The effect of adding radials

The first tests were conducted with a single vertical and the 25 radials which we have always used on 160m so far. Find below the impedance chart:

Now, after adding another 50 35m long radials the impedance on the same vertical looks like this:

The S11 / VSWR curve is sharper (as a proper vertical should look like) and the impedance dropped from 20 Ohm down to 15 Ohm. This means that we reduced the losses by 5 Ohms!

80 radials in place

Below is the simulated (NEC2) impedance curve of our vertical. (17m tall, a 35m long, slooping T-hat and MININEC ground (13mS and epsilon 26)).

The picture above shows the radiator of our 160m array

Above the simulated SWR curve is shown

And finally the simulated impedance is shown as well

Even if the real antenna impedance is likely to be a little bit lower as simulated (14.2 Ohm), I’m happy with the measured 15 Ohms.

Making the Reflector work (or not…)

After having set up correctly the radiator it was time to install the reflector. The reflector was another vertical, 18m tall with an almost horizontal T-hat. At the feedpoint an additional roll inductor was connected between the reflector and ground. The roll inductor (0.5… 15,8µHenry) was used to adjust the reflector for a maximum front / back ratio.

Macbook + DG8SAQ Vector Network Analyzer + Reflectorbox

In order to measure the front / back ratio, we installed a probe (4m tall vertical, terminated with 75Ohm) in a distance of approx. 250m behind the reflector in the field. While transmitting with low power on the vertical (array) I used the DG8SAQ as a Spectrum Analyzer in order to optimize the reflector length for optimum f/b.

The chart above show the result. The green line is the vertical (without reflector) and the black line shows the connected reflector. Unfortunately, the F/B did not exceed 3dB, which is of course very poor.

I’m still struggeling for reasons… Probably the most likely reason is mutual coupling with the 22m tall tower (with a 2el 40m yagi) just behind the reflector.

Coupling between radiator and reflector

Next I measured the coupling between the radiator and the reflector. The chart above shows the feed impedance for the two cases

1. Reflector connected to Ground (red)
2. Reflector not connected (black) -> invisible to radiator

This measurement confirmed that at least some coupling is happening between the two elements. The simulation shows the following SWR and antenna impedance for the array:

The chart above is the SWR curve of the 2el vertical array simulated at the feedpoint of the radiator

And this chart above shows the simulated antenna impedance

Impedance of the reflector

After optimizing for the best front/back ratio, I also measured the impedance of the reflector (while have the radiator disconnected).

The chart above shows the SWR and impedance measured without the roll-inductor. The self resonance of the reflector without roll inductor is located at 1.87 MHz.Unfortunately, the antenna impedance is 25 Ohm, which means that the earth screen of the reflector is still quite lossy.

In the chart above, the roll inductor (2,6µHenry) make the reflector resonant at 1.81 MHz, approximately 20kHz below the radiator.

Conclusions

Unfortunately we couldn’t verify yet the desired antenna performance. It is not clear what is the reason for the low front / back. Two possible reasons could be:

- Too little coupling between the two antennas

- Too much looses on the reflectors ground network. More radials must be installed in order to reduce the losses

- The 23m tall tower behind the reflector is resonant on approx 1.8MHz and distorting the antenna pattern.

… investigations to be continued

In the pictures below, the measurement setup can be seen. I’m using a high precision USB Network Analyzer made by DG8SAQ (90dB dynamic range), a Mini-Circuits BNC Calibration kit and some Mini-circuits attenuators.

A few notes on measuring amplifiers:

• When measuring active components on a network analyzer DC must not be applied at any time at the Network Anlyzer’s input terminals. Just with a few Volts you can brick your (expensive) measurement devices. A good way to be make sure than DC reaches the VNWA’s terminals is to use a coupling capacitor.
• Amplifiers can easily overload your VNWAs input terminals. Caution is needed, especially if the gain is unknown, as in my case. My VNWA allows me to reduce the output power in 0.1 dB steps, therefor I started with -40dBm and added a 20dB attenuator at the receiving port, just to make sure that no overloading will happen.

