Sunday, June 23, 2013

10M Ringo Ranger Antenna and 1:1 Choke Balun

I recently added a 10M Ringo Ranger vertical antenna to my small collection of antennas. I don't have room for a small beam of any sort so I must resort to simple dipoles or verticals.


This picture shows the base of the antenna, the rest of it above is just a plain old boring length of aluminum tube ;)

I have a multiband dipole which works well on 10M but feeling that there was room for improvement and being a fan of verticals, I splurged and put up a 10M Ringo Ranger.

The Ringo Ranger designs have been around for a long time with basic Ringo being a design by W1BX. This antenna design is available for 10, 6, 2, and 440 HAM bands and also commerical bands and was also used below 10M for CB and other uses.

The 10M Ringo Ranger is basically a half wave end fed antenna where the circular ring is an inductor and a coax tuning stub is a capacitor which provide the matching circuit for the feedline to the antenna.

For some time I have been putting a 1:1 choke balun at the feedpoint of my antennas as well as in the shack. These are relatively simple and inexpensive to make and this time rather than winding parallel wires around a ferrite core I decided to try coax. In this case I used RG-142 of 10 turns around a dual FT240-31 core wrapped with glass fiber tape and with type N connectors on either end. The type N connectors are crimp on style and all together made for a simple easy to make and assemble choke balun. This was all mounted in a Carlon 4x4x2 junction box. This in turn was mounted to an aluminum plate which in turn was attached to the supporting pipe with U bolts. the picture below was taken just before I tidied up the windings a bit more and screwed the cover on.

The ferrite cores where purchased from "the Toroid King" W8DIZ through is online shop: Kits and Parts


I used my I2TZK designed SWR analyzer to sweep the choke. The plot is below. This shows SWR from MF through 30+ Mhz. The red line is the choke and the purple line is my 50 ohm reference.


I still haven't figured out a good way to use the SWR analyzer for testing common mode rejection yet, but I am still experimenting.

 Every good antenna installation requires good attention to detail. For every antenna project I put together I religiously use stainless steel hardware and a product called Penetrox (do a search, you will find many links) and good practice for sealing all feedline connections.

Penetrox is described as fine zinc particles in a petroleum base and is used to prevent oxidation of metal to metal connections and joints. Use it on the antenna's tube to tube joints and electrical connections. Many use a silicone grease in an attempt to waterproof PL-259 connections but instead I use just a wee dab on the threads to prevent seizing.

For sealing PL-259/SO-239 or Type N or whatever feedline connections I used to use a product similar to Coax-Seal. Coax-Seal is a self amalgamating rubber tape that when stretched and wrapped around your connector and coax would provide a good weather and water proof seal. The finishing touch was to wrap the outside with black electricians tape - bottom up - so as to provide a path for water to run off.

I used that technique for many years but just recently have switched to 4:1 shrink double wall with adhesive  3/4" heat shrink tubing. A 3" length will cover any connection and once shrunk into place will provide a weather and waterproof cover as good or better than anything else. The 3/4" is a tight slip over type N fittings but easily fits over PL-259's and will shrink just right for RG-8X (mini RG-8) cable.

cheers, Graham VE3GTC



Saturday, March 9, 2013

672,222 Miles per Watt

In my continued adventures in QRPp QRSS and after my earlier success of having my signal copied in Florida on Bill's W4HBK Pensacola Snapper while transmitting a BIG signal of 3.6 mW (yes milli Watt), I further reduced my power level by 3dB to 1.8mW.

Tests were run for two evenings and my signal was successfully seen on the Pensacola Snapper once more. These being on the evenings of 2013-03-06 and 2013-03-07 Eastern Standard Time.

The distance between Bill's location and mine is approximately 1210 miles so that makes it 336,111 miles per watt at 3.6mW and 672,222 miles per watt at 1.8mW!






10 minute grab kindly provided by W4HBK.

The time of the 10 minute grab is 2013-03-08 02:30 UTC which is 2013-03-07 21:30 Eastern Standard Time, my local time. My ident can be clearly seen around 10140030 in amongst all the other signals that night starting precisely at 02:21 UTC.

Next up is to try 40 meters.

cheers, Graham ve3gtc

Wednesday, March 6, 2013

Hold the presses!

In my last posting I reported on my QRPp QRSS signal being copied in Florida for a miles per watt of 77,778. This all based on my calculated transmit power being 14.4 mW and the distance between me and Bill's Pensacola Snapper of 1120 miles.

Well, it seems that for some reason I couldn't keep Vpeak versus Vp-p (peak to peak) clear in my head and I mis-applied a value in my calculations.

I measured the output of my MEPT at 1.2 Vp-p using an oscilloscope.

