My thanks to Lee (G0MTN) James (M3YOM) Terry (G4MKP) and Aidan (M6TTT, Scout) for getting our new station on the air for a first-time-out on WPX.
We also roped in Chris and Dan, two new foundation student contest Scouts for the spotting on the Mult Station. Barry M0DGQ also gets a big thank you for supplying hundreds of meters of 75 ohm coax for James’s stub-filter project and Charles at Moonraker for sponsoring the large number of required PL259 and T pieces.
Pictures here: http://www.m0mcx.co.uk/gallery/index.php?/category/131
We ran a pair of very old Yaesu FT1000MPs (non-Inrad versions) which were completely swamped by QRM to a number of interesting antennas including our new super all-band Mega-Loop (horizontal delta loop at 85 feet) delivering about 12dbi on 20m to US at 10 degrees elevation (more on higher bands). However, it also delivers 10dbi to EU and most of Russia at a very low angle, hence QRM flooding. James’s stub filter project worked but still needs some tweaking. Thanks to K1TTT for helping James get his head around this. Next time, James will have finished Bob Henderson’s filters as well which should sort out any final interference between bands. Poor James soldered nearly 100 PL259s last week. Don’t worry James, fingers should re-grow by CQWW!
The mult station ran Terry’s A3S at 30 feet on my hydraulic tower and also switched in a 200 foot doublet at 80 feet across the tree canopy behind the Scout Hut for the low bands (which worked great on 40m DX but rubbish for 40m NVIS). Need some switchable low dipoles for EU.
We had an initial target of 2,500 QSOs and 1,000 mults and just missed both by a whisker.
Band QSOs Pts WPX
1.8 152 301 50
3.5 574 1513 313
7 866 2203 264
14 722 1378 269
21 102 254 63
Total 2416 5649 959
Score: 5,417,391
We had two breaks of 30 minutes each to sit and have dinner / lunch as a team, an important lesson to keep morale and spirits high. Some day we might not be able to afford time off, however whilst we’re still novices and part-time, we can afford to have a lazy lounge around. We sent our score to GETSCORES every 5 minutes automatically fed by N1MM on a local wireless LAN picked up from my house about a 900 meters away. S51A and ourselves played ping-pong on the scoreboard for the whole 48 hours and we’ve since become competitive friends.
We particularly liked GETSCORES since it’s a way of interfacing with the rest of the world and having even more fun. I don’t understand why more stations don’t use this system. The USA seem to embrace this stuff quicker than others.
There were many highlights. Working VK on short path AND long path on both days on 40m was a privilage. Many more experienced contesters might have done this before but at last a first for me. Having the young non-licensed Scouts successfully finding some RED mults on N1MM was cool. Being called in just to work them was even cooler! Handing the headset over and telling them, “Great. Find some more!” was even better than cool! James’s run into South America was nice on 15m on Sunday, as was the long run on 20m band. Being spotted three times in 5 minutes from the West then the East then the West again was like using a very high gain vertical (which was the bloody trouble actually since we couldn’t dial out the QR Mary).
Like all (good?) contest teams, we’re now working on massive improvements since the station only came together on the Thursday and we started transmitting essentially 90 minutes before the off. Everything worked, nothing broke. Amazing.
73
Callum,
March 31st, 2009
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callum |
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Not much to report this month and I’m only typing because I’ve currently got man-flu and feel like sh*t warmed up.
The Mega-Loop is working superbly at the Scout hut, although I’m trying to find something better for 160m. The impedance is already slightly low on top band and with a 4:1 balun in line at the feedpoint, it seems throws the SWR out by quite a bit. The ACOM 2000 seems to handle such a mis-match, in fact, it only trips out with a return power equating to around 575 watts. Technically, does this means that I can fire 1,000 watts up the coax and have nearly 600 watts come back to me? I don’t know - and certainly not above 1,850 anyway (UK band plans & license conditions etc). I’ll need to check.
