Really, More Baluns - Now What?

Well,

You may recall my musings on the topic of Baluns back here:

http://g0mgx.blogspot.co.uk/2013/04/baluns-baluns-baluns-whats-that-about.html

A Balun is a kind of transformer to take a BALanced signal and convert it to an UNbalanced signal (or vice verse).

So, in my traditional have a bash style, I've made this:

Now, the schematic of the thing looks like this:

Now, the B2/C1 junction is ground and C2 and A2/B1 are the balanced outputs. The unbalanced port is between the same ground point (B2/C1) and A1 for a 1:1 and A2/B1 for a 4:1.

So here I am injecting a 4MHz signal into the 1:1 unbalanced port and monitoring the two balanced outputs with the 'scope:

This looks exactly as expected - the purple line is the sum of the two balanced outputs and for two signals perfectly out of phase should be a flat line. Here is the same thing at 7MHz:

Again - nothing short of perfection!

Here at 14 MHz:

the signals are still out of phase with each other, but the amplitudes of the two balanced ports is no longer equal, and here at 18MHz:

The two ports are no longer anything like out of phase....

So this homebrew device looks like it's good to about 10MHz and not much further. Its been made using FT240-61 ferrite material.

I need to now make something similar using a different material and see what the difference is.

Interesting though, hug?

Is this what I was waiting for?

Well,

I'm still in A71 land, but I have been checking my WSPR beacon that I left running on 4M from time to time. I mentioned about it here:

http://g0mgx.blogspot.co.uk/2013/05/movements-are-afoot-its-all-go-you-know.html

But here's what I found this time:

So my 20 watts on 4M has made it all the way to PA0O - clearly there has been some propagation while I am away (typical).

Good, egh?

A what-un? ah, A Balun!

Well

Whilst musing about being able to run SO2V or SO2R back here:

http://g0mgx.blogspot.co.uk/2013/04/so2v-so2-what-ah-2-vfos.html

there are quite a few things to consider. If I am going to operate with 2 radios at the same time, the most important factor will be protecting the radio in receive from the high RF generated by the radio in transmit - this could result in some very expensive damage if not catered for correctly - more on this later.

The other thing I need to accomplish is a second antenna for the higher bands. Lets say I want to run on 20M and 15M at the same time, clearly I can use the MA5B on one radio, but I don't currently have a second antenna for either of these bands. The simplest solution (as very much a starter for 10) is to cut and hang up a simple common multiband antenna - a G5RV. I've cut one using some hard drawn copper wire I had here, some 450 ohm ladder line and a commercial balun...... hence the confusion and lack of understanding.

I've always been bothered by baluns - what do they do and how do they do it? Whats the difference between a current balun and a voltage balun - whats a 4:1 balun for? Whats a 9:1 balun for? Why don't I just go out more and not worry?

Over the coming weeks I plan to run some experiments to answer these questions, to run some tests against a commercial 1:1 balun, and to construct some baluns for myself and see what they actually do.

So, starting with the newly strung G5RV which I've included a commercial balun between the 450 ohm feedline and the coax to the shack, I see this with my newfangled antenna analyser thingamabob:

Now, I only plan to really use this antenna connected to a second radio, but as a starter for 10, the antenna looks like it's OK ish. As a quick test (clearly the SWR on my dummy load will be better!) I left the antenna and radio WSPRing on 30M last night:

So, I conclude that the antenna radiates and it looks like I can transmit a signal using it.... so it's not just a dummy load. This is a good start.

So, the next project will be some kind of band stop filters for the radios so certain radios can only be used on certain bands - this should allow me to experiment with SO2R in an RTTY contest.

Now, back to baluns.... A balun should be used where we go from a balanced arrangement (e.g. a dipole) to an unbalanced arrangement (e.g. coax cable). I would therefore expect that the output of the two balanced ports of a balun would be out of phase with each other when compared to the ground point of the input port. Here I am feeding a 10MHz signal into a commercial balun and measuring the two terminals of the balanced output:

So, the yellow and the blue (please ignore amplitude) are the two output ports and the green is the sum of the two signals.... they look to me to be about 45 degrees out of phase - this is not what I was expecting at all! I thought they would be 180 degrees out of phase such that the sum of the two was as close to zero as makes no odds.

Unfortunately (or fortunately, depending on how you look at it), I'm heading back to A71 land again today.... I'll be picking this up in about two weeks when I get back.

I'd like to hear from anyone who understands the 'scope output above though, confusing - egh?

SO2V - SO2 What? Ah, 2 VFOs!

