Posts Tagged ‘KiwiSDR network’

My End-Fed Half-Wave (EFHW)

The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. A half-wave at the lowest band of interest will also work well on all harmonically-related bands which has become particularly attractive to those wanting a quick portable wire antenna.

It looked like an interesting antenna to try, as I was in need of a good 80m radiator and following several days of fine summer-like weather, I was able to get my new 80 / 40m wire vertical completed ... a half-wave on 80 and a full-wave on 40m. It’s built as an inverted-L, going up 80’ and the remaining 50’ being horizontal at the same height. It’s fed at the base through an impedance matching transformer and was pruned for the CW end of the band.

There's always a great sense of anticipation when first testing a new antenna and the experience only comes around once in a rare while ... it always brings back memories of my teenaged ham years, quickly scrambling off of my parent's steep three-story roof and tuning-up the DX-20 to see if the latest antenna was going to be something special. Yesterday was similar, except for the roof-top scrambling and the old DX-20.

By mid-afternoon everything was wired up ... but before waterproofing all the connections against the west coast rains, I went to the shack and warmed-up the FT-1000mp, setting it for exactly 10W out. Tuning across 40m, I immediately heard fellow NRR’r Howie, WB2AWQ down in Reno, calling CQ on 40m with one of his military transmitters. He came back immediately and we had a short chat, so at least I knew the new antenna worked!
 

 
Having  waterproofed all of the connections, I ventured to the shack once more, now just 45 minutes before sunset. I’ve always found that a quick way to gauge relative antenna performance is listening for my low-power signal via the vast KIWI online SDR network

With the power still set at 10W on 40m I listened on several east coast SDRs, from NH, PA, MD, NY, VA and immediately heard a surprisingly good signals on all of them. Even at 5 W, the signal was copyable. Several of them produced an audible copy when I reduced power to just 1W.

I then tried two SDRs in Brazil and immediately heard the 10W signal again! How about KH6 ... still late afternoon out there? Yes, easy copy in Hawaii as well. 

Dare I push my luck and try one more ... one of the SDRs in Iceland? 

I almost fell out of the chair when the 10W signal was good copy there as well ... still 15 minutes until sunset and with bright sky outside the shack window. 

One last thing to try was 80m although it was still very early here for 80 ... the SDR in MD returned a nice copy at 10W to complete my quick round of pre-sunset testing. 

From these early observations it would appear that the new antenna is working well but I had yet to do any A-B comparisons with my benchmark best performer, a 40m half-sloper which will be hard to beat. 

The 40m half-sloper has always outperformed any other antennas that I have tried. It's the same one that I completed my Tuna Tin 40m W.A.S. on, so its been well tested.

The following evening, I had a chance to A-B test the new antenna, listening on the Kiwi network once again with my power set at 10W.

N8DTT/6 (California)  EFW 1S unit better
NO2CW (Florida)   EFW slightly better
Jersey Shores, NJ    EFW slightly better
TF1VHF (Iceland)  EFW slightly better
ND7M (Nevada)     equal with slight edge to EFW
KA7EZO (Utah)      equal
RTM (Dominican Republic)   sloper ~ 1/2 S unit better
KP4CA (Puerto Rico)   equal
Paraguay   equal
PY2GN (Brazil)   EFW ~ 1/2 S unit better
AI6VN/KH6 (Hawaii)   equal
VE7HUN (BC)   equal  (groundwave)

Unlike 1/4 wave verticals that require a fairly robust counterpoise / radial system for effective operation, the counterpoise requirements for a half-wave are far less-demanding. Mine consists of about fifteen short turf-pinned radials and the first 50' of the coaxial feedline's shield. A common mode choke (CMC) is installed on the feeder at the 50' point, keeping any RF out of the shack and the rest of the feedline from radiating.

I was actually pretty surprised at these results but how they will relate to everyday operating is yet to be determined. My main goal was to get a good-performing 80m antenna and anything that works well on 40 would be a nice side benefit but not really required. Unfortunately I don't have another 80m antenna to run some A-B checks with but from what I can tell, performance on 80m seems to be good.

