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Have you Really? Wow!

January 15, 2017, 8:20 am
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Well,

This isn't really radio related, but I'm scribbling here to document my steps (well, thats what a blog is for - isn't it?).

At home we have a really pants copper telephone line based Internet connection provided by Sky. Now, nothing Sky can do really as its the infrastructure that makes the connection speeds so slow. We have also been having issues with Wireless speeds generally and also often hit a "bonkers" (as far as I can work out) restriction on the number of devices that can connect to my network. For some reason the DHCP works fine up to 16 devices, but as soon as device 17 tries to connect it fails.

Often this will be my Spectrum Analyser but also it happens to be the visiting sprogs laptop - all very inconvenient.

So today I've bought a TP-Link router with 5GHz and 2.4GHz wi-fi to replace the Sky provided box. The man in the shop told me this was impossible, as Sky will not release the username and password needed to connect to their network.

So, hacking hat on, here's how I've done it:
  1. First, I downloaded some software called Wire Shark from here. 
  2. Then I installed the software on a PC connected with a wired connection to my Sky router.
  3. Start Wire Shark recording network traffic and then re-boot the router so we capture the network traffic as the router starts up.
  4. Once re-booted, stop the software capture.
  5. use the filter in the Wire Shark software to look only at "udp.port == 67"
  6. In the search results look for "DHCP Discover"traffic and expand
  7. In the expanded area you will find "Option (61) Client Identifier"
  8. Right click and find the option to copy as printable text
  9. Paste the results into a text editor (I used Notepad++)
  10. Low and indeed behold, there is your Sky username and password in the format "=username|password"
I then quickly connected to the router and noted down the MAC address from the "Broadband Port" section of the config screens.

So, armed with this information I plugged in my new shiny TP-Link router, selected "Sky Broadband" as the ISP and entered my username and password. Bingo! I then checked the help on the router and changed (or rather cloned) the MAC address of the Sky router - this is so that from an external perspective you can't tell that the router has been changed.

Result: Much faster wi-fi and no restriction on the number of devices I can connect.

Local conditions.
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Fiddling with a Transistor

January 18, 2017, 7:47 am
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Well,

I found myself scratching my head the other day trying to remember the difference between Class A, B and C amplifiers and how that impacted a transistor bias.

To help me, I've drawn this quick schematic:

Now, you will see that R1 has a "*" next to it; that's because we are going to play with this value.

The transistor base will switch on when the voltage on the base is greater than 0.6V.

So, if we place a 10K resistor where R1 is, we place the base at DC voltage of about 1.6V. If we now apply a 2V peak to peak signal to the base (in my example it's a 100KHz signal), then the lowest point of the signal the base will be at 1.6V minus half the voltage peak to peak = 0.6V. Therefore the transistor will be switched on for the full input signal cycle.

The voltages on TP1 are in yellow and TP2 in blue. Here the first example with 10K as R1:


You can see that all of the input signal is above the dotted line (which is at 0.6V) and therefore the transistor is biased on throughout - this is Class A operation. Harmonically it looks like this:



Now, lets change R1 for 39K which will place the base at DC voltage 0.6V and apply the same 2V peak to peak signal. This time the transistor is only switched on for about half the cycle and the resultant voltages look like this:


Here we have 180 degrees of the input signal turning on the transistor - this is Class B operation. Harmonically it looks like this:


Finally, if we remove R1 completely, then the base of our transistor is at DC ground (being pulled low by the 4K7 resistor). If we now apply our signal we see this:


So the transistor is only on for less than 180 degrees of our input signal - this is Class C operation.

Harmonically it looks like this:


Now, you may wonder what use Class B and C are? Well, in an audio amplifier - none at all! You would hear all that distortion and harmonic content and it would sound completely awful. However, from an RF perspective, we can easily remove the harmonics from the output and retain just the target frequency - they all seem pretty much the same now - agree? And Class B and C amplifiers consume much less power (because the transistors aren't turned on the whole time) so are far more efficient. We just need a suitable low pass filter at the output and we can "reconstruct" our signal.

Interesting, egh?
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A Lawful what?

