Home brewing a Vertical for DXing

Recently, I’ve been bitten by the 80M DXing bug.  Its not so much that 80M has taken hold, as it is that I have managed 140+ confirmed on both 40M & 20M now so all the ‘easy pickings’ are gone.

My main antenna is a 102ft ladder line fed dipole aka G5RV up ~45 feet at the Apex.  Whilst this antenna takes QRO in its stride, and puts out one heck of a signal, it also features a whole lot of ‘high angle’ radiation on 80M & 40M.

Whilst I’ve managed 30 countries on 80M running some power (which was needed), I always found received signals to have poor SNR.  As such, I decided to once again revisit the Vertical – primarily as an RX Antenna for now – to see if it could help.

Here is the pattern difference, in theory.  Note the huge amount of high angle radiation the G5RV (broadside) picks up compared to the Vertical.  Although the low angle figures look close, remember the G5RV has a ‘peanut’ shape even at 45ft, so when the G5RV is facing ‘narrow side’ the Vertical has over an 8dB advantage below 15 degrees.

Screenshot 2017-05-21 19.46.50

Continue reading for more pictures and information about the project 🙂

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Solving Stereo / Home Theater Radio Frequency Interference caused by Ham Radio

Having suffered DX withdrawal, I decided it was time to put up a new antenna.  The antenna in question was a Icom AH-4 Tuned Dipole of about 36M length in total, about 9M high at the apex.  Whilst I realize it is far from optimal in many ways, I was interested to see how it would perform on the higher bands, and thought it might significantly improve my local contacts on 40M & 80M.

It seems to have delivered on 80M, my local Winlink Winmor speeds on 80M have gone from 100 Bytes / Minute to a huge 1100 Bytes / minute, and I’m once again hearing the local farmer’s nets!

However, there is much testing to do, and the story today is about the problem the new antenna caused!  I like to play on JT65 at night, when there isn’t much going on, and I’ve setup my radio so I can do so remotely via my laptop.  Whilst relaxing in bed playing JT65 on 20M, I decided it would be a good idea to listen to some music, but my new antenna thought otherwise!

My home stereo system is pretty basic but nice.  It consists of an Audio Engine DAC (usb sound card), and a Miniwatt N3 3.5 Watt Tetrode Amp.  A good friend of mine, Peter VK3OJ, had recently given me some old (but working) 12AU7 tubes, and I was keen to see how they sound compared to some of the newer models.  However, the moment I transmitted on 20M, the left speaker would buzz, and the computer dropped the soundcard!

At first, I decided to tackle the buzzing speaker.  I added some chinese (ebay sourced) snap on ferrite cores one by one and transmitted, until the buzz died down.  It took 12 snap on cores to achieve a decent result, however this didn’t stop the computer from dropping the soundcard.

I then put 4 snap on cores on the USB lead, but that didn’t help.  I added another 4, and hey presto! I could now listen to music and DX!

The moral of the story is that the age old solution to RFI of snap on cores works, even with cheap ebay sourced chinese cores!

If you’re like me and enjoy listening to music while using digital modes, or have a neighbour who has issues with RFI on his sound system, you couldn’t do better than buying a bunch of snap on cores on ebay.  Many Chinese sellers will sell them in bulk (shop about, put ’10’ in your search etc), and I was certainly glad to have these ones in the shack!

My Current Home (Australian) Station

Hi Everyone,

Below is a few pictures of my current station in Australia.

It basically consists of the following:

  • Icom IC-7200 HF/6M Transceiver
  • Yaesu FT-101E HF ‘Hybrid’ Transceiver
  • Yaesu FT-857D HF/VHF/UHF Transceiver
  • Icom AH-4 Remote Antenna Tuner
  • Daiwa CN-801 ‘HP Type’ 1.8 – 200 MHz Cross Needle VSWR Meter
  • Daiwa CN-801 ‘V Type’ 140 – 525 MHz Cross Needle VSWR Meter
  • DOSS SPS-8400 40 Amp 0-15v Power Supply
  • Mac Pro Desktop Computer

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Photos from Koh Rong Island

Hey Guys, the IOTA team have a few issues with my QSL Card design, and may not accept it for IOTA AS-133.  I’m working with them to see if we can find some middle ground.  In the meantime, here are some pictures from Koh Rong Island in Cambodia (which is designated IOTA AS-133).

Jake the Owner of ‘Bongs’ (Cambodian for ‘brother’), who kindly let me setup out the front of his establishment and scribble all over his bar:

Jake Bongs

Myself Pretending to Operate Outside Bongs when the WX was OK but the Bands Not So Much.

Operating Outside Bongs Close

The Local Kids Enjoy the Spectacle.

Local Kids

It was Kind of Windy (The 12M Spiderbeam Pole Didn’t Care)!