Measurement setup – Regulated Powersupply (with current limiter), USB Vector Network Analyzer and the W7IUV amplifier

A closer look in the VNWA and the W7IUV Beverage Amplifier

A detailed picture of W7IUV Beverage Pre-Amplifier. Note the 20dB attenuator at the output port

The amplifier shows a satisfactory behaviour. Over the whole shortwave band  (1MHz … 30MHz) the gain (S21) is 20dB, decreasing to approx. 8dB at 100MHz. Also the input impedance (S11) is good from 1 MHz to 30MHz.

In overall I’m happy with the gain and the input impedance. Of course a few other important measurements (e.g. IP3) are missing. Since I don’t have the necessary means to measure the IP3 I’ll accept the amplifier as is. For the contest I’ll put the Amplifier behind a Lowpass / Bandpass filter just to make sure that no unnecessary intermodulation products are generated.

]]> http://www.dh1tw.de/w7iuv-beverage-pre-amp-2n5109/feed 2 _IGP8042 w7iuv Beverage amplifier W7IUV Beverage Preamp Messung DK1NO Beverage Preamp 100MHz http://www.dh1tw.de/w7iuv-beverage-pre-amp-2n5109?utm_source=rss&utm_medium=rss&utm_campaign=w7iuv-beverage-pre-amp-2n5109 http://feedproxy.google.com/~r/dh1tw/Mnut/~3/3rIsSPznu4c/2el-vertical-array-for-160m http://www.dh1tw.de/2el-vertical-array-for-160m#comments Tue, 10 Jan 2012 06:40:18 +0000 Tobias http://www.dh1tw.de/?p=1619 In CQWW 160m we are planning again a serious participation. This time we want to errect a 2el vertical Array for 160m towards the US. In this post you will find some detailes regarding our unique situation and some design thoughts.

ED1R Contesting site

Even while having more space than the average ham, at ED1R we are restricted when it comes to lowband antennas. Our 80m and 160m antennas have to be installed the day before the contest and be removed the night after the contest. Fortunately the friendly neighbors allow us to use their  fields during the weekends. Here is a 3D model of the ED1R contest station. Note the two (brown) areas which mark the fields we can use for our 80m / 160m antennas.

Hight is everything

When it comes to 160m, vertical antennas are hard to beat. During the last year we used sucessfully (subjectively measured) a 15 tall inverted L-Antenna. The L-Antenna is a poor man’s T-Antenna. The reason is because the L-Antenna has a rather significant high angle radiation which is usually not desired. On the other hand, the equally long horizontal wires of a T-antenna cancel effectively the high angle radiation.

On 160m a Lambda/4 radiation is almost 40m tall. This results in an antenna radiation resistance of 36 Ohm. Unfortunately it is impossible for us to errect a 40m tall antenna. The maximum height is defined by our 18m tall Spiderbeam poles. The main problem with verticals lower than Lamdba/4 is that the antenna radiation resistance decreases. With a low antenna impedance it is extremely important to have an excellent ground (radial) net. Otherwise, most of the power will be lost in the earth.

There are several ways to make a 18m tall antenna resonant on 160m. Here are some of the more popular designs:

1. Adding an inductor at the feedpoint
2. Extending the antenna with a horizontal wire (L-antenna)
3. Adding a slooping T-hat
4. Adding a horizontal T-hat

No Pain, no gain

Antenna pattern

Comments welcome

 Read on for pictures, online log & QSL information.

Operation

During my stay I tried to work on all bands from 10m down to 80m. I had great pileups on 15m and 20m from JA and the US. In the evening I enjoyed very much the operation on 80m CW. During the time of the European sunrise (06:00Z – 08:00Z) I worked EU, NA, JA and ZL at the same time!

Online Log & LoTW

Thanks to everyone who gave me a call. The check your callsign in the online log below. The log will soon be submitted to LOTW as well.

QSL Cards

In case you are interested in a QSL card please send it to my address or through the buro via my German Callsign DH1TW.

Pictures

Here are a few pictures of the operation:

Albertos great Station with Monoband antennas from 10m to 160m. Usually the group of HD2A operate from the station. If you hear them the next time, give them a call!

