KiwiSDR 10 kHz to 30 MHz now online.

Listen to my SDR

Access other SDR from around the world.

Buy one online.


In April 2016 the KiwiSDR project was born on Kickstarter, the plan was to produce a software-defined radio (SDR) covering shortwave, the longwave & AM broadcast bands, various utility stations, and amateur radio transmissions, world-wide, in the spectrum from 10 kHz to 30 MHz.

Fast forward and the project has now been completed with the first units having been dispatched


The first time I used one was when Dave G7UVW added his to the website.

After using it for a few weeks via the web browser I was sold, it was ideal for HF monitoring, and with remote access with up to 4 independently tuneable receivers.

The idea of having your own web based SDR always online, and accessible from anywhere in the world was very appealing and coupled with an active antenna the performance if very good. The advantage of the active antenna is it works well over the entire HF spectrum, its especially good below 5 MHz.

I use the Wellbrook loop mounted outdoors at around 5m, but you may be interested in a much less expensive project version as detailed by George M1GEO.

The SDR software has a built in WSPR decoded that works really well, and with time they hope to add further features.

Ive been updating the station text, its work in progress but I’ve added quite a few of the medium wave station names.

Have a listen with the my SDR, I understand Safari, Firefox and Google browsers work best. The display is not mobile friendly at the moment, but it does seem to work OK on the IPad.

Be sure to let me know how it works, leave us a comment and don’t forget to include your town / country or callsign.

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MX0SNB Operating CQ WW WPX RTTY Contest

This weekend was the CQ WW World Prefix Contest (WPX) and RTTY has never been so popular. The bands were once again packed with RTTY, with most of the big contest stations making their mark. I used the Secret Nuclear Bunkers club call MX0SNB, as its quite rare and was more popular than a standard M0 call this weekend.

The basic setup is here.

The Expert 1.3k-FA purring along at 400w.

Using just a doublet antenna and a 10m vertical and I was active on 7, 14 and 21 MHz.

Its possible with a small antenna and some power to have some fun on the bands, here was a spot added to DX summit from DL2SAX “Big Pile up RTTY

7 MHz was mostly EU although the band can throw up the odd surprise later in the evening. Operating time was casual, just fitting in some RTTY in between other tasks. In total I managed to work 359 stations in 52 DXCC.

I used the Expert 1.3K-FA solid state linear amplifier, with around 5w drive and 400w out. This was the first time I had tried the linear with sustained contest style usage, and it coped very well. Even with frequent CQ calls the temperature never passed 43 C.

Most of my contacts were around EU, although a few DX did get worked.

Maps produced by SH5 contest log analyser

Enjoyable few hrs on the band, thanks to everyone we worked. The prefered QSL method for MX0SNB is LoTW and EQSL.CC, although we will reply to any cards via the bureau (VIA M1GEO).

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Canvey Radio Rally 2017

The first rally of the year Canvey, organised by SEARS can sometimes be snowy, cold and wet being in February. This year it was quite mild, so no need for the snow boots thankfully.

Transport was provided by Peter G0IAP, and we were joined by Dave G7UVW. We arrived in good time around 9.45 and noted people already starting to congregate outside the door, we opted to remain in the warm car and await the door opening. The doors opened shortly after 10, and just £2.50 provided you entrance to the multitude of lovingly used vintage items (OK junk) on display in 2 halls.

The main hall was busy with the usual mix of traders and Special Interest Groups. Peter M0PSX from Essex Ham had information and a display video showing 2016 events.  It was good to see Charlie M0PZT from Ham Goodies  both very busy, in fact I didnt really get a chance to chat with either Peter or Charlie as they we both so busy dealing with punters!

The RSGB has a book stand and this was well staffed with the usual helpful volunteers from team RSGB.

Walters and Stanton had a good display of items, giving Essex amateurs a chance to ask about the changes to their business model.

Tea, coffee and the infamous bacon rolls were on offer from the serving hatch in the main hall. I think we all remember the year Canvey rally didn’t serve any bacon, it almost caused a riot in the streets. Thankfully special attention has been give to catering, and further disasters has been averted.