Well,

During a two day break from work, I've been fiddling about with Writelog and Logger32 (the programs I use for RTTY) to try and experiment with the 2 receivers I have in the main FT-DX-5000 here.

The idea being that I can have:

1. Main receiver to an MMTTY decoder providing the main RX window
2. A clone of the main receiver window running an alternative decoder (2Tone)
3. The second receiver on the same or a different band into a third decoder running either/or MMTTY and 2Tone.

So far, In logger32 I have achieved everything I set out to do:

I have the two receivers in the radio, both with frequency read from the radio correctly and the ability to receive in both 2Tone and MMTTY on both.

Now, in WriteLog I almost have the same thing:

But not quite! I have two receivers feeding two versions of MMTTY with the main receiver also having a clone using 2Tone. What I can't get to work is reading the receiver frequency of the 2nd receiver within the radio. Eventually, of course, I would like to be able to TX back to a signal received on either receiver i.e. TX on the main or sub receiver frequency; I suspect that may be asking just a bit too much, although I think it's possible if I had two separate radios, so I dont see why not...

I'll keep trying, I wonder if anyone else has this set-up working?

Complex, egh?
 

EA RTTY Test

Well,

Home from A71 land for a week and had a bit of a dabble in the EA RTTY contest, here is the now obligatory map from the log, not sure why I have grids on the map, but hey ho:

Good though, egh? 

RTTYing in A71 Land

Well,

Its been snowing hard in the UK (so I understand), but I'm stuck in A71 land this weekend....

The Qatar Amateur Radio Society were doing a stall at an exhibition recently, I called by to see them, here's the set up:

I've actually spent some time at the QARS main site today, you may remember I visited them a while ago:

http://g0mgx.blogspot.co.uk/2013/02/a7-land-a71a-ah-qatar.html

I've been running RTTY using one of their FT-2000s. You may recall I made an interface for my FT-450 a while back:

http://g0mgx.blogspot.co.uk/2013/01/hows-interfacing.html

Well, here it is on top of the FT-2000 - plus an adapter for the rig end of the cables:

So been running on 20M RTTY today with the callsign A71A. Been quite hard work as at times there were many stations calling, but no single signal decoding, I guess I perhaps need to consider working split next time.

Fun though, egh?

WPX? Ah, Worked All Prefixes!

Well,

Been playing in the CQ-WPX RTTY contest this weekend, managed 512 QSOs for 1446 points and 352 unique prefixes in 61 DXCC entities.

As is becoming the norm, here's a map of the logbook:

Very pleased to manage to get some RF all the way to New Zealand; but who wouldn't be?

Fun, egh?

FT-5000 AFSK

Well,

Over the past few weeks I've been trying to get my FT-5000 to function in AFSK based modes; the radio is setup with the audio from my digibox (the one that feeds all the other radios) into the packet connector on the back. I've been seeing some very strange behaviour which I've captured in a short video:

Any thoughts on what's going on here would be very much appreciated!

** UPDATE **

I've discovered (more by luck than any judgement) that this problem goes away when I enable the RX audio filter for Packet mode. I had set menu item 083 and 085 both to OFF; if I change 083 to 100Hz (or any other value) then the problem disappears.

I don't begin to understand this as I though the filter set by menu item 083 and 085 were RX audio only....

Maybe someone can explain?

Weird, egh?

Where do the knots come from?

Well,

I've been checking some wiring today; there's a great deal of it in my shack and it's always in a spectacular knot!

I saw some SWR movement during the XE contest at the weekend and thought it was worth investigating... as normal I have found a PL-259 connector soldered in the most appalling way possible - I suspect this may be the culprit so it has been duly replaced.

Whilst I was doing this I decided to draw a diagram of what is connected to what -  was getting in a bit of a muddle, so here it is:

So at least I have a known reference point to look back at now.

Not very exiting, is it?

XE test? Ah, Mexico!

Well,

Been dabbling in the Mexico International RTTY contest this weekend:

http://www.fmre.org.mx/concursos/2013/rtty/rules-rtty-2013-english.pdf

Running pretty much maximum allowable bananas for my full UK license and trying to get as many Mexican states as possible (these count as multipliers to your total score). Mexico is a fair distance from the UK (like 5,300 miles) and conditions didn't seem that good. So given that most of my late afternoon CQing was with the antenna pointed at the appropriate part of the world, my sum total of 3 Mexican stations is rather pants.

