Monthly Archives: May 2007

My pole connector

Aluminium Pole Clamp

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!

WAN Wireless project comes closer

Grid AntennaLooking 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!

 

SG-230 ATU Review

SG-230It’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.

Heil Goldline with Studio Insert

Heil Goldline Microphone - Studio ElementCompeting in the Baltic 80m contest last night, an operator broke off from his pile up and asked what radio I was using. He really liked the audio. I was using my standard FT1000MP Mk5 – but with the Studio Element on my Heil Goldline. This has to be one of the smoothest elements in the world and it really suits the FT1000 series. I have tried the ‘thin’ elements but they don’t suit me. I have a deep (and loud!) voice and with the studio element,  it all comes together in one broadcast type sound.

It’s fun sounding very different – when everyone else has thin DX and Contest type microphones, mine is strong and fat. A bit like my stomach!

On the subject of these Heil Stick Microphones, I bought the matching Heil Boom stand for the Goldline. The problem is that the microphone isn’t heavy enough for the boom stand so I have to be very careful that it doesn’t ‘launch’ the microphone up to the ceiling on its springs – and it really does actually fly upwards and the mic comes out of the holder and all hell breaks loose!

I wrote to Bob Heil and asked him if the thing was adjustable. He said not but he does know people to put brass weights and stuff on the clip to compensate. It turns out that there’s some really heavy microphones in the Heil stable, not just these baby Goldlines so I guess the heavy ones must suit this boom better. Anyhow it seems a bit of a rip off that I paid getting on for £100 UKP for a boom that doesn’t work right. Oh I forget, the boom squeaks and moans when I turn it. Apparently it’s supposed to be silent. Bob, get yourself a better subcontractor, these don’t work right OM :)

Bigger picture here: http://www.m0mcx.co.uk/gallery/picture.php?/389/category/5

Helically wound 40m vertical

Helically Wound 40m verticalChris (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.

20 meter quarter-wave vertical antenna experiment

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.

Picture below shows typical far-field plot for a quarter-wave vertical.

vertical-gain-at-30-degrees

80m vertical -vs- 80m horizontal loop

Vertical vs Horizontal:

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.

skywave-prop

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.

Narrowboats?

Does anyone have any experience of operating HF from a narrowboat? We’re about to order one and I need to start considering what gear I’ll have. I’ll probably put one of my spare FT1000 MPs on it with a SteppIR vertical right down to 80m. Guess the ground plane might (or might not?) work.

If anyone has experience of using HF on a 70 foot steel boat, please make contact with me. Thanks.

Aquila Clapshaw and Salmon Narrowboat

Dedicated 80m Vertical

80 meter loaded vertical

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.

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: http://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.