Monthly Archives: February 2015

Using the PC Link Feature of the Mini60 Antenna Analyzer

This is how I setup the frequency sweep functions on the Mini60 antenna analyzer on 64-bit Windows 7. Your mileage may vary depending on your operating system. You will need a USB cable with a mini USB connector on one end and the Mini60 itself. Start by downloading and installing the PC link software which can be found here. The software is in a ZIP file. It is a DOS based program so just decompress and place in a convenient folder. Next plug in the Mini60 to the PC USB port, turn on the MIni60 and press “set” once after it initializes until PC link is displayed. Then press down and the display will indicate that it is waiting for a link. Meanwhile Windows 7 should install the necessary drivers for the USB to serial port link. The drivers install a serial COM port that is equivalent to the USB connection used on the Mini60. Use Windows control panel to look up which COM port number is used. This will typically be either COM3 or COM4. Once the drivers are installed and the Mini60 is indicating “waiting for link” you will be ready to run a sweep. To do this open a DOS command window by typing “CMD” in the Windows search box. This opens a DOS window. Change directories to the folder containing the PCC-sark100.exe file.

Now lets say you want to run a sweep for the 10m band and collect data every 10 kHz to save into a file called 14mtest.csv. Assume the COM port used is COM4. The command line for this would look like:

pcc-sark100 -cCOM4 -s14000000 -e14350000 -t10000 -o14mtest.csv

Here is an SWR plot of my Ultimax DXtreme antenna from 1 Mhz to 30Mhz as installed at my location:

dxtreme Custom

The Mini60 then runs the sweep and saves the data into a comma delimited file called 14mtest.csv. Open the excel file called sark100-zplots.xls. Load the data file and you will see the data plotted. A variety of information can be displayed using this spreadsheet. That’s all there really is to it.

There are some direct commands that can be applied to the Mini60 when in PC link mode. See appendix I of the Sark100 manual for these commands. You will need a terminal program like hyperterm to connect to the COM port of the Mini60. You can then pass commands to the Mini60 and receive the resulting data back from the device.

Review of Mini60 Antenna Analyzer

I mentioned in a previous post that I had purchased a Mini60 antenna analyzer. I am going to post a quick review on this device now that I have had a chance to use it. The Mini60 is a Chinese made copy of the Sark100 antenna analyzer developed by Melchor Varela, EA4FRB. This was originally an antenna analyzer provided in kit form. He has since discontinued production of the SARK100 kit and is now building a much better featured analyzer called the Sark110 which sells for about $389. It should be noted that although the Mini60 is a derivative of the Sark100, Melchor provides no support of any kind to these devices nor is he associated with their manufacturers.

mini60

The Mini60 is sold on Ebay from a variety of sellers with the average street price of about $130 delivered. This review focuses solely on the ones marked Mini60. I mention this because there are similar devices marked as SARK100 that also sell on Ebay for about $100. The Mini60 arrived at my QTH in a box and was wrapped in bubble pack. Nothing else arrives with it. No manual, no cables…just the device itself. It turns out that the instructions for operating the SARK100 apply completely to the Mini60. The following are links to the most useful files available for the Mini60:

The SARK100 Manual

The SARK100 Basic PC Control Software

Zplots for the Sark100

The complete archive of the Sark100 can still be found on Melchor’s website here. Regarding the manual, you can skip the sections devoted to assembly and test of the Sark100. The interesting bits are related to how to operate the Mini60 as well as items in the appendix on using a serial link for PC control. The Basic PC control software is DOS based software which allows you to run a sweep across a range of frequencies and saves the collected data into a comma delimited (.csv) file. This file can be opened within the Zplots Excel spreadsheet for graphic display of a variety of antenna measurements. Note that the Mini60 can be used stand-alone but the addition of the PC based sweeps provides considerably more data across a wider range of frequencies.

The Mini60 is powered either by its internal rechargeable battery or by an external 12V power supply (not included). I typically plug the Mini60 into a USB port for charging of its internal batteries. One thing to be careful of is that if the device is left on for more than a minute or so it shuts down to save power. It is important to note that this only shuts down the display and continues to draw current if the power switch remains in the “on” position. The timeout can be adjusted but I have on occasion drained the batteries by forgetting to switch the power back to “off” after a timeout.

The Mini60 is built solidly with a sturdy metal case. It is about the size of a pack of cigarettes. There is a single PL-259 connector for attachment of the antenna or feedline, a single power switch a mini-USB port and an external power port for 12V DC. Upon Power up it displays frequency, SWR and impedance magnitude. The device powers up in impedance mode by default. Other modes include complex impedance, capacitance, inductance and off mode. The off mode can be used to measure any RF feilds in the vicinity. Frequency coverage is from 1Mhz to 60Mhz in 13 bands. Pressing scan will scan across the selected frequency band and will beep when an SWR match below 2:1 if found. After a successful scan, the device will display the bandwidth and be set on the frequency of the minimum SWR found.

