Kruger Park Satara, Pretoriuskop and Berg en Dal camps

Back from our morning drive near Satara on Saturday morning, I was on 40 meters at lunchtime with a 569 report from Barrie ZS6AJY. Band conditions were definitely down from the evening before. I then checked into the AWA (Antique Wireless Association net) and met Andy ZS6ADY and also a call from ZS6PTA  (Pretoria Radio club), Ray who was looking for points towards the QRP contest.

On Saturday evening we went for a drive towards Orpen Gate. Fantastic! We witnessed two young male giraffe 'necking' in the middle of the road. We watched them tangling with each other for quite some time competing for dominance. Thereafter we returned to camp for an evening braai under the stars. The  piri piri chicken was certainly spicy but went down well with a couple of glasses of red wine....

On Sunday morning we were up bright and early and heading along the S100. There they were! Two massive male lion walked out of the bush just in front of our car and crossed the road.

One of the large male lions crossing the road in front of our car.

We were treated to a wonderful private viewing. We switched off the car engine and watched them walking silently down to the river for a good drink.

At 9:30am I had a QSO with Monk ZS4SF. He was using a vertical half wave. His signal was definitely down (559). But he had worked some PY (Brazil) stations earlier. This is definitely a DX antenna.

We then headed for Pretoriuskop camp about 150 kms to the south, stopping for a pie and ginger beer lunch near Skukuza atop a granite outcrop 'called a dwala where we come from' with a 360 degree spectacular view of the veld.

Pretoriuskop and the surrounding bush has a much different feel to Satara. This being thick bush with fewer game. Ideal Rhino country. We checked into a rondavel with a great view of an open space area looking towards the swimming pool which is built into the side of a granite outcrop. Most picturesque.

My end fed antenna here was excellent. Completely in the clear. A sloper configuration. One end at 20ft and the other at 8ft. The band at 06:15 pm was in good shape with 569 reports received from Barrie, Bruce ZS6BK and Evert ZS6AQW (599). Evert  was using a fb older rig which I believe was a Halicrafters but not completely sure. QRM was high but the band was open for mid-distance 500Km QSO's with no problem.

Lamb Chops Sunday evening. Oh how we will miss South African lamb chops when we return to the USA!

On Monday April 21st I was up early, before the sun, listening to DX. Initially South America and then North America as the sun was rising. By 7 am the band was short enough that I was able to establish excellent contact with Peter ZS1JX in Cape Town (559/QSB), Barrie and Monk. We were surprised that the band was so good so early in the day.

End Fed Half wave wire at Pretoriuskop camp. In the clear and high

After an excellent hearty breakfast of roosterkoek, bacon and eggs at the outdoor bush restaurant I spent some time optimizing my antenna. I was able to get both ends up above 20 ft and completely in the clear. Judging by the 589 reports from Monk ZS4SF, this was a superior antenna. We spent about an hour comparing signal strength's from ZS4SF as he tried different lengths of end fed wire on 40m. The conclusion was that a true half wave of 66ft 4 inches yielded marginally better results when compared to a better balanced 61 ft antenna. This was an interesting set of experiments.

The view from our hut at Pretoriuskop

 At 11 am om Pierre ZS6A gave me a 579 report. It was nice to talk to Pierre again.

After a leisurely time spent swimming and exploring the camp I was QRV at 3pm. QSO's and good signal reports were made with Eddie ZS6BNE who was running 15 Watts, and another round with Monk. Thanks chaps!

Our evening game drive was fully rewarded when we came across two young male elephants fighting for dominance right in the middle of the road. We spent about 30 minutes watching them clash and push against each other in a show of strength. Eventually one of the young elephants stormed off into the bush and started to push over a number of small trees as if to emphasize his superior strength. At one point we were obliged to reverse the car to give then space. Certainly we had never experienced anything like this before.

That evening back at camp I enjoyed my contacts with Eddie, Evert and Monk before a dinner of braaied borewors and a glass (or two) of good red South African wine. Good night...

On Tuesday morning after a relaxed breakfast we set out for our final destination in the south of the park near Malelane Gate. A camp called Berg en Dal. We had about 60 kms to drive. Soon we were amongst a large group of elephant feeding on the lush vegetation.What a pleasure it was to watch these majestic creatures going about their daily routine in their own habitat.

By lunchtime we had arrived at Berg en Dal. Here in this lovely wooded camp we had the pleasure of meeting up with my brother Ed and his wife Linda. We spent an enjoyable few hours catching up on news while we sat in their caravan camp overlooking a large river. 

I deployed my antenna into some nearby trees and reasonably in the clear. Up about 20 ft. and sloping down to 15 ft. I received a good signal report from Monk before we headed out for our evening game drive.

We could not believe it when a young Leopard casually walked out of the bush in front of us and ambled down the road to the drift crossing the river below. What a magnificent sight! We crept down the road to obtain a second glimpse before the leopard was gone. This was the first time Berry and I had seen a leopard in the wild. Memorable indeed.