Nice to catch up with so many friends from LEFARS, Secret Nuclear Bunker CG, Essex Ham and the RSGB. I has a nice catch up with Dave G4ZST and Riche M0TYA while browsing some junk.

Here you can see Dave G7UVW giving the sniff test to a recently acquired vintage light meter.

A chance to rest your feet.

So what bargains did I find ?

A couple of project boxes and some heat shrink, but rallies arent about the junk you buy more about the people you meet and a chance to chat.

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5 MHz WSPR signal reports over 24 HRS

George M1GEO has recently been running a SDR decoding WSPR on several HF bands at the same time.

Very much work in progress, I thought it would be good to try WSPR spots over a 24 Hr period and then graph the results. George is located on JO01OK and thats 119 KM away from my JO02CN location. In the winter you would expect 5 MHz to support QSO through the day, with the band closing around sunset.

In reality the band is often open for just a few hrs in winter, and the graph provides a good demonstration. The data set is made up from 62 WSPR reports, collected by M1GEO. I set my QRP labs U3S to TX at 200mW every 10 minutes.

The total number of samples we could have collected was 6 (Per Hr) x 24 = 144, although in reality George was unable to receive my signal from around 17:00 Hrs till 07.40. This would account for 14 Hrs, approximately 80 samples.

The samples that are missing (no signal received) have been replaced with -30 so they are plotted on the axis, in effect -30 indicates no signal detected.

The yellow line on the left indicates sunrise, and on the right the black line is sunset.

Some points to note on the data have been highlighted. Its interesting to note the band opens shortly after sunrise and closes shortly after sunset. On this day while the band did open around sunrise, it sparked into life once around 08:10 but didn’t really support good signals till after noon.

From around midday, till around 14:00 hrs it was quite stable, but you will notice signals deteriorate from around 14:00 till around 1630. It has one little flourish of activity around 1710 before closing at 17.15.

This can sometimes be seen, as darkness approaches the band improves just before it closes.

As the lighter evenings approach you would expect the band to stay open for longer, and even support inter G all night.

Its interesting to see how not just daylight but time of day has an impact on the bands propagation.

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QRP labs Ultimate 3S Part 2

Welcome to Part 2, the project started in Part 1 and this covered the initial build and setup of the Ultimate 3S. Changes to the TXM are possible but require you to manually change the LPF and input a new frequency via the software.

QRP labs have developed a relay switched LPF kit, and Part 2 covers the assembly and operating of this unit.

Building this kit twill allows you to increase the bands from 1 to 6. The relay kit has space for 5 further LPF, and you can continue to use the 1 from the original kit giving you a total of 6 band operation.

LPF are available for all bands from 136 Khz to 50 MHz.

I chose to order and make up the following 3.5 MHz, 5 MHz, 7 MHz, 10 MHz and 21 MHz. The process of assembling the  LPF is very easy, the circuit is standard and simply requires different values of capacitor or inductor to achieve the correct roll off characteristics. The  Low Pass Filter kit is based on the G-QRP technical notes, a design by Ed Wetherhold W3NQN. Ed has published an interesting article on band pass filters published in QST dated 1998.

Winding the toroids without doubt takes the longest, and with 15 to wind I spaced it out over the course of the day. Here you can see the 5 MHz and 10 MHz (left) LPF assembled and ready for installation.

The winding of the toroids for the LPF was interspaced with adding the relays to the band switching relay kit.


The kit uses Panasonic TX2-5V relays, the kit includes 6. One is to mount on the Ultimate 3S main board.

Here you can see the kit is completed, and awaits LPF. Its important to note the highest frequency LPF must be fitted in position 1. The positions are numbered 1 to 5, with position zero being on the main Ultimate 3S board.


The next stage is to mount the relay LPF on top of the main Ultimate 3S, the system has been designed to stack on top of each other, providing a very neat solution. In this example I have 3 LPF fitted, with room for a further 2. Its seems logical that you should arrange the LPF in band sequence, I don’t think this is strictly necessary but it helps the planning and programming later.


The completed item is installed, working from right to left 21, 10, 7, 5 and 3.5 Mhz. I also installed a SMA socket onto the relay board, as the RF is now routed from here after the expansion. RF can be coupled in one of 3 ways, the board has options for SMA upright, SMA side mount and pin connections. The SMA upright doesn’t provide enough clearance with the LPF directly above it, so you could try a right angled SMA socket. I didnt have one so opted for the SMA mounted on its side.