Anyway, I'll be entering my log for a laugh, but here is the (now traditional) map of my contacts:

The maps I create of my logs are done here:

http://www.adventureradio.de/analyzer/

Odd isn't it, how I find myself beaming to the north west (300 ish degrees), working mainly stations in Europe and then suddenly work a VK4 in NE Australia.

Cat was trying to help keep log:

Fun though, egh?

5MHz Short Dipole

Well,

Having had my 5MHz NoV renewed in early January, I decided to have a go a fitting a dedicated (shortened) dipole into the garden.

I started with my preferred on-line calculator here:

http://www.k7mem.com/Electronic_Notebook/antennas/shortant.html

A truly magnificent tool, and ended up with this design:

 

I've managed to fit this antenna into the back garden today without getting it too close to anything else. My MFJ Antenna Analyser thingamabob suggested that the SWR and impedance of the antenna was good at the target frequency; after getting some RG58 and running it back to the shack, the radios seem to agree also. Time will tell, but it seems that I have a dipole for 5MHz!

 

 

I also payed a visit to Lam Communications today, rummaging through their shop a FT-1000 took my eye, the PSU for the radio was described as broken and the radio was sold with "no warranty implied or given"... so I've had a punt. Here's what I found inside the PSU:

 

 

 

 So I very quickly concluded that the PSU is all sorts of broken.

 

The radio requires 13.8V at 3A and 30V at 15A (for the PA), so a replacement shouldn't be so hard to manufacture from something.

 

Watch this space, I'll keep you posted.

 

Here's the Geddy cat mid tea munching the other night:

 

 

All good fun though, egh?

ARRL RTTY Roundup

Well,

Had a play in the ARRT RTTY roundup this weekend, conditions seemed quite poor, 10M wasn't open at all and most of these contacts were on 20M and 15M. I'm a bit dissapointed really, would have hoped for a bit better:

 

What do you think?

DDSing once more

Well,

I've been out of the country for a while; been working in the US of A. Great place, visited Chicago, Pittsburgh and Houston this trip - got myself some great boots!

Today I have broken up for Christmas and am looking forward to some good time at home with family, friends and, of course, my hobbies!

I've been fiddling today with the DDS signal generator I made here:

http://g0mgx.blogspot.co.uk/2012/02/dds-running-well.html

And would like to improve the design a little. It would be good to follow the DDS with a broadband RF amplifier, perhaps the one I used here would be a good starting point:

http://g0mgx.blogspot.co.uk/2012/06/its-been-ages.html

Who knows? I would also like to add a stepped output attenuator that's controlled by software and also feedback the RF output to one of the Analogue inputs of the Arduino so I can have a dbM display on the LCD, much like the separate meter I made recently:

http://g0mgx.blogspot.co.uk/2012/11/calibration-complete.html

So, my starting point was to replicate the existing project and then add the AD8307 logarithmic amplifier circuitry:

So here we are again, another project is born.

I'll keep you posted, fun though, egh?

Scaling the heights of power

Well,

Having finally got a working digital and software based power meter, I have been running some experiments today - already this is proving to be a useful instrument. I think it might be worth making an alternative version of the system to be a stand alone power meter (rather than a directional meter with SWR calcs). However, the main enhancement today has been the inclusion of a (rather humorous) meter scale for the analog SWR meter:

All I did was remove the metal scale that came with the meter, scan it into the computer and then use MS Paint to alter it. I've printed it and stuck it to the old one with "pritt stick". Looks kind of fine to me:

The instrument display is looking pretty good too:

There are two switches on the front panel (as per the W7IEQ design). So I've modified the software to either sample the RF in a short mode or a longer, more time between samples mode. Hence you can see "Sht" for "Short" - this changes to "Lng" or "Long" when the 1st switch is set. Similarly I've added some code to peak hold the meter and this can be turned on with the second switch; the display shows "Norm" or "Hold".

I need to do something better with the front panel of the case and also I'd like to illuminate the meter.

Not bad though, egh?
 

The Power is with me...

Well,

After all the antics with this power meter project, I've finally got a working project; however, not quite through the route you would imagine.

Having spent even more time studying the assembler code for the W7IEQ power meter, and realising that I would need to change all of the vast lookup tables used to convert the AtoD readings into dbM, I then found something in the code comments that made my heart nearly stop...

"This routine uses a packed 16-bit floating point value that I developed to reduce memory usage in a look-up table relating power in watts to measured ADC values for forward and reflected powers.

The packed values contain a 10-bit "reduced" mantissa (m) and a 6 bit shifted exponent (s).  All values are assumed positive so there is no need for a sign bit. Also, the first bit in the mantissa, which is always 1 except when the number id 0, is suppressed.  The offset value for the exponent is 27. A shifted exponent of 0 means the number is 0."

