An INDOOR loop on 472kHz TX?

Over the last few days I have been receiving quite strong WSPR signals on 472kHz from Richard G4KPX who is in Ely, some 14km north east of me.  Looking on the WSPR database I see he has been copied up to 573km on the band using WSPR. Now, in a email from Richard today he revealed his secret: he is using just 1W RF into an indoor 3m x 2m single turn loop made of 10mm pipe leaning against the wall of his spare bedroom!  The EIRP is at most 100uW and probably a lot less because of the losses with mounting it where he does and the capacitors used to resonate it. This is a pretty amazing set of results.

Richard has been spotted across the Atlantic on 160m using the same indoor antenna and has similar magnetic loop antennas for all HF bands I believe.

So, if you believe you have no space for an MF band TX antenna, and you don't even have a garden to put a couple of earth-electrodes in the ground, you could always follow Richard's example.

Some months ago I believe one of the German 136kHz stations (DF6NM?) tried something similar using a large coax as a big indoor loop on 136kHz and also got some quite decent results. Never say you cannot erect an antenna!  What you need is a bit of ingenuity.

.....and NOT a TS-990 - something better!

Just to put some perspective on things, this is a small CW transmitter that just about anyone could build for a few pounds only and use it to work stations all over the world with a modest dipole antenna or similar. The OXO transmitter was designed by GM3OXX and is a classic design.

http://www.qsl.net/g3pto/OXO.gif

Power from the OXO is around 800mW - 1.5W depending on the band and on the final transistor and its emitter resistor. I have used this design on HF and had hours of fun with it. Long after a rig like the TS-990 would be gathering dust, this little beauty will carry on giving pleasure with each and every contact.

Kenwood TS-990 - UK price

Well my fellow blog readers, I have some good news for you!

The new Kenwood TS-990 is now available to order for Martin Lynch, and I expect many others, for only £6600 with deliveries expected February. I am sure many will buy this fine radio, but as this is about ten times my budget (once every 10 years or so) for a new HF transceiver, I will not be one of them. 

http://www.jayceecoms.com/images/Kenwood-ts990s-1.jpg

472kHz update

With nearly 2 weeks of operation on the new band with very low EIRP levels (varying from typically 5-10mW with 100mW on just one occasion) perhaps it is time to summarise how things have been going. A check of the WSPR database shows almost 70 unique reports across Europe of my signals from just a few km away to 1736km. I have still not managed to be copied by TF3HZ in Iceland at just over 2000km and this is my next target. To achieve this will need me to re-erect and better optimise my Marconi vertical. With some optimisation it should just about be possible achieve 200mW EIRP.

Unique WSPR spots in the last 2 weeks on 472kHz

On CW I have received a report from over 160km away when I was calling CQ. A JT9-1 QSO with G3ZJO at 79km is still my best 2-way QSO, although I believe it should be possible to work much further with this mode (I worked OR7T in Belgium with it on 500kHz).

So, pretty satisfying results so far. This has been helped by the huge number of stations currently monitoring WSPR on the new band - frequently over 40 people at any one time. Right now there are 59 stations monitoring!

On 136kHz the challenge with small antennas and low power is considerably harder on WSPR as there are too few stations monitoring: even if the signal was getting several hundred km, one can only tell if someone is at the far end and reporting it.

Solar activity this month

A quick glance at the solar data over the last week or two will convince anyone that things are looking up. Many believe that a second peak, not that uncommon, is likely soon and that this peak will actually turn out to be the real peak of cycle 24. It is some time since we have seen sunspot numbers as high as this for so many days in a row. In the end, the peak is usually based on smoothed sunspot numbers so it will be very many months into the future before we will know if the recent upsurge has helped to make a new smoothed peak.

I see there is a possibility of M or X class flares in the next two days which could affect propagation, although I think it improbable these will be on a scale likely to knock out power stations and satellites. At some future point, most likely long after all of us are long dead and at a time when the cycles return to huge numbers of sunspots, it will happen though. Of course large solar flares can happen at any time, so you never know.

For more data on the recent solar activity see http://www.solen.info/solar/ .

Albrect AE2990 Albrect12/11/10m Multimode handheld

Albrect AE2990 multimode

On G4ILO's blog I noticed a reference to Julian's Albrecht 10m/12m handheld transceiver. A quick search on the net and I see these on sale via eBay for £159. See eBay item number 181059871622. This is also sold as a Magnum 1012.

Although I have used the FT817 handheld lots of times on 15 and 10m and had some excellent contacts with it using a small base loaded whip (a counterpoise definitely helps), I have no experience of the Albrecht unit, which looks like an oversized VHF handie.

Has anyone here used one seriously for handheld DXing? If so, how did it perform?  The interesting thing is this unit can be programmed for 12m, CB or 10m use by changing some solder pad links under the PTT rubber.

I can imagine that this handheld could provide hours of fun during a summer sporadic-E opening, although I would expect results to be disappointing without a counterpoise if using it handheld with ether the supplied whip or a longer whip.

