Tag Archives: Antenna Analyzer

Mini60 Bluetooth Retrofit – Epic Fail

I was going to make one last attempt at getting the mini60 Bluetooth module to work by removing it and redoing the baud rate programming step. Too many applications of the soldering iron affected the small solder pads and traces on both the module and the Mini60. I removed the module and put the Mini60 back together again. Everything is still working as before but no Bluetooth goodness. Better to just but the Mini60 with the Bluetooth module installed.


Mini60 Bluetooth Progress – Nothing is Ever Easy!

I soldered the bluetooth module onto the Mini60 at the five solder pads. At this point I installed the battery and shorted across the switch terminals to test ot. The Mini60 comes up ok and I can place it into PC Link mode but the module is not powered up. Turns out there is is no 3.3V coming in at the pad I soldered it to. I have removed the module and rechecked the voltage and there is no power. Sigh…

There is not schematic or PCB layout for the Mini60 but it is very close to the SARK100. I found 3.3V coming out of the USB chip but have not found how its piped to the second PCB. So work has stalled and I’ll have to check all the required signals by tracing manually.

Update 5/16/17: Ok I think I found the problem. There are three pads that need to have jumpers installed to connect the top board to the bottom board. These three pads bring in the UART RX and TX signals and the 3.3V to the pads where the Bluetooth module is installed. Will solder the module back in place and test later today. The instructions at http://www.die-jetzis.de/bt_install.htm indicated only two pads. Looks like there are several variations of this board. I have noted that several folks have reported issues with the  Bluetooth module not responding. This is the likely cause as it is not clearly documented. Here is the board and the three pads are just left of the BT module:

Photo May 16, 9 34 26 AM

Disassembly of the Mini60 Antenna Analyzer

Opening up the Mini60 Antenna analyzer is fairly straightforward. Fours screws on the side remove the back cover. This will expose the battery which can be removed easily by disconnecting the molex connector.

Photo May 14, 2 13 21 PM

The circuit board needs to be removed completely which requires the power switch and coax connector to be desoldered from the board. Desoldering tools and braid are highly recommended. Remove the four corner machine screws and the board should come out. Flip the board over and you will see the silk screened area where the bluetooth module is soldered.

Photo May 14, 2 41 11 PM

Surgery on the Mini60 Begins…

I started the bluetooth module retrofit of the Mini60 Antenna Analyzer today. First step is to configure the BC04-B Bluetooth module as the only baud rate supported is 57600. To do this I needed to buy a USB to TTL module from Ebay:


Instructions for programming the new baud rate and wiring the module can be found here: http://www.die-jetzis.de/mini60_bluetooth.htm. The painful part is making the connections to the USB to TTL converter. I had to solder four small solid wires to the necessary pads which is tricky as the pads are small and its hard to keep everything positioned. I needed a set of third hands, magnifiers and pair of tweezers but I got them on. The programming went as advertised. Once programmed I removed the wires and prepared to install on the Mini60.


The RigExpert AA-230 Zoom

One page that folks following my blog seem to gravitate to is my review of the Mini60 antenna analyzer.It is the Sark 100 copy sold on Ebay and produced in China. I personally have found this analyzer to work quite well and I have used it exclusively to test out my antennas. Your mileage may vary.

Now that I am doing some additional antenna work I have purchased a RigExpert AA-230 Zoom. This unit is a bit pricey compared to MFJ units and certainly to the Mini60 but from what I have done with it thus far it is well worth it. I’ll publish a comprehensive review later but for now I am sold on it. It is light, provides accurate and quick scans, has an impressive array of features including cable TDR testing and a great USB interface. The software works great with a PC and can save files in a format that Zplots can read.I used it for the first time in the field on the 40m loop and it made short work of tuning it. The interface takes a little getting used to but overall is very smooth to handle.

I will not be getting rid of the Mini60 as for quick and dirty measurements it still can’t be beat for the money. The RigExpert will be for more advanced testing and data collection and will of course help me with 2m antenna work.


Third Time Out with the 20m EFHW Antenna

Setup the 20m EFHW as a vertical on the 30ft travel mast as before. The mast is lashed to a chain link fence post and the match box is just off the ground. Checking the antenna at the feed point with the Mini60 antenna analyzer showed a bandwidth of 588 kHz with a 1.11 SWR at 14.175 MHz. The antenna is resonant across the 14.150-14.350  Mhz voice band. Then through a 50ft piece of RG-8X coax the SWR increased to 1.24 but the antenna remained resonant. Here is the station in operation:


There was a couple of QSO parties going on this afternoon so there was a rich field of domestic contacts. I operated at 45W using the FT-817ND and the amplifier.Partly cloudy day today so there were period with no direct sunshine. The following power statistics were noted:

After 1 hour Solar panel provided .644Ahr and the rig consumed .380Ahr

After 2 hours Solar panel provided 1.146Ahr and the rig consumed .904Ahr

I was unable to take a final reading as I accidentally pulled the plug on the solar panel erasing the counts. The 52W fold up panel was able to keep up with my duty cycle at full 45W.

