Posts Tagged ‘WSPR’
472kHz WSPR using earth-electrode antenna
October 14th, 2014 | 
Author: As an experiment this afternoon and evening I am using the (short baseline) earth-electrode antenna. I am being copied by G0LRD (25km) and G3ZJO (79km) so far. It is now 1620z. Initial results suggest G0LRD is getting me very slightly better on the earth electrodes, whereas G3ZJO is getting me slightly weaker. This is comparing the earth-electrode “antenna” with the HF /VHF antennas with strapped feeders tuned against mains earth. In the latter case I resonate the antenna with a 110mm diameter coil with many taps.
One end of the earth-electrode is tied to mains earth. The “far” earth is a 1m long earth rod driven into the soil. The connection to the far electrode is 32 x 0.16mm PVC covered wire running along the fence at a height of about 2m. This wire dog-legs and is about 15m long. The spacing between the “far” electrode and mains ground in the shack is about 12m max. At the old QTH the baseline was more like 20m.
I think the earth-electrode antenna acts a bit like a loop so best results tend to be in the line of the loop. It also means there is not a huge difference between the two systems. You could say they are both equally bad, but the earth-electrode system needs no matching coil. I have optimised the resistive match using a 3C90 toroid (step up) between the transverter and earth-electrode antenna. At the old QTH it looked close to 50 ohms so the toroid was not needed.
When fitter, I’d like to try an earth-electrode system with a much bigger baseline.
There is no doubt that my 472kHz antennas can be much improved. The question is, “how seriously do I want to try?”
AutoCAD files for Ultimate 3
I’ve used AutoCAD for a while (because I had a work licence) but since being promoted I didn’t need CAD software…boooo (I also had an inventor licence but that wasn’t used as much). Anyway, back to the point.
I made a couple of front and rear panels for the QRPLabs ultimate 3 WSPR transmitter and thought that someone else might like to make one. Well if you do the dxf files are below. You can modify them easily in Draftsight (A free 2D bit of CAD software) that accepts AutoCAD files. The file shows the parts embedded on a sheet that can be used for laser cutting and your local FabLab or similar.
Anyway enjoy
630m Trans-Pacific WSPR
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| Courtesy: https://www.google.com/maps/ |
This is particularly noteworthy in view of the relatively low power used for John's beacon....around 200W. With the typical backyard antennas being used at these frequencies, efficiencies are very low and John's actual ERP is less than 5W. The transpacific reception of John's signal by VK2DDI confirms what most LF'ers already know....that small suburban lot amateur installations can have positive results on 630m without the need for huge antenna systems.
The WG2XIQ beacon was operating in the WSPR mode, which has become very popular amongst 630m experimenters as well as those just interested in listening-in. WSPR is not a QSO mode but strictly a one-way 'beacon' mode. Although two stations may each spot each other, it is not considered to be a valid two-way QSO. A check of evening WSPR activity will often reveal dozens of stations actively spotting what they are hearing.
Like most LF stations, John's is mostly homebrew.
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| WG2XIQ/KB5NJD |
I'll let him describe the details:
"I have a few ways of making RF in the shack. I can do CW with a very nice waveform using the GW3UEP VFO/Driver coupled with a GW3UEP 100w amp with waveform shaping. The other way is via the MF Solutions transmit downconverter, developed by John Molnar, WA3ETD/WG2XKA. I have two of those boards, one is a backup. I use a GPSDO for the LO and use that signal to drive two parallel GW3UEP amps with max power at 125 watts each. The W1VD Ø degree hybrid combiner brings them together in phase for close to somewhere between 200 and 250 watts TPO depending on how hard I drive and how close I match the TX levels entering the combiner. I filter the output with the W1VD KW LPF that was built by Dave Robinson G4FRE (ex WW2R). I power the amps with a pair of BK Precision 30V 6Amp variable power supplies (variable current limit threshold also). Scope match is used to resonate and match the the impedance. IF Rig on 630m is typically a Yaesu FT920. These days RX antennas are the VE7SL multiturn loop or the TX vertical, both of which have their own merits depending on the conditions at the time."
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| John's 630m Vertical |
"Antenna is an 80 foot asymmetric T-top marconi with 100 foot and 200 foot legs....radial system is almost 3 miles of radials connected via various busses. 26 ground rods around the property. I monitor current in the shack and sample via a Bauer current transformer from an AM BC ATU."
