Search Results for – "wellbrook"

Comparing the Wellbrook Loop to a Doublet Antenna

This evening I decided to complete a test using two different HF setups in an effort to compare the receiver performance of my antennas.

Radio 1, Kenwood TS 990, doublet antenna 10m per leg @ 9m

Billy offers support.

Billy offers support.

Radio 2, Elad SDR, Wellbrook RX loop @ 3m

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I decide the best way to test on receive would be to leave both radios receiving on 7076 KHz for 90 minutes, using WSJT-X. Both receivers had been set to 3 KHz bandwidth, and over the course of the next 90 minutes they each collected over 600 measurement reports.

The test started at 1830 Hrs and continued to 2000 Hrs. The doublet collected 633 measurement reports, and the wellbrook 740. This was the first indication that the Elad coupled with the Wellbrook was out performing the Kenwood / doublet setup. The next stage was to look in detail at the reports, WSJT has an option to write all received data into a text file, this includes time, s/n and decoded text. I used this to select at random some calls that represented a selection of EU (and DX if possible) and compare the relative signals received at the very same time on both radio 1 and 2.

The following table shows a selection of data points

wellbrook v doublet

After reviewing the data it was clear the Wellbrook loop improved the quantity of stations decoded, and in many cases also improved the s/n received.

This is by no means a definitive test, but it does indicate the Wellbrook loop (as many others have reported) work well in somewhat noisy urban environments.  The wellbrook loop can be reviewed online at the Wellbrook communications website, the version I used for the tests was ALA1530  its 1m and designed for medium and shortwave 50 KHz to 30 MHz. Steve Nichols G0KYA completed a review in January 2012 Radcom You can see the Eznec plot as photo 3 in the review.

The other factor to consider is the loop antenna has some directivity, I didn’t rotate the antenna at any point during my tests. In many cases rotation will improve / reduce signals as the antenna has directional properties.

The Welbrook performed well on 7 MHz, I suspect it would be even better on 1.9 and 3.5 MHz… to be continued….

Dave M0TAZ

Broadcast Overload on Kiwi SDR

The Kiwi SDR and Wellbrook loop provide a very good single antenna solution for 0 to 30 MHz shortwave reception. The Kiwi is capable of displaying the complete band of 30 MHz, but the disadvantage is the very high power from some of the LW and MW stations can cause the receiver to overload in the evenings.

One approach would be to build a notch filter to attenuate just the one or two strongest signals, in my case this would have been 909 kHz Radio Five Live from Brookmans Park, and 1332 kHz Christian Radio. The problem I had was in the evening this would often change, and at times some of the continental AM stations would become an issue.

The alternative would be a bandstop filter, that would just attenuate the MW band. We also have two amateur allocations at 472 kHz and 1.9 MHz that I would like to receive, with the medium wave band in the middle. The solution would seem to be a bandstop produced by Nooelec. The units retail for around 11 dollars in the USA, you can get them from Amazon or eBay for around 16 GBP with free delivery.

They say on their website “We designed Distill:AM to provide sufficient attenuation for broadcast AM frequencies (>40dB typical) while ensuring adjacent bands, such as 160m, are minimally affected. The -3dB rolloff of the filter is 350kHz and 1900kHz. Minimal out-of-band insertion loss means the filter can stay in place for most any application, though we do recommend removing Distill:AM from your setup when not listening to HF frequencies. As a true bandstop filter, you are able to pass-through DC (bias power) when it is required.”

You can view the data sheet below.

I found 909 kHz reduced from around -20dBm to -50dBm so this helped reduce any signal overload.

You can read more or use the Kiwi receiver here.

The Welbrook look is an active broadband receiving loop antenna.

Nooelec have a range of products online.

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

 

Receiving Non Directional Beacons (NDB)

NDB are low power beacons in the 250 to 550 KHz range. The beacons are usually situated at a landing strip/airfield / oil platform to aid navigation. They are non-directional so use a vertical omnidirectional antenna, and reasonably low power. The ERP is very low, as the physical size of the antenna restricts the efficiency and the desired range is usually not more than a few tens of miles.

Photo credit Original uploader (and claimed/alleged photographer) was Mintaka10.

The beacons transmit in double sideband AM, so you can often see the carrier AM frequency and then on both the upper and lower side of the carrier the CW ident. The CW consists of one, two or three letters, and the morse ident is unique so can be used to geolocate the beacon.

Wikipedia contains further information on how these are used by pilots to navigate, although most shortwave listeners are simply interested in identifying the signals and working out their location. The frequencies used to lend itself to some considerable distances at night, although its often the noise floor of the local area in this bands that limits the receiver. I found my doublet antenna was poor to useless at these frequencies, and it was the Wellbrook Loop that provided a significant improvement on this and other LF, MW bands. George M1GEO has also provided some details of a homebrew version of the loop, and details can be found on his site.

If you don’t have a suitable HF receiver and aerial a good way to start is by utilising one of the online SDR receivers.  Some have a text above the receiver window showing the name/location of any beacons received. You can often click on this text and the receiver will set the correct frequency and mode.

Keep in mind that local conditions and time of day will as it does on other HF bands influence the stations that can be received at any time.

The expanded version shows just one NDB, located at Epsom and using the CW ident EPM. The AM carrier can be seen in the center, with the morse ident either side. Its helpful to be able to look up any decoded and confirm the location, the simple ident EPM does not provide you with much of a clue to its location. I found Sean G4UCJ website very helpful as it contained a list of his received beacons.

On occasions, the received signal is very weak, and local noise can often obscure the signal. In some circumstances, it can be helpful to use software to enhance the signal. The software is often used in QRSS very slow/low power CW, and works be building up a number of samples of the signal as we know the same information is repeated time and time again.

NDB finder is another excellent choice for finding the hard to detect signals, you can try that for free for 21 days.

If you like exploring the HF bands below 500 kHz the world of NDB can provide some interesting conditions. If you enjoy NDB or you want to share any further information please get in touch.

KiwiSDR 10 kHz to 30 MHz now online.

The SDR is online 24×7 for your enjoyment. If you find the SDR useful consider making a small donation to help with its upkeep.

 

Listen to my SDR

KiwiSDR User guide 

Access other SDR from around the world.

Buy one online.

Background

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, worldwide, 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 SDR.hu website. Dave has recently moved his SDR to a remote site in the Secret Nuclear Bunker Kelvedon Hatch. You can listen to this  SDR online.

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 tunable 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, it’s 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.

I’ve 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 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.

© 2015 Dave, M0TAZ