The RF is now routed to the side angled SMA, here you can see the modular design with the GPS module to the top.

QRP labs to stock cases for the completed project, and I have recently ordered one to provide the finishing touch.



Further thoughts and lessons learned.

I need to investigate why the o/p power has dropped on 14 MHz, as a single band unit I was getting 250 mW, but this has recently dropped to 100mW. I suspect this may have something to do with the LPF arrangement, as all RF must now pass via the LPF placed in position 1. This shouldn’t present an issue as LPF 1 should pass anything below 21 MHz, but without a spectrum analyser or a Vector Network Analyser I haven’t been able to investigate further at this stage. Other bands have an o/p between 200 and 300 mW.

Its worth mentioning again you need to take out the original U3S board and add a relay and diode before LPF zero. This isn’t required unless you have added the LPF relay kit.

You will need to cut jumpers previously installed on the U3S, you need to cut W0 – W1 and W2 – W3.

Configuration in the menu system for multi band operation is a little fiddly, but once you understand the steps needed its easy enough to follow.

You will need to change the menu option  TxS to increase the amount of transmit slots from the default 3 to 6 in order to make use of the enhanced LPF.

Typical display options explained. starting from top left

1] is the sequence number, this indicates its the second mode option (zero then one)

1 This indicates it will select LPF 1 (check this corresponds to the correct frequency LPF) For example number 5 here would select the LPF in slot 5

021,096,125 is the frequency for TXM. You can find a complete list of freq in part 1 of the ultimate 3S construction.

JO01 is my locator, shown when in txm

23 is my power in dBm

93 is the symbol number (WSPR is 162 for a complete message)

0 is the tone currently being sent.

If you want to add additional tx sequences, then this can be done by editing the menu system, just ensure you have the correct frequency and LPF slot set.

This is covered in great detail in the firmware manual.

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GPS Track my Cat

Have you ever thought I would really like to know what the cat gets up to during the day? No, OK its just me then. Anyhow, I was surfing one of the many ChinaBay websites the other evening and spotted a rather cheap “Pet tracker”.

Marked as D69 Pet Locator, the advert suggested it could record GPS locations and pass these to your mobile phone via a downloadable app called “there”. As with many of these Chinese products the online description is somewhat unclear, so it comes down to price and if you want to take a chance.


The online description claims the following:-
Standby time 6 Days using the  MT3337 GPS chip, and a weight on 32 Grams. Size 16x56x38 mm. Search terms seem to be GPS tracker D69 GSM, and this should locate the product for around £25 to £30 UKP.

You will need a SIM card, this can be pay as you go, so long as you have GPS data and the ability to send and receive text messages. I purchased £10 of credit with GiffGaff, as they seem to offer good value and your credit doesn’t expire to 180 days (longer if you make / receive calls)

                                     Tracking options

Real time, you click on the app and it attempts to locate your pet and return a position on the screen. Its often not clear if this is live or historical, but it does work if you have a GPS fix.




Historical, you can set the tracker to upload spots every 1 or 10 minutes.

By sending a text, you can text your pet using url# and the device will return a text message and a google maps link showing the last known locations. It will also return “NO GPS” if you don’t have a GPS fix at the time of location request.



Example of text received

Locate date:2017-1-26
Locate time:4:52:15


Calling the tracker

You can phone the tracker and speak to your pet (no I dont know why) or call and mute your audio so you can hear the location your pet is in. This can be especially handy if you suspect moggy is visiting other houses in your street.

Does it work

Yes its adequate but you need to keep in mind the following. It has two position modes GPS providing an accurate fix to around +/- 10m. If GPS fails it will use Location Based Services, this provides an approximate fix but for the purposes of tracking your pet it’s useless.

Cats often sit, rest and stalk in locations that are not GPS friendly, under cars and in bushes and this can cause the GPS fix to be infrequent.

Its also possible to setup a white list number, so only this number can call and text the tracker and Geofence your pet!


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© 2015 Dave, M0TAZ