Category: Auto ATU

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160m Band NVIS Antenna Experiment

Following on from the 80m Band NVIS Antenna Experiment I spent some time using the same setup on the 160m band.

To recap, the NVIS antenna is a 30m long end-fed wire that is between 3 and 4m above the ground over it’s entire length. This is the longest wire I could get into my tiny U.K. garden and so I wanted to see what was really possible with such a low short wire on the low bands. My goal was to get good Inter-G signals so that I could chat with other U.K. and close European stations during the summer months. The tuning is done automatically by the CG3000 remote ATU I picked up very cheaply on Ebay.

Having very anti-antenna neighbours I have to tread carefully not to upset them as I have already rattled some cages having the 20m EFHW Vertical on an extending fibre glass pole at the end of the garden overlooking the farmers field.

The CG3000 remote ATU matches the 30m wire nicely on the 160m band with an SWR of less than 1.2:1 across the entire band with multiple retunes. It’s certainly very convenient to have such a setup.

Setting the power output on the radio to 25w which is the maximum I use for FT4/FT8 on the Yaesu FTDX10 I started WSJT-X and waited to see what I could hear. With the background noise swinging between S7-9 most of the time I was surprised at how many stations were being decoded. Some of the stations were barely visible on the waterfall but, I got consistent reliable decodes.

Stations heard during a 1 hour period on 160m NVIS Antenna Experiment

As you can see on the map above I was hearing stations from all over Europe and well into Russia. There certainly isn’t the proliferation of stations on the 160m band that there are on the 40m band but, there were enough for me to get some good results.

It was nice to reliably copy some U.K. stations on 160m FT8 even though I didn’t hear a single SSB station on the band.

Map showing stations that heard M0AWS on 160m during the NVIS Antenna Experiment

Over a period of about 3.5 hours I was heard by a good number of European stations but, wasn’t able to work all that I heard as I was struggling to compete with the much more powerful stations. Limiting my transmit power to 25w to protect the PA on the radio does tend to limit my success at getting through to stations at times but, I am a firm believer in being able to hear better than I can shout, especially on the low bands.

Map showing all stations worked during the 160m NVIS Antenna Experiment

Over the test period I didn’t work a huge number of stations but, I did manage to work stations over a large area of Europe with the best distance being 1004 Miles into Finland, much further than I ever thought would be possible with such a simple setup.

I’m sure that when the band is in better shape with lower noise levels and better propagation the antenna will post probably perform better but, it’s certainly proved it can do the short hop NVIS comms that I was looking for.

I have designed a new NVIS antenna for the garden which manages to incorporate considerably more wire into the same space that is resonant on the 80m band. With the CG3000 remote ATU it should tune up well on 40m-160m and give much better results. This design does require a 10m fibre glass expending pole which I need to purchase before I can erect it in the garden. I’ll get all the information for the design onto the Antenna section of the website soon.

So to summarise, a 30m end-fed wire at between 3 and 4m above the ground will give good NVIS results on 40m-160m with a very low visual impact. For those like me that have a small garden, a simple antenna like this is much better than no antenna at all.

More soon …

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40m Band NVIS Antenna Experiment

Since setting up the new station at my U.K. QTH I’ve not had any Inter-G contacts. This has mainly been due to the fact that the antennas I’ve currently got in place are all designed for chasing DX and so have far too low a radiation angle to be able to talk to other U.K. stations.

One of the things I do like about radio is the local chatter on the low bands. In the summer months working Inter-G on the low bands is most enjoyable so, I decided to put up a simple Near Vertical Incident Skywave (NVIS) antenna ready for the summer.

Unlike my French QTH, here in Suffolk we only have a tiny garden and so it’s a challenge to get any length of wire up that is anywhere near long enough for the low bands.

A quick measuring of the garden I worked out I could get 30m of wire approximately 3-4m off the ground at best. I’m very aware of my anti-antenna neighbours and so it needs to be as stealthy as possible.

I decided to use some 1.5mm wire that I had in the workshop and utilise the high washing line poles that are already in place to get the wire along the max length of the garden.

With the wire in place and connected to the CG3000 auto remote tuner that I got off of Ebay for a song, ground post and radials connected I found that the antenna tunes up fine on all 3 low bands, perfect!

Tuning up on the 40m band I had an SWR 1:1 anywhere on the band. I could hear a number of strong U.K. stations and a few Dutch and German stations too. Since I’m on the East Coast of the U.K. The Netherlands and Germany aren’t that far away as the crow flies.

Setting the radio onto 40w SSB (First time on SSB in a very long time!) I put out a call. First station to come back was G8VVY, Robin in Malmesbury Wiltshire. Signals weren’t particularly strong and I gave him a 4/4 report and got a 5/5 in return.

Next station was PA3GLK, Dave in The Netherlands. Again signal reports were 5/5 and 5/6 but, perfectly readable.

Next up was G0SXC, Kevin in Lancashire. Signal reports were 5/9 both ways this time, very strong and fully quietening, the high angle radiation was doing its thing!

Last call was ON3PAT, Pat in Belgium. Very strong signals both ways, 5/9++ at a distance of 153 miles. NVIS propagation is working very well. I turned the output down to just 25w and Pat still gave me a 5/9 report.

Later in the day I decided to run some FT8 QSOs on 40m to see how far I could get reliably with no more than 25w. I was hoping that I may just be able to get 1000 miles as an absolute maximum but, be able to work stations at 100 Miles or less with ease.

Map showing NVIS FT8 contacts on the 40m band

As you can see on the map above, 1534 miles was the best achieved, RX3ASQ just east of Moscow. The thing that pleased me most was the number of U.K. stations I could hear with the closest being just 43 miles away. Most European stations were easily worked even with reduced levels of power (10w) and so I’m hoping that this simple end fed NVIS antenna will become my goto antenna for local chatter on the 40m band.

What was very interesting was what I could hear on the antenna, I didn’t expect to hear any DX stations at all however, I was surprised to see stations from Mongolia, Japan and the USA popping up in the WSJT-X window.

Obviously I couldn’t get back to them as my angle of radiation was far too high to get a signal out over those distances but, it just goes to show what can be a heard on a very low long wire.

Map showing stations heard on 40m using NVIS antenna

By the end of the evening to my surprise I had been heard in the USA, I was amazed to see where I’d managed to get into with such a low antenna. The main cluster of stations were in the U.K. and Europe of course which is exactly what I wanted from this antenna.

Stations that heard M0AWS on 40m FT8 using NVIS antenna

So the next test will be on the 80m band, I’m hoping to get similar results on SSB with inter-G stations being easy to work. I doubt I will be able to get anywhere near the 1500 miles I achieved on the 40m band but, I’ll be more than happy with U.K. and EU stations.

More soon …