Monday, 27 February 2017

HF activity plus Shack Computers: some thoughts.

I was disappointed to have missed Dave, G4FKI, who was passing through the area recently. Altered plans due to some snow meant our paths did not cross. Dave mentioned that he is active on 160m WSPR. I decided to give it a try and failed to get a match on my cobbled-together antenna. However, I did spend that day on 80m WSPR instead. It was quite interesting - all Europe except for EA/LA3JJ. Good to see Jon Ove on my screen again, and to work Africa after a long gap!
80m WSPR activity at GM4FVM on 23 February 2017.
 My regular forays onto 40m have also been quite good (by my standards) this past week ...
40m contacts (mostly JT9) at GM4FVM 20 to 27 February 2017
Click to enlarge if necessary.

It was good to reach Afghanistan on 40m, which is a first for me. Especially nice is that I have not really been trying, just coming on for a contact before going to bed.

There is something pleasing about working a few stations on a simple low dipole.
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Shack computers? Me?

Well after a few issues with MSK144 and one specific type of processor, which we will leave aside for now, I have been pondering about what makes a good shack computer, and what factors are worth taking into consideration in selecting one. So here are some questions and I hope useful answers.

1) Do I need one at all?
No. There is a lot of joy to be had just working with a rig and a key or microphone. You can keep a paper log (if you need to keep one at all) and use paper QSLs (if you bother with those as well). No problem with that.

All you will be missing is a well organised log, instant QSLs, and superb digital modes such as PSK, JT9, JT65, WSPR, MSK144, ...

2) Will a computer not make radio noise and interfere with my reception?
Yes, probably, but there are steps that you can take. Firstly, try turning the computer on and off while listening to the band noise. A small amount of noise from a computer is inevitable. It depends on where your antenna is placed in relation to your shack, and where the noise is coming from.

If there is a lot of noise you can still take some measures to reduce it.

Most desktop computers have metal cases and these form Faraday screens which stop a lot of the noise getting out. However, the leads coming out of the computer leading to the rig often conduct and then radiate noise. The main weapon we have against this is the clip on ferrite or the ferrite ring.
Clip on ferrites come in many grades and sizes. The more turns of cable you get the better.
I have dozens of these in place. The closer you can get to the plug the better. If I cannot solve it that way I can always use a ferrite rig, which allows a lot of turns.
There are various diagrams you can see on the web showing how to wrap cables through clip on ferrites and rings. With the ring, you can reverse the direction of coil half way through for even more effectiveness.

So you have stopped the computer itself radiating thanks to the metal case, you have stopped the radiation from leads, what else can go wrong? Well the display screen itself can radiate. There is not much you can do about that, other than to try a different screen...

3) Do I need an expensive, highly rated computer?
No. Generally most amateur radio programs run with very little use of computer power. The only exception I have encountered recently is the real time decoding on MSK144. This is heavy but most reasonably powered computers can handle it. For any other mode a fairly moderate standard is all you need. For example, you can buy a Linx Windows Tablet on eBay currently for £89 (a bit more for one including the plug-in keyboard). Here is the Linx running JT65 (not a great photo, sorry)
The station at the other end does not know I am using a low powered tablet computer (for interest, the processor is a 32-bit Intel Atom single core running at 1.33GHz with 2.0GB of RAM).

Be wary though. This is a Windows tablet. You can get some of the main amateur software for other operating systems, but if you use Android, Chrome, Linux, Apple or other operating systems your choice of commercially available software is quite limited.

Conventionally, laptop computers differ from tablets (in addition to being bigger) by having more powerful processors, more RAM and more storage. This division is becoming blurred, as is the convention for laptops to have mechanical hard discs. Many now have solid state storage. The Linx above has the feel and look of a laptop when it has the keyboard attached, and with solid state storage it runs for ages on battery power. Great for operating "holiday style" from apartments in Portugal.

Having said all that, a laptop with more power is more at home in the shack. More capable of handling the data, the log and QRZ.com all at once.

The failing of both portable computer types which arises when it comes to shack work is often the noise created by the power supply. You can run on battery power, for a while anyway. Many of the supplied power supplies radiate lots of noise, and generic ones bought on eBay are usually worse. If you find a quiet power supply, guard it carefully.