On returning to camp I had a nice chat with Barrie and Monk at 6pm. Excellent band conditions once again.

After an enjoyable evening with Ed and Linda we crept into bed for our last night in the bush. Hyena could be heard throughout the night calling from somewhere deep in the bush. When would we hear that sound again?

I awoke early on Wednesday, our final morning. It was still pitch dark when I called CQ. To my surprise I was answered by Adrian ZS1TTZ at 05:45am (439). The band was wide open to Cape Town and Welkom! After an enjoyable chat with Adrian and Monk, Ed and I were at the gate by 6 am for another early morning drive. This time we were rewarded by the sight of three Rhino sleeping side by side sardine fashion and a Hyena standing quietly by the side of the road. Surely the litter must have been nearby. 

What a lovely end to a wonderful trip!

Hyena near Berg en Dal

Rhino sleeping 'sardine fashion' at Berg en Dal

Our hut at Pretoriuskop

  

The operating position at Berg en Dal

A kudu bull with a large pair!

Pretoriuskop

The little table is perfect for QRP operations and can easily be moved around

My lovely wife Berry. How can I ever thank her for her tolerance of my hobby :)

QRP Field operations. Lessons learnt from the Kruger trip and many other field trips

Herewith in this blog are some of the practical lessons learnt on the Kruger trip and other field operations during my time in South Africa. These observations pertain to the deployment of a end-fed wire halfwave (#18 awg) and a counterpoise of 8ft 6 inches in length and the use of a tunable tank circuit as the coupler.

These comments relate to a simple operation where the aim is to get on the air easily in order to make local (South Africa wide) contacts and then to take down the system easily and quickly after a day or two of operations. It is assumed that a minimum system has been packed with very limited spares. In my case my whole station plus antenna and accessories easily fitted into a plastic container the size of a shoe box. Refer to my previous blog showing pics of the packed station.

For this type of deployment it is absolutely NOT necessary to try to get the wire up more than 15 - 20 ft in the air. Attempting to get it higher will almost guarantee difficulties in the form of multiple launch attempts, tangled cord and wire, frustration, and if it goes really badly, the loss of the whole antenna system.

1. Be very patient when un-winding the cord and antenna wire. The total length of my 40m system is 66ft of wire with a 60 ft cord attached. If you let this get in a tangle then it can take another 20 minutes to un-tangle it. I wind this up over one hand and turning the wrap around every 10 winds or so to prevent it twisting. This can be easily un-wound by releasing each turn carefully. Once the wire and cord is lying on a nice bare piece of ground, make certain that the coils are laid so that the end of the cord is at the 'top of the pile.' It will then uncoil during the launch without incident. Use slippery plastic cord as found in the hardware store. 
2. Make sure that the end of the wire that will connect to your radio is fixed before launching. Preferably tied to a convenient tree branch about 8ft above the operating position. Here I am assuming that the most likely deployment will be a sloper with one end up at 20ft and the other end up about 8 ft. Trust me it is no fun to watch the whole system end up in the tree. Been there done that!  
3. If an error is made in the launch and you need to retrieve the cord then disconnect the weights before pulling the cord back through the tree. Do this every time and don't take a chance. The weights will hang.
4. Consider a spare set of detachable weights. The chances of hanging in a tree are extremely high. The most likely is a situation where the weight and cord does not drop to the ground after the launch. Now you are forced to retrieve the cord by pulling it back through the tree. Very often the weights will snag in the 'Vee' of a branch joint making it impossible to retrieve. A good strong cord is an asset in this case because heavy pressure can be applied in an effort to try to dislodge the weight.  
5. Spend time and be patient in carefully selecting the tree to launch over. Preferably launch over a tree as opposed to trying to select a specific branch. The tree is much easier to aim for. An ideal launch tree would be about 25 ft high. Select a tree that has smooth branches and few leaves if possible. Do not select an Acacia thorn tree! Optimize the tree selection taking into consideration the fact that you want to be QRV quickly, you want the weight to drop to the ground and you want to be able to easily recover the wire and cord after the operation.
6. 1.3Ah battery easily lasts a week provided it is in good working order. I had many lengthy QSO's during this 5 day trip. This assumes the use of minimum power on 40m. In my experience it is easily possible to make regular QSO's throughout most of the day on +500km path lengths using 1.5Watts output power maximum. Refer to the battery power measurements below.
7. Try to get as much of the antenna up in the air and horizontal to the ground. Ideally both ends at 20ft above ground between two trees. An inverted L with 46 ft horizontal and 20 ft vertical. It is amazing how much this configuration improves the signal strength. This is why I carry two cords. The same set of weights can be used to deploy each cord.
8. Put some plastic putty over the joint between the cord and the antenna wire. This will allow it to glide through the tree easier.
9. When laying the 8ft counterpoise along the ground be sure that it is not a safety hazzard. It is easy for people to trip over this wire.
10. Pack away the radio and accessories each time after use. Leaving it set up is an invitation to the monkeys to pull the counterpoise and to try eating the battery.
11. Take a small portable plastic table. One of those small green ones. They pack easily in the boot and allow the operating position to be set up comfortably under a tree. It can also be moved as the sun position changes.
12. Consider using a length of coax between the radio and the tuner to avoid RFI issues. I certainly experienced RFI/common mode on this trip on one occassion when I had the tuner directly connected to the radio. I believe the end of the wire and tuner were too close to the radio.
13. Build the coupler with a link switch so that you can connect the coax/ground to the counterpoise end of the secondary coil. Sometimes this will improve the match. Sometimes it will cause RFI.
14. Make the coupler tunable with a small variable capacitor. The resonant point can change by up to 30pf depending on deployment conditions.
15. If possible try to get the wire in the clear. However if it has to snake through the tree it will still work fb and no problem.  
16. If possible have a variable power output rig so that when conditions are good you can reduce power and save battery. In South Africa the rig only needs to operate on a single frequency of  7020Khz CW. A simple DC Rx can be used with RIT and an attenuator. BCI is not an issue during daytime operations, however it is an issue during early evening unfortunately.   
17. Always carry a Leatherman of Swiss Army type knife. Preferably with one of those spikes that used to be used to take stones out of horse's hooves. This spike can be used to loosen tight knots. The knife blade is useful for cutting off snake's heads and for general defense.
18. Wear a hat and stay hydrated.
19. Look after the XYL and the kids.
20. Enjoy!