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| 630m Radial System |
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| 630m Antenna Loading Coil & Variometer |
John's system does indeed work well...just last year at this time, his 630m signals were copied by KL7L near Anchorage, Alaska.
Of course, equal credit must be given to VK2DDI for having a system good enough to hear John's signal all the way down on Berry Mountain, New South Wales, Australia! It is there that David has set up a fine LF station, 500m above and overlooking the Tasman Sea...an ideal location for weak-signal LF work.
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| VK2DDI - Berry Mountain, NSW |
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| WG2XIQ Signal As Heard in VK |
David also runs the Berry Mountain Grabber, providing other VK and ZL experimenters a handy way of checking their system progress or propagation conditions.
If you have been doing any WSPR work on HF, you might be surprised at what you can hear down on 630m, even without a dedicated antenna for that band. Surprisingly good results can often be had with a non-resonant antenna as the signal to noise ratio can often be better even though signals may sound weaker. Give it a try and spot what you hear!
If you are interested in learning how to receive WSPR, here is a nice tutorial by ZS6SGM.
Should you be interested in knowing more about obtaining a Part 5 licence to transmit on 630m, John will happily guide you through the process. He can be contacted via email or you can find him hanging-out most nights on the ON4KST kHz (2000-630m) chat page.
To keep on top of what is happening or who is on-the-air, most LF'ers rely on three sources:
- the RSGB LF Group reflector
- the Lowfer list
- the LWCA Message Board
10m – quiet here so far today on WSPR
Sunspot count is 82 (disturbed) today and 20-30MHz propagation is forecast to be “poor”. It seems unlikely I will see F2 propagation today on 10m, but you never can be sure on 10m. My PC stopped WSPR running around breakfast time (more updates?) and on restarting the software just G0LRD (25km) spotting me so far. Es is always possible.
I may return to 472kHz later today if things stay quiet on 10m.
UPDATE 1950z: Well, 10m is always a band of surprises! CX2ABP (11127km) was copied several times after tea by N-S F2 and CT1JTQ (1843km) by Es. The PC was off (being swapped) most of the afternoon so I may have missed some of the action on 10m.
UPDATE 2000z: Will be going QRT on 10m shortly. 472kHz (maybe) tomorrow night.
New band tried with "compromise" antenna.
This afternoon I tried 80m WSPR with the “compromise” antenna (V2000 + 2m halo with strapped feeders) with some success. On 80m I copied M0BLP and PA0WMR although there were very few stations active. I was not copied by anyone. I was going to try 160m but decided there was too little activity.
Later I used 40m and 20m with the Par end-fed. On 40m, just one transmission resulted in 10 spots in 7 countries. The next transmission resulted in not a single report, probably because I was sitting on the frequency of a very strong station who was TXing at the time?
I later returned to 10m, and spotted EA5CYA (1376km) and LZ1OI (2145km) by Es around teatime. The Spanish station was pretty strong but the LZ was much weaker.
11 August Beacons of hope
Unenthralled by the prospect of a life lived in bed, hoisted from pillow to pot, I have allowed myself to believe that I’m not going to “beat the bugger”, in other words survive the tumour with sufficient faculties intackt to lead a normal life. I have decided to leave my whissper beacons running for as long as I’m capable to supervise them.
472kHz – improvements?
Using the strapped feeder to my Par 10/20/40m as my 472kHz antenna rather than my 2m/70cm feeder, the antenna current has nearly doubled with the antenna current meter now showing 30-33uA whereas it was 18uA before. This suggests ERP has increased by around 4-5dB (ERP proportional to I^^2), but we’ll see later. The Par antenna itself is lower than the 2m/70cm antenna and runs horizontally to a tree. Average height is around 3-4m AGL. The losses may be greater.
The picture shows the 472kHz coil used (a ferrite rod would be fine but since moving it is “lost”), the 472kHz homebrew transverter (left) and the 3C90 matching coil between transverter and antenna (towards centre, LHS of coil). The small meter measures antenna current and registered 18uA last night and 30-33uA now with the Par antenna with strapped feeders.
UPDATE 1420z: G8HUH (250km) is copying in daylight a full 8dB S/N better than last night. Encouraging.
UPDATE 1448z: M0PPP (182km) seems to be coming in stronger than last night too and in broad daylight.
UPDATE 1700z: M0PPP is now spotting me at 1456z, 1538z and 1620z i.e. in daylight. He was not copying me at all last night, so I think my signal IS stronger.
