Thursday, 30 June 2011

APRS beacon using CW

Automatic position reporting QRP HF beacon using CW

I have been thinking it might be a an interesting exercise to develop and build a PIC controlled device that takes the GPS serial NMEA strings, extracts the info that is required and then encode the pertinent information into CW and transmit this on a low power HF beacon. The beacon will then transmit the position say once every 2 minutes?

For example:

VVV de ZS6A = 1300 S25.123 E024.567 <AR>


VVV de ZS6A = 1315 KG01DC <AR>   Using the Maidenhead grid system.

This will be a very basic form of APRS and will enable tracking without the need of computers etc.

Long live CW !!

Has this been done before? Not much point in re inventing the wheel……

Wednesday, 29 June 2011

Hiking and Amateur Radio

I am writing this after reading some emails received from a fellow Radio Amateur.

John ZS6AA and friends, are planning to undertake a 12 day hike in the Drakensberg. The question was, what would be the most appropriate communication medium to use.

APRS via VHF, amateur satellite, HF radio or sat phone?


The APRS would be a novel and interesting option, but the chances are good that the coverage would be erratic and most likely be unavailable when needed most. The situation could be assisted by a well placed base station with a serviceable digi-peater and I-gate. On the plus side, it serves a locator beacon that could be used during an air/ground search.

The amateur satellites could work, but at this time we cannot rely on them in a life and death type situation. The FM easy satellites are not always available due to various problems being experienced at the moment.

I believe a low powered HF station on 40M would work very well indeed. A simple low dipole, that is easily erected would work fine. This should result in reliable communications from 400 to 800 km and from zero to 800 km (no skip), when the foF2 allows NVIS propagation.

I would recommend setting up daily schedules with 1 or 2 base stations, that in turn will keep track of the hiking group, their present position, their plans going forward and relaying any other info as required, including passing on weather forecasts that will affect the hikers.

This info can in turn be placed on a Blogsite or Facebook or some other facility, where the family and friends can follow and share their experience.

Sounds like fun…

Sunday, 26 June 2011

Flaw discovered in EFHWA matching unit

There has been a very interesting development in my quest to know a bit more about the End Fed Half Wave antenna (EFHWA).

A posting made by Mike ZS6BIM here:

 This got me thinking. I did quite a bit of research and it seems Mike ZS6BIM is correct. The T50-2 toroid seems to be way too small to be effectively used in the EFHWA antenna matching unit as is described by many, including Steve Yates AA5TB on his web site.

The values of peak AC Magnetic Flux (B) appear to be much higher than what would be considered acceptable. This will result in very high core losses.

My calculations reveal the following (hopefully they are not incorrect):
T50-2  -- 7 MHz – 3 turns – 10 watt (31.6 V) è Peak Flux (B) = 303 Gauss and a core loss of 15274 mW/cm^3
The recommended maximum value of (B) is 57 at 7 MHz.

If the toroid was replaced with a T130-2 then the data looks much more acceptable.
T130-2  -- 7 MHz – 3 turns – 10 watt (31.6 V) è Peak Flux (B) =  49 Gauss and a core loss of 278 mW/cm^3

I suspect that we sometimes under estimate our  5 watts QRP and we use components that are not really suited for the task.


Friday, 24 June 2011

QRP station Bert PA1B

I was very pleased to discover the very interesting web site of Bert PA1B

Bert is a huge QRP and QRPp fan. His web site contains a wealth of interesting facts pertaining to the subject. I enjoyed looking at the statistics to see what he has achieved. This is quite remarkable considering the antenna and the power he is using.

We here in South Africa can only dream of achieving such results. IMHO Our only chance of getting our QRP DXCC count up is on 15m and 10m if and when the conditions will permit us to do so.

With the latest predictions by the scientists we might have to be a little patient. I sure hope their prediction about us moving towards a new Maunders minimum is incorrect.

Wednesday, 22 June 2011

Switched inductor ATU

This is a work in progress.

This is my attempt at documenting the build of a small low power LC-Tuner.

The concept is nothing new, but I made a few changes to suit my way of thinking. The inductance is provided by bunch of inductors (toroids) connected in series. Switches are placed over each inductor that allows the inductance to effectively be shorted out or to remain in circuit in series with the other selected inductors.