February 7, 2017, 10:53 am
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Well,

Back in the spring of last year we removed a load of trees from our property and also had some fairly extensive works undertaken in the garden. The net result was that the antennas at the property became much more visible from the road.



Now, one of my neighbors who is particularly grumpy, decided to question the legality of the mast(s) and antenna(s) at the house with our local council.

In accordance with the planning laws, they all should be subject to planning permission. However, theory says that because they have been in place for in excess of four years the council are unable to take enforcement action. Unfortunately, the onus is on me to prove they have been in place for that time.

Thanks to this blog and my obsession with taking photographs, I was able to generate a very comprehensive document containing a load of google dated photographs stored in the cloud showing each of the antennas and masts in place with a photo upload date.

Finally, after a long bureaucratic process, my Lawful Development Certificate has been issued.



So my grumpy neighbor can go stick his complaining!

Local conditions. 
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Tek 2465 Teardown

February 8, 2017, 1:23 am
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Well,

I have a Tektronics 2465 'scope that has some issues with it's timebase:


The sweep A is all out of bonk - there's a 10MHz signal applied and at a 50ns sweep time per devision we should see 5 sinewaves - we see 8 :-(

Sweep B is correct at 20ns however.

I've started to take the 'scope to bits and will use this blog entry to document things as I go. Here are the initial shots of the 'scope in bits:




So here you can see both U700 and U900 removed, I'm going to try the 'scope with these two swapped round as they are the same component but for Sweep A and B:


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Really? Wow!

February 20, 2017, 7:23 am
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Well,

How about this then?

I seem to be having a phase of collecting old 'scopes. I kind of love them, especially the old Tektronix devices.

There's a You Tube channel that I subscribe to by W2AEW where he does loads of fab and groovy things in general, but when I saw this, I just had to have one!

Using an Arduino Uno, a very primitive resistor based DAC and a bit of code, we end up with this, here on the scope I just repaired, a 2465:



Just fantastic!

This is the W2AEW actual video itself including the links to the code:


The Arduino and the DAC look like this on my bench:


and here running on an old 465 'scope:


Local conditions.
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6&4M Antenna and other Musings

March 7, 2017, 11:54 pm
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Well,

I decided a while ago to remove the large 6/4M combined antenna I have - it's very big and heavy:


So, I decided a while ago to replace the 6/4M antenna with a 3 + 3 ele version that we originally bought for the UK ACs; this antenna had very little front to back so I wasn't happy with it for home. I've now decided to purchase the 4 + 4 ele version. All these antennas are from Innovantennas.

Now, I've bought quite a few antennas from them in my time - perhaps 10 or more. Every single one has had either no manual (sent by email normally), missing parts, the wrong parts or even one had the boom drilled incorrectly. This 4 + 4 ele is a bit better, it only had one broken pipe clamp. The instructions you receive from InnovAntennas are poor at best, but this example has to be the worst yet; take a look:


Now, there's something scribbled in the top right that looks like "ADD over Cap" - no idea what that means.

There's a box drawn on the 4M driven element and then scribbled out.

There's a box drawn on the 6M driven element with a scrawl that says "Plate oh tend Point" (I think this is plate at feed point) so we conclude that this was first scrawled on the 4M driven element and then crossed out.

Nothing to tell me which bolts to use where or anything resembling how to put it together.

Great antennas - rubbish quality control and instructions!

I've also continued the theme of 'scope obsession by making a circuit from W2AEW. This is a means of converting a composite video output (from say a camera) and displaying it on a 'scope screen by using the X, Y and Z inputs:



My build looks like this:


and it works a treat!

When Miss Luna Cat rolls on her back like this in front of Elmo Dog, this is interpreted, in human speak, as "thank God it's spring".


Local conditions.
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13cm Antennamabob

March 10, 2017, 12:52 am
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Well,

You may recall back here I installed a 13cm antenna on the mast, and here I built the 13cm VLNA from @DXING G4DDK. The VLNA is now mounted masthead with the associated switching and a separate feed for TX and RX as I described here:


I've also recently acquired myself a much wider frequency coverage Spectrum Analyser; it's a very old HP8593A which covers up to 22GHz and came from here and has nice things like a 2 year warranty:


So, using the Signal Generator I made back here, and a cheap Chinese directional coupler being used the "wrong way" round;



like this:


I can leave the Device Under Test port open circuit and see the amplitude of the signal from the sig gen on the Spec An. If I then connect the antenna to the DUT port and calculate the difference between the open signal and the signal with the antenna connected - that should be the return loss in dB:


So apologies for the really rubbish photo, but the higher peak is with the DUT open circuit - so a really pants SWR and the lower peak is with the antenna connected. That's a difference of about 30dB. So using the maths we established back here we can deduce that the SWR is about 1.07:1 - which is bang on the money.