DH1TW operating CW on 80m with a Kenwood TS-450 and a SB-220.

My host Alberto, HC2AQ (right) and me (left)

Disclaimer & WARNING

WARNING! Do not perform ANY work on your amplifier if you are not exactly sure what you are doing. The amplifier is using high voltages up to 3000V which is LETHAL. Touching the wrong part inside the amp can KILL YOU. Again – if you are not absolutely sure, contact RF-concepts or your local dealer. Perform everything which is written here under your own responsibility. It has worked for me, it might work for you, but it might also not work for you. This article claims no professional advice.

AGAIN: With the slightest doubts, please don’t experiment with high voltages. Look for professional help from your next dealer.

The broken amplifier

While I couldn’t figure out the root cause of the tube’s failure, the symptoms where quite obvious.

The most likely theory is that one of the tubes was damaged during the shipment. The broken tube then caused the remaining good tube to overheat and finally burn out during the commissioning tests.

During the comissioning, I noted three strange behaviors of the Alpha91b (across all bands):

1. The tuning peak became extremely sharp; slight readjustments of tune/load would cause the amp to go into error-modus
2. The tuning meter wasn’t really useable; Tuning had to be performed with the max-output indicator; Once max output was reached, the tuning LED would always remain 3-4 LEDs right to the center.
3. Max output was limited to approx. 1000 Watts

Damage Assessment

Initial measurements

Ordering a matched pair of GU74b / 4CX800

Gettering / Conditioning GU74b / 4CX800 tubes

Schematic of Alpha91b power supply board (Heating is directly connecting to J3)

Alpha91b Power supply board without any modifications

Alpha91b Power Supply board with CX5AO method to only apply heating voltage. HV connector is disconnceted!

Alpha91b Power Supply Board - CX5AO method - different view

New Chimney

Applying HV & power

Thanks to…

More resources

1. Google Reader

Say goodbye to the times when Ham Radio magazines were the only way to learn about Amateur radio related topics outside of your local club. Today, there are many Hams publishing high quality articles on their blogs & webpages. However, keeping track on all of them becomes difficult. That’s when Google Reader comes into the game. Google Reader is an aggregator which let’s you monitor activity across websites. Whenever a new article appears on one of your subscribed sites, it will be highlighted in Google Reader.

The Technology behind Google Reader is called RSS (Real Simple Syndiaction). Today almost all websites offer a RSS feed.

Best: It’s absolutely free.

2. Penzu.com

Earlier this year I realized that I had already forgotten the details of experiments and prototypes I made years ago because I didn’t write up anything. At the end of the day, it comes down to writing a diary. You simply have to sit down, invest a few minutes and write up your personal notes. If you don’t do so, your memories will be lost over the years. There are many ways to avoid this. You could write a classic diary with pen & paper, or using any kind of Text editing software.
While I try to publish results on my webpage, I often have personal notes which I don’t want to have in the public domain. I decided to go with Penzu.com. Penzu is an online diary service. It’s easy to use, allows proper tagging (and search) and offers a wide variety of helpful features. Communication with Penzu  is secured by SSL and personal notes are encrypted by AES 256 on their servers.

Penzu is an easy and convenient way  to write a (Ham Radio) diary. The basic version is free and the Pro version costs just 12 USD a year.

3. Dropbox

Dropbox is a remote storage access which connects your computer(s) with the “cloud”. This service allows you to store files in a secure manner in the internet. I’m using Dropbox to sync my folder of Ham Radio related files (PCB design, antenna notes, Microcontroller software, interesting PDFs I came along, etc.) between my computers. Dropbox integrates smoothly with all Computer Operating systems (Windows, MacOS, Linux, Android, iOS…). When I’m abroad I’m using the Dropbox client on the iPad to access the documents. No manual interaction is necessary. Just move your files into the dropbox folder and they will get synced automatically.

Best: the first 2Gbyte of storage are for free.