So I very rapidly concluded that I stood little or no chance of getting to grips with this in a hurry, and I was close to despair already with this anyhow!

So, here's what I did.... Firstly I ripped the main board out of the box and threw it in the bin. Then I replicated the Sample and Hold op-amp circuitry plus the amp used to drive the meter on some veroboard. This board plus an Arduino

www.arduino.cc

board I had were introduced into the box....

So, I have the original AD8307 boards, but everything else has been replaced. I opened a blank arduino "sketch" (or project) and started from scratch to write the code....

Because the Arduino code is written in a high level language and there are very few memory or other limitations on the board itself, the code doesn't need to be especially well optimised for speed or size. Also the high level language and the library routines that come out of the box mean that all the "tricky" bits associated with reading the AtoD or setting the PWM et cetera are already available for use - so the software is really quite easy to write and also easy to read and modify by other people.

Here's a link to the code:

http://www.qsl.net/g/g0mgx//BlogFiles/power_meter.ino

and also the spreadsheet that I made to calibrate it:

http://www.qsl.net/g/g0mgx//BlogFiles/Power%20Meter%20Calibration%20Arduino.xlsx

So the LCD display is currently set up to display the forward and reflected power in Watts and dbM plus the calculated SWR. The SWR is also indicated on the meter.

The code took an evening to start and then about 6 hours to complete going with my ever favoured method of write a bit, test a bit.

There's lots left still to do, like a front panel and a meter scale. I will also introduce the concept of average power readings and things like that. But I think I need to see the unit in use before I can decide exactly how I want it to behave.

Cat's not impressed:

Good though, egh?

It's Becoming a Real Power Struggle

Well, blimey!

How hard can it be to get a piece of PIC assembler software to display some characters on an LCD display? The answer seems to be very.

I've started putting my power meter together, it's the one I started here:

http://g0mgx.blogspot.co.uk/2012/10/a-bit-of-power-struggle.html

Well, eventually I managed to assemble all the parts and put the boards into an enclosure I have here:

I've actually made quite a good job of the metalwork so far, I've intentionally not cut the hole for the display as I don't yet know which one of the many I have here I would end up using. Here's the view of the front panel as-is now, the meter looks OK but isn't the large meter I found, as that's just too big for the case!

So, PIC programmed, LCD display wired in, power on - nothing. Just some very faint black squares on the display that I can make more evident or go away using the on-board contrast control.

So, still not knowing if the software is intended to interface to an HD4470 compatible or not, the question was what to try next?

I ended up cutting the software back to just the display routines and simply programming the PIC with the code to display just a few characters on the LCD. Result - nothing.

So, next I added a simple loop at the end of the LCD routine calls to turn on and off one of the digital output ports every second. I attached a suitable LED to the port and tried again - as expected the LED started to flash. This told me a few things:

• My PIC programming was working and my software was making it into the chip;
• The software was reaching my loop for LED flashing so it wasn't getting stuck anywhere;
• The routines for the LCD weren't working.

Now, you may (or may not) recall I did quite a bit of fiddling with LCD displays and Pinguino and more recently Arduino back here:

http://g0mgx.blogspot.co.uk/2012/02/four-isnt-quite-same-as-2.html

So from that messing about I had a reasonably good idea how the initialisation of these LCDs should look, and the code I was staring at didn't quite look the same. So I changed the sequence of numbers sent to the LCD to initialise it, re-programmed the PIC and tried again. Nothing.

Hmm, next I looked at the delays in the software between writing the Enable line on the LCD high and then low again - you kind of have to do an "open sesame" on the LCD every time you send it either data or a command and the delays in the assembly software I was looking at used the processor "nop" instruction. This is really a null operand and hence takes one (I think) clock tick to execute. I changed this to be a 1ms delay and.... Bingo! We have characters on the display:

So, my next puzzle was the fact that I could display the characters 0-9 OK, but any attempt at alpha characters resulted in, what looked very much like, Japanese characters appearing on the display. After much cursing, general muttering and many re-programming of the PIC to try different things, I found a short between two of the address lines on the board. Doh! It took me over 6 hours to find that as I was only looking in software....