Here’s some fun. The picture shown is the design for a Hyper-Mega-Loop, this is twice the size of our current Mega-Loop at 340 meters in length sitting at 18 meters height with a design sag of 5 meters in the middle of each leg. Using MMANA, it seems to still develop amazing potential for 40m band. How about 8dBi at 10 degrees take off for the US? I wish I hadn’t thought this up, I’m tempted to build it. Yes, the RF will fire just North of West at around 285 degrees.
Last Monday night, Tim and James helped me to demonstrate amateur radio to the Beavers. We did a standard JOTA style 90 minutes with little ones starting with Morse code, continuing to QSL designs and passing greeting messages on 80m. Thanks to Chris, G0MLY who was was an excellent victim in managing the little ones pass their greetings message. Also thanks to the many others who helped including our friends, Barry (G0DGQ) and Chris (G0EYO).
At the Exec Committee for Dorridge Scout Group last night, I was asked to step in as an Interim Group Scout Leader for 6 months whilst we find a parent to fill these boots. I accepted and I’m very keen to get stuck in. I immediately announced the 2009 mega-clean-up. If you do live anywhere near Dorridge, we’re going to be after all the white paint (gloss, undercoat and matt emulsion), brushes and sandpaper that we can get our hands on. Every Beaver, Cub, Scout and Explorer will contribute in painting the hut from top to bottom, inside and out. A clean floor and a new kitchen is also planned. If you are reading this and you can help, please let me know.
This also means that we can get the technology room built and set up for remote control ham radio too. We already have three Dell PCs and matching LCD monitors together with a Dell 2400 server to donate to this project. Internet will be sent from my house to the hut via a point-to-point 2.4Ghz link. It’s only 900 meters, so a very interesting project. We’re on the look out for anything that we can either use or sell for funds for our TS2000 appeal or use. We’ll also need PSUs, coax, connectors etc, etc. Can you help?
Callum.
January 28th, 2009
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I’m currently constructing monobanders for 6m, 2m and 70cms on a 6 meter mast using Barenco off-set rotator platforms on T and K brackets.
Today, I noticed that the 70cm is supposed to mount (to a mast) at the rear, after the reflector. However, I’m mounting the 2m and 70cm antennas half-way down their respective booms on a fibre-glass 50cm (2 inch) mast. I notice though that doing this might mean a kink in the radiation pattern of the 70cm yago in particular because the mounting hardware is quite hefty in comparison with the actual wavelength.
How big a problem will this be I wonder? I’ve gone to all the trouble of spending £30 on a fibre-glass mast only to have the U clamps fail me? Some research required me thinks.
June 16th, 2007
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callum |
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I had a bit of a struggle finding the service manual for the FT1000MP Mark V (200W) version so I’ve uploaded it here for your pleasure!
WARNING - LARGE FILE 113 Mb file - SUGGEST YOU SAVE TO HARD DISK - DON’T JUST CLICK IT.
June 7th, 2007
Posted by
callum |
Amateur Radio |
7 comments
You’ll see in a number of pictures, the use of a large slab of aluminium that I had to make up to allow the bottom section of my 12 meter mast to clamp to a pole. A pair of standard of 2 inch double clamps wouldn’t fit Moonraker’s fibreglass mast. The bottom diameter is 58mm (about 2 1/4 inches). I found this slab on eBay and won it for a tenner. It’s heavy though - don’t think it’s a light just because it’s aluminium. Of course, in steel it would be loads heavier.
It is such a handy piece of hardware that I sometimes wonder what I’d do without it, particularly as I was bright enough at the time to drill a few extra holes in case I needed them (which I do for the 40m dipole!)
I’ve also discovered that the top 8 meters of my fishing pole fits perfectly on the 12 meter mast with a piece of plumbers tube as an “insert”. The 12 meter mast fits on the 6 meter aluminium pole too. That’s a 5/8th for 40 meters or a full sized quarter-wave for 80m!
See: http://www.m0mcx.co.uk/gallery/index.php?/category/42
May 31st, 2007
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callum |
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Looking back in the archives , you’ll see that I wanted to transmit the internet all over the place using a parabolic grid dish on a rotator mounted on the roof. The project is now closer, last night I successfully added a router to my local LAN and connected a PC on a different subnet - this means that anyone connecting will not see my home network. Important for me!