4) Why do you use a desktop then?
I use up to 14 USB connections, plus two on the front for temporary use. Most laptops only have three or four USB connections. I find that almost all the external USB extender units I have used have caused lots of radio noise. I prefer to have the important USB plugs connected directly to the computer motherboard, either on the provided sockets on the board or using extension sockets plugged into the header sockets on the board.
Left - USB3 sockets with header socket plug, Right - USB3 plug in PCI-E board
Another terrible photo - I would encourage you not to click to enlarge this one. Must take better photos in future. Anyway, with a desktop you can add sockets, whereas with laptops and tablets, generally, you have to use noisy outboard boxes, which are also slower.

I prefer the direct sockets plugged into the header pins on the board, but the PCI-E plug in boards are OK for things that do not matter if they are slow to connect (not rigs!).

I use a desktop because I can mix and match the elements I use. Everything is in a nice metal box for screening. It all hides beneath the desk which puts another metre distance between the antennas and the computer. Also, they can have mighty fast processors at lower prices than fast laptops. And finally, I can buy cheap add-on bits and fit them myself.

I am not saying that a desktop is for everybody, but it works very well for me.

5) So you don't get any noise then?
Erm, yes, sometimes. You never know how much noise something is going to make by looking at it.
I had this desk top PC power supply for several years before trying to use it in the shack. It made terrible noise on 40m
Perfectly suitable computer parts outside the shack become demons inside. Yes I could try to solve the noise problem with this power supply but I have another to use instead. 

I have had similar problems with display screens. Having had two good ones of a certain make, the next one put a nasty carrier right on the 4m calling frequency. Actually, I would not have minded that carrier being just about anywhere else in the spectrum, but it decided to appear right where I did not want it. Fortunately I could just move the display screen onto a non-radio computer somewhere else.

These are the trials and tribulations of managing in the modern "sell 'em cheap" world.

My philosophy is to avoid noise problems by shifting problematic items to other duties outside the shack (which I can do, luckily).  That is another reason why I do not use laptops in the shack, as they are pricy items to buy to find a noise problem which cannot be fixed.

For other things, there are ferrites.

6) How do you keep track of it all?
With several things going on at once, good question. I use two display screens.

I segregate the data programs and the rotator information and put them on one screen (with everything in the same relation as the rig are in the shack, e.g. IC-7300 bottom left). Then I use the main screen to show QRZ.com, DXMAPS, browser, email etc.

One computer, two screens.
Left hand screen - radio data, rotator etc.
Right hand screen - browsers, log (usually minimised), email, etc.
The shack photo on my QRZ.com page shows it working. I cannot actually keep track of it all unless I segregate it this way.



You can add an extra screen to many tablets, and almost all laptops and desktops. With a desktop you can also add a hardware laden display card which takes a lot of the display processing off the main computer processor.


In the past I have used two computers at once I found it very difficult to manage. Controlling them from one keyboard and mouse involved a KVM switch which was noisy (of course), using the home network to control them was slow, there was more noise ... I found it simpler for me to work with one computer and two screens.


7) So why don't you route everything through something like Ham Radio Deluxe.
I have no problem with HRD, and I do use it for certain data modes. I do not use it to try to control everything because I have several rigs and two rotators. Yes, you can have rotator control with HRD, but then I would need multiple instances of HRD and that is getting crazy. I found trying to route other data modes through HRD caused latency problems. 

I have also tried the remote control software from Icom and Kenwood. It is fine, but I think I am at the limit of what one person can control through one computer.

So I just turn the VFO knob, or cycle through the memories. Call me old fashioned ....
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OK, that is the way I do it. Others will have different ideas. 

But I would suggest, 
 - do not spend too much in case what you buy is very noisy, 
 - there is no need to go for something expensive or even new (my current shack computer is based on a second hand, i.e. used, £79 eBay cast-off). 
 - noise is a problem but it is worth trying to sort it out.

I would encourage anyone to try to get the best out of their shack computer. Those data modes are great.

73

Jim

GM4FVM

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