Audio Record by Jan ZS6BMN. Thanks Jan!

Audio Record by ZS6BMN.

Transcript of email received from Jan ZS6BMN.

"Hello Dick,

It was good to hear this morning that you were safely back in Fourways :-)

I have followed your Kruger Park trip/adventure all the way (with atllas and maps too) and it was obvious that you were enjoying the Park, the game and the QRP operation tremendously! Thank you for all the interesting CW operation from the Bush. I cannot recall when last there was such a lot of CW activity on 40m and also never realised how well the band was performing over these medium distances early in the evenings. Your 1.5 W Norcal did a sterling job and has often peaked at S9 on my simple setup with the small indoor whip antenna and TS-140S. Just a great pity that I was without an antenna as I have heard you calling CQ when nobody else was around and you thought that you were not getting out. Still, I have enjoyed listening and must thank you for again for providing such a lot of listening pleasure and for giving QRP operation so much positive exposure! You have even managed to get my old friend Evert to operate 40m after dark :-) BTW: I have listened on the little Rebel to his last QSO with you and then his signal was the first CW signal that could register a reading on that set's stingy S-meter - all of S2, but the reception was great and I could even hear the DX in the background. The Rebel was set up with the single band whip in the dining room while I also had the TS-140S running in the 'shack'.

I have a great recording of your first early evening's operation with Monk, Barrie and Dave all calling in. Later that same evening OM Monk, OM Peter, ZS1JX, and you were calling at different times on the same QRG and just missed each other. At that time OM Monk was putting in the strongest CW signal that I have heard to date and it has sounded like FM with 100% quieting! I have had a lucky break in that the noise was completely gone that day and the S-meter was idling at S1-S2 on background noise.

So all-in-all in the terminology of "1066 and all of that" your enjoyable weekend in the Park has been a 'good thing' for many others as well :-)

73 for now!"

BATTERY AND RIG TEST MEASUREMENTS

MEASUREMENT                            START OF TRIP                     END OF TRIP (after 5 days operations)        
Battery Voltage Radio OFF                   13.01V                                        12.3V

Battery Voltage Radio ON                     12.99V                                        12.22V 

Battery Voltage KEYDOWN                  12.75V                                        11.92V

Current RX                                           19.9mA                                       19.9mA 
Current KEYDOWN                                                                                 190mA
Power Output                                       1.58W                                          1.4W

NOTES: Measurements taken at 7020KHz with Keithley multimeter and AD8307 Power meter using a 36dB attenuator.

Kruger Park Satara Camp

Here we are at the lovely Satara camp. The 569Km drive here from Joburg was quite uneventful in spite of the heavy traffic and packed facilities. This being Easter weekend. Our self catering bungalow is basic but very clean and pleasant. We are in a circle of rondavel huts numbering some 25 with a nice green space in the center with many trees.

Of course I had to deploy my antenna upon arrival. A single launch had the EFHW over  a strong branch about 20ft high. A non-thorn tree! Soon I was QRV using my Norcal 40A at 1.5 Watts. The following in my log:

LOCAL   RST (R)  RST(S)    CALL
17:08         599         599        ZS4SF  Monk in Welkom indicating some QRM but a FB signal
17:20         599         599        ZS6AZP  Dave in Centurion indicating rising QRM
17:30         549         599        ZS6AJY   Barrie in Benoni / QRM

The band was definitely going long and an hour later I was unable to make a QSO as I heard european stations coming in. The reports received were very satisfying, convincing me that the system was working ok.