Using a Buffalo WBR-G54 Router, I’ll be connecting 10 meters of Heliax (Thanks to Barry, M0DGQ)Coax directly from my shack up to a new rotator on the roof. This will give me a loss of only about 2dB - fingers crossed. My first target is the Scout Hut. I need internet down there!
May 31st, 2007
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callum |
Amateur Radio |
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It’s only good for 150 watts or so but I’ve just loaded up top band on a half-sized G5RV at the feedpoint with this little beast. Tunes from 160m through to 10m. I run 12 volts to the loft with a spare run of RG58 (I knew that coax would come in handy!).
You can load up almost anything with this. I’ve always wondered how well the kids trampoline will transmit!
The manual talks about 150 watts being the maximum but elsewhere it discusses 200 watts. I hope that this will be the perfect little friend to my 200 watt FT1000MP Mk5 and I’ll leave my older FT1000MP to partner with the Ameritron.
May 31st, 2007
Posted by
callum |
Amateur Radio |
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I’ve just watched a great video on YouTube. Although aimed at the US, it has a great message. I definately want to show this to my Cubs: http://www.youtube.com/watch?v=zULytRI2Kt0
Cool. Check out Walter Cronkite’s presentation on Amateur Radio Emergency Communications: http://www.youtube.com/watch?v=5Z9136_Nhh4
May 21st, 2007
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callum |
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Chris (G0EYO) kindly modelled my 40 meter vertical with loading coil (http://www.m0mcx.co.uk/?p=44) and mentioned that he felt the take off angle may be higher than I would like it.. He suggested experimenting with a helically wound vertical. Chris recalls a team event last year where they needed to get on 40m fast so a fishing pole and about 10 meters of wire were produced along with 2 elevated radials. The problem was that the fishing pole was only about 7 meters long. The team simply wound the 10 meters of wire on to the fishing pole and hit the TUNE button on the rig to swallow up any mismatch.
I tried the same experiment with my 8 meter fishing pole and 10.6 meters of wire. Why 10.6 meters? Simply because I cut the wire a bit long intentionally. Using 4 elevated radials, I found the resonant 1:1 frequency with a near 50 ohm match was 7.7 Mhz. Way above my requirement however the SWR bandwidth curve was very strange with a flat 2:1 SWR all the way from 7.2 Mhz right up to 7.6 Mhz. Indeed, the TUNE button easily swallowed the incorrect size of this antenna for the whole of the 40m band. I needed to make this longer though so I could run high power in a comfortable manner.
Stripping off the 10.6 length, I found a 100 meter roll of 6 core telephone wire and chopped 15 meters off it. I wound this on to the fishing pole which gave me 6.8 Mhz. A couple of attempts later and about 50cms of wire short, the vertical tuned in to 7.05 Mhz with a very large bandwidth, certainly better than the loading coil version.
Later in the evening I heard VE1KF managing a European pile up from his QTH in Nova Scotia. My vertical broke the pile in one shout. He emailed me later, “Your signal was a nice strong 59“. Thanks for the report Brent.
I give a thumbs up to this antenna; I believe I am getting a lower angle of radiation. It’s the best 40 meter vertical I’ve made yet but remember - these only work from about 1,000 miles upwards. If you want lots of QSOs, you’ll need a dipole or a loop to compliment this.
More pics: http://www.m0mcx.co.uk/gallery/index.php?/category/40
Postscript: I recommend using a 1:1 choke balun on this design to stop the feedline radiating and to ensure that all the RF goes where it should. See here http://www.hamuniverse.com/balun.html for some regular designs.
73, Callum.
May 19th, 2007
Posted by
callum |
Amateur Radio |
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Not content with attempting to understand and build 40 and 80 meter verticals, I’ve decided to build a 20 meter version tonight. This has 4 x sloping radials at 45 degrees with a feedpojnt up at about 7 meters in the air. On receive, it’s actually pretty good; only for extremely weak or barely readable signals is it beaten by the 40m loop or my attic mounted half-sized G5RV. For the record, it performed straight out the box with dimensions of a whisker under 5 meters for both radiator and radials.
