Ham Hum April 2016
The official newsletter of The Hamilton Amateur Radio Club (Inc.) Branch 12 of NZART - ZL1UX Active in Hamilton since 1923
Hamilton Amateur Radio Club Inc. Serving the Hamilton Community for over 90 Years
ZL1UX
Next Meeting 20th April Disclaimer: The Hamilton Amateur Radio Club (Inc) accepts no responsibility for opinions expressed in this publication. Where possible, the articles source details will be published. Copyright remains with the author or HARC. All rights reserved.
Contact Details Patron: Russell Richardson ZL1RWR President: “Jono” Jonassen ZL1UPJ zl1ux@nzart.org.nz Vice Presidents: Gary Lodge ZL1GA Gavin Petrie ZL1GWP 843 0326 zl1gwp@nzart.org.nz Secretary: Phil King ZL1PK 847 1320 zl1pk@nzart.org.nz AREC Section Leader: “Jono” Jonassen ZL1UPJ zl1upj@nzart.org.nz Deputy Section Leader: Phil King ZL1PK 847 1320 zl1pk@nzart.org.nz Treasurer: Tom Powell ZL1TJA zl1tja@nzart.org.nz Committee: Brett Pascoe ZL1FPG Mike Sanders ZL2MGS 855 1612 zl2mgs@nzart.org.nz Robin Holdsworth ZL1IC 855 4786 Sam Birch ZL1OBI Terry O’Loan ZL1TNO Ham Hum Editor: David King ZL1DGK 579 9930 zl1dgk@nzart.org.nz Ham Hum Printer: John Nicholson ZL1AUB 855 5435 ATV Co-ordinators: Phil King ZL1PK 847 1320 zl1pk@nzart.org.nz Robin Holdsworth ZL1IC 855 4786 Market Day Co-ordinator: harcmday@nzart.org.nz Robin Holdsworth ZL1IC 855 4786 Webmaster: Gavin Petrie ZL1GWP 843 0326 zl1gwp@nzart.org.nz Club Custodian: Currently vacant QSL Manager: Gary Lodge ZL1GA Net Controllers: 80m net—Phil King ZL1PK 847 1320 zl1pk@nzart.org.nz 2m net—Phil King ZL1PK 847 1320 zl1pk@nzart.org.nz NZART Examiners: ZL1IC, ZL1PK & ZL1TJA
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From the Editor This issue is somewhat late. My apologies for that. I’ve almost got a proper VHF/UHF aerial up and running at my new QTH. Well, it’s in the air and secure, I just have to find some time to attach the N-Connector to the rig end of the coax (once I find my fine solder again). HF is waiting on the selection of a couple of good trees after some long overdue maintenance is done. Finally, Jaycar have released their 2016 catalogue. The electronic version is available at http://www.jaycar.co.nz/catalogue
Next Committee Meetings 2 September and 7th October nd
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SB PROP ARL ARLP015 ARLP015 Propagation de K7RA All solar and geomagnetic indicators declined again last week. Compared to the previous seven days, from March 31 through April 6 the average daily sunspot number slipped from 28.1 to 19.4. Average daily solar flux sank from 88.8 to 83.1, while average daily planetary A index went from 11.9 to 9.4. Average daily midlatitude A index went to 7.6 from 8.6. The latest prediction (from April 7) has solar flux at 92 and 90 on April 8-9, 95 on April 10-15, 78 on April 16-17, 80 on April 18-22, 78 on April 23, 80 on April 24-28, 82 on April 29 to May 1, 78 on May 2-5, 82 on May 6-7, 80 on May 8-12 and 78 on May 13-14. Solar flux then continues to dither between 78 and 80 over the remainder of the 45 day forecast. You can find daily updates of this forecast at ftp:// ftp.swpc.noaa.gov/pub/forecasts/45DF/ . Predicted planetary A index is 15 and 8 on April 8-9, 5 on April 10-12, then 12, 20, and 8 on April 13-15, 5 on April 16-20, 8 on April 21-22, then 5 and 12 on April 2324, 10 on April 25-26, 8 on April 27, 5 on April 28-29, then 22, 8, 15 and 12 on April 30 through May 3, then 8 on May 4-5 and 5 on May 6-7. The big factor in bringing the week's average sunspot number down nearly 9 points was the fact that the daily sunspot number was 11 on March 31 through April 2. 11 is the lowest sunspot number we can possibly observe, unless there are 0 sunspots, then the sunspot number is 0. Each sunspot group is counted as 10 points, and these are added to the total number of sunspots which count as one each, so a sunspot number of 11 is what you get with just one sunspot visible. Spaceweather.com reported early Thursday that on April 7, Earth is expected to cross a fold in the Heliospheric Current Sheet, which could trigger unsettled geomagnetic conditions. The Heliospheric Current Sheet separates regions of solar wind where the magnetic field points toward or away from the Sun. See http://bit.ly/25MG4lW for a continuous animation of this effect from 2001 until 2009.