After a delicious braai of short ribs and salad we retired for a good night's sleep.

LION SPOTTED!
This morning we were up bright and early before sunup and joining the queue of vehicles waiting for the gates to open at 6am. We headed for the famous S100 road where there are purported to be a large pride of lions in residence. Yes we were lucky! Right there walking alongside the road were a beautiful lion and lioness. This was certainly the highlight of the morning for us. What a memorable sight to behold in the golden morning sunlight.

We stopped at a nice picnic spot where we rented a 'skottle' with which to cook our breakfast consisting of eggs. tomato, fried banana and tea.

What a great start to our Kruger trip..

Picnic spot near Satara camp and overlooking Mozambique

Kruger Park Easter April 17th - 23rd

This coming weekend we are excited to be going to the Kruger Park.

We will be in the park from the afternoon of Friday April 18th through the morning of Wednesday 23rd. We will stay in self catering accommodation at Satara, Pretoriuskop and Berg en Dal. This should be fun!

I am taking along my QRP 40m station as stored in a plastic food container, including my end fed halfwave system. I do hope that I will be able to make a few CW QSO's with my CW friends.

Thank you in advance for trying to work ZS6RSH.

I will take my laptop along and thus I plan to post blogs covering our experiences at the park.

Details of my working conditions as follows:

OPERATOR: ZS6RSH

QTH's:      April 18th evening - April 20th morning SITARA

                 April 20th afternoon - April 22nd morning  PRETORIUSKOP

                 April 22nd afternoon - April 23rd Morning BERG EN DAL

OPERATING TIMES  Noon 12:00-1:30,  Early evening 18:15-19:00, Other casual times.

QRG: 7020KHz

MODE: CW

RIG: NORCAL 40A, 1.53 Watts

ANTENNA SYSTEM: End Fed Half Wave (66' 4") + Tank coupler + 8" 6" Counterpoise

PADDLES: Palm field model

POWER: 12V, 1.3Ah SLA, Car Battery power as backup

------------------------
List of Equipment:

1. Plastic Food storage container
2. Norcal 40 A, 1.53 Watts output, QRP, 40m Rig. 
3. Granadila Tin homebrew end fed half wave coupler
4. LED SWR Meter
5. Palm Paddles
6. 66ft 4inches, #16 AWG, 40m Halfwave antenna, with launch cord attached.
7. 8ft 6inch Counterpoise
8. Launch cord with 3 fishing weights attached
9. Spare cord (20ft)
10. 2 X BNC barrel connectors
11. SLA Battery, 12V, 1.3Ah
12. SLA power cable and 2A fuse
13. Car Battery extension power cable
14. 2 X 2A fuses
15. Keyline
16. Earphones
17. Leatherman
18. Mini Multimeter, Radio Shack
19. Plastic tuning screw driver
20. Pen
21. Paper
22. Operator ZS6RSH 

Some interesting links:

Kruger Game Park.  http://www.krugerpark.com/

Satara Camp http://www.krugerpark.com/self-catering/satara-restcamp/
           GPS :-24.3976800 (latitude), 31.7777800 (longitude)

Pretoriuskop Camp http://www.krugerpark.com/self-catering/pretoriuskop-restcamp/
           GPS: -25.1722 (latitude), 31.2692 (longitude)

Berg En Dal Camp http://www.krugerpark.com/self-catering/berg-en-dal-restcamp/  
           GPS: -25.4200(latitude), 31.4512 (longitude)

End Fed Halfwave SWR test

In preparation for our up coming trip to Kruger National Park over the Easter weekend, I performed some more tests on my EFHW Granadilla tin tuner to see if I could improve the SWR from the previously measured 1.7:1. The plan for this trip is to take along the Norcal 40A 2Watt 40m rig with a minimalist station with all station components stored in a plastic food container. The 40 A was used for these tests.

Based on further reading on the EFHW I removed the grounded link between the secondary and link turns. This to reduce the chances of common mode RF flowing along the coax cable. The BNC connector was replaced with an insulated version.

I depoyed the EFHW just behind our apartment in the park area with an 8.5ft counterpoise lying under the antenna. I found that 3 Turns on the primary is ideal and results in a perfect 1:1 match. The Tx was connected via a 1 foot coax to the LED SWR meter which was connected to the tuner via a barrel connector.

Interestingly the tuner tuned to resonance indicating some capacitive reactance (about 13pF) at the wire feed point. After reducing the length of the wire by about 2 feet no change in the feed point reactance was noted. Could this reactance be predominantly the effects of stray capacitance? The tuner may exhibit less capacitive reactance if housed in a wood or plastic enclosure as opposed to the steel food tin?