4. Trello

As soon as more than one person becomes involved in an activity it’s becoming difficult to stay organized. Trello is a flexible and easy way to keep track on tasks. Trello is so flexible that it can be used as a workflow tool or just an assignment tool for tasks. During the preparation of the CQWW CW contest at ED1R we used Trello to organized ourselves. Each team member had access to the Trello board where he/she can comment, change the status or reallocate tasks. Changes are visible to all users instantly.

I’m using trello as a “to-do” list on a daily basis.

Best: The use of Trello is free

5. Google Docs

Online Collaboration has never been so easy. Instead of spamming your friends / colleagues the thousandth copy of a word file through email, it is way more convenient to work on the same document (or speadsheet) in Google docs. Granted that it isn’t as powerful as Microsoft Office, it still provides 98% of the needed functionality. Very neat is the versioning / revision history. With this it is so easy to see who modified which part of the document.

I’m using Google Docs to prepare for example my podcast interviews together with the interviewee or when I’m writing a technical paper togehter colleagues.

Google Docs is also free.

And you?

Which productivity tools are you using on a daily basis? Feel free to share them by leaving a comment!

Ulf, DK5TX created a serious of cool stop motion videos of the antenna work. Unfortunately, including the moment when one of the 17m tall masts came down and damaged the mounted A3S severely.

Fortunately nobody was injured and the A3S still worked, even being a bit deformed.

Making things happen

A part from the two running stations we planned to operate an additional Multiplier station. So during night time, three stations would need to use the same beverages simultaneously. At that point I decided to build up Beverage distributor. My friends Ben, DL6RAI and Ulli, DK4VW from the Bavarian Contest Club published more than a decade ago a great design which has been proven to work during the various Multi/Multi expeditions of the BCC, including the World-Record as CN8WW. All the details were published in a CQ magazine article.

Requirements

1. Six receiving antennas shall be switchable to three stations (40m, 80m, 160m)
2. All three stations shall be able to listen any antenna they want at any time
3. There shall be no influence and restriction between the three stations
4. Remote control and the RF signals shall be done with just one cable

Design & Assembly

Patrick, TK5EP has documented his version of the BCC Beverage distributor on his website and I can highly recommend to follow his design.

Since there were no more PCB designs available I created my own. I used the standard design with a LM3914 but instead of driving each relay with a dedicated transistor I used a ULN2003 darlington array IC. The PCBs were manufactured by OLIMEX in Bulgaria. They have a turn-over time of 3-5 days and the total cost of a double side PCB, incl solder mask and component print is just 30 € (excluding shipping & VAT). The shipment with FedEx took less than 24 hours!!!

The reason why we can listen on the same antennas on 40m, 80m and 160m in parallel is due to the fact of using bandpassfilters for each band. The bandpass filters are designed to have 50 Ohm impedance in their transmission band, but have a high impedance outside of their transmission bands.

Example: Having 50 Ohm in parallel with 50 Ohm has a high impact and result in 25 Ohm. But having 50 Ohm in parallel with 1500 Ohm result in 48,4 Ohm which is rather negligible. That’s why we can connect the three bandpass filter in parallel with almost no influence between them.

The Box itself is still not finished, but we sucessfully burnt it in during the CQWW CW finishing with 15% over the old European M/2 record of RU1A.

Here are some preliminary pictures:

The picture above (click to enlarge) shows the S21 curves of the 40m (blue), 80m (green) and 160m (pink) beverage filter. Measurements where performed with a DG8SAQ Vector Network Analyzer. The bandpass filters have a passband attenuation of approximately 0.5dB – 1.5 dB which is ok since the Beverage itself is a lossy antenna.

The filter plot above (click to enlarge) shows the S11 (blue), S21 (black) and absolute Impedance (pink) of the 160m filter. Note that the 160m has an absolute impedance of 500 Ohm on 3,5MHz and 1600 Ohm on 7 MHz.

The picture above shows the three bandpass filters. For all coils, a stack of three cores (Amidon T68-2 or T68-6) was used. If you want to calculate coils I can warmly recommend the free software MiniRingkern-Calculator published by DL5SWB. I’m using SMA connectors. They are a bit expensive but make it easy to connect to the Network Analyzer.