I operated for 3 hours and made 16 QSO’s mainly in the Washington State area.No difficulties at all making the contacts and received solid 59’s across the board. Propagation during this time favored North America but Europe started opening up towards the end. I was able to copy QSO’s in progress with stations in Italy and Germany. I was not able to break the pile ups though.

All in all I am impressed with the performance of this antenna and with the ability of the solar panel to let me operate for an extended period even with periods of cloudiness. Here is a view of the antenna and the antenna fed point.


Using WSPR to Compare HF Antennas

Playing with WSPR over the last few months has got me thinking about how this data can be used to compare the performance of different HF antennas. My thought is to setup two WSPR stations at the same QTH running the same band and power output over a 12 to 24 hour period. I have done this with my homebrew magnetic loop antenna and my end fed Dxtreme antenna on 40m and 20m. The data is then downloaded and reporter data is compared over time. Attached are the results as well as the raw data for this initial test.

Using WSPR to Evaluate Antennas

20m WSPR Data

40m WSPR Antenna Test Data RevA Temp

My apologies for the rough data files but I am still working on how to crunch the numbers efficiently. The methodology appears sound and opens the door to quite a bit of additional potential experimentation.



Inching Closer to a QSO with the EFHW Antenna

I took out the EFHW antenna matchbox this afternoon with the intent of trimming a length of #22 gauge insulated speaker wire for 20m. I setup a little over 10m of wire with a 1m counterpoise. This was stretched out across the yard and supported by some shrubby about 4 to 5 feet off the ground. The match box was about 3 feet off the ground attached to the Mini60 antenna analyzer through a very short length of coax patch cable. The Matchbox was set at the resonance point found earlier for 20m. Initial SWR was over 3.5 at 14.1Mhz. Sweeping the frequency downwards I could clearly see the SWR improving until the reactance got to Zero and SWR was indicating just over 1:1. The wire was resonating but at a frequency much lower than I needed indicating the wire was long. I set the analyzer to 14.2Mhz and started trimming the end of the wire bit by bit until the SWR dropped to around 1.8 or so. I ran a sweep and found that the minimum SWR was right at 14Mhz while 14.35 Mhz was well above 2:1. The bandwidth was measured at 455kHz so I set the analyzer to 14.35 Mhz and trimmed until the SWR dropped to about 1.8. Here is what the SWR plot looks like finally:


I have purposefully left it a bit long as I intend to run this as a vertical and am not sure what the effect on matching will be in its final position and with feed-line attached. I just charged up the FT-817ND and hopefully I’ll be able to take this outdoors tomorrow for a test.

EFHW Matchbox Wackiness

As I mentioned in the previous post, I had completed the EFHW matchbox and tested with a fixed 1.8 K Ohm resistor with the 6:1 turns ratio. I decided to try and setup a wire for 20m. I connected a 10m wire and a 1m counterpoise and started getting some strange results. Basically, I was getting no results.Adjusting the wire length didn’t cause a significant response nor did adjusting the cap. I was starting to wonder if I should have gone with a higher turns ratio. It was fairly easy to change the ratio as all I had to do was remove one leg of the secondary and pull it through the toroid. I opened up the matchbox to do this and all my sloppy work came back to bite me. The wire to the center of the UHF connector broke off and I noticed a loose solder joint to the capacitor.I really should have taken my time with these connections but I was rushed to finish the matchbox.

Lesson learned…

I did change the turns ratio to 9:1 and changed all the wiring in an attempt to reduce the stray capacitance. I put everything together again and tested the matchbox as before with a 3.9K Ohm resistor across the antenna terminals.The results were very similar to the 6:1 ratio settings. I hooked up the antenna wire and counterpoise and this time noticed a response. The wire is still needing to be tuned but I expect that it will work this time. The capacitance did change and I am just able to tune 10m but 40m is still out of range.I need to make some measurements and check my capacitor wiring but I am sure I can get this working on 20m now for some testing. Hope to get this on the air on the next go around.

Next test of EFHW Matchbox

I received the type 2 toroids and started to play with them as before by wiring up the parts and testing with the Mini60 Antenna analyzer. This time I tried 24 turns of #22 magnet wire with a 3 turn secondary. I just could not get a match unless I had 5 or 6 turns on the secondary. The frequency was also way off. This didn’t make much sense. So attacking these issues one at a time, I came up with some fixes. First the frequency was off because of the stray capacitance in the leads I was using to hook up things temporarily. I shortened the leads and started getting better results. As for the matching problem, I first put together a spreadsheet that calculated the amount of inductance for various turns on the T92-2 toroid. Then I added some columns that calculated the frequency range of the capacitor I was using. With this data I can find which winding combinations would give me the tuning range I needed. Then I added columns to calculate the turns ratio and the fixed resistor needed to tune to 50 Ohms impedance. I am attaching this spreadsheet but it is not pretty. It tells me that I can ideally use 18 turns of primary with either 2 or 3 turns of secondary for a match. At 2 turns I need a 4k resistor to tune to 50 ohms. With 3 turns I need 1.8K Ohms to tune.This should let me use the match box to tune 40m through 10m. I’ll provide some plots as I get the matchbox built into its case.

EFHW Matchbox