If you are on Facebook, there is a lot of good discussion and information available on the End Fed Half Wave Antennas group.

My New 80 / 40m Antenna

80 / 40m wire vertical groundplanes, now removed



For the past several years I have employed wire vertical groundplane antennas for both 80 and 40m, mounted a few feet from the ocean.




In the fall I layout the ground radials on the grass and in the spring, roll all of them up again. The main reason for going to the vertical was to eliminate problems with my 80 / 40m half-slopers when using my 1929 single tube power oscillators during the windy conditions usually encountered during the mid-winter '29 BK QSO Party.

The flexing between the tower's telescoping mast sections and the Yagi antennas that form part of the sloper's 'top hat' , cause the half-sloper's impedance or resonance to change ever so slightly. The directly-coupled oscillators respond to these minute antenna changes by constantly shifting frequency by several hundred Hertz, as their output load changes. These high winds can make the low-power oscillator difficult to copy under weak signal conditions as it suddenly jumps frequency. The verticals were immune to this 'wind effect' and performed very well ... sort of.

I've noticed, over the years, that the verticals seemed to produce a much better signal out on the eastern edges of the continent than they do in the central states and in the closer western (PNW) states. I decided to see if an inverted-V might produce a higher takeoff angle and give me a better signal in mid-continent and an 'OK' one on the east coast. The half-slopers on the other hand, always seem to produce a good signal both near and far, but could usually not be used with the one-tube power oscillators when it was windy ... which, during winter here on the coast, is a lot of the time!

Following the removal of the old wire verticals and several days of antenna building, the new 80 / 40m dual inverted-Vs were hoisted to the top of my 85' Balsam. After pruning for resonance, I have been able to run some comparisons between the 40m V and my present 40m half-sloper. The 80m half-sloper had already been decommissioned as it required the changing of a jumper to use and I was never able to resonate it properly for some reason. Oddly there was no problem with either the 40m or 160m half slopers, fed at the same point, as both resonated easily.

The new 80 / 40m dual inverted-V dipoles

The dual dipoles, both resonated to the CW portion of each band, are separated every 10' by 24" varnished and painted hardwood spreaders.



The old 40m sloper has always been a really great performing antenna (except for the power oscillator / mast flexing problem) and it was the one used for my 300mW Tuna Tin Worked All States, back in the fall of 2000. I've had good success with both the 40m version and the 160m version, with 159 countries now confirmed on topband using the diminutive 130' wire.


The 'Half-Sloper' was given a close analysis by antenna guru Jack Belrose, VE2CV, and described in QST of May, 1980. In his article, "The Half Sloper - Successful Deployment is an Enigma", he found that the radiation pattern was almost identical to that of a top-loaded monopole, fed against ground. The radiation field was largely vertically polarized and omni-directional while a lesser component, about 10db down, was horizontally polarized and coming from the sloping wire. The horizontal component had a figure-eight radiation pattern, slightly favoring the direction of the wire. He suggests that this antenna should be avoided due to the difficulty in getting it properly tuned.

My own experience with half-slopers have been mostly very positive, in spite of the tuning problems with the 80m version. To me, it seems like an ideal low band antenna for the small backyard, if you can get it to tune correctly. Assuming you already have a tower with some beams to add top-loading, hanging half slopers for the low bands takes up very little space. With omni-directional low angle radiation along with some higher angle horizontal radiation, all in a small footprint, what could be better for a simple wire antenna? Well, hopefully, my new high inverted-V!

For the past couple of weeks, as described earlier, I have been comparing the new 40m inverted-V against my 40m half-sloper, 'A-B' style, in real time, using the KiwiSDR network of online receivers. It seems that about 75% of the time, my old half-sloper, is just a few db better than the new V ... after all of the work involved, these results were both surprising and somewhat disappointing!

