Tag: 472khz

Resonant antenna tests on WSPR 472 KHz

At the SNBCG operating site we have the opportunity to out up some large antenna, and for some time we had wanted to try 472 KHz using George M1GEO WSPR transmitter.

The plan was using the onsite 50m cellphone mast* to pull up some wire, and with some work hopefully, enough wire to have a 1/4 wave on 472 kHz. We calculated it would require around 150m of wire, and we had a pully on the mast at 42m, so we could pull up the first 50m as a vertical, and then have the next 100m sloping down from the last forming an “L” shape as best as we could into the next field.

The transmitter would be grounded to the mast earthing point, and we would run the 10w transmitter at the base of the mast overnight.

*for the avoidance of doubt we have permission to use the mast from the site owner.

The antenna slops down from 42m towards the ground.With a little bit of tinkering, we had a resonant antenna on 472 KHz

We left the transmitter running overnight from JO01DQ with the call GB0SNB, and was delighted to see a number of reports all around Europe.

Here you can see the tower and yellow wire making its was up from the base, and then into an adjacent field.

 

Timestamp Call SNR Pwr Reporter RGrid km az
 2018-05-06 01:12  GB0SNB -28 0.01  SM2DJK  KP03au 1774 33
 2018-05-06 01:12  GB0SNB -18 0.01  SM3LNM  JP82qg 1558 34
 2018-05-06 00:50  GB0SNB -28 0.01  EA1FAQ  IN71pn 1188 201
 2018-05-05 23:22  GB0SNB -22 0.01  LA8AV  JO59cs 1090 31
 2018-05-05 22:14  GB0SNB -26 0.01  EA2HB  IN93ah 946 191
 2018-05-05 23:34  GB0SNB -24 0.01  LA3EQ  JO28xj 828 24
 2018-05-06 00:10  GB0SNB -15 0.01  GM4OAS  IO76cx 708 329
 2018-05-05 22:08  GB0SNB -23 0.01  DL1KAI  JO42vj 654 79
 2018-05-06 02:56  GB0SNB -28 0.01  EI2KK  IO65ca 651 308
 2018-05-06 00:22  GB0SNB -28 0.01  DF5FH  JO42um 649 78
 2018-05-06 01:16  GB0SNB -21 0.01  DK7FC  JN49ik 645 110
 2018-05-05 23:22  GB0SNB -28 0.01  DL1GCD/1  JN48ar 642 118
 2018-05-05 22:08  GB0SNB -27 0.01  DK6UG  JN49cm 608 110
 2018-05-06 00:16  GB0SNB -25 0.01  DL0HT  JO43jb 597 72
 2018-05-05 23:34  GB0SNB -20 0.01  F6GEX  IN97na 526 190
 2018-05-05 21:38  GB0SNB -28 0.01  DF1VB/15  JO33pl 513 64
 2018-05-06 11:58  GB0SNB -25 0.01  DL/PA0EHG  JO32sq 506 74
 2018-05-05 23:34  GB0SNB -17 0.01  F59706  JN07th 496 168
 2018-05-06 00:10  GB0SNB -24 0.01  DL6II  JO30nx 481 97
 2018-05-05 23:22  GB0SNB -27 0.01  LX1DQ  JN39cq 472 116
 2018-05-05 23:22  GB0SNB -29 0.01  DC0DX/RF  JO31lk 462 91
 2018-05-05 22:14  GB0SNB -28 0.01  DC0DX/MW2  JO31lk 462 91
 2018-05-06 01:24  GB0SNB -24 0.01  DL2ZZ  JO31lo 460 89
 2018-05-06 04:38  GB0SNB -25 0.01  PI4THT  JO32kf 455 80
 2018-05-05 22:00  GB0SNB -29 0.01  PA0SLT/A  JO22xx 411 67
 2018-05-05 21:38  GB0SNB -22 0.01  G0LUJ  IO83ls 322 317
 2018-05-05 23:22  GB0SNB -23 0.01  G3WCB  IO80ei 311 243
 2018-05-05 21:56  GB0SNB -10 0.01  PA3ABK  JO21it 304 86
 2018-05-06 01:40  GB0SNB -28 0.01  PH2M  JO22hc 301 79
 2018-05-06 01:04  GB0SNB -15 0.01  PA0EHG  JO22hb 300 80
 2018-05-05 23:22  GB0SNB -13 0.01  G3KEV  IO94sh 296 351
 2018-05-06 11:58  GB0SNB -17 0.01  PI9ESA  JO22ff 292 76
 2018-05-05 21:38  GB0SNB -12 0.01  PA0RDT  JO11tm 231 93
 2018-05-06 11:52  GB0SNB -12 0.01  G6KSN  IO82xj 178 297
 2018-05-05 23:34  GB0SNB -13 0.01  G4ZFQ  IO90ir 153 227
 2018-05-06 01:16  GB0SNB -18 0.01  M0XDK  IO92ne 97 305
 2018-05-06 13:32  GB0SNB 11 0.01  G4GIR  IO92sd 72 315
 2018-05-06 00:10  GB0SNB -4 0.01  G4FKI  IO92sa 63 306
 2018-05-06 14:22  GB0SNB 1 0.01  G8EMO  IO92uc 61 319
 2018-05-06 04:16  GB0SNB -26 0.01  G3YMN  IO91tj 56 235
 2018-05-05 20:56  GB0SNB 4 0.01  G6AVK  JO01ho 25 112
 2018-05-05 22:14  GB0SNB 1 0.01  M0TAZ  JO01cn 15 203