The clever bit is the choice of inductances used and arranging the switches in such a way that by using Hex code one can quickly determine which switches to open or close as required to increase or decrease inductance. Each inductance is double the inductance of the previous one. For example the inductors can be / 16 / 8 / 4 / 2 / 1 / 0.5 / micro Henries respectively. This will effectively give 0.5 to a total of 31.5 micro Henries in 64 steps:  ‘00’ through ‘3F’

The capacitor will still be a normal air variable unit.

It might be a little time consuming to determine the correct settings for each band initially, but once the best match is determined and noted down, it will be very easy to change from one band to the next.

I did some number crunching and the results can be viewed at the link below:

From this data it is clear that if the ATU will be used for the 80 metre band and higher the range of inductance required is between zero  and  23 micro Henries and the range of capacitance is between zero and 1000 pF. The values of both L and C for 40 metre and above tuner will be half of this.

This presents a new obstacle in the design. This means additional high voltage padding capacitors are needed to switched in to extend the range of the normal 1-140 pF air variable capacitors. Note from the table provided this high value of capacitance is required when the impedance is around 100 Ohms. This situation won’t occur if the wire is cut to a length anywhere near a multiple of a half wave length long.

With all the extra components I am starting to think it might be better to limit the matching range and stick to the high impedance EFHWA antenna.

Tuesday, 21 June 2011

Advantages of EFHWA over Dipole antenna

All the discussions pertaining to EFHWA and the ZS6U Mini Shack Special might create unrealistic expectations of the performance of one being better than the other.

A dipole antenna is a dipole antenna. It does not matter if the dipole or ½ wave length wire is fed at the center or at the end or anywhere in between. The only difference is the impedance at the feed point.

In the case of the traditional center fed dipole it has an impedance of around 70 Ohms and that normally suits us nicely with a reasonably good match between the antenna and the coaxial feed line and our transceivers without the need of an ATU.

When the same ½ wave length antenna is fed at the end as in the EFHWA then the impedance is very high in the order of 5000 Ohms. This in turn means we must use some form of antenna matching unit to transform the impedance to 50 Ohms.

What is the advantage of the end fed half wave antenna (EFHWA)??

An EFHWA cut for 40m is approximately 20.8 metres long and will work on the 40, 20, 15 and 10 metre bands and on 80 m at a push. The normal center fed dipole of the same length will work on 40m and on 15m at a push, and that is all.

The EFHWA does not require a feed line. In ultra light portable operation this is a big issue. The coaxial feed line is heavy and cumbersome.

Colin mentions that the capture area advantages and I tend to agree with that thinking as well.

When using the EFHWA we must still strive to place it as high above the ground and clear of surrounding objects as possible.

There is no free lunch !!

Monday, 20 June 2011

ZS6U Mini Shack Special Vs EFHWA

With me doing research on the End Fed Half Wave Antenna or EFHWA antenna it dawned upon me that this idea is not new at all.
The link below is to a rather poor copy of a reprinted scanned article that Colin Dickman ZS6U wrote for Radio ZS in January 1973 on a antenna he refered to as the "Mini Shack Special"
I am not suggesting that Colin was the original designer of this antenna, but due to the articles he wrote on this antenna, the “ZS6U - The Mini Shack Special” The antenna becane very popular in the 70’s and was used by many South African operators.
I am sure we all will agree that this antenna is the same  as what has now become known as the End Fed Half Wave (EFWHA) antenna.
The included graphs make it clear why the ½ wave lengths (or multiples thereof) of wire is used. It was never meant to be a random length wire antenna.
Does anyone have a better or clearer copy of the above article? I would also like to get a good copy of the original article. The one I have is of very poor quality.
An article titled "The ZS6U Mini Shack Special" was published in the April 1981 edition of QST magazine.

Useful references to EFHWA antennas:

Sunday, 19 June 2011

QRP Fun and portable antenna musings

Operating with low power QRP is amazing.

Today I spoke to Chris 9J2RI in Zambia some 1600 km distant on SSB and much later in the afternoon I heard Chris on 14.060 MHz this is the QRP calling frequency. He was not awfully strong I guess a RST 559. I decided to turn the power all the way down and gave him a quick report. I honestly did not think he would respond. The output power meter on the rig did not move at all. I will have to measure to be sure, but I suspect the power was only a few milli watts.