Perhaps I shouldn't be surprised after all, since the inverted-V configuration for a dipole is certainly less than ideal and the included angle in my antenna's normal position is only about 90 degrees. As well, the feedline attenuation losses for the new antenna are about 1db higher than those of the sloper. During the winter, I will be able to move one leg over to the far side of my neighbour's property which will open the apex up to a full 180 degrees. Recent testing at this angle has made the antennas neck and neck with one beating the other about 50% of the time, but the inverted-V is always better to the closer states.

Unfortunately, I have nothing to compare the new 80m antenna against but from listening to the signal on various SDR's around the continent and into the Caribbean, I have every confidence in it providing a much better signal than I have previously been able to muster on that band ... it should really help during the '29 BK QSO Party and the next NRR CW Party.

So what has been accomplished with the new installation? I have gained what appears to be a very good performer on 80m, as well as a 40m antenna that seems to be as good as the known good performing half-sloper, and should not cause any frequency-hopping with the one-tube power oscillators. My signal into the nearby PNW and central states has been improved. As well, now I can also avoid the annual radial deployment and retrieval needed for the wire verticals.

I'm still testing both antennas but conditions have been less than co-operative over the past few weeks. Hopefully when propagation picks up again, some of the European and far out Pacific SDRs can be used to further compare the two antennas ... there may yet be more to come!

An Online Alternative For Comparing Antenna Performance


Over the past few years, the Reverse Beacon Network (RBN) has been utilized by thousands of amateurs to gauge the performance of their antenna systems, to check propagation or to compare their station's antenna performance against another nearby amateur's system.



For those not familiar with the RBN, it is the opposite of a network of 'on-air beacons' and consists of a network of 'on-air receivers', usually SDRs, that automatically skim a wide range of frequencies within the CW bands and report back what they hear, along with a definitive signal strength report ... all posted immediately back to a central website where you can read the data from the various stations that have heard your signal. Calling 'CQ' or sending a few 'TEST de' signals, followed by your call sign, will trigger the desired network response.

I have recently been testing a new 40m antenna, an inverted-V dipole at 80', against my long-used half-sloper, but have been using a different online receiver network to make my real-time comparisons ... the KiwiSDR receivers, mentioned in previous blogs. I'll have more to report about the new antenna and its performance in an upcoming blog, once everything is finished and the antenna is fully optimized.


When it comes to real-time 'A-B' antenna comparisons, I found the KiwiSDR network much more interesting and informative than using the RBN. If hard data is what you want, then the RBN will provide it, but not in the same real-time, 'A-B' style that the Kiwis can offer. Once set up so that the two antennas may be fast switched, 'A-B' style, you can actually hear the difference immediately, with your own ears, as if sitting at the online receiver hundreds or even thousands of miles away. By sending a continuous series of dashes while switching between antennas, the comparison can be strikingly obvious, as the propagation variances experienced in an RBN comparison are no longer a factor. One might argue that using longer RBN comparisons, averaging the signal strength over a period of minutes, may yield a truer picture of antenna performance ... but this method lets you hear the second-by-second differences as they happen.
 
My antenna testing is not yet complete, as much of the initial time was spent trying to determine which online receivers were suitably quiet enough to utilize. Many of them were rejected for being far too noisy to be useful while many others were found to be ideally quiet. I am slowly working my way through the list!

So far, I have been able to listen to my transmitted signal and compare the two 40m antennas on numerous receivers from coast to coast, both near and far, as well as into the Caribbean and South America. I have found the best power to use is between 1 and 5 watts, as making the signal intentionally weak at the receiver end makes subtle differences of just a few db easier to detect.

The gathering comparisons are fascinating as often the signal strengths between my two antennas are very different. Often the sloper and the inverted-V are neck and neck, while in different directions or at different distances, one or the other is a clear winner. On many far-off receivers, I was easily able to detect my signal with all power controls set to '0' with no indication of any output showing on my meters, a rather surprising observation and another reminder of how RF just loves to radiate ... even at very low levels!

If you want to try this yourself and can quickly switch antennas 'A-B' style, here are the direct links to a few of the receivers that I have found to work very well so far ... with low noise levels and no man-made crud, while listening on 40m.