Now, Vpeak = Vp-p / 2 and Vrms = Vpeak * 0.707 or Vp-p * 0.3535

The formula I was using to calculate power is:

Power (W) = Vpeak Squared / 2 x R  where in this case R = 50 ohm

Plugging 1.2Vp-p into the above formulas first to get Vpeak and then Power, I calculate not 14.4 mW but rather 3.6mW - a whole 6dB less!

That makes the 1120 miles to Bill's Pensacola Snapper using 3.6mW a miles per watt value of 311,111! Still not a record but pretty impressive in it's own right.

And to show that it was not one time thing, I noted again this morning right around local sunrise that my signal was clearly being seen on Bill's grabber.


The error in my math was kindly pointed out by John VK6JY which prompted me to give me head a shake to clear out some cob webs, and to do some reviewing of AC theory.

cheers es 73, Graham ve3gtc

Tuesday, March 5, 2013

More Adventures in QRSS

I recently posted about some testing I have been doing using one of N3ZI's DDS VFO's as an RF source for a QRSS MEPT.

I put my MEPT on 30 meters last evening using a W8DIZ RF amp and 30 meter bandpass filter as a quick and dirty power amp for the DDS VFO.

My measured output into a 50 ohm load is 1.2 Volts peak to peak.

Calculating power is Power (in watts) = Vp-p Squared / 100 which in this case give a BIG 14.4 mW  - yes, that is 14.4 milli watts!

I checked Bill's W4HBK Pensacola Snapper QRSS Grabber for my signal and there it was, clear as day right around 04:00 UTC on 10140035 hz.






Now, working that out to miles per watt where Bill is 1120 miles from my location makes that 77,778 miles per watt. Now that is no world record by any means but it is pretty impressive in it's own right.

Testing continues and I will check Bill's and a few other 30m grabbers for more results over night. I have as previously reported had a 30m signal copied in New Zealand but that was in comparison a much more powerful signal of about 250 mW!

cheers, Graham ve3gtc

Wednesday, February 27, 2013

The Continuing Adventures of QRSS

Recently I have been experimenting with one of N3ZI's DDS VFO kits as a RF source for my 2G QRSS MEPT.


Doug is great to deal with and has been making nice small kits like this for some time. You can purchase directly from his web site or from his listings on eBay.

W4HBK and NU7Z have both written about their use of Doug's DDS VFO as a QRSS MEPT RF source.


My attraction to Doug's DDS was it's relative simplicity, single package completeness, it's ability to be controlled via RS-232 and the good reviews I have read about. The kit was an easy build and does work quite well. I added a crystal oven controller to help maintain the temperature and hopefully the frequency of the DDS's crystal oscillator.



The oven controller is mounted over the crystal oscillator on the left side of the board, the three wires connected top and just right of center go to my Arduino NTP synced MEPT controller (still in prototype on breadboard), black and red wires are 5 V power for the DDS separate from the Arduino's power, and the small wire connected to the top left corner is a make shift very short and inefficient antenna so that I can run the DDS and test it's stability and keying, monitor it on my radio and QRSS grabber and monitor other QRSS activity on whatever frequency I want to test. One of the BIG advantages to something like the DDS MEPT RF source is the ability to quickly and easily change frequencies - up or down slightly and bands. 

My impression of Doug's DDS VFO. Well made and packaged kit, a wee bit pricey in respect to similar devices that can be found but not overly so or off putting. Where it really shines is in the firmware which controls the features and it shows in the tuning with the encoder and switches.

But there is a bit of trouble in paradise and it is no fault of the DDS VFO that I can tell. 

For the most part, the device operates very nicely and the RF out is consistent and relatively stable. I did notice at first that it did wander. This was before I added the crystal oven controller. My first observation was that it was considerably more stable by the simple act of resting on top a largish type N to BNC adapter. This added considerable thermal mass with respect to the 8 pin DIP size crystal oscillator and in turn had a very positive impact on stabilizing the output frequency of the DDS. Remember, the crystal oscillator is 80 Mhz and is driving the DDS to produce whatever frequency you have dialed up. Up to this point my DDS has spent much time on 30 meters where I have noted it's wanderings.

With my success by using a makeshift heat sink, I decided that I would try the crystal oven controller which I glued to the top of the crystal oscillator. I have the crystal oven controller configured to provided a temperature of about 50 degress C which it seems to maintain quite nicely.

As I type this, I have the MEPT running on 40 meters and the output appears to be good and steady.