Reports received from Monk ZS4SF were 549 at 1:15pm. The antenna was deployed as an almost horizontal wire about 10 feet - 8 feet above the ground.

The end of the antenna was then raised to about 20 feet and sloping down to about 8 feet to a branch above the operating position. Now I received a consistent 559 report from ZS4SF clearly showing the benefit of height.

Many thanks to ZS4SF for hanging in there as usual during this field test.

Tuner & counterpoise efficiency tests using an RF Current sensor

The objective of these tests was to try to determine:

 1) The most efficient combination of tuner and counterpoise that will produce greatest RF current in a half wave, end-fed, field deployed, 40m, antenna. 

2) Determine the best combination based on received signal reports by ZS4SF based in Welkom. 

3) Determine the difference in signal strength between the best and worse case.

PROCEDURE: refer to the attached detailed schematic and pictures showing:

1) Test configuration.

2) Local conditions at the test site

3) Receiving station ZS4SF details

4) The 3 tuner details

5) The test results

GENERAL CONCLUSIONS

1) The combination of the 'Granadilla' tuner and 17ft counterpoise produced the best 'stable' result showing a marginal single S point improvement of 569 over the average signal reports of 559 using 2 Watts transmitter output.

2) The combination in 1) above also showed good consistent output on the RF current meter although the combination of the Granadilla tuner and 8.5Ft counterpoise showed a higher RF current, however the setup was unstable and variable.

3) The Z Match showed the worst performance of the 3 tuners with all 3 counterpoises. The DC meter sensitivity control had to be increased in order to obtain an RF current report. However 559 and 549 signal reports were still received.

  

KEY CONCLUSION

1) Based on the signal reports from ZS4SF there was a marginal difference of  less than 1 'S' point (estimate 4dB) between the best and average cases. Indicating that all combinations are acceptable for real field deployments.

OBSERVATIONS

1) It was difficult in a real field deployment to get a consistent RF current measurement with the output varying depending on proximity effects. 

2) None of the combinations were completely stable indicating that tweeking is required to reduce the ground currents and to obtain a resonant antenna with minimum reactance present. (difficult to achieve in the field).

PROXIMITY AFFECTS

1) Upon terminating the Granadilla tuner on the bench with a 4.7K resistor after the field tests, it was determined that the resonant frequency was at 7.487MHz. This is 7.487 - 7.020 =  467KHz difference. Assuming the tank circuit inductor is fixed at 4uH, this reveals a capacitive contribution of 16pF from the antenna/counterpoise system contribution. If this contribution came entirely from the antenna wire then the effective antenna length can be calculated as 71.4ft (as opposed to 66.66ft actual length).  This seems to be a big difference in length and may explain why the system was unstable during the tests.

GRANADILLA TUNER ADVANTAGE

The Granadilla tuner has two key differences when compared to the Altoids tuner. It uses an Air variable panel mounted, screw driver adjustable, 30pF capacitor, in parallel with a 10pF silver mica capacitor with a 500V rating. The Altoids tuner uses a 150pF polyvaricon capacitor. Both tuners use the same T-50-2 inductor. The Z Match utilizes two polyvaricon capacitors. Could it be the polyvaricon capacitors that exhibit losses in this environment. 

Assuming a radiation resistance of 3000Ohms and 2 watts, the peak-to-peak voltage across the tank circuit = SQUAREROOT( 8 X P X R)  = SQUAREROOT(8X2X3000) = 219Volts. Does this voltage stress the polyvaricon capacitors?

This was a fun project and very instructive! My thanks to my friend OM Monk in Welkom ZS4SF for hanging in there and providing 12 signal reports. Thanks Monk! 73.

Z Match, Granadilla Tuner, Altoids Tuner

View of the RF current sensor connected to a sensitive DC analog meter (0-1mA)

View of Antenna, Cedar Lakes upper picnic table, Fourways, Gauteng, South Africa 

Granadilla in South Africa is known as passion fruit in the USA. Yummy!

The 7020Khz capacitor pure resistive position terminated in a 4.7K resistor. Antenna reaction is tuned out in the field.

QRV in Morrisville North Carolina as N4HAY

During our stay in our home QTH of Morrisville, NC (near Raleigh NC) where we are enjoying time with the kids,we camped out in our home for a few days. Of course I had to get on the air.

My challenge was the fact that I had access to only a limited amount of gear. I had a Sprint ATS III. This is a 2Watt transceiver built into an altoids tin and optimized for the Spartan Sprint. I remember winning 3rd place in this contest with this rig. This rig is all SMT and gave me excellent SMT soldering practice back a few years ago. This kit was built by Steve Weber KD1JV  http://kd1jv.qrpradio.com, check out Steve's website. The rig has all the bells and whistles and is fully microprocessor controlled.

I also had a QRP Balanced Line Tuner (BLT) from Doug Hendrick's QRP kits http://www.qrpkits.com.