No photographs today because it’s now dark and in any case, it almost looks the same as the 40m and 80m other than the fact the feepoint is higher!
Temporary conclusion: The noise factor may be a slight problem I think, although I’m currently listening to a net between two Italian stations and a couple of US based ones and it appears a good all-rounder, just a little bit more noise than the loop. I know verticals are noisy but I was hopefull of some quieter receive. I’ll try out some TX tomorrow.
May 14th, 2007
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Overview: The first thing that I noticed was that during daylight hours, the vertical was utterly hopeless. Inter-G signals were virtually unreadable, to the point I thought it wasn’t working. Indeed, being daylight, I couldn’t hear a thing, just noise. Switching my NVIS loop in to circuit brought the band to life with usual weird discussions of carrot growth and weather. As nightfall fell, the vertical started performing but nowhere near the performance of the loop. By 22:00 UTC, the Russian and nearby European stations started coming in stronger, but again sounded better on the loop and it didn’t seem to matter what antenna I used to transmit on either. One German noted on comparison tests absolutely no difference on TX.
I called for RP3PRP on the loop (he was loud) and he had some problems receiving me so I switched to the vertical and we exchanged reports and my confidence rose. Again with 9A7KM, I started the exchange with the loop because that’s where he sounded so good but flipped to the vertical to complete. Confidence grew higher. Then UP0L in Khasakstan for a 3,500 mile hop again on the vertical. But this isn’t the whole story. Don’t think the vertical performed better on TX than the loop everytime - this isn’t the case. This particular vertical is one heck of a compromise; remember, only about one ninth wavelength and only three meters above the ground.
My loop on the other hand is a proven high performance antenna that’s got a history of DX to the Far East and North and South America. After a couple of hours and 48 QSOs across 20 countries, I realised that for 90% of the QSOs that you make on 80m, an inverted V, a regular dipole or perhaps a delta loop (like mine) at around 30 feet will be fabulous - and you’ll have the advantage of being able to have a QSO in your own country. Occasionally, having the flexibility of switching the vertical in gives you an added interest but it’s hardly worth the effort. A 4-square would be a different story though, and for the uninitiated: a 4-square is 4 x ¼ wave antennas phased in a square, quarter wavelength apart that ‘pushes’ a lobe of RF (db gain) in a specific direction at the push of a button. However it’s hardly an event antennal, more suited to permanent installs.
For me though, I don’t think this test was completely conclusive. I’d like to build a full-size quarter wave with full-sized raised radial set to complete the test with a feedpoint at 5 or 6 meters above ground: in other words, doubling the size of this little twig and maybe I can aim at building it for this year’s NFD. I have a feeling that it was the loaded radials that was restricting my efficiency, not the loading coil in the driven element. My experience of a 40 meter quarter wave gives me some confidence in this arena but I’m also wary of the different characteristics of 80 meters which maybe much more suited to higher dipoles.
There was though one small advantage that I haven’t documented, and that’s the use of a vertical as a dedicated QRM receive antenna. I scored many points by finding distance stations between strong UK stations. I can reduce UK stations by around 40 db by switching in the vertical, whilst at the same time keeping the target station clear in my headphones.
In conclusion, verticals for 20 meters and above may well be good performers and I’ll certainly have a bash at a 20 meter version of this shortly but for 40 meters and below, be clear about what they’ll do for you. I do not recommend them as your primary antenna unless of course you are very restricted on space - and even then, there are shortened alternatives that can be squeezed into small plots.
May 12th, 2007
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callum |
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I didn’t document fully last weekend that my 40m vertical experiment gave me a rather good match on 3.8Mhz. This gave me the idea of building a better 80m vertical this weekend by loading up both the vertical - and the radials. As I type this as I discover that first time up, I’ve achieved a resonance (of sorts) at 3.456 Mhz however, I’m not getting 50 ohms. The SWR is at best just under 2:1. I have reduced the legs of the radials a bit because of the loading coils (which all have 68 turns on my favourite 40mm plumbers pipe). I shall now adjust only the vertical coil. I know I should in theory adjust all the coils to keep them in unison however, the actual length of the radials is not precisely known; only that they are ‘about’ 9 meters plus a loading coil - and in any case I can just shorten the radials for fine tuning.