I was rather hoping I could hear the Leicester beacon GB3LES on 2320.955MHz - but I can't. So there may be a number of reasons for that - including my poor N-Type connector soldering, so I will have to look further.

But progress none the less!

**UPDATE**

The Leicester beacon has a fixed antenna beaming 160 degrees from its location - that's almost completely in the wrong direction for me! I've tuned to the Telford beacon on 2320.870MHz and I can hear the beacon just fine - RX working!


Local conditions.
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Finally - All coming together

March 22, 2017, 9:39 am
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Well,

There have been many musings recently all building to a 13cm (2.3GHz) system:


  1. The Transverter
  2. The VLNA
  3. The masthead enclosure and switching
  4. The antennamabob
  5. The sequencer
So now I'm trying to glue it all together!


The case is a bit tall, but it's all I had. I created a very simple PSU based on a 723 voltage regulator and a 2SC5200 as a pass transistor - I have tried to over-rate the power supply (please excuse the terrible layout below):


That plus the transverter and sequencer we played with previously.



The Gubbins basically remains the same as designed:


So, there is a VLNA at the masthead next to the antenna and two co-ax feeds back to the shack - one for TX and one for RX. The TX is 15mm Web-600 and the RX line Westflex 103.

This is all driven from 423 Mhz multi-mode transceiver - I plan to use the IC9100.

Now for the linear amplifier, I picked up one of these for basically scrap metal value:



There is information on modifying the unit for our purposes here.

As ever, the first thing required is to take it to bits, once you get the bottom off this is revealed:


then that board comes out and slung to one side:


then we remove another million screws and get the screen out of the way:



and then the top of those two boards gets slung:


Now we need to lift a cap off the board and connect in where our RF feed will be:




Now for the bias for those lovely MOSFETS....  here's the board with my bodged bias circuit:


I reached out through the UK Microwavers Yahoo! group and have received some very useful information including this:


I've added an Arduino Nano into my enclosure and may have a bash at reading some of those control signals:


And throughout, Florrie the Ham cat has been assisting:


Next, a bit of testing.....

Local conditions.
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I'm about there!

April 7, 2017, 5:57 am
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Well,

You'll remember last time I started modifying the 13cm PA I had acquired. Well, I think it's about done.

What we have is the modified PA, an Arduino Nano plus some software to monitor:
  • PA Temperature
  • Forward power
  • Reflected power
  • Bias current (driver, Left and Right PA MOSFETs separately)
and trip if anything goes out of bonk.

The Amplifier now looks like this:


I've just to wire up the Analogue inputs in this image. There are three "status" LEDs on the front panel; one for "All OK", one for "It's gone horribly wrong" and a final one for "TX". If you connect the serial cable to the Nano then there is a status line repeatedly output giving the details of all the inputs read and their values.

The connector on the main board of the Amp is configured like this:

and it was therefore a fairly simple case of wiring the various pins to the I/O of the Nano and writing some code. I stole a lot of the ideas for the code from Mike G0MJW - but there are quite a few differences between what I have ended up with and what Mike created a few years ago.

The 9V line to the bias and other bits of the board is permanently on; the 28V line is also enabled all the time but switched bu a FET switch under software control. This switch is the same as the one in the sequencer, it's just altered slightly for 28V:

I've stuck the source code here if anyone is interested.

Time now for some testing.....

**UPDATE**

A couple of minor software mods (updated on the link above) during testing and all seems to be OK. I am not entirely convinced about the scaling values used to convert from the ADC readings into the value units, but time will tell.

Here's the whole system - there's an IF cable from there to my IC9100 which is used on 70cm as the rig for the transverter:



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A tracking what?