KA7U SDR - Idaho

K1RA/KW4VA - Virginia

W0AY - Montana

K2SDR - New Jersey

G8JNJ - England

K2ZN - New York

WA2ZKD - New York 

KD4HSO - Kansas

VE6JY - Alberta

W3SWL - Pennsylvania

N6GN - Colorado

N8DTT/6 - California

VE6JW - Alberta 

Kingwood - Texas

TWR - Bonaire

EA8DGL - Canary Islands

Wellbrook ALA1530LNP - Southern Finland

NO2CW - Florida

Pardinho - Brazil

I will continue to update this list as more receivers are tested ... now back to some outdoor antenna tweeking!


Evaluating Online SDRs For MW Capabilities

courtesy: https://sdr.hu/

In a previous blog I described the amazing KiwiSDR network of online receivers. A quick check of the network as I write today's blog shows that there are presently 207 active online receivers distributed throughout the world!

Over the past year, there has been a growing interest in using many of the online receivers during the monthly CLE NDB listening events, all focused on the medium frequency (MF) part off the spectrum just below the AM broadcast band. Some use the SDRs to search for unlogged beacons while others use them because their home locations have become too noisy to hear anything using their own radios, a growing problem for listeners everywhere.

One ardent NDB DXer, Dan Petersen, W7OIL, (located in Vancouver, WA) has become a regular Kiwi network user as well as a regular contributor to the very valuable RNA / REU / RWW list of worldwide beacon activity. Over the past year, Dan has been keeping careful notes on not only what he has been hearing but also on how well many of the online radios perform on the MF NDB band.

As it turns out, many receivers perform very well on the HF bands but are dreadfully inadequate when it comes to the medium wave frequencies. Many are plagued with high noise levels, switching power supply signals, intermod or inadequate antenna systems, making them unusable for weak signal DX work below the broadcast band.

Other receivers however, are superb performers, as evidenced by their quiet low noise locations and well engineered antennas, providing the ideal opportunity to conduct some serious medium wave weak signal detection.

Dan has now produced the start of an ongoing guide, mainly focusing on the various Kiwi Network receivers that he has tested, rating them with regard to sensitivity and local noise, when used in the 200 - 500 kHz range only.

His SDR EVALUATION LIST (in .pdf form) can be downloaded from here, and will be updated periodically, as other online receivers are evaluated.

If you are plagued with local noise on the MF band yet would like to do some weak signal DXing, especially during the monthly NDB CLE activities, the online SDRs may be of interest to you. With Dan's helpful groundwork already giving you a leg up, hopefully you can give them a try sometime soon!

                          *********************************

Speaking of monthly CLEs ... the recently completed weekend event (CLE232), was a rough one, with worldwide lightning noise as well as an active geomagnetic field hampering reception for all participants. In North America, all three nights were terribly noisy and propagation was poor.

As is so often the case, Friday night was the 'best' of the three nights but only 18 stations were heard here. My log is shown below.

It was nice to hear POA in Pahoa, Hawaii, still going strong as it is located close to the present volcanic eruptions.

All signals were heard on a Perseus SDR feeding an inverted-L antenna, resonated to 300kHz.

26 09:00 325.0 YJQ Bella Bella (Campbell Island), BC, CAN
26 09:00 326.0 YQK Kenora, ON, CAN
26 10:00 326.0 DC Princeton Municipal Apt, BC, CAN
26 06:00 328.0 YTL Big Trout Lake, ON, CAN
26 09:00 328.0 LAC 'Lacomas' Fort Lewis, WA, USA
26 09:00 328.0 5J Coronation, AB, CAN
26 06:00 329.0 YHN Hornepayne, ON, CAN
26 09:00 329.0 YEK Arviat, NU, CAN
26 09:00 329.0 X2 Athabasca, AB, CAN
26 10:00 329.0 PMV Plattsmouth, NE, USA
26 09:00 329.0 PJ Robinson (Whitehorse), YT, CAN
26 09:00 330.0 0O UNID, XUU
26 09:00 332.0 XT Terrace, BC, CAN
26 09:00 332.0 WC White Rock (Abbotsford), BC, CAN
26 10:00 332.0 VVV Ortonville Municipal Apt, MN, USA
27 09:00 332.0 VT Buffalo Narrows, SK, CAN
26 12:00 332.0 POA Pahoa - Hawaii Island, HWA
26 06:00 334.0 YER Fort Severn, ON, CAN