I was pretty pleased when Chris responded with ZS6?  Once we were in QSO I noticed his signal was also quite a bit weaker and down to 539, maybe he also dropped to QRPp levels.

I have been contemplating the portable antenna setup again. I must be honest I am a big fan of the simple link dipole. The only disadvantage is that one needs a feed line. Maybe I could consider using a short piece of twin flex (rip cord) of about 7 metres as a balanced feed line the followed by a small 1:1 balun then a very short piece (2 or 3 metres) of RG58 coaxial cable.

The reason for the twin flex is weight saving and portability. The RG-58 does not like being coiled up and has a mind of its own. 10 metres is normally the minimum practical feed line length. I think the losses on a 7 metre piece of twin flex should be minimal even on 14 MHz?

I had better build and test such an antenna before my trip. I guess I should really consider doing A/B comparative tests with a standard coax fed dipole before making up my mind.

Has anyone else tried the same antenna system  ??

Saturday, 18 June 2011

QRP - Operation Leipzig

It has just been confirmed, I will be going to Europe as mentioned in an earlier post.

Using VOACAP online predictions it appears that I should concentrate on using 40m if I wanted to gain maximum benefit from operating QRP from Germany. The conditions on 20m would be such that I will be short skip to much of EU. 30m might be an option also, but I don’t know if it would be worth the effort?

I am planning to take along my HB-1A transceiver, DCP paddle. I most likely will use an external battery holder with rechargeable NiMH batteries.

I need to get organized and build myself a 40m End Fed Half Wave (EFHWA) field antenna and ATU. The EFHWA antenna has several advantages over other portable/field antenna options:

There feed line is very short, 2 or 3 meters at the most.
Apparently low ground losses and as such there is no need for radials or counterpoises.
The EFHWA needs only one support such as a tree limb.
Can be used in vertical, sloping, inverted vee and inverted L configuration.
No guys or other supports required.
The QRP antenna matching unit is very simple, small (compact) and weighs almost nothing.

I sure hope all the hype about the EFHWA antenna is true.

Mike AA1TJ - 1D Cell QRPp

The following info copied from the QRP-L reflector.

Man, I just love this “wacky stuff”

Mike AA1TJ and his wife are on a long hike in Europe. The YouTube video shows him working a few stations with his minimalistic QRPp (75 mW) self built 20 m transceiver that operates from a single D-Cell battery.  

Notice how the RBN network also spotted him. Ironically the very same skimmer S50ARX, decoded my signal the other day.

IMHO Amateur Radio at its best ......

73, Pierre ZS6A

Dear All,

We're are in Engelhartzell tonight; only two more days of walking before we reach Passau. Everything has been FB so far except perhaps the propagation...but I won't complain given the beautiful weather we have had.

Tonight I finally managed to upload a short clip to YouTube.

I mistakenly list the call "OH6QP" near the end of the video. It should read "OH6BG". I also show the SNR as "7am" should read "7dB." The blisters are on my feet not my fingertips, so I'm afraid I have no excuse for the typos.

To date I've worked one station in Belgium and had RBN signal captures in Slovenia, Findland and Norway.

I hope to make a better presentation once I'm back at my home computer.

All the best,
Mike, OE/AA1TJ/QRPp/p

Friday, 17 June 2011

QRP - Does it work ?

Is the band open, where is my signal reaching, how well am I getting out?

I have no doubt we have all pondered the above questions. Are we getting out and if so, to where and how well are we being received?

Relying on someone answering a CQ call is not a very good indication of the above for a multitude of reasons. Some wont reply to a CQ if the already have the DXCC entity on band and mode, others simply don’t feel like chatting others might feel the signal is a bit too weak , so the list goes on…..

Well due to the brilliant work by a few very clever individuals we now don’t have to rely on QSOs to answer these important questions.

This system works like a charm. There are some 50 plus automated skimmer stations placed around the globe that monitor the various frequencies. The automatically decode CQ’s and the call signs and this info is placed on the RBN – Reverse beacon network for us to see in real time.

Looking at the results on the RBN site it is pretty obvious who is getting out well and who is not. You will notice when a big DX’er call he will be spotted immediately by some 10 skimmer stations.