May 15, 2017, 6:54 am
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Well,

As part of the fiddling I've been doing on 13cm, I've been using the new to me (read old) spectrum analyser I have. It covers from about 9KHz up to 22GHz.

You may also recall not so long ago, that I made a signal generator that covered up to 4.4 GHz.

As this spectrum analyser has a 1st IF output socket, it struck me that I could probably make some kind of tracking generator to go with it. Actually the IF output will be doing the tracking, all I need is a signal and a mixer.

Some experimentation allowed me to discover that on the low range, the Spectrum Analyser has an IF output of 3910 MHz plus the tuned frequency.

I've made myself a simple Arduino Nano and AD4351 combination:


The source code for the above is here. I've not done anything clever at all, just used the Analogue Devices software I showed here to calculate the required registry values and then hard coded them into the Nano.

That gives me the 3910 MHz signal required. We then subtract that from the IF output from the Spectrum Analyser using a simple and small Mini Circuits mixer:


Then I've added a low cost return loss bridge from ebay:


Whilst it's not lab grade, in this example you can clearly see the resonant frequency of the antenna that's connected as the Device Under Test:


The difference between the trace with the DUT socket open (the thicker line) and the other trace is the return loss at the specific frequency.

You can see that the open circuit sweep is nowhere near flat - so there are all sorts of issues with this setup, but as a basic antenna analyser up to about 3GHz this works just fine.

All the while, Florrie the ham cat has been sitting on my rotator manual which I am consulting as the display bulb has died:



Local conditions.
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Telly - really?

May 28, 2017, 11:15 am
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Well,

I've started to play with Digital Television and the broadcasting thereof. The fist part of the puzzle was to construct a means of receiving my own signals so I chose the Minitiouner from the BATC of which I am a member.

I bought the PCBs and the bits and bobs from the BATC shop and have built the project:





The transmit side of things will be from the well publicised BATC project the Portsdown. 

There is quite a bit to this project, hardware wise, but initially we need a Raspberry Pi and some software to run something they call "Ugle Mode" whereby you can send a picture across the shack.

Well, it works:


So its time to progress the hardware some more and move forward with the transmitter side of the project.

Interesting start, egh?
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Portsdown where?

May 30, 2017, 7:49 am
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Well,

As part of the project I mentioned last time, I've started to construct the hardware for the BATC Portsdown project.

The fist board I have tackled has been the LO filter. This goes post the AD4135 LO which uses the same development board as we used on the 4.4 GHz signal generator.

This is extreme, extreme soldering! I've invested in a flux pen of decent quality from Farnell and that's made my life much easier. Previously I was using some cheap eBay sourced flux which was a load of dingos kidneys.

Here's the results of my days soldering:




There's basically a 2 bit input thats status determines which of the three on board filters are in line (or bypassed on 23cm). I've tested this and can see three filters, not too sure about their shape though.

4M:


2M:


70cm:


23cm:


Looks a bit odd to me, but lets see.

Local conditions.
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I think its working

May 31, 2017, 12:59 am
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Well,

Following from my musings last time on the BATC Portsdown project; I think mine is now up and running.

I've been working on a box for the project and the various bits and bobs are now inside:





So, following the suggested test setup I've configured the transmitter to TX on 1255 MHz using 2000KS (thats the symbol rate) and my newly invented DATV receiver from here sees this:


So I conclude it's working. Now to try and stream some video and then think about external amplifiers and filters!

Local conditions.
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Filters Filters Filters

June 3, 2017, 12:03 am
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Well,

Following on from the success of last time; it was time to make some filters around the 146.5 MHz DATV frequency on the NoV allocated bit of spectrum we have above the 2M band.

I've also built up a kit I have had here for a while, it's a PGA144 from G4DDK.


So at the top we have the PGA144, middle is the LPF and bottom is the BPF. The designs are really quite simple - just ask if you need the details. Here's the spectrum from all three:


The yellow is the PGA144 - it has a 20dB attenuator at the input so the signals are actually 20dB higher than shown - the gain at 145MHz is exactly 20dB.

The purple is the LPF being swept and looks just fine.

The Blue is my BPF which I am very pleased with - it looks great.

