40 meter quarter wave vertical with loading coil

Base Loaded Vertical 80m and 40m

This afternoon, I’ve been playing with an 8 meter fishing pole in the garden, clamped to a 3 meter aluminium pole with 2 x 10 meter elevated radials sloping from the feedpoint at 3 meters to fence height. It’s got a bottom loaded coil to get on 40 meters. I wound the vertical just very slightly helically so that it didn’t flap in the wind however I can guarantee this had no effect on the loading.

After some experimenting, 13 turns gave me a good match between 7.0 and 7.2 with SWR not exceeding 1.4:1 – and I managed to do the final tweaking by shortening the radials by half a meter.

There’s a number of conclusions here. The most surprising is the accident concerning a certain 80m vertical; I started life with 66 turns on the former which gave me an 80 meter vertical antenna. More of that later), the main experiment seems to have worked in giving me a vertical for 40 meters but I also discovered a resonance at 23.6 Mhz which confused me.

However, comparison listening tests between this new vertical and my horizontal delta loop gave me some interesting results. Local signals this afternoon were barely copyable on the vertical but 59+ on the loop. I’ve just been listening to a couple of German stations, probably about 500 – 600 miles away and there is no discernable difference between antennas but a Spanish station that I’m listening to at 1,000 miles away is certainly 1 S point better on the vertical, more often than not. Clearly at distances of 600-700 miles, the vertical starts to outperform the delta loop, certainly on receive.

On transmit, further tests demonstrated to me that more often than not, long distance contacts were slightly more reliable on the vertical than the loop, however since most of my contacts on 40 meters are within 2,000 – 3,000 miles, the loop will be my long term favourite for higher quality contacts and more of them.

More pictures: https://www.m0mcx.co.uk/gallery/index.php?/category/40

73

Slinky Antenna

I have just bought 2 x slinkys from Maplins. They appear smaller than the “old fashioned” ones but it should be fun making an antenna. I’ll try and stretch them out and see what they do.

I’d be interested in knowing what you did with your slinky. Anyone built a vertical?

Callum.

Vertical HF antennas

My attitude to verticals changed recently whilst in Devon on holiday. I didn’t have enough physical space for my favorite 80m loop so I had to do with 20m instead. I started as a horizontal dipole but over a few days became a vertical. Being about 30 yards from the sea probably helped but apparently I was a very healthy 20 over in the USA. Verticals rule OK.

2 inch scaffold tubes

I found out the other day that you don’t phone a scaffolding supplier and ask for 2 inch scaffold poles. The girl won’t have a clue what you are after. Instead, ask for: 1 & 29/32 inch diameter, 7swg wall, round aluminium tubes, in grade 6082 T6. Apparently, they weigh 1.652Kg per metre.

Installing Windows XP

Tonight, I put in the latest XP install disk into an old PIII machine from my latest (Jan 2007) Microsoft Action Pack Subscription (MAPS) to build a thin client (RDP) for my ever-expanding 2003 Terminal Services empire. After a few minutes, I get to the place where XP tells me that in 24 minutes, I will be on my way on a clean install. Several bloody HOURS later(!) I’m still downloading update-after-update and later.. Service Pack 2! Why-oh-why wasn’t SP2 already on the build for the latest MAPS XP install disk? Good Lord – I’m hanging around in the middle of the night just to get a clean install up and running!

Worse though is when you select from the Microsoft Update site to install the latest update.. you hang around and answer a few YES and NEXT buttons and wander off, looking over your shoulder watching that the update is being downloaded. After 40 minutes, you come back expecting the update to have been applied to see yet another bloody dialogue box to have you agree some bloody licence agreement and 40 minutes of your total life has been wasted! I already committed to the frigging MS agreement when I installed XP didn’t I?

Some day I WILL be out of MS. In the meantime, my advice is to shout “Grrr”.

My little helicopter

I am pleased to report that my birthday present helicopter has a mind slightly bigger than a Huey. He thinks he really is a helicopter. We put a camera and a microphone on-board and this is what we discovered!

Maybe there’s a 160m quarter-wave vertical antenna waiting to be flown here?

Map of Europe Game

I have just achieved an avergae of 70 miles and 89% accuracy on my fourth try for the game. If you are a Radio Amateur in Europe, this game should be easy. You may need PowerPoint installed on your computer for this to work. It’s a .PPS file.

Here we go, it’s here: https://www.m0mcx.co.uk/pictures/MapofEuropeGame.pps

Postscript; June 2007: For some reason, this particular posting has attracted a huge volume of spam comments that I keep deleting. This is a pretty big overhead. Some days I get over 50 posts, all selling v1agr@ etc.. I’m going to either leave these comments for a bit of fun – or delete this complete post. I’m wondering if I can close this post to comments instead? I’ll figure a way. Thanks for visiting.