The Set button allows the device to adjust step size, suspend timeout, calibration and the PC link functions. I’ll describe the operation of the PC link functions is a separate post.

Overall, I have found the Mini60 easy to use. I verified the output frequency with an oscilloscope and found good matching. The default suspend timeout is a bit short but is easily extended. I like the USB charging feature and PC link function. The PC link feature is a key feature for me and now that I have used it I would not want to use an analyzer that did not have some sort of data download feature. The analyzer made short work of setting up a homemade Buddistick antenna on both 20m and 10m and is very useful in comparing actual with modeled antenna results.

The only negatives I have noticed have been fairly minor. Adjusting the frequency is a bit tedious particularly at the band crossings. This can be compensated by running a PC link sweep but that is not always convenient as a PC is required. The Inductance measurement feature on its own is somewhat strange. I get different readings on different bands. I ultimately used a series RLC circuit with the L being unknown and running a frequency sweep with the PC link feature. It is fairly easy to find the inductance value by reading the frequency of minimum SWR on the sweep and calculating the Inductance value. I’d say that the inductance values are only good within 15 to 20%.

For $130 this has turned out to be a handy and useful tool. Used analyzers can often be found for similar pricing but lack the PC link feature that really differentiates this unit at this price point. I plan to keep using it and will update if there are any quality issues noted down the road.

40m opens up tonight

Propagation on has been pretty bad the last few days. Not much luck on 10m during the day. Today even 20m was slow. Started looking at 40m about an hour after sunset and the lower part of the band started to come alive. I like that DX starts to show up in the Extra part of the band. Ended up working three DX stations and two stateside contacts including a nice ragchew with a station in north Texas. One station tonight eluded me…from Peru. The pileup was moderate but some rude operators showed up on the calling frequency with the typical hijinks…whistling, talking over calling stations and such.

Solar Powered Portable station on the Air!

Tested the deployment of my solar powered portable station today with success.There are basically three components to the system. The first is the radio and power case. This is a foam lined aluminum camera case that contains, the FT-817ND radio, Z817 tuner, two 7Ahr sealed batteries a solar charge controller and the power hook up cables.

Photo Feb 21, 12 01 49 PM

Part two is a homemade buddistick and associated guy wires, radial and radial stand. I’ll be working on a suitable case for the components but for now the system breaks down into components no longer than about 48 inches.

Photo Feb 21, 3 29 25 PM

The last part is two 15W Solar panels and a watt meter:

Photo Feb 21, 12 06 17 PM

The station takes about 15 minutes to deploy. I started by setting up the two solar panels, wattmeter, batteries and charge controller. The whole thing is wired up using Anderson Powerpoles so connections are easy. The two solar panels and the two batteries are wired in parallel. Since this was the first deployment I made sure to carefully measure the load output to ensure the FT-817ND would be happy. I was reading 12.6V at the load.

Next was setting up the homebrew buddipole for 20m. This was the second attempt at getting this antenna to work and today was a windy day for it. As before, I setup the antenna on a camera tripod and setup three guy wires from kite winders using paracord. For operation at 20m, I extended the 9-1/2″ foot whip out fully, installed the 20m coil and setup the radial. Rather than measure the radial i counted the number of turns off the kite winder. Turned out to be 17 turns. A check with the Mini60 antenna analyzer verified SWR less than 2:1 across the 20m band. I used an electric fence post to hold up the radial. These are handy as they have a place to use your foot to drive it into the ground and are plastic. It is about three feet off the ground when deployed. Here is the station fully deployed:

Photo Feb 21, 12 27 58 PM

First contacts were made on 20m QRp to Mississippi, Florida and Michigan. Next up was 10m. Changing bands was easy. The whip was shortened to three sections or 56″. The radial was shortened to 7 turns on the kite winder. Confirmed SWR was below 2:1 across the entire 10m band. First contacts were made with a station in New Jersey and another in Michigan. All were made on 5 watts on a day with fairly bad band conditions (SFI=118). Overall pretty happy with this setup. Only thing I will add soon is another wattmeter to monitor the battery charge state and I am planning to hing together the two solar panels and make a handle to make carrying easier. This station is not backpack portable but it is car portable and should serve well in camping, field day and emergency deployments. Looking forward to playing some more with this as the weather continues to improve.

Is my Antenna Still up???