True handheld DXing can be quite a challenge, but great fun.  Actually being able to move  the handheld around to get the best angle can sometimes really help, especially on signals coming in at odd angles. Some time ago I was going to see how many countries I could work on handheld SSB, although I've not seriously tried this lately. I much enjoy handheld DXing when on holiday in Devon from clifftop sites overlooking the sea as in these locations many dB can be gained by chosing a nice location with a slope towards the sea. One of my best contacts was a YV station on SSB (8000km) from my late mother's back garden.

Thoughts turning to 136kHz again

After a few weeks on the new 472-479kHz band, my thoughts are again turning to 136kHz, a band that I experimented with a year or more ago now. This band is MUCH harder work than 472 or 500kHz with around 20-30dB more of everything (!) needed.  By this I mean that for the same power, the "effort" to get a contact or report seems to be about 20-30dB more. This is partly because the short antennas I use have a very low radiation resistance at 136kHz so losses become more significant. Also, noise can be even more of an issue.  Despite all of this, I plan to make a 136kHz version of the transverter I did for 472kHz, but maybe with a bit more RF output (in the 20-30W region). Most of the design is ready done (in my head) so it should only take a few days to do. The plan is to TX using my earth-electrode antenna.

On 136/137kHz there are fewer stations using WSPR, so I will probably use QRSS more. In the past I have made QRSS crystal controlled beacons for this band, but with a transverter and my FT817 I will be able to generate a QRSS signal wherever I want in the band and also be able to have QRSS QSOs.

Does anyone have recommendations for SIMPLE PC program that will allow me to generate QRSS (various speeds) as an audio tone? 

This way I can use my SignaLink USB interface and VOX to send QRSS (or DFCW) using audio tones. Please don't suggest Spectrum Lab unless you can give me a "Noddy guide" on how to use it for QRSS! This is a very good program, but to a simple soul like me it seems like you need a PhD to drive it. In the past I've used it for VLF reception, but it took me weeks to work out how to drive it and every time I go back to it I need to learn it all again. I just want a simple QRSS tone generator.

Earth electrode antenna conclusions (472kHz)

With some further tests today I am now able to arrive at some conclusions from my experiments with an earth electrode antenna at 472kHz. Many people including Jim M0BMU and Rik OR7T have been particularly helpful in analysing the data.

My current 472kHz earth electrode "antenna" - can you see it in the grass?

These are my conclusions:

1. The earth-electrode antenna at 472kHz (2 earth rods in the soil 15-20m apart fed from the TX output) behaves like an H-field loop transmitting antenna.
2. It has directivity, with strongest signals in the line of the loop and weakest signals at right angles to it.
3. It works as an effective RX antenna too.
4. In my environment the loop looks like about 50-60 ohms resistive, so a good match to my transverter directly without matching.
5. The structure works because much of the return current flows deep within the soil and rock beneath the earth-electrode antenna. In my case Rik OR7T calculated that the loop area in the ground is effectively 290m sq with a radiation resistance of 0.017 ohm and a loss resistance of 66 ohms.This is a BIG loop!
6. Performance compared with my 9m high top loaded Marconi antenna averages only around 8dB down, not a bad figure at all, even with the connecting wire on the ground and not elevated at all.
7. Where no other antenna option is available, the earth-electrode antenna is well worth trying both on 472kHz and on 136kHz both for RX and TX. Although it works well here, your geology may be different and results not the same.

These last few days have been most interesting and, with the help of many people - listeners giving me WSPR reports, advice from others on the Internet forums, suggestions by email - I have been able to do some quite useful science. Thank you one and all.

472kHz RX and TX with Marconi antenna last night

Overnight I was using a 9m high top loaded Marconi antenna on TX and RX WSPR on 472kHz. I have since taken this down so it doesn't interfere withe the latest earth electrode antenna tests.

The performance of this larger,"in the air" antenna was certainly better than the earth electrode antenna, although not by a huge amount (2-14dB). As you can see, I managed my first transatlantic amateur reception on the new band WE6XGR at 5640km amongst the 27 unique RX spots.

472kHz RX spots on Marconi antenna

On TX with the same antenna, results were equally satisfying with 34 unique station reports.

472kHz TX spots on Marconi antenna

472kHz earth electrode antenna: nothing in the air

Today, I took my experiments with an earth electrode TX antenna for 472kHz to new levels by placing the connecting wires on the grass i.e. not elevated at all.  The theory developing is that the earth electrode antenna works by forming a buried loop in the ground with the earth return path being in the soil and rock beneath the structure. If this is so, then even with the wire sitting on the grass there should still be a loop within the ground, so some radiation from it. Results this afternoon prove this is indeed the case. The following are the results with a 20m baseline between the far earth rod and the copper pipe ground at the home end and with the connecting wire just laying on the grass lawn.

472kHz WSPR reports with earth electrode antenna with wire on the lawn