Loaded Dipole Tuning

I am not a regular operator on Top Band so, at this time of year when the RSGB Club Calls Contest arrives, it sees me dragging the tangled mess of wire that is my 160 meter dipole out of hibernation in the shed and getting it back into active service.

Like many urban dwellers, I do not have the requisite amount of space to hoist up a full size dipole for top band so have constructed a shortened version with loading coils in the centre of each leg. This affords me a resonant dipole but with a much restricted usable bandwidth, but, at least it gets me on the band and able to score some points for my Radio Club (S&DARS).

My prefered mode of operation is CW and most of my antennas are resonant dipoles that are tuned to the low end of any band. As the Club Calls Contest is a Phone one it requires shortening the antenna to tune it for the Phone segment of the band. This is usually simply a matter of folding back the ends of the dipole and fastening with a few cable ties. But by how much?

My usual approach to shortening a dipole for the phone section of the band is to use the trusted magic formula; 468/Freq to calculate the theoretical length of the antenna at two different frequencies; that at the low end of the band for CW and that of the new required frequency in the Phone section and noting the difference between the two lengths. This normally gives a fairly good guide on how much to fold back before fine tuning with an analyser but, with my loaded dipole, this proved to be wildly inaccurate.

Using the magic formula, the difference in length of each leg between an antenna resonant at 1.818 and 1.920 MHz is 6.8 feet, or approximately 82 inches. In practice, for my shortened dipole with quite hefty loading coils at the centres, the actual difference turns out to be just 22 inches.

I realise that the effects of a loading coil are more complex than simply one of wrapping some of the wire into a coil. For me though it makes the use of an antenna analyser so much more valuable. At the time of purchase I did baulk at the cost but have subsequently found its value to be inestimable.

73 and hope to work you on the bands, whatever the mode.

2014 2 Meters FISTS CW Award

Delighted to receive a certificate for 1st place in the 2104 FISTS CW Club 2 meters activity event. 

It was particilarly satisfying as the VHF activity was a FISTS tribute to Angie G0HGA and I did meet her many years ago when we both sat our CW test together. I was then G1UUM and living in High Wycombe, a particularly poor VHF location at the bottom of a deep valley. That was the original inspiration for learning CW in order to get the treasured "A" licence and to be able to work on HF.  While I was struggling to reach the necessary 12 wpm, she was, even back then, rattling it out like a seasoned pro. She did make quite an impression on me then and I was saddened to hear that she went SK.

Many thanks for all the QSO's that made this award possible.

73 

SDARS 2015 Rally

FSK and Meteor Scatter on 2 meters

My local Raadio Club, Spalding and District Amateur Radio Society (SDARS), recently had a video presentation, talk and demonstration on the use of FSK with WSJT  Software for making long distance contacts on 2 meters using Meteor Scatter.

This was a very timely talk as the Perseid Meteor Shower was due in a few days along with a DXpedition to IO41 by EI9E.

I must say that I had used this mode before, or I should say I had WSJT working before, but I had never made any contacts with it. I simply did not really understand what Meteor Scatter was all about. I certainly did not realise that this was a mode that can be used at any time as Meteors are constantly entering the Earth's atmosphere.

The video was by GW8JLY which told us what FSK and Meteor Scatter was all about. It was a very comprehensive video that didn't get bogged down in too many technicalities. Further explanation was given by Bob, G1ZJP, and then a practical demonstration was given by Julian, G4YHF, in the Club Raadio Shack which put the theory into practice. 

Still fired up with enthusiasm, I couldn't wait to give this a try at home and the next day was on 144.370 listening out for signals. I saw some decodes on the screen from OH6KTL and decided to give him a call. After a few QRZ's he got my call and after some time sending info to and fro, we completed the QSO.

So I had made my first Meteor Scatter QSO using FSK and WSJT software. OH6KTL is in KP02OJ, a distance of 1649 Kms and just using 30 watts to an 11 ele Tonna at my end.
I think that this is a mode that I could get into and will definitely be trying it again.

Thanks to SDARS for being such a pro-active Club. This is not something that I would have achieved before the presentation. Thanks guys.

73 De Jim GØHGH

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Deaf????

At some point every Amateur Radio operator must get filled with self doubt and wonder whether or not his signal is getting anywhere. Likewise, when listening to a fairly deserted band, is it imagination or is there actually a signal in that noise that I can just not make out. It must be sign of my insecurity in that, when I get some adverse criticism, I always think that it is me to blame.

In July, FISTS started a two meter activity event for an hour on Saturday evenings and another hour on Sunday mornings. In that first month I received more listener reports than I had QSOs. On the Yahoo group conversations it became evident that many operators were using low power and a  vertical antenna: the cross polarization losses are quite large so I was not too concerned.

In August, a suggestion was made that I was running huge power and  was extremely deaf! Perhaps someone should talk to me about it? Comments like this only fuel my anxiety so was starting to become a little concerned. I usually run 75 watts to an 11 element beam up about 10 to 15 meters agl depending upon wx conditions (and whether or not I got up early enough to pump up the mast).

Fortunately I have been competing in the RSGB UKAC Contests for a few years now and, if nothing else, they have given me a very good idea how well or poorly my signals have been radiating around Europe. For instance, when I first started contesting it was with a vertical antenna and 8 watts. Not surprisingly, my signal did not get very far, a maximum of 100Km, so it wasn't long before I upgraded to a 6 element 2 meter beam. That made a huge difference and I was working stations up to 250 Km away without too much trouble. Next came an upgrade to my current set up; an 11 element beam and 100 watts. With this station I find that I do fairly well and am confident in having a good idea on what I can expect from it. attaining 450 Kms is not unreasonable.

CW is a mode much more suited to making longer distance contacts so I was quite keen when the FISTS 2 meter activity sessions were announced. When I look at the log and analyse the QSOs they are however a bit disappointing. I have had two, quite hard work, contacts at 300 and 220 Kms where I gave 429 reports and received 579. Most other contacts have been quite local.

Interestingly, during one session I was called by a Contest station in IO75 and we exchanged very good signal reports (not unsurprising for contests!) but the QSO was pretty much as I expected - easy copy both ways and that was at 479 Kms.

So am I deaf or do FISTS members just not put out big signals? As I mentioned earlier many are using verticals, assuming a cross polarization loss of 25 Db and my antenna has a gain of 12 DB (assuming I have them perfectly aligned) that still leaves a loss of 13 Db. If the other station is running 5 watts from an FT817 or similar, that 13 Db loss is extremely significant. Not surprising then that if I am not perfectly aligned they are simply not audible here.

G0ILN has installed an HB9CV antenna at his stataion in JO00 square and he runs just 5 watts. I gave him a 429 report and I received 579 in return at a distance of 217 Kms. Another station in IO83 has a dipole sellotaped to his wardrobe door and can hear me, but I cannot hear his 5 watts. I really do not find that very surprising. Or am I too easily satisfied?

73 es good dx de Jim GØHGH 

70 MHz UKAC

I have never made any bones about it, I am just not really a /P operator. My last venture onto 4 meters was from a good, high location in Somerset and I did abysmally. Four meters is not a band that I had any equipment for so all of it was borrowed. Unfamiliarity tends to add the general state of confusion that I find myself in while portable operating. Fortunately there are not many 5th Tuesdays in the month to worry about so I have lived with the situation.

For this months 4 meter UKAC I was at home and determined to do a bit better. I ordered a 4 element beam from Andy, our "antenna man" at SDARS and also spent a bit more time setting the station up. The Transmitter was the same borrowed kit, An FT690 with transverter and small linear giving 20 watts. As usual I checked out the band plan to make sure where I knew where I was supposed to be going. 70 MHz is a bit different from other bands in that the bottom segment is for beacons and not CW. Phone and key share a calling frequency of 70.200 MHz.

The biggest improvement to my station was the addition of my shack headphones. I had taken them along last time but had the wrong 1/4" to 3.5mm adapter and could only hear from one earpiece!

Conditions were quite flat for the contest and that is fine by me as when others score very well, I tend to just score a little better than usual. A flat band tends to even out the "luck" of sporadic E contacts.

I passed my last efforts within the first hour so was well pleased. I went on to make 42 contacts in 12 multiplier squares.

I was happy to work several squares that often evade me, IO90, IO94 and IO95 but still cannot manage to find the number of squares more experienced contesters can conjure up.

Overall it was an enjoyable contest with a mixture of search and pounce along with some sessions calling CQ.

Many thanks to all for the points and hope to work you again in the next UKAC.

73 de Jim GØHGH

June 17th 23 Cms UKAC

23 Cms is a fairly new band for me and it is one that takes some getting used to. Not only do you operate the radio but you also have to arrange skeds using KST. It certainly adds another dimension to Contest operation.

Being fairly new to the band it should be quite easy to better your last score and so far things have been going in the right direction. This was certainly a personal best result for me. It wasn't down to the number of QSO's but to the number of multiplier squares worked - a total of 15 which I was very pleased with.

There was a lot of deep QSB on most distant signals with total fade out at some points so some perseverance was required on both ends of the contact.

I was pleased to say that CW played a small part n pulling in some of the weaker signals. Certainly G3YPQ/p in IO70SS would never have been worked on phone. I gave him a 529 and I received a 449 so it just goes to show how useful CW is in difficult conditions.

I run 10 Watts to a 55 ele Tonna up at 12 meters agl so low power but with high gain. A very sharp antenna so constant tweaking of beam heading made more difficult by QSB made it all quite hard work but most enjoyable.

There were a few SDARS stations on including G4YHF, G4ODA, G4NBR and G4KIY. Strangely I did not hear G4ODA all evening despite the fact that we are fairly close to each other.

73 es tnx fer all points.