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See https://en.wikipedia.org/wiki/Heliospheric_current_sheet for more information. Sure enough, early on April 8 at 0007 UTC the Australia's Space Weather Services issued a geomagnetic warning: "The geomagnetic conditions are currently at minor storm levels and are expected to remain at these levels for the next 6-12 hours. This is a combined effect of sustained strongly southwards IMF Bz (see http://bit.ly/1S6H68D ) starting from 07/1800 UTC but with stable, weak solar wind speeds (380 km/s). However, the solar winds are expected to gradually increase later today in response to a small recurrent southern hemisphere coronal hole moving into a geo-effective location on the solar disk. The aurora may be visible from as low as some parts of the state of Victoria, Australia, on the local night of 8 April. Increased geomagnetic activity expected due to a coronal hole high speed wind stream from 08-09 April 2016."
F.K. Janda, OK1HH reports: Geomagnetic activity forecast for the period April 08-May 04, 2016 Geomagnetic field will be: quiet on April 17-18, 21-22, 27-28, May 4 mostly quiet on April 19-20, 29, May 1, 3 quiet to unsettled on April 10, 14-16, 23-25, May 2 quiet to active on April 8-9, 13, and 26 active to disturbed on April 11-12, 30 Amplifications of the solar wind are expected on April 9-10, (14,) 20, (24-25,) 2830
Parenthesis means lower probability of activity enhancement. If you would like to make a comment or have a tip for our readers, email the author at k7ra@arrl.net. For more information concerning radio propagation, see the ARRL Technical Information Service web page at, http://arrl.org/propagation-of-rf-signals. For an ex-
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planation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earththe-ionosphere. An archive of past propagation bulletins is at http://arrl.org/w1awbulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/. My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 . Click on "Download this file" to download the archive, and ignore the security warning about file format. Pop-up blockers may suppress the download. Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation. Instructions for starting or ending email distribution of ARRL bulletins are at http:// arrl.org/bulletins. Sunspot numbers for March 31 through April 6 were 11, 11, 11, 38, 23, 27, and 13, with a mean of 19.1. 10.7 cm flux was 81.7, 82.1, 81.5, 82.3, 83.4, 83.4, and 87.1, with a mean of 83.1. Estimated planetary A indices were 7, 3, 22, 15, 7, 5, and 7, with a mean of 9.4. Estimated mid-latitude A indices were 5, 2, 15, 13, 6, 5, and 7, with a mean of 7.6.
Can you turn it down a bit please? Attenuators are a handy piece of kit when working on circuits ranging from audio up to RF and beyond. Being the sort of person who always has something on the go I have acquired a collection of attenuators that I regularly use when taking measurements of radios and test gear and will discuss one that I built for a fraction of the cost of purchasing something new. At the top of the picture are 2 HP step attenuators that give me a range of 0db to -
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81 dB in 1 dB steps. These are rated from DC to 18 GHz so for accurate testing these are used quite a bit. They are rated up to 1 Watt each which is good but, what if I am working with a radio that develops 4 watts ? Simple, I put another attenuator in front of the stepped attenuators. In the picture above there are 2 “N� type attenuators with the black finned center, both are rated at 5 watts and offer 20 dB of attenuation. I picked them up at a Hamfest a few years ago for $5 each. So if I run say a 4 watt signal into the 20 dB 5 watt attenuator before the stepped attenuators this will reduce the 4 watts down to 40 milliwatts, a level the HP's can handle quite easily. Sounds good you say, what if I want to run 100 watts into a power meter that can only handle a few milliwatts, something like a HP 432 ? Again insert another attenuator in front of the 20 dB 5 watt attenuator to reduce the RF power to an acceptable level. Just make sure it is rated for the power which it will be dissipating, in this case 100 watts. This was the situation I was faced with the other day, I needed a portable and accurate power meter with the capability of reading up to 100 watts, and I didn't want to have to pull my bench apart again, what to do? I had some RF dummy load and attenuator chips left over from when I was building the dummy loads last year so I had a look and found a 20 dB, 150 Watt attenuator
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chip in the parts box. The difference between an attenuator and a dummy load chip is one tang. The dummy load chip has one tang (lead) to solder to and the other side of the chip is “earthed” to something like a heatsink. With the attenuator chip there are 2 tangs or leads, one input and one output from the chip ( at the specified attenuation ) and the mounting is earthed as well.