Ground Wave Propagation

Is everything I have ever learned on the “ground wave” topic is a complete nonsense? This magical world between line-of-sight and ionosphere bound signal propagation; what is it and does it exist? In my experience, HF signals do mostly one of two things: They either refract/reflect off the ionosphere or they are “line of sight” (or almost line of sight). I realise that there’s meteor scatter, back scatter, tropo and other specialist propagation paths but lets face it, most propagation for the average HF Jo Ham is either line of sight or ionosphere refracted.

Last Monday evening during the 80m CC contest, I had QSOs with several of our local club stations over a circumference of about 10 miles. Most of the local stations were consistently 5 and 9 or better, sampled during the whole 90 minutes. I have since discovered two stations that couldn’t QSO with me at all and they tried many times over the 90 minutes apparently. They could hear me but we couldn’t work each other. So who was ground wave and who was ionosphere propagation? Why is it that over a circumference of 10 miles, I can almost always have a guaranteed QSO with a local station and other times they can not be heard at all?

If ground waves existed, then we could all communicate, all the time. Does this mean that all the other club members I spoke to locally were via the ionosphere? I have therefore made a conclusion that most signals on 80m are ionosphere bound propagation other than the very local 1 mile away station.

What do you think?

G7OJO Silent Key

Reg Brown, G7OJO, passed away on 22nd January 2007. Reg was a member of Wythall Radio Club and in the words of Chris Meadows (Chairman), a “stalwart” of the club. Today was Reg’s funeral and a quite a few of the club turned out at Robin Hood Cremetorium.

He was “Piped” up the driveway by a Scottish piper, all the way into the chapel. The vicar’s sermon included references to Reg’s fishing and radio hobbies and afterwards, Reg’s Brother-in-Law was invited to say a few words. It was a very moving speech and he said goodbye to Reg using the radio ham terminology, “G7OJO, 73 Old Man”.

Afterwards, at the British Legion, Stratford Road, we compared stories about Reg’s exploits. I loved the one about Reg having an accident with a car on a slipway at a harbour. He was launching a small boat and his kids were watching at a safe distance with Pauline his wife (who told me this story) sitting in the car. Pauline said that something went wrong and she ended up at the bottom of the harbour inside the car. Reg dived down and got her out! Amazing.

After Reg switched off one night after having a natter on 2m FM, Chris (G6KMQ) and myself noticed a carrier come up on the frequency and we could hear someone in the background clearly tidying up and generally making human noises(!). Chris and I discussed who it might be and all of a sudden Chris said, “I know”! and disappeared. Shortly afterwards, I heard a phone ringing in the background from the FM set that was emmiting the carrier and then Reg’s voice, “Bl**dy hell”, he shouted to Chris’s advice and took the MOX switch off. He had pressed that instead of the ON/OFF switch! I believe his vocabularly may have been slightly worse than that quoted in this text!

I’m gonna miss you Reg. Rest in peace OM.

C McCormick, Tues 6th Feb.

Andrew 2400 Grid Antennas arrived!

I’ve had loads of fun tonight putting together the Andrew Grid antennas (well one of them) and duly installing it on an old brass curtain rail in the shack, pointing towards the kids PC in the “little lounge” (as we call it). The signal shot through the roof when I got the lobe on the sweet spot, bearing in mind that the lobe is only a few degrees wide, so get it wrong and you don’t see a signal at all! This is good news though and proves that my 2.4Ghz antenna designs were utterly rubbish 🙂

Andrew Grid Parabolic Antenna 2.4Ghz

I tell you, it’s even bigger than this picture! Like all good antennas, they are bloody huge if you muck about with them inside a shack. Clearly designed for a roof on a rotator (in my view!!), I have decided that it would be a waste to put a wireless router on the roof, instead I am going to see if I can bring some Andrews Heliax down the wall and straight into the shack. Perhaps a kind amateur may help with a 20 meter run of scrap heliax? That way, I can play wireless networking, general purpose radio and anything else that tickles me!

The only thing that worries me is the polarisation. Should I mount this vertical or horizontal? I was going to go horizontal for a point-to-point wireless bridge but now I’m not so sure. I’ll have to mull that one over – I have a feeling that horizontal polarisation works better over long distances, we’ll see.

One problem though, the guy that sold these to me seems to have “lost” one of the antennas. He thinks he shipped 5 grid antennas according to his letter. However, I received 4. Something odd has happened. [Later] He’s emailed me saying that he’ll investigate on Monday because he didn’t pack them himself. [Later again] He only sent the four and now the fifth is missing so he’s sending a cheque for £10 as compensation.

