Tuesday, January 17, 2017

40 meter Delta Loop

Here's a nice little project for a 40 meter Delta Loop I found while browsing the web from a German Amateur called Patrick Henry DJ0IP.

It would make an ideal weekend project.





 

CONSTRUCTION DETAILS:

The pole should be about 12m high (minimum 11m). (39’4" to 36’). Higher is better, but then you will have to re-adjust the total length for resonance.

The feedpoint is located in either diagonal side near one corner of the antenna, enabling vertical polarization. This makes the antenna an excellent DX antenna.

The length of the diagonal is not very critical and may be adjusted to help find a better fit in the space available, but the distance from the feedpoint to the top should be one quarter wavelength.

The exact total length will vary depending on ground conditions at your QTH. Begin with 42.7m (137’ 10") and then shorten the horizontal leg to bring the resonance up to the desired frequency.

Adjust total length by adjusting the length of the horizontal wire. (Easiest way).

The horizontal leg of the antenna on the bottom should be 2 to 3m high (6’6" to 9’10") high enough for humans and animals to walk under. Changes to the height will require adjusting overall length.

The insulator shown directly on the pole at the 2m level is for mechanical reasons. Secure the insulator to the pole, and then pass the horizontal leg through the insulator, reducing sag in the horizontal leg.

The insulator in the horizontal leg near the left is an option for convenience. It enables easy adjustment for resonance by removing or adding wire. For disassembly, disconnect one side from the insulator and then roll the antenna as a single wire. Each time I changed my QTH, I had to re-adjust the length of the jumper. I just let the jumper wire hang down. For permanent use, you may leave this out.

The antenna will have an impedance between 90Ω and 100Ω. A quarter wavelength matching stub of 75 Ohm coax will provide a good match to 50Ω. RG-59 is good enough for about 500w.  If you want to run more power use RG-11

Thursday, January 12, 2017

Repairing the K2

So after diagnosing the problem with the K2 after I had inadvertently wrecked it by transmitting with the FT9000 when the K2 was switched on! I now had to fix the issue.

After a thorough inspection, the problem seemed to be that two PA transistors had blown and so using Don Wilhelm's advice to purchase the K2PAKIT from Elecraft - (that kit has matched PA transistors plus  replacements for Q11 and Q13 both PA2222a), I set to work removing the suspect parts.

Q11 and one of the PA transistors had definitely blown big style and no wonder there was a bang from rig when I tried to transmit. I couldn't see any other issue and I would double check when putting everything back together a by simple series of voltage tests.

Q11 blown to smithereens!
 
 
The blown PA Transistor (the one on the right!)

After a good clean up I carefully read Don's excellent instructions.
"Install Q11 and Q13 first, then check the voltage at the base solder pads for Q7 and Q8.  It must be zero during receive.  Then do a TUNE and measure the PA transistor base solder pad voltage.  If it is not in the  range of 0.60 to 0.64 volts, investigate the resistors in the Q11/Q13  circuit. Only after those checks should you install Q7 and Q8. That should get the base K2 working".

The K2PAKIT finally arrived from Elecraft and I could begin the repair. Removing the old parts proved difficult to say the least, patients and a steady hand is required using the copper flex to remove the old solder. I used an old needle to make sure the holes in the circuit board were back to their correct size, (a little tip I picked a long time ago!) finally without damaging the circuit board I managed to remove all suspect parts. Replacing them was just a case of referring from the manual to make sure everything was correctly placed.

 
You can see where the PA transistors should go right in the centre of the picture, 3 holes in a row,

Unfortunately one of the smaller transistors (Q13) got damaged so I had to replace, which took another few days to order. But finally with much perseverance I got there in the end and after reading up in the manual and following Don's instructions to the letter, everything fitted back together. A quick test with a multi meter all looked good and I switched on, it was working perfectly.
I'm going to keep it as a QRP without the 100 watts, I hardly ever used more than 10 watts anyway so I might as well keep it as the original QRP Rig!