What I find even more exciting is that we now have a means of seeing if are getting out on QRP.

Who needs anyone on the other side to answer the CQs now??

This is a great QRP tool.

Thank you !!

Thursday, 16 June 2011

SOTA Ossewakop ZS/MP-004

I was pleased to find and work the following mountain goats that activated Ossewakop  ZS/MP-004 during a SOTA adventure: Chris ZR6LJK, Willie ZS6WBT, Tom ZS6TMO and Gert ZS6GC.

Sure hope they will provide us with a trip report and some photos.

I see the scientists are predicting that we might be heading towards another “Maunders minimum” What a miserable thought. I sure hope they are wrong. I cannot help, but think trying to second guess the Sun is a waste of time. Maybe the Sun surprises us with a solar maximum that exceeds the 1958 cycle. Now that would be nice?

I have been monitoring 21.060 MHz all day and nothing heard. Scary stuff, maybe my antenna is unplugged?

Tomorrow 17 June is World QRP day. Maybe we get lucky…..

Have Fun !!

Wednesday, 15 June 2011

Europe on 5 Watts a day

There is a pretty good chance that I will be based somewhere in Europe for a month in September or August. I most likely will be based in Leipzig, Germany. I should have rather gone on an earlier tour so that I could be there in the EU Summer.

I cannot tell a lie, one of the major reasons for me  agreeing to go and work there on a short contract, is to explore the amateur bands from an EU perspective. I plan to take my K2 or the tiny HB-1A along. From past experience, I know operating from a hotel room is not worth the effort due to wideband QRM that is ever-present, but I think operating a small portable station might do the trick? I suspect or hope that the QRP activity will be much higher than what we experience here in South Africa.

I wonder what is required to operate from Germany. Do I simply use DL/ZS6A or must I first seek permission from the local authorities? I do have a HAREC certificate. I might end up in Finland, Estonia, Sweden, Poland or Luxembourg and I don’t feel like too much red tape.

Any help with the above will be appreciated.

Antenna testing: On the air evaluation

I found the topic discussed by Mike ZS6BIM on the SARL forum most interesting.

It is a crying shame that the SARL forum will be only available to members of the SARL from next month. Hiding such valuable contributions from the general public (non-members) will be a mistake IMHO.

Monday, 13 June 2011

Half Duplex operation via AO-7

Operating Half Duplex via AO-7 and other linear transponder satellites.

This procedure was developed so that we had a system whereby portable stations that are limited to using half duplex radios such as the FT-817, FT-857 and FT-897 are able to operate on the linear transponder satellites, without having to rely on the use of CAT control and still enabling the use of SSB and or CW.

The procedure has been used on a several occasions and has enabled us to work some rare DX entities via AO-7. The system will work with any satellite with a linear transponder, but the frequencies will obviously have to be adapted to suit.

The procedure:

·    The half duplex station must transmit on a fixed up link frequency of 432.145 MHz at all times (don’t change the up link frequency). Any frequency within the pass band could be used, but 432.145 MHz happens to be in the center of the pass band.

·    It is imperative that half duplex station, call’s “CQ” often and repeatedly, pausing only to tune the down link, listening for replies.

·    The portable station will have to tune from 145.940 to 145.960 listening for replies. The portable half duplex station must actively search for stations replying to his CQ, after contact has been made with the calling station only slight corrections of the down link frequency will be required to correct for Doppler.

·    It might be an idea to announce during the CQ that the station is “half duplex, fixed up link” to alert the other users to the fact that they must track his down link and not the last station as we normally do.

·    All the other stations must find the calling half duplex stations down link and net on that frequency and thereafter remain locked to the half duplex stations down link. The first station to respond to the CQ will also have to give fairly long calls until contact has established thus giving enough time for the half duplex station to find the correct down link, thereafter it should be easy, all stations must follow the half duplex stations down link.

·   “Round Robin” QSO’s are not a good idea, after each exchange, the over must go back to the half duplex station so that he (the half duplex station) controls the frequency.

·    The above procedure can only work if we understand that that all stations must follow and net on the half duplex stations down link frequency.


·    The normal full duplex stations must not make blind calls to raise the half duplex station as this will only create chaos and should be avoided at all times. The half duplex station is relying on a response to his CQ and in turn this will allow all the users to net on the correct frequency (i.e. the down link frequency of the half duplex station). If anyone chooses to ignore this request they will spoil it for all the other stations wishing to work the half duplex station.