Ofcom Prosecution Statistics

For those readers who live outside the UK, the government department responsible for policing the radio spectrum is called Ofcom.  Ofcom has recently published its 2005/2006 prosecution statistics. This shows that their resources almost exclusively spent their time shutting down unlicenced broadcast stations (that operate on the 88 to 108Mhz FM band I suppose) and unlicensed Private Business Radio operators.

Out of 52 prosecutions, they secured 52 convictions. A case of making sure you have very strong evidence I assume. However only 4 warning letters were sent out to the hobby market; these four letters covered all those 27Mhz stations running 500 watts, those ops on 6.6Mhz and all those radio amateurs broadcasting music on repeaters (eg GB3 Charlie Fox middle of January 2007) and generally causing a mess of QRM. Not a single prosecution.

Looks like you can get away with murder then? 

Yaesu FT1000MP Mk-5 IDBT controls

I’ve just found this page on the internet whilst I was doing a search to track down exactly how the IDBT control works on my Yaesu FT1000MP Mark IV (Mk 5). It stands for something like Interlocked Digital (analog) Bandwidth Tracking and it’s part of the EDSP controls. Thierry explains it better than me, however I’m a happy bunny now because I can get the Mk5 sounding like my original MP 🙂

Anyway, these deeper (advanced..?) instructions beat the instruction manual hands down. Merci Thierry!

Shortened / loaded 40 meter dipole for attics

This morning, I removed from the loft, a pair of nested dipoles for 40 and 20 meters fed with one coax feeder. The 40 meter dipole was loaded with some coils so that I could fit it in the attic.

It gave me 40, 20 and 15 with a push because although a 40 meter dipole should give you a resonant 15 meter antenna, in this case – with the coils for 40 – it mucked the maths up and caused the ATU some trouble. On 40m, it worked a treat.

If anyone is interested in making up the “shorty forty”, you may find my experience of interest: Each coil was made from 3 meters of hard drawn BT downlead, coiled around a PVC plumbers pipe of around 25mm diameter and about 30 turns or thereabouts. The actual spec from the dipole centre was as follows:

  • Dipole centre to coil: 3.7 meters
  • Coil to end of dipole leg: 3.3 meters
  • = 7 meters each leg + length of the coil

I replaced the nest was replaced by a half-size G5RV in a “lazy” inverted V configuration, tucked up in the rafters. Good for running a second radio and it gets me on 10m as well as the WARC bands.

Incidentally, when I was testing this original dipole, I started off with 8 meters for each leg and ran it through the MFJ analyser. It was resonant on 6.66 Mhz. An old favorite pirate band that some people may remember. Adding the coils raised the renonant freq from 6.6 to 8.5, so cutting a meter off each side to get the whole thing working for the amateur bands was necessary.

So there you have it, a 45 foot long 40m band dipole.

Pringle Tin Waveguide Antenna 2.4 Ghz project

Not being able to resist the pull of the decibals, I raided the larder tonight for a Pringle tin to build a wave-guide antenna from scrap parts. This is the story of that project.

Manufacture: I soldered a 30.5mm (quarter wave) element to a UHF bulk-head connector and drilled out a hole in the Pringle for hot-glueing. Exactly how far away from the base of the tin I should fit the element took ages – and lots of conflicting web pages. In the end, I aimed for 1/4 wave from the back of the tin. Someone is going to tell me that this is probably the most awful place to stick it – I can believe you 🙂

Pringle Tin Waveguide Antenna 2.4 Ghz

My multimeter couldn’t get a reading on the foil inside the can so I used kid’s water based glue to stick sheets of tin-foil to the outside. This tinfoil was grounded to the base of the tin, although I had some difficuty in doing this because there appears to be some sort of laquor applied to the base. The copper wires seen in the photo were to act as a physical and an electrical assistant; to provide a good ground to the outside of the can.

Ater connecting the Pringle-Wave-Guide to a buffalo wireless access point, I turned it in the general area of the kids room that was running NetStumbler on their network card. I waggled the can around in my shack, and went to the kids room to check if the signal strength had risen at all during the waggling. No luck. So far, it’s as much use as a dummy load.

It just goes to show that some experiments just fail.

Homebrew 3 element yagi for 2.4 Ghz

I needed to get an antenna higher for the kids computer room but a quarter wave vertical didn’t seem to have the gain I wanted, in fact from the kids room I couldn’t even see the network. I hunted for a Pringle can to make a “Can-Tenna” (see https://www.m0mcx.co.uk/?p=17) but apparently we were out of stock(!). A small yagi was the answer:

2.4 Ghz 3 element yagi

I made the driven element directly out of the lossy RG58 coax so that the centre conductor became one side of the driven element and the braid became the other. I used solder to give the wires some strength.

