Category Archives: Antennas

DXpedition antenna testing: the Bonito Boni whip and a 240 metre barbed wire fence

 

Hi there, a few days ago I posted some reception videos comparing the performance of the Boni whip with a 30 metre longwire antenna at home, with a further check against the performance of the H field Wellbrook ALA1530 active loop. The conclusion of those tests was essentially confirmation that E field antennas don’t usually perform very well under a blanket of ‘electrosmog’ and that only on Longwave, did the Boni whip prevailed over the longwire; otherwise there was no usable difference in performance between the two.

                         Sony ICF-SW55 receiver                                     ‘Quiet’ location for Boni whip test

This prompted a number of my subscribers to ask when I would be taking the Boni whip on a DXpedition for an outdoor test against the Wellbrook and either a substantial longwire, or the 200 metre Beverage. Time is limited right now for a full test, however, I managed to throw together a kit of parts necessary to run a quick set of comparison tests with the whip, against the barbed wire fence I use for ad hoc DXing when out walking the dog! Over a period of an hour or so, I managed to copy a few stations on 31 and 49 metres and thus recorded signals using the Sony ICF-SW55 receiver with the Boni whip and barbed wire fence. Now previously, I have used that fence as an antenna for the excellent little Tecsun PL-310ET, with some nice results. However, after this series of tests, my views on the fence have changed a little. Obviously it might be somewhat directional and earthed along it’s length, neither of which I’ve checked, however, notwithstanding these performance-related factors, the performance of the whip which at home had been terrible, surprised me greatly. Text links to a set-up video and the reception videos on my Oxford Shortwave Log YouTube channel follow directly below, with embedded videos at the end of the post. 

Finally, if you’re looking for a well performing, compact and portable active antenna for outdoor use in quiet environments and of course, DXpeditions, I would definitely recommend the Boni whip. Just bear in mind that the SNR it delivers at home might not be usable for anything more than casual listening.

Thanks for watching/listening/reading and I wish you all great DX!



Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

Southgate ARC: What Is a Balun and How to Make One Cheaply

(Source: Southgate ARC)

Ham Radio – What Is a Balun and How to Make One Cheaply

A Balun is a transformer which allows coaxial cable, which is an unbalanced lead to be connected to a balanced load, for example a resonant aerial.

The 1:1 balun is often called a choke balun, it works by eliminating Radio Frequency currents flowing on the outside of your coaxial cable, this is important because it prevents the pattern of the dipole becoming distorted and prevents the braid of the coaxial cable radiating.

Connecting coax to your resonant dipole which can be configured in a V shape or in a sloping fashion, however serious power loss and feeder radiation can occur without the use of a balun transformer. No one wants to induce Radio Frequency currents into Television receivers or Broadcast equipment as it may result in disputes with neighbours and could possibly lead to your station having to close down. Try to keep the centre of your aerial away from buildings as it may induce Radio currents into the mains wiring.

Building a choke is not difficult all you need is some plastic pipe available from many Do It Yourself outlets and warehouses. I use a length of about 1 foot of plastic pipe and 21 feet of coaxial cable, the length of the pipe and diameter is chosen because it works well if using R-G-5-8 coax the ends of the pipe can be sealed after placing a SO-239 connector for your coaxial lead. I use two bolts and solder tags at the other end of the pipe to connect the ends of the dipole to the choke.

When wrapping your coax around the pipe don’t use too much force as it may damage the inner braid and space the turns away from each other by a millimetre or two. R-G-2-1-3 coax around 21 feet used with 5 inch pipe will handle 400 watts pf power. Wire ties can be used to hold the turns together along the length of the pipe. Using these measurements your choke will cover all of the ham radio bands from 1.8 Megahertz through to 28 Megahertz and will keep the radiation pattern.

Using a dummy load connected to the choke and transmitting 100 watts from my transmitter indicated an S.W.R. readings of around 1.5 to 1 at 3.5 Megahertz when testing 28 Megahertz the S.W.R. reading came down to 1.1 to 1 which is an excellent match. Using the choke as it should be at the feed point of a dipole cut for 40 metres give an S.W.R. reading of 1.2 to 1. The highest reading was 1.5 to 1 when using 18 Megahertz but the rest of the High frequency bands gave me very acceptable matching.

By
John Allsopp G4YDM
https://g4ydm.blogspot.co.uk/

Article Source:
http://EzineArticles.com/expert/John_Allsopp/1925417

Article Source:
http://EzineArticles.com/9615600

Urban DXing: testing the Bonito Boni whip against a 30 metre longwire & the Wellbrook ALA15030

Hi there, if like me, you live in an urban environment, chances are QRM is having a negative impact on the quality of the signals you’re receiving at home. The presence of electrical noise makes antenna choice very important, particuarly if you’re planning to spend more than a few £££s on something more sophisticated than a length of wire. Recently I was considering the the purchase of a second compact antenna, for use at home in my shack and out and about on DXpeditions. I already had the excellent Wellbrook ALA1530 H field antenna, but at more than £250, it’s very costly and thus it seemed rather extravagent to buy a second one, if I could find something with similar performance for less expense. Space is at a premium at home and of course I take much of my equipment out on DXpeditions, so the Bonito Boni whip active antenna appeared to be an ideal choice. A wideband active antenna (from 20 kHz to 300 MHz) operating from 12 to 15V DC, with a very compact form-factor definitely ticked all the boxes. Furthermore, with reasonable second and third order intercept points of +55 and +32.5 dBm respectively, the Boni whip, on paper at least, looked like a pretty good buy at around £100.

 

Now, clearly, an E field antenna such as the Boni whip is not going to match the SNR provided by the H field Wellbrook ALA1530 in a noisy, urban environment. I have uploaded a few reception videos to my YouTube channel to demonstrate this, making a direct comparison of the two. However, what about the performance of the whip versus a simple longwire in an urban environment? Is there a delta in performance? The value proposition of the whip is primarliy in it’s performance, coupled with portability I suppose, but that must be considered a secondary requirement. The whip might be 10 or 15 times more expensive than a reel of cheap equipment wire, but will the reception justify the cost delta?!

Text links follow directly below, with embedded videos thereafter; you will find 3 reception videos comparing the whip and a 30 metre longwire, on shortwave and one each for LW and MW. At the end of each video there’s a section with the Wellbrook loop, just to calibrate where the longwire and whip are in terms of a much more effective H field antenna. The result? Well, there’s not much to separate the longwire and Boni whip, except on LW, where the whip prevails. A friend told me recently, if reception is rubbish at home under a blanket of QRM, don’t blame the antenna, the noise is the real problem. He was right. So, the next tests are to be undertaken out in the field, where the whip has a real chance to shine. I’m rooting for it because to have an antenna that performs as well as, or close to my loop out in the woods, yet can be packed away into a small case would be brilliant. Thanks for reading/watching/listening.



Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.

The company and history behind the Boeing 707 HF antenna coupler

(Source: Boeing)

Many thanks to David Giba who shares the following via the Gary J. Cohen’s Shortwave Listeners Global Facebook page:

The Boeing 707 is my favorite commercial jetliner. If one looks at the tail they will see a probe pointing forward off the top of the tail. That is the HF shortwave antenna.

(Source: VIP Club)

It was matched by an antenna tuner/transmatch much like we have in our HF radios. This is the story of the Univac Coupler. Very interesting.

Click here to read on the VIP Club website.

Why good antennas need to be fed with good coax

Dennis Walter, of Bonito Radio in Germany, has just posted an excellent article on his blog regarding the importance of quality coaxial cable to fight local radio interference.

Click here to read his post, “Why even good antennas need good Coax cable.”