MF WSPR Reception

Following on from the previous post, WSPR reception continues mostly 24×7 with a focus on MF. As previously described the setup has been operating for a couple of weeks now, and its a good time to review the WSPR spots.

Best DX Spotted

472 KHz

Call Grid Pwr km az
 WA4SZE  EM65 0.2 6826 45
 AA1A  FN42pb 5 5281 53
 EB8ARZ/1  IL18uk 0.2 2915 24
 EA7HPM  IM67xj 0.2 1650 15
 EA5DOM  IM98xn 1 1446 1
 HF7A  JO91oq 0.2 1308 277
 EA4GHB  IN80hu 1 1222 12
 LA8AV  JO59cs 0.2 1105 219
 EA3AER  JN12kd 1 1066 350

52 unique calls received, you can download the complete list online.

Setup includes WSJT-X band hopping (via CAT) Wellbrook loop antenna, Elad SDR receiver.

WSPR Reception 24×7

WSPR reception 24×7 has always been something I have wanted to try. The problem is trying to find a transceiver, computer, antenna combination that will allow this with minimum fuss.

472 KHz Reception

 

Computer

You won’t need a very high spec computer, but if you are leaving it on 24×7 low noise and power consumption will be high on the priority list. A laptop is one option, although they often have fans and may not be noise free, so you may want to consider one of the new breeds of “minicomputer”. Low power consumption, and low noise with many running on 12v. I opted for a second-hand minicomputer, silent running and powered from 12v. It uses the Intel Celeron J1900 with 4 cores and I added a 128G SSD so it boots in 3 to 5 seconds. These are good value and should provide a reliable machine, with a very small desktop footprint.

Antenna

If you looking to cover multiple bands then you need a broadband receive antenna and this typically doesn’t work well on a simple unmatched G5RV or doublet antenna. I completed some receiving tests using my doublet and a Wellbrook and found the loop outperformed the wire antenna significantly below 5 MHz. You can read more about receiving loop antenna on this page. George M1GEO has provided a very interesting article and instructions on how to build a low-cost Wellgood loop on this page. The Wellbrook loop I use seems especially good at 136 and 472 KHz, providing some interesting spots on these bands. The antenna is shared with my online SDR providing connectivity to the ELAD and Kiwi via a 2 port antenna splitter.

Transceiver

I use the ELAD SDR, as its very low power consumption, and I can CAT control the band changes to suit the time of day.  The radio is connected via USB to the PC running Joe Taylor WSJT-X program.

The transceiver draws around 500 mA on receive and the Mini PC  around 600mA at 12V. I have used a 12v SMPS designed as a computer power supply, its rated at 5A and runs cold.