Since I had my desk in a bedroom on the 2nd floor looking out to our beautiful garden it made sense for me to consider a 40m end-fed halfwave wire. In the garden there is an extremely high pine tree with a branch up at about 55ft agl. I could construct an inverted L type wire with the end terminated at the bedroom window.

I had, on hand, a T68-2 toroid core, some magnet wire, a 100 pf trimmer capacitor, a piece of scrap PC board, a short piece of RG174 and a 7 foot piece of 300 ohm ladder line. I didn't have a separate SWR meter or any way to measure SWR other than the built-in SWR meter that is integrated into the BLT. This LED SWR indicator is the one developed by Dan Tayloe N7VE.

I had a plan. The half wave wire would connect to a parallel tuned circuit. I could then link to the circuit with a balanced link coil wound to match to the 300 ohm ladder line. The ladder line would then connect the BLT sitting on my desk to the tuned circuit. Based on my previous experience I would need a 6ft 6inch counterpoise wire strung along the bedroom floor.

I assumed that the more inductance I could get from the toroid the better, since this would assist in improving mutual coupling efficiency. I am not sure if this thinking is correct? The greater turns would also reduce the Q of the resonator. A number of factors to consider here. (I really need to do some experiments in this area to better understand it). I calculated that 30 turns would result in a need for 99pf of capacitance in order to resonate the parallel circuit within the 40 m CW band at 7.030KHz. I had a 100pf trimmer. I had a plan that would work in theory at least.

The solution came together as follows. I built the resonator on the scrap piece of PCB and taped it to the window sill. A counterpoise was run along the wall and taped in place. Using my slingshot I was able to deploy the half wave wire from a branch about 55ft in the air. I then connected the resonator to the BLT via the 300 ohm ladder line.

The following procedure was used to align the system. I first connected 3x100 ohm series connected 1/4 Watt resistors to the output of the BLT. I then quickly tuned the BLT to indicate an SWR of  1:1 as indicated by the LED being extinguished. Yes the resistors did get hot! One very good feature of the Dan Tayloe circuit is the fact that it terminates the transmitter in a 50 Ohm load when in the 'Tune' position. I then moved the 300 ohm load to the far end of the 300 ohm ladderline and confirmed a 1:1 match. I now connected the ladder line directly to the coupler and was able to obtain a 1:1 match directly into the antenna system. I was pleased to see that the trimmer was almost fully meshed which lined up with my calculations.

We were only in our house for a short time but I did manage to make a number of good QSO's including one DX QSO with F6FTI om Pierre near Abbeville France around midnight. Pierre gave me a 549 report. Great! I also QSOed with K5TF, AA1PL, WA4SQQ, W8RT & KC2QKU.

It would have been interesting to experiment with different settings of the BLT and the coupler. I wanted to see if I could connect the BLT (which is a Z match) directly to the halfwave. This would require that one side of the balanced input be connected to the counterpoise.

Dullstroom N Drakensberg

We were invited by our friends to accompany them to their fishing syndicate near Dullstroom. Great fun was had by all including an opportunity to try out hand at some fly fishing in the beautiful Lunsklip river. We also enjoyed some walks in the vicinity including a visit to a waterfall where the Lunsklip cascades down the escarpment to the valley below.

I deployed my usual field station including my K2. I was able to erect my EFHW from the farm house verandah to some eucalyptus trees. The wire was in the clear and up about 25ft in the center.

Condx on 40m were not as good as they have been. I received mainly 559 reports except from ZS6JBJ OM John in Witbank. I was able to copy all stations on the AWA net including the two ZS5 stations. All 599+.  I also had three SSB QSO's  including ZS4SF and ZS6AJY which was most enjoyable as a change.

Lunsklip river

Pete and Berry

Looking down at least 1000ft at the escarpment far below

Farmhouse. Over 100yrs old. Ghosts there were!

EFHW Measurements coupler comparisons

I wanted to compare my T-50-2 coupler with my T-200-2 coupler. The measurements did not line up with what I had measured previously.

Antenna:  66ft 8inch wire in my garden. Vertical approx 20ft. Horizontal approx 38ft. Other end hanging down 8ft.

Resonant frequency: 7020Khz

Coupler 1:  T-50-2. 28:3 turns. Impedance ratio 10:1 (50*100=5000ohms). Resonated with a variable capacitor.

• Counterpoise 1: 6ft 8inches.  SWR 1:1. 2:1 BW to 7.1Khz. (0.06wavelength)
• Counterpoise 2: 23ft 1inch.   SWR 1:1  2:1 BW to 7.1Khz  (0.17wavelength)

Coupler 2: T-200-2  18:2 turns. Impedance ratio 9:1 (50*81-4050ohms). Resonated with a length of coax.

• Counterpoise 1: 6ft 8inches SWR 1:1. 2:1 BW at 7.080Khz (0.06 wavelength)
• Counterpoise 2: 23ft 1inch   SWR 1.8:1. (could not achieve a good match)

In both cases the most stable system was achieved with the short counterpoise.

