as fast as I could it drew just under 1 amp. That’s very reasonable. One BIG issue is that with “direct drive”, the set screws would unloosen – this is because the shafts of the stepper are stainless steel and there is rattle when you microstep.
Now I understand why Palstar and others use belt driven auto tuners with these large components!
Posted on July 16, 2017
There is more than enough torque for the large Palstar variable capacitor. There was little extra power drawn, but not much.
I’ll try the roller inductor later today.
Posted on July 16, 2017
VOACAP Online with its new grey line time mapping. This the time I worked Manuel this morning.
A year ago I worked LU for the first time on Top Band. I ended up working 5 new one’s between June 21 and September 21, so it was a good summer. I had been working on 160M RX antenna systems, and am now 100% set antenna wise for as long as I am at this QTH. I just worked LU5OM and it took some effort – I am sure I was hearing him better than he heard me.
So far this summer, I’ve worked one new one on Top Band, and I expect maybe a couple more – I’m hoping for V47 and T88, but with lightning to the East of me, I think South America and the Pacific are the best directions.
I still heard LU5OM CQ-ing right at his sunrise. He was still 559 – there was no “enhancement” as there was a few days ago.
The biggest factor on 160M is that there just aren’t many DX stations on this band. Its understandable given how hard it is to make even garden variety DX QSO’s. Trying to be effective on Top Band from a small lot took me years to get it figured out, and I ended up with a pretty unique antenna – one I have never seen mentioned or modeled before.
In fact, no kidding, I’m loving the Mod Bob + u.RAT a lot more than the N6BT DXU-32, which was my previous “favorite” antenna. Cracking the low band nut is a real challenge and a great feat when you finally do.
Posted on July 15, 2017
I’ve been so busy this week getting the u.RAT to work, and work is busy as well that I did not even have time to start playing with the Rigol DS 1024z. I at least have a square wave on it, using a procedure you use to calibrate your probes.
A little tour of the Maker part of the shack.
I have a list of about 12 things I’m doing that are “odds and ends”. I’ll be adding a piece of plexiglass up where you saw those insulators, because it helps with heating and cooling making the shack completely “double paned”. I was able to create a Noobs and Raspberry Pi Jesse Lite boot SD mini card for the Raspberry Pi Zero W, but that little processor died after just a few reboots. I think it’s very important to put these processors in cases right away, else they are susceptible to static and other damaging things. The larger Pi board seems impervious to such problems.
When it isn’t 100 plus degrees out, I will take that old tuner chassis you see above and add rails for the stepper motors. I’m actually more excited about giving presentations and sharing the u.RAT project than retrofitting my Mod Bob remote tuner. Just leaving the BT1500A tuned to 160M is all I need until Bouvet. For me, DXCC just isn’t very exciting any more and adding entities won’t help – its still watching the grass grow.
I am booked to give 4 presentations about it already, and I have floated an idea for a very advanced KPOD at Elecraft and they like it. It’s an extension of my simple project, that’s all I can share right now.
I will be getting the OLED and replacement Raspberry Pi Zero W this week, so will try again.
There are other odds and ends, but the success of getting the u.RAT to work this week was, and I am sure will be a huge milestone moving forward.
A great week and weekend indeed!
Speaking of that, we are half way between kids getting out of school and going back to school. Sort of like summer is half over.
My favorite season is Fall, so, this is cool.
Posted on July 15, 2017
Posted on July 14, 2017
For a couple of hours this morning I listened to LU5OM who called CQ during the different phases of the grey line. He was only ESP when we were both in night time darkness. But his signal steadily got better during each “progression”:
He was Q5 during this next “phase”. As always, you can’t go by S meter on Top Band – its all about signal to noise ratio, and the Mod Bob is great on TX and RX. In fact it sometimes beats my other two RX antennas, which hardly ever happened with my previous RX antennas – and I have tried them all last summer.
He was very strong during this phase – and stayed this way until his sunrise – right when the final transition to sunrise took place. The most interesting thing is that right now – Manuel is in his Winter, and so he has his longest and slowest greyline. I have my fastest being this far north.
You know, since LU5OM is about 2/3rds of the way to 3Y, and because Manuel runs an Inverted L with only 500 watts, I am starting to think that Bouvet could very well be workable on Top Band.
Lets use VOACAP Online to analyze Bouvet in October 2017 and January 2018 – just to line up with post Autumnal Equinox and post Winter Solstice:
Roughly 0430 utc, and the West Coast evening should be very possible. Because they will be running 1500 watts and its almost entirely a water path, I am now much more convinced that the Low Bands will be super important for Bouvet in October, but lets looks at when 3Y0Z will be there:
VOACAP Online covers the year grey line wise – so I am using December 31 here. What I have learned from this is that from October through when 3Y0Z are on the air, the West Coast should be able to work Bouvet on all low bands, but particularly 160M.
Competition will be the only real deciding factor, and as long as the team asks for West Coast Only, we might do well. Now I am especially happy that I have the Mod Bob with URAT and the SPE Expert 1.3K FA.
I’m as set as I can be – and have done all the right things to get ready for Bouvet.
While I’m waiting I will be mostly “Making”. No watching the grass grow or experiencing the “DX Doldrums” here!
And thanks again, Jari, OH6BG – these new VOACAP Online features now match the analysis that you can find in the ON4UN Lowband DX-ing Book – a must for any serious DXer.