Here’s the resonant coil adjustment chart for the vertical coil:
- 68 turns: 3.456 Mhz
- 67 turns: 3.470 Mhz
- 63 turns: 3.535 Mhz
- 59 turns: 3.600 Mhz
- 55 turns: 3.690 Mhz (1:1 SWR dead)
- 54 turns: 3.691 Mhz (I tightened up the radials which had an adverse effect so that the resonant frequency hardly moved)
- 52 turns: 3.740 Mhz (SWR rising a whisker now)
I finished on 53 turns in the end. I’ve started keeping a couple of turns or more spare, never cutting off all the ‘dead ones’ as I take them off so I can wind them back on if I overshoot. My ‘best’ spot frequency is now 3.715 at 1:1 SWR with a 2:1 SWR curve starting at 3.6 and going all the way beyond 3.8. In fact, 3.8 has an SWR less than 1.5:1. I look forward to testing its RX and TX capabilities tonight on the CQ-M contest. I’ll do a quick single-band entry on 80m. I’ve also fitted a load of ferrite clip-ons as a type of current balun up by the feedpoint.
More pictures: http://www.m0mcx.co.uk/gallery/index.php?/category/39
May 12th, 2007
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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: http://www.m0mcx.co.uk/gallery/index.php?/category/40
73
May 7th, 2007
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callum |
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I’m about to build and test an 80 meter qtr wave vertical antenna with elevated radials. I am assuming that one can build the radials smaller if you use a loading coil? Anyone ever tried this? I’ll post the results here.
Thanks to Dave, W8NF; he confirms that one can load elevated radials just as one would load up both sides of a dipole.
Callum.
May 2nd, 2007
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callum |
Amateur Radio |
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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.
May 2nd, 2007
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callum |
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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.
April 14th, 2007
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callum |
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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?
February 7th, 2007
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callum |
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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 :)
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.
February 2nd, 2007
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callum |
Amateur Radio |
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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?
January 31st, 2007
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callum |
Amateur Radio |
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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!
January 29th, 2007
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callum |
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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, see here for one of the coils: http://www.m0mcx.co.uk/gallery/picture.php?/96/category/12. 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.
January 27th, 2007
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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. The photo project is here: http://www.m0mcx.co.uk/gallery/index.php?/category/37.
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 :)
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. This can’t be right though, so I’ll have to do some more evaluation.
To date, the most reliable antenna has been the 1/4 wave vertical. I’m just waiting for those Parabolic dishes to turn up. Then we’ll have some fun!
January 26th, 2007
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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 http://www.m0mcx.co.uk/?p=17) but apparently we were out of stock(!). A small yagi was the answer:
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!
2.4 Ghz, three element yagi pictures: http://www.m0mcx.co.uk/gallery/index.php?/category/36
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!
2.4 Ghz quarter wave vertical antenna pictures here: http://www.m0mcx.co.uk/gallery/index.php?/category/35
January 25th, 2007
Posted by
callum |
Amateur Radio |
no comments
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 |
3.2 dB |
| 144 MHz 8.5 dB |
4.5 dB |
| 200 MHz 10 dB |
5.4 dB |
| 300 MHz 13 dB |
6.2 dB |
| 432 MHz 15 dB |
7.5 dB |
| 1000 MHz 27 dB |
13.0 dB |
| 2450 MHz use Westflex 103 |
19.1dB
|
| 3000 MHz use Westflex 103 |
27.8 dB
|
| 5000 MHz use Westflex 103 |
34.1 dB
|
January 24th, 2007
Posted by
callum |
Amateur Radio |
no comments
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:
January 21st, 2007
Posted by
callum |
Amateur Radio |
no comments