So next will be a 60W "brick" amplifier for 146.5 MHz - waiting for the bits but I have to go work in foreign parts for a week or two so will pick this up on my return.

Local conditions.

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Its brick time!

June 11, 2017, 7:53 am
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Well,

To compliment the DATV transmitter I made here, I've been building a PA rated at 60W RF out - it will be used at way less than this, but for any kind of TV transmission we need loads of overhead in the PA to avoid nastyness in the output.

The PA is this design here, the PCB from G4DDK.

The module itself is a RA60H1317M1A and I got mine from Anglia Live.

The heatsink feels like a great find, I saw it listed on eBay by JPG Electronics in Chesterfield; as it's just up the road I paid a visit - what a find! Loads of goodies!

Anyhow, here the PA under test:



The TX RF from the Portsdown will come in through the LPF we tested last time; then through the PA and out through the SMA relay. The RX Signal will pass through the BPF also from last time, and to the Receiver we made here.

The relay was one of a number I found some time ago; they are Ducommun latching 12V SMA relays. These need a driver circuit which I made like this:


and that's built on the veroboard you can see at the front of the PA block. The output lines do this when the PTT is grounded and then disconnected:



All I need to decide now is what to set the Bias voltage to on the PA - not sure about that!

Throughout Miss Luna Cat has been supervising from a distance:


Good, egh?
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EMC 'n' all that Jazz

July 1, 2017, 12:10 am
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Well,

I've been having some issues when I TX on 6M CW. Very strange in my Radio PC (the one sending the CW) shuts down - it doesn't crash - it performs an orderly shutdown.

This is definitely an RF issue as it only happens when the TX power is above a certain value.

So, by using a process of elimination, i.e. removing cables from the back of the PC one at a time and seeing if the problem goes away, I concluded that it's probably the DHMI cable to the monitor (well, one of the monitors) that's causing the problem.

This has lead me to question the effectiveness of ferrite suppression and other such gubbins.

Now, all of us hams will have purchased a bunch of clip on ferrites at a rally; these are supposed to be made of type 31 material which is rated up to 500MHz.

I mean something like this:


Now, these are designed to clip on a cable, effectively providing one turn through the ferrite. How well does that work then? So here's the spectrum analyser showing 0 to 100 MHz and a simple loop back from the generator to the input - no ferrite here:


So, lets now add a single turn of the clip on ferrite and see what difference it makes:



So the answer is, quite expectedly, not a great deal. So, let's increase that to 5 turns:



So, thats much more like it.

We have to conclude that clipping these ferrites onto cables around the shack is next to useless at HF - we need at least 6 turns through the material before we see any significant attenuation.

There are a number of larger ferrites available, using the same material, but bigger:


These will allow you to get multiple turns of coax or mains cable, or in my case a HDMI lead through the core, and most importantly they are also clip on.

I've tried a few combinations of different cores on my HDMI cable so see what works best; there are all sorts of other issues creeping in now though, like the resonant frequency of the cable itself:




The bottom picture above effectively gives me 6 turns by using 6 cores; the image above uses much more expensive cores and passes the wire through multiple times. They both have much the same impact.

So, I plan to add the cable above as an extension to my existing HDMI cable and see if the problem is solved.

Here's our very beautiful Elmo enjoying the fact that summer has finally arrived:


Local conditions.
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More InnovAntennas Fun

July 11, 2017, 1:37 am
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Well,

You may remember my sharing an instruction sheet from an InovAntennas purchase back here and basically explaining how poor I though the instructions were. Well, here's another excellent example:


So, credit where credit is due - this time I didn't actually have any missing parts for the antenna itself; however I did have some spare bits for the antenna (some extra end caps and element clamps) and unfortunately the antenna to boom mounting plate and associated u-bolts are missing completely.