The KiwiSDR Online Network

Online SDRs (Software Defined Radio) continue to grow in numbers and popularity.

Listening on a receiver that is running in another state, province or country can fulfill a number of functions for you, depending on your particular interest.

The network that I have explored several times and one that works nicely with most web browsers (no software to download or 'extras' required) is the SDR.HU network of Kiwi SDRs ... just choose your receiver and away you go in a matter of seconds. It's all very slick and if you have never played with an SDR before, it affords a nice introduction to this amazing technology. Although it won't work with my ancient version of Internet Explorer running on Vista, it did fine with Firefox and even worked very well on my old I-Pad! Here is a 30-second YouTube video to give you an idea of what it looks like.



There are a huge number of choices from all over the world available on the Kiwi network. As I write this, there are presently 199 receivers online! Any particular receiver can support a maximum of four users at a time so if the one you want is full, simply check back later or go to your second choice.

Although all receivers have the same appearance online, not all will offer the same performance. Although most seem to cover 0-30MHz, I see at least one that is limited to the VHF range and several that don't go all the way to the bottom of the VLF band. The antennas used seem to favor wideband loops, both large wire styles and smaller active versions as well as active e-probes.

The best way to determine any particular receiver's operating performance is to try it out using test target signals that might indicate good performance from that location. If you're interested in BCB capability, test some of the European ones to see if they can hear any TA signals around sunrise in Europe. Many SWLs will use these receivers to compare what they are hearing at home with a receiver located closer to the suspected DX target signal. I myself found the network particularly handy for listening to my Tri-Tet-Ten transmitter on 10m CW a couple of years ago when the muf was much higher than it is nowadays. I'll be trying a few of them out this winter, listening for my 630m CW signal, at various locations.

Some of the receivers appear to offer good, low noise reception on LF, MF and the BCB but the vast majority are not DX machines oriented for this part of the spectrum ... this was the opinion of one notable BCB DXer who checked many of those in eastern NA as well as western EU. The jury is still out on the westerern NA receivers and those in the Pacific / Far East ... a worthwhile listening project when there is some spare time. Even though the receivers used on these lower frequencies did not usually offer stellar performance, they may be real workhorses within the ham bands or on the international shortwave bands.

It would be worthwhile to see some form of 'performance rating' or feedback page for each individual receiver. Although there is a 'vote' tally associated with each receiver it's not clear what this actually represents as receivers that have been online for longer periods would naturally have a higher tally.

A lot of additional information about the KiwiSDR network can be found here.

No doubt you can think of your own good reason to have a remote listen to some of the network's growing list of online receivers and put them to the test ... there may be some real treasures to be found.


Subscribe FREE to AmateurRadio.com's
Amateur Radio Newsletter

 
We never share your e-mail address.

Please support our generous sponsors who make AmateurRadio.com possible:

Ham Radio Deluxe

KB3IFH QSL Cards

Hip Ham Shirts
DMMCheck Plus
R&R SpecialTEES

morseDX

Ni4L Antennas
R&L Electronics
antennas.us


Do you like to write?
Interesting project to share?
Helpful tips and ideas for other hams?

Submit an article and we will review it for publication on AmateurRadio.com!

Have a ham radio product or service?
Consider advertising on our site.

Are you a reporter covering ham radio?
Find ham radio experts for your story.

How to Set Up a Ham Radio Blog
Get started in less than 15 minutes!


  • Matt W1MST, Managing Editor




Sign up for our free
Amateur Radio Newsletter

Enter your e-mail address: