CQ WPX RTTY

I recently received back my Expert 1.3K-FA linear back from its holiday in Italy. I noticed some months ago that it would sometimes fail to start and require repeated presses of the power button. After a short holiday in Italy, the manufacturer replaced two relays, and I thought WPX RTTY was a good baptism of fire.

Apparently, these are the faulty items, now replaced under warranty. Linear was working flawlessly and allowed me to complete 218 QSO on 7 MHz.

Using the doublet antenna, I wasn’t able to find much DX, but using the club call MX0SNB did provide some interest on the bands.

 

 

Even after some prolonged CQ runs the liner was able to deliver 400w RTTY and remained under 50 C

Interesting to see the VSWR at 1.01 and the temperature at 50C.

Bands seemed busy, I opted to only operate on 7 MHz and so conditions provided mostly contacts to EU. I was able to work into the USA, and I did hear China and Indonesia although was unable to work them.

I put together this map showing QSO mostly over the EU.

I managed to work 45 countries, with the best DX being Peru.

Always nice to see the bands busy, and RTTY has never been so popular.

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Multi Mode Digital Voice Modem with HAT

Let’s start with the name, MMDVM (Multi-Mode Digital Voice Modem) with HAT(Hardware Attached on Top)

The HAT has been designed by Flo DF2ET and Mathis DB9MAT and is compatible with the Raspberry PI or PI W Zero. The board will support MMDVM so that’s DSTAR, DMR, P25 and Fusion using the excellent software by Jonathan G4KLX.

The Raspberry Pi zero W (WiFi)

The board that brings together the UHF module, the STM32F103 CPU that is plugged directly onto the smallest Raspberry Pi, the Pi Zero W. The hotspot can be configured on the dashboard to operate on any or all digital modes and to operate on the UHF frequency of your choice.

I have mine setup on to provide a digital access point on 435 MHz, but your allocated frequency will vary by local usage and regulations. It has around 10mW of power, so ample to provide access all around the house using a handy.

A close look at the MMDVM_HS Pi Hat

The screen can be anything of your choice, I opted for a small OLED screen but in hindsight, it should have been a little bigger as one’s eyes get older!

Blue OLED Screen

Craig W1MSG has produced some excellent video on setting up your hotspot and on setting up your DSTAR radio.

The project and parts are detailed on Github

Support is available in  Groups.io or Facebook 

Who is behind PI-Star

Here you can see both the DMR and DSTAR radio screen.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Thanks to George M1GEO for help setting and configuring the access point, and John M0UKD for running over some of the local settings.

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Receiving HF Weather Fax

If you have spent time listening to HF you may have noticed the distinctive sound of HF Fax, something I thought had disappeared 20 years ago.

FAX seems like a very old technology now, although before the days of email the FAX machine was the only way to send near real-time images between people. HF Fax uses the same principle, but instead of squirting the tones down a phone line we modulate them onto an HF carrier.

It’s still very slow, but if you are on a yacht in the middle of the Atlantic its a very low-cost alternative to using a Sat phone and data. The charts are still transmitted from a number of locations around the world, using very high power 5 to 20 KW HF stations, so reception is easy even with a modest antenna.

How to identify Wefax on the HF bands 

The history of Radiofax

Worldwide Marine Radio facsimile broadcast Schedules

You can use one of the online KiwiSDR to display the maps, this allows you to select the FAX overlay option in the top right-hand box, then region and download the image.

FLdigi can also be used to display the images on your screen. Using the schedule of transmissions tune your HF radio to 4608.1 KHz USB and set up FLdigi to your sound card. You will need to set the OP Mode to WEFAX then WEFAX-IOC576,

If you miss the start of a transmission don’t worry, just leave the receiver and program running and it will sync and start decoding on the next image. The transmission schedule is quite extensive, so you never have to wait long to resolve an image.

Here is an example from 4608 KHz decoded at 12:58 Hrs on 1/1/18

The transmitted images change based on a schedule, one typical example is included below.

Schedule:

-----------------------------------------------------------
TIME   Chart                                  Valid   I.O.C.
------------------------------------------------------------
03:41  MSLP ANALYSIS FOR 00:00                00:00    288
04:31  500 HPA CONTOUR/TT (1000/500HPA) 
       ANALYSIS FOR 00:00                     00:00    288
04:40  MSLP 24-HOUR FORECAST (VT 00:00)       00:00    288
08:06  MSLP 48-HOUR FORECAST (DT 00:00)       00:00    288
08:12  MSLP 72-HOUR FORECAST (DT 00:00)       00:00    576
08:18  NORTHERN HEMISPHERE SURFACE ANALYSIS   00:00    288
09:29  SEA/SWELL ANALYSIS FOR 00:00           00:00    288
09:35  SEA/SWELL 24-HOUR FORECAST             00:00    288
09:41  MSLP ANALYSIS FOR  06:00               06:00    288
10:00  500 HPA CONTOUR/TT (1000/500HPA)
       T+24 FORECAST                          00:00    288
10:10  SEA/SWELL 48-HOUR FORECAST             00:00    288
10:31  NORTH ATLANTIC INFERENCE               00:00    576
10:42  MSLP 24-HOUR FORECAST (VT 06:00)       06:00    288
14:12  UK SEA TEMPERATURE ANALYSIS            00:00    288
15:41  MSLP ANALYSIS FOR  12:00               12:00    288
16:02  NORTH ATLANTIC SEA ICE CHART           00:00    576
16:22  SCHEDULE: MARINE PRODUCTS              05:00    576
16:30  GENERAL NOTICES (if any)                        576
16:41  MSLP 24-HOUR FORECAST T+24 (VT 12:00)  12:00    288
17:08  500 HPA CONTOUR/TT (1000/500HPA)
       ANALYSIS FOR 12:00                     12:00    288
20:12  SEA/SWELL  ANALYSIS FOR 12:00          12:00    288
20:18  SEA/SWELL 24-HOUR FORECAST             12:00    288
21:41  MSLP ANALYSIS FOR  18:00               18:00    288
21:52  SEA/SWELL 48-HOUR FORECAST             12:00    288
22:22  MSLP 48-HOUR FORECAST (DT 12:00)       12:00    288
22:30  MSLP 72-HOUR FORECAST (DT 12:00)       12:00    288
22:41  MSLP 24-HOUR FORECAST (VT 18:00)       18:00    288
23:33  MSLP 96-HOUR FORECAST (DT 12:00)       12:00    288
23:40  MSLP 120-HOUR FORECAST(DT 12:00)       12:00    288
------------------------------------------------------------
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6E beam for 70 MHz

70 MHz has become increasingly popular since Icom added it to some of their new transceivers. Since owning an Icom 7100 and enjoying the UKAC and portable events I decided to make a beam for the band.

I had some aluminium from a previous order at aluminium warehouse, and so decided to look around the web for a suitable design. Martin K7MEM website takes you to a javascript page that allows you to specify what material you have available. This is quite a flexible approach and gives you the ability to make something without being too prescriptive in the early design.

In my case, I had some lengths of 8mm and 10mm tube and a 25mm box for the boom. The website allows you the flexibility to specify the desired frequency and then select the required gain or boom length. Thankfully the design can be created in both metric and imperial measurements, you just specify the sizes in the design.

Program output.

The current design is an antenna for 70.2 MHz. It has 1 Reflector, 1 Driven, and 4 Director Elements. Estimated Gain is 8.917 dBd.

Antenna Dimensions

Cumulative
Spacing (mm)

Element

Element
Length (mm)

Zero

REFL

2094.58

854.11

D.E.

2068.64

1174.4

D1

1933.49

1943.1

D2

1918.83

2861.27

D3

1901.45

3928.91

D4

1884.12

Insulated elements

This is specified at the time of the design, it is interesting to see the design with and without insulated elements. Insulating the elements from the boom has the effect of shortening them slightly, but why not have a play with the calculator and see the difference. The insulators I used were 4mm ABS plastic, cut into strips but you can use anything to hand.

Driven element

Often the most difficult parts to complete, as it requires a split and insulation from the boom.

Options.

1/ Place a small plastic tube inside both parts of the driven element, thus making them rigid and then mounting this to the plastic insulator on the boom.

2/ Fix the driven element directly to the plastic insulator using 2 plastic clamps on each section. This should provide enough support to stop the element sagging or twisting.

3/ Commercial VHF style dipole centre.

Parts list / Supplier options.

Aluminium warehouse can supply lengths of aluminium in both imperial and metric sizes.

Black Plastic Nylon P Clips Mounting Cables Tubes Pipe Brake Motorcycle Car. These can be used to fix the elements to the insulator, they are available in various sizes. The clips allow the elements to be removed by simply pushing/pulling the element into the clip, and are therefore ideal for portable use.

Something more robust would be needed for a permanent solution.

 

 

 

Stauff clamps can be sourced online. These are more expensive than other options, but ideal for a permanent antenna build.

 

 

 

 

VHF dipole centre available from your local rally, eBay or junk box

 

 

 

Element insulator, search using 4mm ABS plastic sheet.

 

 

 

Closing thoughts

The antenna is a little quirky, the dip shows a good match at 70.200 and the bandwidth is wide enough to cover the entire 70 MHz band. The dip shown on the RigExpert is a little nonconventional, but it certainly has gain and good F/B ratio from the testing on site.

Alternative designs by DK7ZB

Audio clips from testing.

GM4NFC Alex 520 KM

GI4SNA David @530 KM

July 2017 70 MHz Trophy Cup.

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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.

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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

 

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© 2015 Dave, M0TAZ