I remember a conversation with a broadcast Mate many years ago discussing the “dark arts of RF” and I remember something he told me about any RF construction in general…. This was to “keep the leads short”. I scrounged up a pair of panel mount N connectors and a jiffy box and built the attenuator. I checked it out on the bench, the results were at least surprising… As you can see the attenuator chip sits on a bed of copper that is mounted onto the back of the case. I chose copper for it's heat transfer capabilities. Directly underneath the copper and the back of the box I have mounted a small heat sink with plenty of heat transfer compound. Either side of the box are mounted 2 panel mount N connectors with a nut each side of the box for the adjustment of the depth of the N connectors into the box. This was necessary as the two connectors were
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too close together inside to fit the attenuator chip between so I had to space them out a bit. I think the picture tells the rest of the story :-) So how did it measure up ? The first test was to check the frequency response of the attenuator over 500 MHz to see how flat the attenuation was. In a perfect world the attenuation ( in this case, 20 dB ) would be ruler flat from DC to 500 MHz but as we all know not many things are perfect…. I took some measurements and was very happy with the results… You can see that I was getting a 0.2 dB variation across 500 MHz and was off the magic 20 dB mark by only 0.3 dB at the worst case. These are quite good results for a “homebrew” attenuator and I was encouraged for the next test, input VSWR. As the attenuator would be connected directly to the output of a transmitter I needed to find out what sort of impedance it would present to the transmitter. So with a 50 ohm precision termination on the output of the attenuator I swept the input for Return Loss ( VSWR ) and these are the results that I achieved.
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You can see that I was getting a 0.2 dB variation across 500 MHz and was off the magic 20 dB mark by only 0.3 dB at the worst case. These are quite good results for a “homebrew� attenuator and I was encouraged for the next test, input VSWR.
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As the attenuator would be connected directly to the output of a transmitter I needed to find out what sort of impedance it would present to the transmitter. So with a 50 ohm precision termination on the output of the attenuator I swept the input for Return Loss ( VSWR ) and these are the results that I achieved. At 15 MHz I measured a VSWR of 1.08 to 1, at 52 MHz I measured a VSWR of 1.09 to 1, at 146 MHz I measured a VSWR of 1.12 to 1 and at 435 MHz I measured a VSWR of 1.24 to 1. Any transmitter would be happy transmitting into these VSWR's ! The chip is rated at 150 watts but I doubt I could run that sort of power for any length of time as the heatsink is too small for that sort of RF level. I have run 50 watts into the attenuator for a minute and I could still pick it up in my hand so I am happy with that. Short term peaks over 100 watts are fine with a bit of safety margin as well. The other bonus with this is the cost, the RF attenuator chip was $ 15, case $ 4, N connectors $ 10 and a few bits and pieces laying around. Total cost for the project was roughly $30. I had a look on that famous auction site starting with “E” and I was looking at over $100 for something similar and second hand… not bad at all! All in all a successful project and a useful one too! The next project is a 100 ohm dummy load to test VSWR meters :-) Cheers and 73, Rob VK3BRS
The BIG List of RTL-SDR Supported Software A web site, http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software lists many free and low cost software applications, running on multiple operating systems, utilising the RTL-SDR (RTL2832U) DVB-T Tuner Dongle. Although some of the links are broken, a search may be made on the application to find a working software repository. The site also refers to an improved version, the R820T2 Tuner, being backward compatible with the earlier RTL2832U device. Free Virtual Audio Cables are available via http://www.dxzone.com/5-free-virtualaudio-cable-software/