Last but not least, here are two pictures of the assembly:

Here is another picture of the Beverage switching box in action at ED1R. All we had to do was manually allocating the station’s receiving cable to the appropriate band (through connecting the station’s cable to the appropriate BNC plug).

Each Station has it’s own remote control to select the proper listening antenna. Here are two more pictures:

Since we had only two beverages available they were labeled “EU” and “NA”. Each station had exactly the same control unit. The remaining four (unlabeled) positions of the switch are unused.

The picture above shows the network of resistors which is used to select on of the six beverages through the LM3914 IC in the Beverage switching box. The RF signal is decoupled from the DC signal through a 1nF ceramic capacitor.

Conclusions

The BCC Beverage switching box worked as expected. During the CQWW CW we could significantly increase our score. In total 20% more than the SSB team and 15% above the old European Multi/2 record. The beverage switch worked reliable and has already been considered after one contest as a fix station asset

However some minor rework has to be done. Due to my perfectionism I want to manufacture another stack of PCBs, eliminating a few little design mistakes. I have also forseen some LEDs to indicate which beverage is selected by which station. I expect have the project completed until CQWW 160m contest 2012.

The location

The location was selected very carefully. The station was located in bay on the northern tip of Quatar surround by almost 260º of salt water. Due to the nature of this bay, the water was very shallow and even with stronger winds, there were no waves on the water. From the Gulf region, Europe and the US are the same heading direction which favors a simpler antenna setup.

Antenna setup on the Highbands (10m…40m)

On all highbands (10m…40m) we used a phased array of 2x 2el N6BT Bravo verticals.  These parasitic two element vertical arrays consist of a driven element and another element which can be alternated with a coil & relay to act as a reflector / director. The big advantage of these antennas are their physical dimensions. They can be easily installed by one person. With their two resonant radials no additional radials have to be installed.
The driving element was fed through a W2DU current balun. Driving the antennas with 1,5kW heated up these baluns excessively. After 39 seconds keydown you couldn’t touch them any more. A few seconds later they went into saturation and significantly and worsened the SWR of the antenna.
I’m not sure if these high amount of common mode current is a design problem of the antenna (feeding the antenna not on Lambda/4)  or selecting the wrong kind of ferrite material for the W2DU balun.

Anyhow, the antennas worked great. Supplemented with a W0XB Stackmatch II Plus (enabeling InPhase / Out of Phase) we were able to cover 3 direction with each double pair of verticals.

1. Endfire (Reflector + Driver) towards EU / NA
2. Endfire (Director + Driver) towards VK
3. Broadside (The two vertical arrays out of phase) towards LU/PY and UA

Unfortunately, one of the stack matches was wired wrong and we transmitted the first day on 40m always broadside. The deep null in the antenna pattern towards EU/NA resulted in very little QSOs. Fortunately we found the problem the second day so that we could at least recover a bit.

The only Yagi we had was a A4S connected to the 10m station. Within the same beam direction, the verticals were always louder than the Yagi. However the Yagi became useful in working multipliers which were off the main beam directions of the vertical array.

two N6BT parasitic vertical arrays phased with 0º or 180º with halfwave spacing

15m and 20m N6BT vertical arrays with 80m 4-Square in the background

Sunset: Vertical arrays for 10m, 15m, 20m and 4-Square for 80m

An A4S was used on a crankup tower as the secondary antenna on 10m; located next to the shack

A plastic chairs ensures that the Stackmatch does not get in contact with the water during high tide

Antenna setup on the Lowbands (80m & 160m)

On 80m we set up a classical 4 Square with two elevated radials for each vertical. The antennas were standard aluminium tubes sold be DX Engineering. The 20m tall verticals were phased with a Comtek Coupler enforcing the right current at the feedpoint with a Quaterwave 75 Ohm Transformation line.

160m had another 20m tall aluminium vertical with an L-extension making the antenna resonant on 160m. Two elevated radials were added.

All antennas performed amazingly good. Especially the front/back and front/side of the 80m 4-Square was very impressive.