Some days its easy…others near impossible. I actually did have to see if my antenna was still up tonight (in my defense it had been very windy here).  I only worked two SSB contacts today. One in Hungry and another in Venezuela. I heard several calls on 20m and 40m but did not break through the modest pile-ups or just plain wasn’t heard. Propagation has not been too good of late with SFI of only 118. This is probably contributing. We’ll those are the breaks…just have to be patient and wait for more DX openings.

RadioShack

Love it or hate it I for one am sorry to see it go. Went through three local stores and picked up some Ardunio shields, RG58 feed lines, wire spools, a few miscellaneous parts and a SWR meter. Sad to see that there is no local places to buy parts any more. Sure they were grossly overpriced but when you needed a cap or resistor or opamp you could drive a few blocks and keep your project moving. Now I am gonna have to wait (and pay) for shipping from Internet sources.

When I was a kid I loved the shack. I bought and still have some ARRL publications from the 70’s that bought there. The 100 in 1 electronics kit was a great start to my Career as an electrical engineer. Back in the day the only RadioShack was in downtown Brownsville so it would be months between visits. I also remember the one across the street from the Alamo in San Antonio. Stores were often disorganized but were great fun to look through. When the TRS-80 came out I wanted one but had to be content to use the one in our high school computer lab. RIP RadioShack and thanks for all the help through the years. You will be missed.

Modeling antennas with EZNEC

Went ahead an bought a copy of EZNEC to do some antenna modeling of the Buddipole and Buddistick. Buddipole has models for various antennas in their portfolio for EZNEC. Lots to learn with this but already giving some good insight into the designs.

Portable power

Wired up the portable solar generator for the FT-817 using Anderson powerpoles. Turned out to be pretty easy with the crimp tool. I wired up two “Y” cables. These are to connect two 7Ahr 12V batteries in parallel and two 15W 12V solar panels in parallel as well. Also wired up some harnesses to connect everything to a solar charge controller. This is all installed in an aluminum case that holds the two batteries and the radio. Will test the power supply this weekend and measure the charge rate.

First tests with homebrew Buddistick

Reasonably good weather here yesterday afternoon so decided to try the home brew Buddistick out on 20m with the FT-817. I had mixed results. Setup took about five minutes. The antenna was mounted on a fully extended light camera tripod bringing the feed point up to about 66 inches. The 9.5 foot whip was fully extended and the 7 turn coil was used. I then extended the radial out to about 15.5 feet and two feet off the ground. So far so good.

Plugged in the mini-60 antenna analyzer and ran a sweep. The minimum SWR was high indicating I needed more radial deployed. I added three feet and it swung the other direction. I started having some problems with the analyzer. I had left it on and drained the batteries, doh!  Ok, so I let analyzer charge a bit and plugged the antenna into the radio. The tuner found a match and I started scanning the band. Reception was quite good with a noticeable reduction in background noise. I scanned the band a bit more and started noticing an intermittent drop in signal strength that finally just stayed down. Now I plugged in the analyzer again and got really odd results on the next sweep. So odd I wondered if I fried the mini60 somehow. Checked all the connections and did not notice any issues. The SWR sweep showed the same weirdness.

It was starting to get dark by this time so I tore down the setup and brought everything inside. I plugged the mini60 in to get a full charge and later verified that it was working correctly by measuring a series RLC circuit. Next was to look at the antenna again in detail. Found a bad solder joint on the banana plug going to the feed point…doh!

Although I failed to complete the tuning of the antenna or make a contact I am sure now that this antenna will tune nicely now on 20m. I also replaced all the connectors with Anderson powerpoles to make switching in and out easy. Hope to fire this up again this weekend.

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Worked K1N…Navassa Island DXpedition

Navassa Island is a very rare DX station that is currently running a DXpedition. The pile-ups have been terrible. They work split usually over a range of frequencies 5 to 10 kc up from their transmit frequency. Really horrible practices by some hams. First you have the guys on the transmit frequency that don’t bother to check that they are working split. Then you have the folks transmitting on that same frequency to point out that they are working split. Then you have the people doing deliberate QRM, whistling, humming or tuning up on the K1N transmit frequency. On the receive end it is maddening. Everyone transmitting their call signs at the same time. But patience and good operating skills do pay off. When i first started hunting this station I could not receive their signal so i had to wait until propagation improved. Today they were coming in real clear at my QTH. So i setup to work split (also a first for me to use the split mode). It took a few hours of working the station before I made contact. Feels great to break into that pile-up on 100W voice when there are clearly folks pointing full power beam signals their way. That being said there were also QRP stations apparently making it through as well. My point is that working a station like this requires pateince and careful operating skills. Great to work a station that may not be around for another 10 years!