A good test but don’t be fooled. The standard 5/8th antenna shipped with most routers are probably just as good. This yagi needs to be a 5 or maybe 8 element to work better.

I also built a quarter wave last night directly from Westflex W-103, no other components – and although it compared well to the shipped vertical, it only started to match the retail antenna when I gave it some height. Another good (but failed!) experiment!

Coax Loss Comparison

I can never find the comparison charts between RG213 and Henry Westlake’s Westflex W-103. At last, I’ll have this logged forever now. Per 100 meters:

RG213/URM67(Mil spec)
Westflex 103
 100 MHz                      7 dB 5.0 dB
 144 MHz                    8.5 dB ?? dB
 200 MHz                     10 dB 7.5 dB
 300 MHz                     13 dB ?? dB
 400 MHz                     15 dB 11.0 dB
 1000 MHz                   27 dB 18.0 dB

 

Waterproof equipment enclosures

I have just bought some MC to N-type pigtails for the wireless project but now I’m trying to find equipment enclosures to house the router up the mast right next to the grid antenna. Can I find one? Nope. There’s a company paying good money to Google for first place in the rankings for “non metallic enclosure” but the site is so bad(!) and the pages are even named, “NewPage 1” and stuff like that. The MD’s son’s summer project by the look of it. Need to get the pros in!

After much searching, I found a few sources:

AFS 80m SSB Contest

AFS starts soon. I’m here early setting up for it. I can’t hear much, are the bands open? N1MM is working OK but my voice keyer is making nasty noisy QRN from the computer and it’s horrible so I’ve ditched it whilst I consider what to do. This means more fluids (to keep voice in working order!) = more toilet. Last CQWW I used a bucket so I wouldn’t lose my frequency. I’ll just have to cross my legs this time!

I’m logged into the Wythall chat room and waiting for people to join. I love these club activity contests. The anticipation kills me!

         

At 45 minutes before the off, I am holding 3.697 MHz and calling CQ, speaking with MU0FAL (Colin), M3NSQ (Steve in Hornsea), M1EBV (Bristol) and G0ICJ (David from Wythall Club) and I stay on that freq at the off, gradually moving up to 3.698 MHz until 16:21pm with 213 QSOs in the bag. Over the next 100 minutes, I only scored another 45 QSOs, mainly because I lost my frequency through stupidity by deciding I could score more doing some single VFO work, cruising from the bottom of the band through to the top, then I realised what a fabulous frequency I had!

I ran full UK legal power (400 watts) though my FT100Mp Mk5 and my Ameritron 811 amp almost on tickover using a turned-down Class A from the 1000 as the driver for the linear amp. Anyway, finished on 259 which is about 20 QSOs better than last year.

Wythall Chatroom:

15:28:56 [ChrisG1VDP] I am stuck between 2 very loud and wide stations on my running freq…
15:29:24 [g6kmq] m0mcx one of them?
15:45:16 [g0mtn] we’re finished now – time for shopping
15:45:56 [m0mcx] Shopping? Loser
15:46:32 [g0mtn] 133 first hour though. can’t complain
16:50:43 [g7ugc] You swine Chris pinchinf my QSO
16:51:02 [g6kmq] who me?
16:52:21 [g0mtn] back from shopping. now starting cooking… (!)
16:52:26 [g0mtn] scores on the doors so far ?
16:52:44 [g7ugc] 53
16:52:49 [g6kmq] 54
16:52:51 [g0eyo] 54
16:53:24 [ChrisG1VDP] 66
16:54:43 [m0mcx] 234
17:40:54 [m0mcx] Last year: http://www.contesting.co.uk/hfcc/results/2006/afsssb2006.shtml
17:51:23 [g0mtn] remember: fivers to me after the contest
17:54:08 [g0mtn] just received my first log  not even finished yet
17:56:07 [m0mcx] Got called by DL16XXV – sounds like a post code!
18:00:49 [ChrisG1VDP] Do we send the logs to lee to enter the contest?
18:00:58 [g0mtn] yes please.
18:01:24 [g0mtn] i will then send them to myself
18:02:12 [g0mtn] qsy dinner
18:02:53 g0eyo exits from this room
18:03:06 [m0mcx] Me too !

2.4 link signal strength

I have a first class project in tow to put a 2.4GHz link in to the club about 4.5 miles away. I’ve just secured 5 grid dishes with 24dbi of gain for £125. What is a Fresnel zone and how do I spell it?

Anyway, there’s this great site to calculate the potential likelihood of succeeding in putting a link up between one site and another:

ttp://www.atdi.uk.com/WebObjX/default.asp.

It also gives you the dreaded Fresnel Ellipse data which I think I’m slowly starting to understand – essentially, you can block around 40% of the ellipse in one place and the link should still work, but no more. Google it for more.