Both systems exhibited roughly the same bandwidth. (this is different to what I have seen in the past where the longer counterpoise resulted in a wider bandwidth??) 

NOTE: In the case of the T-50-2 the secondary was tied to the primary at the cold end.

Calculated inductance for Coupler 1. ~ 1.8 uH

Calculated inductance for Coupler 2 ~ 4.0uH

Capacitance to resonate Coupler 1. ~ 285pf

Capacitance to resonate Coupler 1. ~ 128pf

Coupler 1  Xc = 79ohms = Xl  (Q= 5000/79 = 63. not sure if this the correct calc?)

Coupler 2 Xc = 177ohms =Xl (Q= 4050/177 = 22. )

However the problem with the above calc is that the input impedance to the antenna/counterpoise must change with different length counterpoises?? See fig3 of the AA5TB efhw writeup.

More to think about here? No wonder this antenna is not well understood!

ZS4SF field EFHW and coupler adjustments

Om Monk sent me this email of his adjustments for his field coupler for his EFHW. Included here per kind permission of ZS4SF.

Howdy Dick,
here is how I tuned the antenna.
Used  T68-2  toroid.   20  Turns  for  the  secondary, 3 Turns for the
primary. Connected a variable cap across the secondary.
Adjusted  swr  to  1.2  to 1, removed the cap and measured it,, 130Pf.
Installed  fixed  cap  of  130Pf and tested. Swr high.Tried small caps
across  but  could  not  find a match. Connected 6" of coax across and
tuned to 1.2 to 1.

Started spacing the coils on the core till 1 to 1.
Pushed  everything  into  the film can. Swr now 1.5 to 1. Removed from
can  and  got  Swr back down. Rub glue over core and wait to dry. Back
into  can  and  again  swr  high  (  1.4  to 1 ) Have a look see where
resonant point is ( 6. 9 Mhz ) Antenna too long, cut abt 5" off and swr
at 7020 now 1 to 1.

Bandwidth is as follows: 7000 to 7065 1.1 to 1
7065 to 7130 rises up to 1.5 to 1
7130 to 7200 rises up to 2 to 1
This is good enough for me so left as is.

Points to note:
Spacing the windings is sensitive,
Stray capacitance a factor to consider
It is better to leave a short piece of coax across the secondary so as
to fine tune at a later stage.
QRP Antenna now ready for field work  Hi!

73
Monk
PS   Antenna length to start with  66 feet 8"
I found that the antenna could be tuned with 27 turns on the secondary
but  knowing  that more inductance and less capacitance makes for less
bandwith.  i am sure that 1 to 2 turns can still come off but as i was
satisfied with the bandwidth I left as is.
.5mm formex wire for secondary and 1mm pvc insulated wire for primary.
CU on the air.

Film can cannister open and showing the fixed cap and coax  variable capacitor

Sealed coupler ready for field deployment. How neat is that!

Follow up information received from Monk:

Hello Dick,
Top  of  the can too weak for my liking, changed to plastic water pipe
with  end  blanks.  Some  what  larger but more robust. Attach rope to
middle section and hoist up, ant horizontal.
Bandwidth  now changed,7000 Mhz to 7080 1.1 to 1 : 7080 to 7110 1.5 to
1. I am happy, don't need higher,no ssb on planned antenna.

Manyane Campsite Pilanesberg National Park

We had the usual great time at Manyane this past weekend where we hooked up with our friends Tony and Pat. They have a great camping trailer and we enjoyed  a number of excellent meals and a good social time there. The weather is still quite decent and mild so no problem staying warm.

From a field radio perspective, this was also a good fun learning experience. The sun spot number was reportedly over 200 which I believe is for the first time this cycle (I am not certain about that). The conditions were thus a bit different on 40meters.

I took along my prototype T-200-2 coupler (see pics below) and was able to preform extensive tests with ZS4SF, my friend Monk in Welkom. Path distance would be an  estimated 400-500Kms?  On Saturday morning I deployed both the 31 ft quarterwave counterpoise along the ground and a .05 wavelength 6ft 6 inch counterpoise. My EFHW was higher than usual. The horizontal part was about 45ft long and at a height of about 20ft. The last 20ft sloped down to my operating position. The band was a bit unstable and thus QSB did play a part. The 31ft was receiving very slightly better reports than the 6ft 6inch counterpoise but the results really were very similar. The only difference was the same as I had seen at home and in my previous park deployment and that was a significant difference in bandwidth.

I was very pleased to note that I had no problems loading up the efhw and achieving 1:1 SWR with both counterpoises. No problem at all.

On the Saturday AWA net I received lower signal reports than usual. Mostly 579 and using 5 watts. I don't know why this was? It could be that the antenna was a bit too high for NVIS work? Or the high sunspot number was affecting propagation? A station from CapeTown om Adrian did call into the net and I copied 549. However he was unable to copy me. He was able to copy the Joburg stations but down in the noise.