So it does seem that I am moving in the correct direction. I have also found that the Assembly code I downloaded from the QST in-depth website for this project, doesn't assemble on my version of MPLAB. I've had to change a few things:

• declared names are clearly case sensitive in my assembler and not used in that way in the code - many capitalisation changed;
• literal values used with the "loadw" command - the decimal declarations used generated value too big warnings, all I have done is declare the values as the hex equivalent and prefixed with "0x" - I don't understand why this is different, but it assembles;
• The declared names in the .inc file for the processor are also case sensitive so again, a number of changes needed there.

I then incorporated my changes to the display routines into the downloaded software and now I am seeing what I expected to see on the display.....

It's time to test the unit, I'll let you know how I get on. I suspect I need to re-make the directional coupler (again) as I posted a photo on the eHam.net homebrew forum and asked for some advice, here's a very polite post telling me what a pile of junk I have made:

eHam comments

Hard work, frustrating but all good though, egh?

 

It's a busy place 30M!

Well,

Been fiddling with wire antennas again over the weekend. Decided to make a good old-fashioned dipole for 30M.

Here is the dullest photograph ever:

But you can, at least, see that when I say an old-fashioned dipole, I really do mean two bits of wire with coax in the middle.

Now, over the last 24 hours I have left one of the radios WSPRing on 30M, here is the general map of the time period:

looks like a very busy place 30M WSPR!

And here is the map showing just people I am hearing or people who are hearing me (or both!):

So, it very much looks like my two bits of wire are working well! Now, looking in detail at the unique contacts involving my callsign, we find this:

Now, the two contacts to VK land (Australia), seem to be between 7 and 8 AM and also 7 and 8 PM; now that just about during the transition between day and night (or vice versa) so I just wonder if there is some grey line influence here?

What do you recon?

Fun though, egh?

How Much Power?

Well,

Myself and my chum Vince, G0ORC headed off to the National Hamfest last Friday, following a lot of consideration I was thinking of changing the Linear Amplifier that I have here for HF work. I have been using a Ameritron 600 watt Mosfet linear, with great success, however I was wanting to be able to run UK legal limit RTTY without pushing things to far.

ML&S had a very intersting linear amplifier at the show which just took my fancy, another great re-shuffle in the shack and it's in:

The linear is manufactured by a company called ALPIN:

http://www.alpinamplifier.com

And contains a single 4CX800A tube capable of 1300W SSB and 1000W continuous CW or RTTY work. The amplifier looks (both inside and out) to be a close copy of the ACOM 1000:

http://www.hfpower.com/

I am told that Alpin are ex-employees of ACOM or something like that (I don't actually believe a word of this).

Anyhow, the amp certainly looks the business:

and it's very easy to tune, I have created a chart of the "starter" settings for my setup and you simply rotate the "load" control as instructed on the LCD display and then peak the "tune" control for maximum smoke (RF out).

There is a good review of the amplifier here from RadCom:

http://www.alpinamplifier.com/images/RadCom%20Review.pdf

The review seemed to say the right kind of things....

I've had a dabble in the CQ WW RTTY contest this weekend and have been delighted with my station performance. This is a map output from my log from this weekend, most of the contacts have been on 10M:

you can see that I have worked far and wide and the RTTY station here at G0MGX is clearly working well!

Cat's not been helping much as normal:

Good though, egh?

Changes at the Top!

Well,

I've not been overly happy with the arrangement to adapt from the top section of my new mast (which is 2" OD box section aluminium) to the 2" OD pole that holds the rotator. This was originally a aluminium plate that had "U" bolts for the pole and some nuts and bolts that fitted through the plate and then through one wall of the top mast section. When the wind picked up there was the risk of:

1. The whole thing folding back on itself;
2. The plate twisting.

You can see the original plate in this picture here:

Now, as I was concerned about this before the changes today, I had actually inserted a smaller diameter pole inside the rotator pole which was secured by a bolt that passes right through the rotator clamp. This smaller pole extends through the top rotator stub mast down into the top section box part of the mast itself. This (I was certain) would ensure that the plate didn't fold back on itself in high winds.

So, what I have done today is use a piece of 3" OD aluminium box section to create a kind of sleeve that sits over the rotator stub mast and the top section of the mast itself, this sketch kind of explains what I've made:

And it looks like this in reality:

And this is a close up of the top section of the mast itself where it enters the new sleeve:

And here you can see how I have made larger (looks like using my teeth) holes in one of the walls of the sleeve to access the bolt heads to ensure the pole and the mast top are hard and fast against the side wall:

and this is the underside of the same bolt:

So, all in all, I think this will enable me to sleep better knowing that the antenna isn't about to land on the back of the house!

What do you recon, better egh? Cat's not impressed, seems to like the new radio though: