Inverted L and results from WSPR

Good results with my new Inverted-L overnight. Running 500mW I got multiple decodes from the stations you can see on the map above.

The tx is the same homebrew amplifier that I have used previously so the antenna is the only item I have changed. With my other antenna, a G5RV, I had only been received once in the USA.

Overall this confirms my initial findings that the Inverted-L pointing at north America is performing very well.

4 metres contest

Screenshot of my QSO's in the 70Mhz Cumulative contest on  25 May 2014

Many years ago I participated in many VHF and UHF contests with the G4VAT contest group so I sort of got drawn into this 70Mhz contest today. I have described my new 70Mhz elsewhere on this blog and this was a good opportunity to give it a good try out with my homebuilt Moxon Rectangle antenna.

The result was that I worked all the stations that I heard, except one who was a long 230 miles away. He heard me on an aircraft reflection but it didn't last long enough for a full exchange.

I was pleased to note that most signal reports I received were reciprocal to those that I gave out. There was deep QSB on most signals and comments made by stations who have submitted logs also note the QSB and generally poor conditions.

Here is a link to my contest QSO's in an interactive Google map

I have just submitted my log to the RSGB contest committee site and I have claimed the grand total of 825 points!

Spring fun with antennas

The part built 4:1 balun

The May weather was very warm at the weekend and so I took the opportunity to put another antenna up. I spent some time trying to decide what to build but eventually decided that anything was better than nothing and just got on with it.

For some time I had thought about erecting the Inverted-L described here cut for the 30/20/17m bands. First though I needed a 4:1balun. I built one described on the website of M0ZPK

I then retrieved from the shed a roll of 32 gauge wire given to me by a work colleague some years ago. I suspect this wire is quite old as it is manufactured by WL Gore, who are now rather more famous as the manufacturer of the waterproof material GoreTex.

This wire is so thin as to render it almost invisible, which makes it difficult to erect but pleasing on the eye in the longer term. I am sure it won't last a winter but it was free so is great for experimentation.

The inverted L was hoisted about 7m into a tree in one corner of the garden with the top running down to a smaller tree at the front of our property. Here I had to bend the final few metres (of 37 metres) to make it fit. The antenna was immediately a good match on 15/12/10m, which was annoying as I was trying for 30/20/17m.

I fiddled around with it for a while (and actually shortened it so there is now no bend in it, but it still didn't resonate on the desired bands) before leaving it for the night. The next day I relocated the balun closer to the ground and the stream that runs along the back of the garden. Hey presto, a 1.1:1 match on 30/20/17m was achieved. Obviously the antenna elves had been out during the night and tuned it to resonance for me! I can only think that changing the angle of the more vertical part of the antenna had a significant effect.

The result is an antenna that is directed towards north America and I can hear Canadian and US stations on it that are several S points down on my more elevated G5RV.

So I am classifying this as a great success, and it has caused me to have more QSO's which is even better. Here are a couple of videos showing the difference between the inverted L and the G5RV, the G5RV is antenna A and the inverted L is antenna B. The antenna input selected is shown to the top right of the frequency display. OK, so you cannot make out the A and B on the video, but take it from me that the inv-L is the stronger signal as I switch between the two.

OK, here is one, I'll add the other later.

70Mhz transverter & Moxon Rectangle beam finished

At long last I have completed my 70Mhz transverter, which I first wrote about here. Since I took that video I have rebuilt the transmit stages using Manhatten style construction. I have also replaced the tx/rx switching circuit with a much simpler arrangement. 

Whilst it is probably not the most sensitive receiver around I am proud of the fact that I built it from scratch. It is the design by EI9GQ published in Radcom in June & July 2009.

The transmit output is now 100mW. To bring this up to a level to drive my Pye A200 amplifier I bought a ready constructed amplifier from SP2DMB For 100mW input this gives 8W output. Using this to drive the A200 gives well in excess of 50W but I have turned the A200 down to avoid over-driving it so it only outputs 50W.

I have learnt so much from this project about receivers, transmitters, construction techniques and fault finding. Unfortunately I have also found, along with my optician, that my close up vision is now very different between each eye. This makes soldering difficult as I find it difficult to judge depth of field, so any sort of SMD construction is definitely not for me. Another visit to the optician is due and I'll try to get a pair of glasses that makes soldering easier.

To augment my horizontal dipole I have made a Moxon Rectangle antenna for 4m using this design. Now this is on the mast I have found that I can receive the GB3BUX, GB3RAL and GW3MHW beacons all the time rather than only by aircraft scatter.

The distance between my QTH and GB3BUX is 153 miles. The path profile is shown below:

My QTH is on the left, the first piece of high ground is the North Downs in Surrey, the second is the Chilterns around High Wycombe and the next piece of high ground is the Peak District south of Buxton.

I have left the dipole on the mast attached to my FunCube Dongle SDR. I'll use this for spotting Sporadic-E openings. I noticed last year that some of the tones I receive around 70.230 - 70.240 Mhz get much, much stronger when there is Sp-E around, so they are a useful indicator of propagation.

Now, roll on the Sporadic-E season!