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Something Technical! The “S” meter. (lifted from Rotorua Br 33 who lifted it from the web) An "S" meter is fitted to Ham Transceivers and Communication Receivers to allow the user to determine the signal strength of the transmission being heard. But what does this all mean? As a guide; S9 on the S meter scale is reckoned to be equal to a potential of 50 uV signal voltage at the receivers aerial input. Also each "S" point is said to represent a 6 db change (up or down). A 6 db change coincidentally represents a doubling (or halving) of a voltage before/after the aforesaid change. Recalling the well-known textbook formula: The relationship of “S" meter reading to input signal voltage obeys the law uV = k 2 s [ k is a constant (derivation shown soon!)] That is; because of the signal voltage doubling for each increase in "S~' point the signal voltage is directly proportional to the base 2 raised to an exponent being the "S" number. To bring this into some perspective: If 50 uV represents S9, then substituting in the above formula 50 = k x 29 therefore k = 50/512 To obtain (say) the signal voltage corresponding to S4 we can substitute in the above formula uV = k 2s = 50/512 x 2 4 = 50/32 = 1.5625 uV Constructing a table of values based on the above we get: db = 20 log v2/v1 substituting values = 20 log 2 = 20 x 0.3010 = 6db “S” reading Voltage at RX input: 9- 50 uV, 8- 25 uV, 7- 12.5 uV. 6- 6.25 uV, 5- 3.125 uV, 4- 1.5625 uV, 3- 0.781 uV, 2- 0.39 uV, 1- 0.195 uV Therefore: as you can see, each change in "S” point represents a doubling (or
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halving) of its immediate predecessor, all referenced to S9 being 50 uV (Some archaic texts suggest S9 as being 100uV), but the principle is still the same.
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Upcoming Happenings & Events Date
Happenings & Events
1st April
NZART HQ Infoline
2-3 April
NZART Low Band Contest
4th April
HF Net, 3.575 MHz, 19:30
5th April
VHF Net, 146.525 MHz, 20:00
11th April
HF Net, 3.575 MHz, 19:30
12th April
VHF Net, 146.525 MHz, 20:00
15th April
NZART HQ Infoline
18th April
HF Net, 3.575 MHz, 19:30
19th April
VHF Net, 146.525 MHz, 20:00
20th April
Monthly Club Meeting
24th April
NZART Official Broadcast
25th April
HF Net, 3.575 MHz, 19:30
26th April
VHF Net, 146.525 MHz, 20:00
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6th May—NZART HQ Infoline 20th May—NZART HQ Infoline 21-22 May—NZART Sangster Shield Contest 29th May—NZART Official Broadcast 4-5 June—NZART AGM/Conference 11-12 June—NZART Hibernation Contest 17th June—NZART HQ Infoline 26th June—NZART Official Broadcast 2-3 July—NZART Memorial Contest 16th July—WIA VK/ZL Trans-Tasman Low-Band Contest 6-7 August—NZART Brass Monkey Contest 13th August—Annual Hamilton Market Day 1-2 October—NZART Microwave Contest 5th November—NZART Straight Key Night 3-4 December—NZART Field Day Contest
For more information on any of the above please contact myself or any committee member.
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Club Information Contacts :Business Meeting:
1930 First Wednesday of each month except January 88 Seddon Road, Hamilton
General Meeting:
1930 Third Wednesday of each month (except Jan) 88 Seddon Road, Hamilton
Homepage: eMail:
http://www.zl1ux.org.nz branch.12@nzart.org.nz
HF Net: VHF Net:
3.575MHz LSB 1930 Mondays 146.525MHz simplex 2000 Tuesdays
2m Repeater: STSP Repeaters: ATV Repeater:
145.325MHz -600kHz split 146.675MHz -600kHz split 438.725MHz -5 MHz split Off air pending channel changes
Cover Photo: Ham Radio Man-Packs. https://nz.pinterest.com/ pin/494340496569739071/
Sender
Hamilton Amateur Radio Club (Inc) PO Box 606 Hamilton 3240