Friday, January 6, 2017

17M Moxon Update

Having built the 17m Meter Moxon and tested the antenna I am very pleased with the results.
Attaching to a 35 foot mast with a rotator however was touching its limits. The mast is in fact one standard 30 foot with a 5ft section added and a smaller section housing the rotator. Normally the mast is held by a large nut and bolt between two smaller lengths of scaffold pole that have been buried two feet in to the ground, therefore providing a clamp to the main pole that can then swivel up and down.

Once in place I can clamp with another nut and bolt that slips in at the bottom, locking the whole thing in place, it worked fine for my 10 meter Moxon but this is a bigger beast.

The problem is that combined weights of the rotator, antenna and cables puts the 35 foot mast at its limit. As I raise it bends quite dramatically and although it does settle when at full height I can't take the risk of keeping it in that position.

So I am going to have to reduce the height of the mast by 5ft i.e. remove the added section, this should strengthen the pole, its just slightly shorter, the attachment is added by a simple scaffold clamp, but the clamp does provide some weakness to the overall mast.

I can live with a 5 foot reduction so long as I know its safe! So at the moment the antenna is lying low with work to reduce the pole on-going. The cable for the rotator arrived the other day and I have already unwound and laid it out, connected to the rotator and it is now awaiting me to insert through one of the walls in to the shack.

 
The antenna and pole resting!
 
With the weekend upon us, I did some final testing I was getting an SWR of 1:2 at 17.185 and a 1:9 at what I wanted at 18.068 right across the band. So it needed a bit of a trim. What I found out later was because I was using pvc covered wire (in fact it was 42 strand speaker cable at around a millimetre width) I inputted the millimetre width within the Moxon calculation, I should have allowed for the PVC cover, so in future this has been noted as I wouldn't mind attempting another Moxon at some stage.
 
 
Anyway I trimmed using the 17.185 as a template, When completed I had shortened the director by 150mm and taken 50mm off the  reflector. This brought the SWR to 1:3 at 18.100, so all was well in the end, just a bit of give and take. The height is now 25 Foot and doesn't seem to be a great difference performance wise, only it feels and is a lot safer to put up and stay up!
 
You can definitely hear the difference when rotating, your up against the cobweb, which is not weak but there's certainly a 3/4 db improvement with the Moxon.
 
 
 
The completed antenna
 

It's taken roughly a week to construct, but it's been good fun and if your looking for a quick project I highly recommend having a go with a Moxon.

Sunday, January 1, 2017

How to Blow Up Your K2 in One Easy Lesson!

OK, my own dumb fault, Friday morning playing with the K2 just getting some QRP work done and I had come off the air with German station feeling quite pleased with myself. I decided to  listen to a  different frequency 18Mhz on the FT 9000MP to see if the newly built Moxon would pick any thing up at a height of about 15 feet.

Forgetting completely about the K2 still being on, I hear a Russian station on 18Mhz via the FT 9000 and think blimey the Moxon is working even at that height! I decide to reply, so tune the FT for 40 watts and hit the CW key.

BANG goes the K2! First reaction Jesus I've blown it up! Panicking I quickly carry out some checks, Switch off, this particular rig is fitted with K2/100 (100 watt kit), so I'm really worried I've damaged that particular option. I switch back on, I can still receive OK, all bands OK, transmit tone is still there but no transmit output, what have I blown?

I start to take the K2 apart trying desperately to remember how its all put together, the manuals come out and I start reading thinking did I really build this radio, it's so complicated, I remove the K2/100, get the top cover off then the sides and finally the underneath, back to the bare bones and then start with the magnifying glass and some bright lighting, looking for anything obvious.

Eventually after combing through various circuit boards I find a PA transistor (Q11) on the main circuit board had been completed shattered, this after finding it remains at the very bottom of the radio. Checking all other PA transistor there's nothing obvious. I check elsewhere, I couldn't find any damage with the K2/100, so fingers crossed, this is the only messed up bit.

 
 
 
No wonder there was a loud bang! 

I contacted the Elecraft  forum and was soon in chat with Don Wilhelm who suggested I get the K2PAKIT which has the PA transistors and also replace two diodes as a precaution in case I've blown something else. He instructs me what I need to check and possibly change.