As soon as we start hearing the ZS stations on the 40M LP morning path I will do a similar analysis using the new and improved VOACAP Online – it will be a lot of fun, and Jari has taken the work out of quickly understanding why stations are Q5 or ESP on the low bands. That is quite a feat!
Posted on July 14, 2017
Here are some key design notes and learnings:
- I had to use a Raspberry Pi due to the fact that the KPOD driver software is written in C and compiled on Linux.
- The KPOD is a proprietary device using the HIDRAW protocol, so its not exactly the same as a keyboard or mouse
- The WiringPi library turns the interfacing part between software and pin outs on the RaspberryPi into basically a “virtual Arduino”. This makes it amazingly simple to use the Raspi GPIO interface / pins
- I do not need the Enable positive or negative lines from the TB6600 drivers
- The TB6600 drivers are probably overkill, but they represent good engineering and stay cool no matter what
- The delay in the program and the DIP switches on the drivers are what set the steppers in the right “zone” as far as response from the KPOD. The DIP switches are – (1 – 6): U,D,D,D,U,U
- The wiring of the drivers is very easy – all grounds are ganged, and the 3.3 and 5V grounds are tied together – meaning one ground wire for everything is all that is needed. Then, only two wires are needed from the drivers – one for direction (DIR) and one for step (PUL).
- I’m splitting the system in two – drivers and steppers out at the tuner and everything else in the shack. Since I will use a 12v to 5V regulated and filtered step down gizmo to supply 5V to the Raspi off of a 12V supply, the 5V stays in the shack and 12v goes out to the tuner. This means 12V + and – wires and 4 wires for the drivers total. Add in two wires for the kill switches and you get exactly 8 wires needed from the control box in the shack to the tuner box
- The Palstar BT1500A is a truly amazing balanced line tuner. It offers pretty much every configurable setting for all low bands with an antenna that is resonant on 160M but used also on 80, 40 and 30. Since the SPE Expert 1.3K FA amplifier requires a low SWR, the Palstar tuner is exactly the right tuner. I did remember to bypass the SPE internal ATU for 160, 80 and 30M, which are the bands the Mod Bob and Palstar will be used on. I do use the ATU in the SPE on my DXE 40M phased array and my 20M homebrew 2 element yagi
- The Mod Bob is the most amazing low band antenna I have used because it covers low bands with very respectable performance – and this is the “holy grail” of antennas. I never expected to finally get a bastardized Bobtail Curtain to work so well. I tried feeding Bobtails twice before against ground and they seemed no better than a single vertical. HOWEVER, this open wire balanced line fed antenna models great and plays better than expected. Sure – a dipole up a half wave, but I can only get a dipole 1/2 wl on 30M, so I’d have a cloud warmer on all of the lower bands. This is where what I read on Tom, W8JI’s web site has to be put in context. Yes, I would always choose one or more elements up 1/2 wl over any vertical, but, to do what I have done on the low bands (and given my crappy terrain down here in the bowl), I truly believe I have conquered the problem with flying colors
- The URAT consumes .75 amps with no load – once I have the variable capacitor and the roller inductor added, I will be able to see the current draw with my variable bench supply. Now I see why a variable bench supply is so important – besides setting current limiting on the stepper drivers (so you don’t burn the drivers up or run them over heated), you can protect what you plug into the supply voltage and current wise. Then, you can monitor how much current the steppers are drawing under load and not under load
- The Raspberry Pi Zero W plus Adafruit Pi-OLED is the absolute perfect device for the processor part of this project – small and has exactly what you need – not a thing more. A VERY elegant design
- The KPOD can be marketed to the much larger Maker community. It is a wonderful ham radio shack automation controller – and its applications above and beyond the URAT seem only limited by your imagination
- I think I am having the most fun I have ever had in electronics and ham radio. This Maker World has expanded my world so far past just sitting in the shack waiting for the next ATNO that its not even funny. I feel like I used to just be an ATNO junkie . . . “Hands on Ham Radio” is my rehab. To be fair – building antennas used to be my rehab – but I’ve run the gamut on that
- I won’t be working on any more DX-peditions, but will instead be making stuff in my shack / lab
- I feel that just doing my first Maker project that its as important as Honor Roll and DX-pedition of the Year. I don’t know why – this is totally an emotional response
- If the steppers don’t draw more than twice what they under no load, it might have been possible to use the Adafruit Pi Hat Motor Shield – which is rated at 1.2 amps per stepper, HOWEVER, because the drivers will go out with the steppers in the tuner box – the Adafruit hat doesn’t work for this configuration. For another project it will be perfect – perhaps with the Nema 17 steppers I have – since they are lighter duty but still quite strong. I felt the NEMA 23’s were best for the torque needed for the L and C components
- When I explained the difference between the Raspberry Pi and Arduino, she asked “Why would you even bother with the Arduino?” That’s a very good question, since the Raspi Zero W costs only $26 and the Arduino – $18.82 (official units not cheap knock offs)
- Writing code for embedded devices is just too much fun – and my C and Python background were both very important. Also – having been an Oracle DBA on UNIX and Linux meant that I had no learning curve with what might be the most technical part of the project. The electronics part is about 8th grade science fair level – the software part a little higher – but kids these days take to this stuff very quickly – don’t underestimate them. Great memories of 1971 building my first Heathkit come rushing back
- I feel like I can be a product designer now – its an awesome feeling – like I can do anything
So – how much is this experience worth in dollars?