But lets take a look at the instructions:

  1. The title tells me it's a 1.4m antenna; I assume that's the boom length, but, oh no, the boom is 1.7m long.
  2. The bottom of the page tells me the boom is 1.7m long - so which is it? Let's get a tape measure and check.
  3. The bottom of the page also also tells me that "guy and supports are supplied" - I don't think so.
  4. So let's look at the shortest element - there are three numbers 1705mm, 1405mm and 903mm. So I think one of these (the 1705) is the distance from the boom end, the 903 is the element dimension - no idea what the 1405mm is - perhaps this is for the 1.4m antenna mentioned in the title that I haven't got? If that 1703 is the distance from the boom end then the first element is nearly a foot from the boom start - that can't be right either.
  5. Then we have the added information "X-POL SIZES"; you have to assume this is for a cross polarized variant perhaps?
But once again, no actual information on which bolts or other bits to use where. One of the driven element clamps is metal - now I assume that's not at the end the feedpoint is and it seems the feed is at the back. I assume I need a coax balun near the feedpoint but that's clearly guesswork as there is no information on that aspect at all.

Local conditions.
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First On-Air Test Complete

July 20, 2017, 12:07 pm
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Well,

Thanks to the help of Col, G4OHV I have tonight tested my Portsdown transmitter on air.


Here's the video Col captured of my TX - Thanks!

Good, egh?
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I'm forever blowing bubbles? No! bulbs!

September 2, 2017, 11:28 pm
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Well,

I have a couple of Yaesu Rotators here, and the controllers were stacked one on top of the other with a small cardboard box propping up the top controller. The cases are kind of slanty topped and the whole arrangement meant that they both fell to the desk regularly. This in turn ensured that the bulbs illuminating the front scale blew farily soon after purchase.

My local friendly emporium LAM Communications sent me some replacement bulbs some time ago, I just never got round to replacing them - mainly because I couldn't find any instruction on how to do so.

So, here's how to replace the bulbs in a Yaesu Rotatorbamob (or certainly the 1000DXC variety).

Firstly we remove the main external case:



Now, the bulb is clearly part of the main dial thingy on the front, so that had to be removed also (there are 4 screws):



The bulb is under the silver paper I've highlighted below:


So it's just a case of peeling back the tape carefully, and soldering in a new bulb.

I've also made a wooden stand thingy so the controllers stack without the need for cardboard wedges and other jiggery-pokery and hopefully the wont fall over any more:


Local conditions.
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The Art of Rotator Control

September 7, 2017, 11:14 pm
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Well,

I decided that there had to be an easy way to computer control my antenna rotators. I already have this on the Satellite antennas in Azimuth and Elevation, but not the "normal" antennas I have here for HF & VHF.

I looked on the big bad internet and found that Yaesu make a rotator interface for the G-1000 rotators that I have, but they are a simply staggering price.

So, there had to be a way....

The first thing I did was connect to the interface socket on the back of the rotator and figure out which pin did what. We have a voltage output that represents the heading, which plotted like this:


Using simple bit of maths we can then create an equation to calculate the voltage at any heading (to save me having to keep moving the antennas back and forth):


There are also two pins on the interface connector that you ground to turn the rotor left and right. There's also a fourth pin you can use to set the rotator speed.

I then figured that Arduino was certainly the way to go, but then I found this:

https://blog.radioartisan.com/yaesu-rotator-computer-serial-interface/

Now, this interface does all I want and a million things more, it's been written in a way that allows you to configure the bits you want and exclude the bits you don't.

To get this to work with my G-1000 series rotator, I configured the following:

#define AZIMUTH_STARTING_POINT_DEFAULT 0

in the rotator_settings.h file; that's about it!

That setting defines the rotator as one that turns around 0 degrees (rather than 180 being the end stop).

Once I had done that and defined the pins (I just used the defaults) and also defined Digital pin 10 as the speed output:

#define azimuth_speed_voltage 10

in the rotator_pins.h file

I compiled the code for a Arduino Nano with an ATMega328 processor (because that is what I had lying around).

I then built the simple interface needed:


Now, the next step was to calibrate the software. Instead of turning the rotator from fully CCW to fully CW (including the 90 degree overlap), I just used the equation I established above to calculate the voltage and set the bench PSU to deliver same.


Then once that was complete, I connected the Arduino board to my Radio Control PC, fought with COM port settings (a favorite hobby of mine) and then configured my logging software to use a rotator controller emulating the Yaesu GS-232B command set.


So now I have this display above, it shows where the antennas are pointing and allows me to click on a heading to send the antennas there. I can also configure the system to auto turn the rotator based on selection of DX spot if I like too.

Neat, egh?
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