Earlier however when I was on 30 meters I noticed that when left alone for the day, the MEPT was quite stable and only shifted up and down 5 hz or so. When I sat down at my desk and started typing or just moving things around but not touching the DDS and in fact staying about 2 feet away, the output starting wandering, sometimes just increasing in frequency and other times moving about quite a lot. This was even with the whole DDS wrapped in fiberglass insulation to help keep the temperature stable. I don't think my proximity was close enough that I was causing enough heating to send the crystal oscillator off thus effecting the DDS. It did seem however that my activities on the desk was causing some effect on the oscillator. But at the moment on 40 meters the output is dead steady. I just can't explain it. Is the crystal oscillator microphonic under some conditions? Why does it seems just 30 meters and not 40? In any case, below is an example screen shot from Spectrum Lab showing the 30 meters changing about.


And this shows the MEPT all wrapped up in it's fiberglass sleeping bag.


I am going to try a different 80 Mhz crystall oscillator and see if that improves my results, it will be a surface mount device. More on the Arduino NTP MEPT controller later.
 
The adventure continues

cheers, Graham ve3gtc

Saturday, December 29, 2012

Setting and Measuring the Yaseu FT-817 Output Power

A wee while ago Roger G3XBM posted a question on teh GQRP Yahoo group concerning the Yaseu FT-817 and it's power output with respect to the power level indicator on the radio's LCD.

Roger has an excellent blog here: http://g3xbm-qrp.blogspot.ca/

Roger's question was basically - What was the power output of the FT-817 when the LCD indicator showed 3, 2, 1 or none bars. Roger used the term blob so I will continue to use that as well.

This was a good question and I thought I knew the answer but it turns out I had it wrong too. I dug out the manual for the FT-817 and reviewed what it had to say - see page 28, text box at the bottom of the page Adjusting the Transmitter Power Output. There it was, the answer. But, it was not absolutely clear.

Several members of the GQRP responded with explanations which helped to clarify. Three Blobs was 2.5 watts, two Blobs 1 watt, one Blog on half watt, and no Blobs was 5 watts.

A bit counter intuitive but some simple testing proved it out. Normally you would expect the more Blobs the higher the power, the fewer the less.

I took this as an excuse to tinker on the workbench and set about to check and measure the power output of my FT-817nd. It was actually very simple, set up the radio on the workbench, supply set to 13.7 volts, attach dummy load with a tap onto which I could probe with my Fluke 85 RF Probe and run up and down the bands and power settings taking measurements along the way.

I have several RF probes all of which I have made over the years except for one and that is my Fluke 85 RF probe. You will find many designs for this very simple device by using Google; some are very simple and others a bit more complex but in the end the all pretty much do the same thing, change the RF AC signal into a DC voltage that can be measured on any high impedance input voltmeter. 

The Fluke 85 RF probe is a well made commercial item and usable up to about 500 Mhz. 

I was lucky and found a new, very reasonably priced one on eBay. 


Using a voltmeter and an RF probe will let you measure the Root Mean Square (RMS) voltage of your signal. Once you have this and knowing that you have been making your measurements with respect to 50 ohm you can apply any number of formulas to convert to whatever form you wish.

With respect to 50 ohms:
 
  •           Power in Watts is Vpeak squared divided by 100
  •           Vpeak is Vrms x 1.414 
And, this is my result:








Zero BlobsThree BlobsTwo BlobsOne Blob
Volts RMSWattsVolts RMSWattsVolts RMSWattsVolts RMSWatts
50 Mhz16.405.3811.402.607.301.075.500.60
28 Mhz15.504.8010.902.387.000.984.900.48
25 Mhz15.504.8010.902.387.000.984.900.48
21 Mhz15.504.8010.902.387.000.984.900.48
18 Mhz15.454.7710.802.337.000.984.900.48
14 Mhz15.504.8010.802.337.000.984.900.48
10 Mhz15.804.9911.002.427.000.985.200.54
7 Mhz15.905.0511.002.427.101.015.200.54
3.5 Mhz16.105.1811.202.517.201.045.250.55

So, there you go. Power output on each setting is pretty consistent from 80 through 6 meters at least for my Ft-817nd.

I didn't check 160M, 2M or 70cm as there was a second purpose to my tinkering.

Recently, the thought had occurred that I would like to try and modify a Bird 43 watt meter element so that I could use it to measure very low power at least on HF. These elements are very simple in design but rather complex in their detail. As a start down this interesting path I purchased a used 5A element - 5W 25 to 60 Mhz and wanted to see what it's response was to a known signal level over the range from 80M to 6M



Bird 43 Actual
50 Mhz >5 5.38
28 Mhz 5 4.8
25 Mhz 4.85 4.8
21 Mhz 4.45 4.8
18 Mhz 4 4.77
14 Mhz 3.35 4.8
10 Mhz 2.55 5
7 Mhz 1.65 5.05
3.5 Mhz 0.5 5.18
-
Results are as expected over the elements specified frequency range. Using this as a basis for a simple calibration chart I could use the 5A element to make relatively accurate measurements outside of it's nominal 25 to 60 Mhz range but lower in frequency I go the more questionable the measurement becomes. 