On Saturday afternoon I erected a 10m dipole at 25ft and was able to copy quite a few DX stations. The band was mainly open to the west and this was the direction that my dipole was deployed. I managed to work one station in India on SSB. I was running about 8 watts. He gave me a satisfying 57 report.

This was also the first time I got to try out my new efhw with the launch cord connected directly. I smoothed over the joint with plastic steel. This makes it easy for the system to slide through the branches. I need to get one more length of the smooth light cord since this slides over the branches so much easier than the thicker cord. The only negative is that if a knot is pulled tight it is much more difficult to undo the knot with the thin cord. I am not sure how to improve this factor.

I also tried out my new modular dipole system. I took only a single center connector/hub. Then I was able to change the dipole lengths accordingly by screwing the different quarterwave lengths into the chocolate strip using my leatherman knife. I found this time consuming and a pain. Give me a doublet any day!

Observations and future actions.

1. The efhw fixed component doubler definitely works in the field without having to tweek it. Next adjust the smaller T-50-2 coupler using fixed components.
2. The quarterwave counterpoise results in greater bandwidth than the 0.05 wavelength counterpoise, however the performance on the air is the same.
3. An efhw deployed higher does not appear to really improve local (NVIS) communications when compared to a 10-15ft high configuration.
4. The new fishing weight launcher is pure pleasure to use and I cannot think of any way to further optimize it. This launcher can be easily tied to any cord using a reef knot at about 3 ft length.
5. The modular dipole system using a single hub to reduce weight is time consuming to erect. Consider using a single wire that is marked for resonance on each band and that is simply rolled onto two shuttles at each end. This system I remember was used in the old days by the Rhodesian Army Signal corp with good success although it is heavy.
6. A coil of wire at the end of a counterpoise does not materially affect the length of the counterpoise. Uncoiling a wire to different lengths and leaving the remainder as a coil at the end makes sense.

I still don't have a good method to sucure the inverted L at the 'knee' point. This trip I tied a knot in the efhw. This came under some strain and I noticed that the pvc insulation had been slightly damaged. How can I solve this problem in future?

My Field gear for this trip. 

Click on pic to enlarge.

Top Left:

1. ~ Quarterwave counterpoise for 40m. 31ft in length.
2. ~ 0.06 wavelength counterpoise for 40m. Approx 6ft 6inches.
3. Four lengths of 20meter slippery cord including the fishing weight antenna launcher.
4. Leatherman.
5. Microphone for the K2.
6. Cable for connecting to the CW Paddles.
7. CW paddles folded away. Palm Mini paddles from Morse Express.
8. Altoids tin variable QRP coupler for EFHW antennas
9. RG58 coax. About 20meters.

Center Left:

1. Short coax connector  for coupler connection.
2. Earplugs.
3. Diploe center hub with 40m dipole connected.
4. Quarterwave wires for 20m, 15m and 10m. Can be attached to the diplole center hub using choc strips.
5. 12V battery cable for backup connection to car battery. (never been needed yet).
6. A bag of different BNC and PL259 type connectors

Bottom Left:

1. Pen.
2. Small notebook.
3. Box with prototype T-200-2 coupler
4. Elecraft K2 full featured Kit Transceiver.
5. K2 custom built carrying case.
6. Small backpack for all the gear in this pic (except the K2)

  

Only in South Africa will you see cooking camp ware like this :)

Tony doing his thing. This is a serious breakfast buddy!

Prototype high power efhw coupler using a T-200-2 Toroid and 115 pf coax capacitor.

Berry, Pat and Tony alongside the camping trailer. Superb!

Pilanesberg National park. Click to enlarge.

EFHW Experiments continued

Further to my EFHW experiments. 

I have now performed some measurements on my system as follows:

Fres = 7020Khz

Toroid = T-200-2

Capacitor = RG58 cable ~ 115pf

1) Primary link turns = 3.5

1.5:1 Counterpoise length = 31ft (I could not get the SWR down below 1.5:1)

Fmax at 2:1 = 7.24MHz

Bandwidth = 220*2=440Khz

2) Primary link turns = 2.5

(Turns ratio = 18/2.5 = 7.2:1. Impedance = 50*7.2*7.2=2592ohms)

1:1 SWR Counterpoise length = 31ft 

Fmax at 2:1 = 7.15Mhz

Bandwidth = 130*2 = 260Khz

3) Primary link turns = 1.5   

(Turns ratio = 18/1.5 = 12:1. Impedance = 50*144 = 7200ohms.)

1:1 SWR Counterpoise length = 5ft

Fmax at 2:1 = 7.090Khz

Bandwidth = 70*2 = 140Khz

If you have a short counterpoise the bandwidth drops, and the input impedance rises.

Why?