 

In the last 24 Hrs

Receiver antenna and band changes biased towards MF and LF

Typically adding 1,000 spots per day

150 spots on 472 KHz and 23 on 136 KHz

I hope to add TX soon, using 200mW from the Ultimate 3S beacon transmitter

 

LF and MF reception in an urban environment

SW listening and the ability to receive stations many thousands of miles away on HF has always fascinated me. Reception on HF, more especially LF and MF has always been a challenge due to the high urban noise floor.

The doublet antenna at home while working well on 7 to 30 MHz, is a poor performer below 3 MHz. This coupled with the high noise floor makes reception of all but the strongest signals very difficult. In part the answer is a dedicated antenna for low frequency reception. Options range from very large beverage / directions arrays to small active antenna. I have no experience with large antenna on sub 7 MHz, as the average urban garden will not support such ambitions projects. The answer for many of us comes from a surprisingly small antenna.

Receive only active antenna may provide a solution, the active part providing some amplification in the receive path. Designs are available for both commercial and homebrew, the price can vary from a £20 homebrew solution to £250 commercial antenna.

I was lucky enough to spot a second hand Wellbrook loop on ebay, reasonably cheap and this gave me a chance to compare the performance with my other HF antennas. It also provided me with an opportunity to monitor WSPR signals on 472 KHz and provide some data into the WSPR network.

Commercial 

Wellbrook Communication have a number of versions available, comparison of models here.

Cross Country Wireless  with a FAQ

Homebrew

PA0RDT has designed a LF / MF Mini Whip antenna, you can read the fundamentals of the mini whip.

M1GEO has recently repaired a Wellbrook loop antenna, his website includes a detailed teardown.

LZ1AQ has detailed design notes on his website for his wideband active loop antenna.

PA0LUX provides a video demonstrating HF reception on his wire antenna and Wellbrook loop. You can see and hear the difference for yourself.

How well does the Wellbrook work on 472 KHz

Well it outperforms my doublet antenna by some considerable margin. Signals that I cant hear just pop out of the noise and for interest I have included some WSPR data for that band.

Monitoring 472 KHz on the evening of 15th and morning of the 16th Jan 17  provided 19 unique calls.

DC0DX, DH5RAE , DK2DB , DL6RCN , F1AFJ , F6ACU , F6GEX , G3KEV , G3XBM ,G7NKS , LA1BCN LA1TN , LA8AV , M0PPP , ON5TA , PA0A  F5WK, F6HCC , G8HUH.

The best DX was LA1TN at 1346 KM

Its also interesting to look at the reception reports over time of day / night.

 

 

 

472 kHz reception on WSPR

Having played around with the Wellbrook loop on 7 MHz the other evening I decided to try some 472 kHz reception on WSPR. I had never tried 472 kHz before, as the combination of local noise and poor antenna has always put me off.

The Elad FDM-DUO seems quite sensitive down to 100 kHz (the specifications says 10 Khz), and coupled with the Welbrook this seems to work really well. The signal to noise ratio of received stations has improved dramatically, and the screen was soon populated with stations all over Europe.

The Elad also has 2 antenna sockets on the rear, one is configured as RX only, and the other TX/RX. Although I didnt transmit this type of set-up works well if you intend to use a separate receive antenna.

Radio user completed a review of the Wellbrook antenna, and you can read that on-line.

The Elad is a QRP radio that works on all HF bands from 1.9 MHz to 50 MHz with power selectable from 0.3w to 5w. RADCOM did publish a review in March 2015, available for members to read. Its a SDR that can be run standalone, and works like a normal radio with a front panel and VFO or connected to a computer.

Dial freq for WSPR is 474.2 USB. Using software available free from Joe Taylor K1JT.

Here is a screen shot showing stations received.

472_rx_wspr

After 24 Hrs I had received the following stations. This data can be represented on a map

472_24hr_v4

Some graphed data, signal v time for PA3ABL/2

pa3abk

 

Graphed data DK7FC signal v time.

dk7fc

 

 

 

 

73 Dave M0TAZ

© 2015 Dave, M0TAZ