We are all very unfamiliar working half duplex. I have no doubt we can improve on the system and identify new pitfalls.

Your comments and feedback will be appreciated.

73, Pierre ZS6A

World QRP Activity Day 2011

The next event is scheduled for 17 June 2011 00:00 to 23:59 utc

Looking at VOACAP it appears we have a good chance to work into Europe on the 15m and higher bands.

With a bit of luck we will hear some increased QRP activity on the bands due to this event. I will be taking part maybe I get lucky and will find and work a few new DXCC entities.

Note that all modes are allowed.

Have Fun !!

Sunday, 12 June 2011

SOTA - South African perspective

I have been monitoring the summits on the air - SOTA watch site for a while now. Unfortunately it seems the choice of frequencies used by the activators in Europe are not very useful for us here in South Africa.

It is great to see that CW is by far the most popular mode during SOTA activations. Who said CW is obsolete?

According to the VOACAP online site we have a fair chance of working into Europe on 15M and above. Most of the SOTA activity takes place on 40M, followed by 30M.

Are there any South African stations taking part in SOTA? If so, please share your info and experiences with us. Use the comment facility below.

73, Pierre

Saturday, 11 June 2011

Hal Lund ZS6WB - Radio Amateur of the year 2011

Last Wednesday I attended the South African Radio Development Trust awards ceremony to collect an award on behalf of Hal ZS6WB.
Hal was awarded the “Garth Milne Technology Award 2011” This was in recognition of his dedication to technology in Amateur Radio and his contribution to the promotion of amateur radio satellite operation in South Africa.
Hal has done much to promote satellite activity in South Africa. 
Hal IMHO is a very worthy recipient of this prestigious award and I am very pleased to see that his efforts have been recognized by the SARDT.
The award function was very well attended and it was great to meet in person some of the voices that I have worked on many prior occasions.
The guest speaker Stafford Masie gave a most interesting and informative talk on developments in the IT industry especially as it pertains to hand held devices (cell phones) etc.

Friday, 10 June 2011

W1JSB QRP tranceiver

Have a look at the following beautifully constructed QRP transceiver. The site also links to a YouTube video showing a QSO between W1JSB and ZS6X using this homebuilt transceiver.

72, Pierre ZS6A

Why have a Blog ?

It seems to me that a Blog site is a very useful system to share information with others.

Information that is placed on the regular discusion forums very soon disappear from the front page and ones contribution is basically lost.

Where it all began:

I became a Radio Amateur (HAM) whilst still in high school in East London. I studied on my own and wrote the class-A license and passed. I taught myself Morse code (CW) and passed the practical 12 WPM Morse proficiency test on the first attempt with the then Radio inspector at the Post Office.

I was licensed as ZS2PW in August 1975. That certainly was a very memorable moment in my life.

ZS2PW My first shack - 1975

36 years later and I am still very involved in this wonderful hobby: Amateur Radio (also known as HAM Radio)

I have had various call trough the years ZS2PW, ZS6BQS, ZS6BB and currently have the following active calls: ZS6A, ZS2AA, C91DD, 7P8/ZS2AA

My main interests at the moment:

Making contacts using very low power (QRP), especially from a simple field station using homebuilt equipment.

I am a big supporter of using CW. I am not very good at it, but hopefully my skills will improve with time.

Weak signal modes and the 6M magic band has captured my interest.

I have had great fun playing with Low Orbit (LEO) Satellites and managed to make some very interesting QSOs via AO-7. I was fortunate enough to share the world best distance via AO-7 for a short while due to a memorable QSO with Josep EA6SA in the Balearic Islands. The distance between us was 7,766 km.

This record was subsequently improved upon by Luciano PY5LF and Joe K3SZH due to a QSO over a distance of 7,843 km.

Enough for now…..

Have Fun !!

73, Pierre ZS6A

Cover page of the South African Radio League (SARL) magazine

My very own Blog site

This is my very first attempt at having my very own Blog site.

I hope to use this Blog to share my amateur radio interest with other like-minded radio amateurs that have the same interests.

Have Fun !!

73 de Pierre ZS6A

My favourite paddle: Begali Signature