Windy

Planned Activation of IOTA AS-133 (Koh Rong)

Koh Rong (IOTA AS-133) Activation

This weekend I plan to activate IOTA AS-133. IOTA AS-133 is actually a group of Cambodian Islands, but I will be located on Koh Rong, which is a popular backpacker hot spot where my brother owns a few Hostels.

The Plan

On Friday the 19th (Cambodian UTC+7 time), I will begin my trip over on the ferry and start setting up the station. I am taking the following equipment:

  • Icom IC-7200 Transceiver (100 Watts Barefoot)
  • Icom AH-4 Remote Antenna Tuner (Mounted at the base of my Vertical)
  • Spiderbeam 12m Telescopic Fiberglass Pole
  • Sennheiser HD-25 Mark II Headphones
  • Turnigy Accucell-6 Microprocessor Controlled Battery Charger

By virtue of the fact my brother has a fishing boat, I have a few decent 100ah batteries available for use. However, Cambodian power often fluctuates between 180-220 Volts, meaning that most of the local chargers (which are linear devices involving little more than a tapped transformer and some diodes), never fully charge a 12v Lead Acid Battery. My little Turnigy charger, although only rated at 4 amps at 12v, easily charges big Lead Acid batteries to full capacity overnight. As such, it is unlikely I will be on the air on Friday, as I will need to charge the batteries up to full capacity in order to get the most out of my radio.

The Antenna

Using a 12M Long Spiderbeam pole, I plan to setup a ‘multiband’ vertical.  The Vertical is ‘multiband’ by virtue of the Icom AH-4 Antenna Tuner / Matching Network that will be placed at the feed point.  The antenna will roughly be constructed as follows:

  • The first meter or so of the spiderbeam pole will be buried in the sand, preferably with some additional hardware to use as an anchor point.
  • Approximately 1 Meter above sand level, the Icom AH-4 tuner will be mounted.
  • The driven element will be approximately 8 meters long, but adjustments will be made to ensure it tunes up nicely on 15M.  8 Meters is pretty close to a half wave, but the tuner should handle this fine.
  • The counterpoise will consist of 4 sloping elevated wires, two behind me, and two going out into the ocean.  Each will be attached to bamboo supports, and the ocean wires will be kept at water height via flotation devices otherwise known as empty plastic bottles.  The counterpoise wires will be roughly 1/4 wavelength on 20M.

Computer modelling and the experience of other DXers suggests this antenna should have a gain between 5dBi and 8dBi, with the highest gain on the higher bands.  These figures are quoted for low angle radiation, between 5 and 10 degrees take off from the horizon. I suspect the pattern will be skewed towards the salt water, however this is not shown by my modelling software.  It is worth noting however that my modelling experience is limited, and I am using a trial version of EZNEC.

The Operation

Beginning Saturday Cambodia time, WX Permitting, I will begin operation as soon as I wake up (this is an unknown variable).  A little bit of time will be spent setting up the equipment, but as I am planning to use a vertical antenna located right next to / in the salt water, I expect this will take less than 30 minutes.

Depending on band conditions, I will be using a mixture of PSK-31 and SSB Phone.  My preference is SSB Phone, so hopefully propagation will be nice.

I plan to operate on the 15M, 17M & 20M Bands, with preference going to the 15M band as it seems to shine in this part of the world.

Why Remote Antenna Tuners Are Not Evil

A lot of Hams hate ‘antenna tuners’, and it’s quite understandable given that there are some common and very bad practices concerning tuner usage.

  

The June 2015 QST Article ‘Don’t Blow Up Your Balun’ explains this better than I ever could – it explains when and how to use a tuner without causing huge losses.  I’ve summarized some of those concepts here, and included some other advantages of using a remote tuner.

  

Antenna Tuners and ‘Loss’

Back in the days of ladder line, having a tuner in the shack wasn’t such a big problem as the ladder line of the day often had an impedance in the order of 600 ohms, and balanced feed lines are less lossy (have less resistive losses) than coaxial cable when mismatched (being driven into a high SWR).  When you combine their high impedance, (which basically means a lower SWR in a mismatch), with their lower losses under mismatch, having a tuner in the shack was not much of an issue.

However when we switched to coax feeds, we should have moved the tuner.  Coaxial cable has a relatively low impedance of 50 ohms, which means that when there is a mismatch between the antenna and the feed line, the SWR is generally higher.  Coaxial cable also has higher losses (higher resistive losses) under mismatched conditions than ladder line, so when you combine these two things, you can burn up a considerable amount of power just in your coaxial cable.  The solution is to move the tuner, or as we should properly call it, ‘matching network’, to the antenna feed point.

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Diamond X510 (X510MA) Antenna Repair Part 2 (Capacitors)

Last night I got an email from John Isabella, K1IF, stating that he’d read my blog regarding my Diamond X510, and was wondering if I knew what voltage the capacitors inside were rated at.

I confessed that I didn’t, as mine did not seem to be in need of replacing, but with a bit of math we were able to ascertain some suitable ratings, namely 300V rated 2pf capacitors.  If you’re interested in the math, continue reading.

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