I've put the radio back together and rebuilt as a the standard transceiver without the K2/100 (I only used about 10 watts maximum anyway) and am awaiting the parts from Elecraft, hopefully it's a small bit of damage and that's it, the cost is around 20 odd dollars, but combined international and import postal duties push it up to nearly $60 so it's a lesson well learned.

There will be more info on the repair when the parts arrive, but just imagine if I had decided to transmit the Ft9000 on 2 or 300 watts instead of just 40, god knows what would have happened to the K2!

Delta Loop Comes Down Moxon Goes UP!

Happy New Year to all, I trust festivities were good?

09.20 UK time on new year's day and already I've had my first QSO of the year. Is there something wrong with me? The XYL thinks there is!

Yesterday the Delta Loop was brought down and I have built a small stand at one end of the scaffolding pole which is attached to a tilt over section for ease of use, so at the moment it is lying on its side. The simple stand is designed for easy maintenance work on any antenna that I fit on that pole. This is now ready to take the newly built 18m Moxon and will be mounted as soon as I have the 5 core cable for the rotator.

The mast at an angle and the Moxon waiting to be transferred!
 
 
The temporary mast will disappear for the moment until another antenna project is in the making, In the meantime the paddock will not resemble a building site (as the XYL states) and normality will return till I get another break off work and it all starts again. The grass has yet to make a real appearance on the new paddock, it didn't help with me installing the stock fence, so I suppose in fairness to the XYL it does look rather a mess at the moment, so much mud!
 

I do want to explore the intricacies of the Hexbeam , but I worry about the size even though one of its sales pitches say it is for the smaller garden. Also whether to make or purchase, I could try and make a slightly smaller version without the 20 meters, we'll have to wait and see what 2017 brings.

Thursday, December 29, 2016

17M Moxon Antenna

Over the Christmas break I had another go at building a Moxon antenna. This time not the 10m but a 17m which is a little bit bigger!
I'd had wanted the 20m but I felt it was going to be too big even in the new paddock so I settled on the 17.

Details of the build can be seen on my Moxon page, but below is a taste of the completed build on the twenty foot fibre glass mast, I've just got to mount it on the 35ft aluminium mast with a rotator at some stage. But all the testing is pretty well complete.

Monday, December 12, 2016

Results From 20M The Delta Loop & Learning About 4:1 Baluns

I completed the building of the 20m Delta Loop antenna over the weekend. The components I needed arrived on the Friday, so it was just a case of picking out some time Friday afternoon and Saturday morning to complete.

In the end I used 42 stranded speaker cable for the wire, the 4:1 balun is a temporary one I purchased off eBay for the princely sum of £19. I put it on the MFJ 259 to test and it was OK and it's recommended maximum power is 200w coverage. (I come back to that later in the post).


A bit of a mess of wires, but you can make out the basic triangle with my 6 meter experiment and the hustler in the background!

Measuring off 71.4 ft (for 14.060 the cw portion) of wire, the raised triangle was smaller than I had originally thought. The 4:1 balun was fed at the bottom left corner as recommended for DX. The only tricky bit was actually the raising of the antenna, but that was quickly sorted.

 
The commercial balun which I will replace with my homebrew at a later stage

Testing and reports so far has been good. Measuring the SWR I get a good 1:1 through to 14.200 where it rises to 1:2 up to 14.300. Only a few contacts so far but they have been good with 5/7 and 5/9 reports and the background noise is so quiet compared to my cobweb.

Coming back to the 4:1 Balun, I'm not too happy with buying one. I'd rather learn about them and build my own, simply because it's a big part of the hobby if your building antennas, obviously it's cheaper to build your own and you have peace of mind that it has been tested and built by you!

Having never built one before I've been looking at the Web to see what designs  are about and I have ordered the parts to have a go at building a high powered Guanella Balun. These are x2 FT 240-31 toroids and some 15 A automotive /speaker wire and a small box to house. I have all other bits in my junk box so that shouldn't be a problem. This should be enough for a reasonable power and should cover more than the UK legal limit.



A typical example of a Guanella balun

The interesting thing when you start learning about Baluns is that you are opening up a wealth of different information which can be quite tricky to understand. To this end I'm actually feeling good about learning a new part of the hobby!

As an update I completed the 4:1 balun. The Toroid's were bigger than I had expected but the actual winding was fairly easy and my impatience got the better of me as my box for containing the balun hadn't arrived due, no doubt to Xmas post, so I used an old butter dish as a container instead which worked reasonable well but was slightly too big!

Anyhow, I did some testing and the SWR was slightly low peaking at 1:2 at 13.600 Mhz. This after research was because my toroid leads were too long (the size of the butter dish). So waiting for the proper container to arrive I trimmed the wires and all seemed much better.


Morale of the story don't be so impatient!!

Finally the container arrived and I fitted the balun. Did some more testing and the SWR looked good , 1:2 spot on the QRP at 14.060. Later that day I did a test transmission on 14.060 and I got a Spanish station who gave me a 589 at 5 watts.



Wednesday, December 7, 2016

Building a Delta Loop for 20 Meters

So far within my new paddock  I have installed my top band antenna, (which seems to work very well). However, I'm getting itchy feet to try another antenna. The one I've always wanted to try is a Delta Loop antenna, specifically for 20 meters.

The one advantage I have here is that my take off points around the house are pretty good especially towards Australia and opposite towards the Americas. I'm fairly high up at about 700 feet above sea level with no major obstacles apart from the odd tree dotted around the garden and they say from the Cotswolds east towards Russia the next high ground you hit are the Urals which are well over a thousand miles away, so you can see my take off points are pretty exceptional.

Reading the reports about the Delta Loop, they are a quiet on receive and with vertically polarized loops good on low angle radiation so I reckon they would work well around here for some serious dxing. I thought about which band I would set it up for and came to the decision of 20 meters simple because there would be a high amount of activity both in the Americas and Australia so I should have no problem with contacts especially in the part of the low activity cycle.


I'd like to use Plan D with the apex at the corner, to maximise a good low angle of take off. I have a spare 30 foot telescopic mast which I can lengthen a further 10 feet should I require it and tying off the bottom corners should not be a problem

Calculations for the antenna are fairly simple, to determine the length of wire needed for the desired band you simply divide the resonant frequency in Mhz into 1005 and because the impedance is normally 90 to 120 Ohms you can either use a quarter wave length of 75 ohm coax to match or a 4:1 balun (which I will be using). You need to have a triangular shape (or near as) for it to work properly and of course an ATU will be required. Better to cut slightly longer and use a good SWR analyser to tune the wire to your desired frequency.

I've had to order some more wire , but so far that's been the only expense. So hopefully this will work out as a fairly cheap project. More updates to follow!





Friday, December 2, 2016

Learning/Practising Morse Code

I received an interesting email the other day from a CW fan called Gerry. Back in the 60s he'd been in the Royal Navy serving as a Leading Radio Operator so was obviously proficient in the use of CW. His last live transmission on air was back in 1968 , he didn't become an amateur radio operator and stayed fairly quiet until about four years ago where he came across MorsePower/CW.Com.

He now uses it daily and has become very proficient at CW once again. He wrote to me to advertise CW.com and to say even if you are not licenced you can still chat in CW via the internet and of course it's an excellent way to learn Morse Code without the pressure of being on air so to speak!

You can send and receive  at your pace and have fun in the process. For my particular CW it's excellent because I can go at my speed and I can practise receiving without any pressure I always feel when transmitting on air (this is entirely down to my head and the stroke I had back in 2015!)
If you need to practise why not give it a try and see what you think .

Tuesday, November 8, 2016

Yaesu FTDX9000MP Forum

I've started a Yahoo forum about the Yaesu FTDX9000MP or D because I can find little information regarding set ups and procedures coming from owners of the rig. It's not much yet but as the saying go's "from little seeds etc!"


I know through experience that it is the owners who have the knowledge about these rigs so I'm trying to bring some together so we can discus the pros and cons of owning this transceiver.
Or even if you don't own one but would like to be involved please join us!

Come to the FTDX9000 forum

73s - M0AUW