160m L-Antenna with two elevated radials during sunrise

Receiving antennas

Unfortunately, both – our beverage towards EU and the K9AY loop didn’t work. While having some kind of ground loop noises on the Beverage (unfortunately we couldn’t find the root of the problem in time) the K9AY worked equally in all directions. I’m personally somehow fed up with this antenna now. I´ve already tried severals in different parts of the world with kits of different manufactures and non of them worked properly.

Team building up the K9AY. Shack & 80m 4-Square in the background

The Shack & Infrastructure

The whole operation was splitted into four temporary housings of different sizes. Two were used as shacks, one for sleeping and one as bathroom and kitchen. All of them had were airconditioned which is in Qatar a necessity rather than  luxury. Within the Shacks we used almost on all bands the same setup:

1x FT2000 or FT1000MP MK-V

1x Microham MK2

1x ACOM2000A

The A73A campsite during the CQWW SSB preparations

Main Shack @ A73A with 20m, 40m, 80m and 160m operating positions

A rented power generator provided more than sufficient power

A73A - DH1TW operating 10m in the secondary shack (15m station is in the background)

The operators

A73A Team CQWW SSB 2011 with some German visitors from the A71DLH operation

A73A consisted of a multi national mainly of the GCC states. Here is the list of operators:

1. A71BX, Ali
2. A71CV, Abdulla
3. A71Co, Khalid
4. A71AM, Saif
5. A71AD, Rashid
6. A71EL, Mohammad
7. A41MX, Farid
8. A61ZX, Ibrahim
9. HZ1DG, Abdulrahman
10. 9K2RR, Faisal
11. 9K2HN, Hamad
12. K5GN, Dave
13. DH1TW, Toby

The Contest

Station:  A73A

Class: M/M HP
QTH: Qatar
Operating Time (hrs): 48

Summary:
 Band  QSOs   Zones  Countries
-------------------------------
  160:   340    13       62
   80:  1134    27       92
   40:  1081    27      101
   20:  2280    40      145
   15:  2815    40      147
   10:  3978    40      161
-------------------------------
Total: 11628   187      708  Total Score = 29,229,805

Lessons Learnt

Conclusion

New friends taking the last picture after the disassembly of the station

Pictures have been taken by A71BX, HZ1DG and A41MX

Are you familiar with the following situation: You are watching the latest Hollywood movie with your girlfriend. You could convince here to watch a thriller instead of a romance, which she would have prefered. Over the time, the story evolves good, there is even a notion of romance (to the satisfaction of your girl) but – the movie really sucks when it comes to technical details. Pseudo amateurs hack themselfs within 5 minutes into a SECRET Pentagon’s network and a 5 page emergency report is transmitted with just 20 morse code characters, beaten with a wrench against an old pipe. The longer you watch the movie, the more upset you get about the ignorance and incapacity of Hollywood (film) and book writers…

But – let me tell you – there is one book which really makes the difference!

…and it’s called Daemon.  I believe that the author Daniel Suarez has created a complete new Genre. Best described as a techno-thriller novel.

Suarez has worked for several years as an IT consultant where he gained an intensive background knowledge in distributed computing. While writing this novel he was actually working as a programmer in parallel. This book is so amazing and I promise that it will simply blow you away. From chapter to chapter it is getting better and better. The amount of details, the preciseness about state-of-the-art computer knowledge (Cloud computing, Spyware, distributed systems, sensor integration, databases, financial transactions….etc) is just spectacular…. and it is wrapped into an exciting, explosive story which show implications of privacy, true democracy and social networks on today’s society.

The title of the book is derived from the Unix world where Daemons are processes which work in the background and do work for you.  I would love to tell you more about the story, but I don’t want to spoil the story. Just get a copy of the book and tell me if you could stop reading, once started reading.

The good news is, that Suarez has already finished his second book which is a follow up on Daemon. It’s called Freedom(TM) and just as spectecular as the first one.

BTW – I have already migrated two years ago to digital books. I’m a big fan of Amazon’s kindle. Especially with the release of the latest Kindle device for just 79 USD, Ebook readers are now affordable for anyone. Can’t remember when I bought my last paper back

Enjoy this amazing book!