There are Bird elements available to measure low power signals across a very wide range of frequencies. New elements are pricey - a new 100H for 2 to 30 Mhz 100W is currently $150 plus. Once you get away from the more common frequency and power ranges the availability of these elements, if they are available, becomes difficult. Besides, there is much more to learn by trying to understand how they work and modify one to do what I want.

For more information on what is inside these watt meter elements:




cheers es 73/72 ve3gtc

Wednesday, December 26, 2012

FOX Delta SWR Analyzer

A couple of months ago a local QRPer, VA3KV posted about his newly built FOX Delta SWR analyzer kit.

VA3KV's FOX Delta SWR Analyzer

I had been messing about with Return Loss Bridges, Noise Bridges, AD8307 based power meters, amongst other things and was in the midst of building something very similar but which would have been more hands on; in other words, take a measurement using a signal generator and a Return Loss Bridge, do a bit of calculating and plotting and so on. The next step would have been to automate it in some fashion. This kit was all of that in one and I didn't have to think twice about ordering one.

FOX Delta SWR Analyzer

Now, this device is very similar to many of the antenna analyzers you will find. It was designed and programmed by Antonio Alfinito I2TZK


http://www.i2tzk.com/

There is a Yahoo Group to support the FOX Delta kits

http://groups.yahoo.com/group/foxdelta/

This device in reality is a scalar vector network analyzer (VNA), in other words a single port VNA. Devices such as the  DG8SAQ VNWA are two port devices and more versatile than the SWR Analyzer. However, with a bit of creativity, the SWR Analyzer can be much more than a SWR Analyzer for use in checking your antennas.

My kit arrived a couple of weeks ago and took all of about one and a half hours of simple soldering to finish off the main PCB but unmounted and ready for it's initial testing. I installed the software and plugged in the analyzer and it worked just fine. The software is Windows only, I have been unable to get it to run on LINUX using WINE and I suspect was written using Microsoft DOT NET.

A powder coated steel case is supplied with the kit and is a very nice touch but I wanted something a bit different. I had a very nice aluminum box which was just about the right size on hand. This was one I had purchased from an eBay store sometime ago and is well made and quite reasonably priced.

eBay aluminum project box rf-1204

These boxes are available in black or bare aluminum and can be easily painted if so desired.


The box was a bit too wide but that was easily managed by mounting the SWR Analyzer to a piece of blank PCB which in turn was fitted to slide easily into the aluminum box.


Don't do what I did and fit the PCB to the box AFTER it was assembled. I should have fitted the PCB to the box without any components on the PCB. I removed the USB and BNC connector to do my final fitting, a bit of a pain of I managed OK. My PCB was about 1/32" too long and a bit of work with file got a nice fit. Remember, the BNC connector will be fastened to one end plate and the two end plates once screwed to the case will keep the PCB in place. The blank PCB need only be long enough so that the SWR Analyzer PCB can be mounted. I used the supplied standoff and bolt hardware to fit everything together.


The aluminum material is easily worked with a common drill and files, a 1/2" hole for the BNC connector and a 7/64" hole for the LED on the front panel and rectangular hole on the back panel for the USB connector.


You will need to make yourself a shorted BNC connector for calibration purposes. Better yet, a short, an open and a 50 ohm. Using a BNC connector to make an open is preferable to just not using anything during the calibration process because it will have similar capacitive and inductive characteristics to your shorted connector provided of course you use the same kind of connectors to make your open and shorted standards. Use the same kind of connector and make a 50 ohm standard as well. In the photo above you see my SWR Analyzer and just in front are my 50 ohm (on the left) and shorted (on the right) standards; I will shortly be making an open as well. The closer these standards are to being as identical as possible with respect to their inductive, capacitive and impedance characteristics, the more accurately you will be able to cailibrate your SWR Analyzer.

Once I had completed my SWR Analyzer I did the obligatory check of a couple of my antennas. No surprises and the device just as advertised. I mentioned a while back that with a bit of creativity you would be able to use this device for much more than just checking your antennas.

As a first venture down this road I used the SWR Analyzer to align and check and 10 Mhz band pass filter.



The filter is one of Diz's 30m band pass filter kits

http://www.partsandkits.com/univbpfilter.php

I fitted PCB SMA connectors to the filters PCB, and using a short RG-174 cable to connect to the scalar VNA and terminating the band pass filter with a 50 ohm termination I was able to align the filter using the SWR Analyzer Software Generator function to adjust the variable caps for lowest SWR or greatest return loss and then plotting the response of the filter using the SWR function as shown below:


I have a few more experiments lined up and a couple of test fixtures planned which should let me explore what else I can do with this device.

cheers es 73/72 Graham ve3gtc