THE FOX DELTA WATT METER REVIEW
You may navigate directly to the FOX DELTA website from the logo on the Main Page.
Our FAQ list with user TIPS .
Basic Calibration information. New version of the software is available at Fox Delta website.
The interface cable and software tutorial V1.10
MINI REVIEW: If you do not have time to read the entire review, take my word for it, this is just about as reasonable a price for a POWER / SWR meter that money can buy. You can have a very responsive tune-up, SWR indicator and WATT meter monitor without breaking your bank account for more commercial units that cost 3 or 4 times the price. Many of those more expensive units do not have a computer interface at 3 times the price of the Fox Delta. What are you waiting for, buy it (mention you saw it here, Cam Radio Net, please) and read the review later...there is more detail for building and using the kit on this page.
Normally I don't write reviews because they go against my grain. I am an old skool person and I have come to understand that "reviews" are like a great glass of beer. The flavor wears off after the glass warms. What I really mean is...the reviewer is generally bought and paid for by perks, ads and other more extreme lobbying techniques by the manufacturer that tips the scale towards a "more biased review". In general, I don't pay attention to reviews because there is too much to be lost if the translation is poor and generally describes a product as less than expected. You will not read an un-biased review in QST...ever !! I can't tell you why Icom designs and introduces a new radio every six months, but I can tell you that QST will review it and it will always be better than the previous model. Damnit, now my beer is warm !!
Lets get started...but first a little about FOX DELTA:
Fox Delta is a small computer and ham radio project business, started a few years ago by VU2FD, Dinesh. There are two others involved who basically support the operation from a different vantage point. The sole proprietorship is maintained and controlled by Dinesh, VU2FD out of Rajkot, India.
Dinesh is a home-brewer. That is to say he develops projects for the amateur radio community because he likes to. Most everything from Fox Delta has the home-brew mentality built in.
Dinesh will tell you, in his own words: "Fox Delta is not a business per-say but a group of people trying to develop and present projects for the amateur community. Yes, I do sell kits, in limited quantity to recover our project development costs. Once a project is complete, we go onto another and basically end the production already proven to be a good project. If a new update comes along, we make kits again."
Dinesh reminds us that..."Fox Delta is not limited to us. We look for more home-brew enthusiasts to join. Recently Dennis, N5VRP has made changes to Mini_TNC project, which was closed by me, and now you will see kits beginning to come back. So, in reality anyone is Fox Delta. Anyone with a sense of home-brewing and loves to meet our needs and challenges head on."
The FOX DELTA website was created by VU2FD:
What is unique is the disclaimer on the main website page.
Radio Amateurs are free to copy any of these projects and Include designs in their project or make their own PCBs. All designs and information provided here are free of any copyright for Amateur Radio.
This is extraordinary in many ways because the Fox Delta team simply places all schematics, images and FAQ pages out there for research and download. You can roll your own, but why, these kits are very affordable. They do warn you that they have never appointed any dealer to sell their products and that all KIT sales are direct from their location and may only be purchased direct Internet. But I don't see that as a problem. They take PayPal and Credit Cards, or you can mail them a check.
That being said, may I suggest you take a look at the website. There is a lot to see and review for yourself. Download the .PDF files and archive them for review or to enhance a kit you purchase. I like the idea myself, you can take leisure time getting familiar with your project before it arrives.
The digital SWR POWER METER...
The KIT I built was the POWER / SWR meter unit model FD-SWM2 by I2TZK. There were at least two others involved in the project, Frank K7SFN and VU2FD. You can find details on all the members of the team on the website. Full kit details are also located here on the Fox Delta Website.
The Build...here we go:
The first thing you notice is the "plain jane" no frill project box. This truly is as simple as it gets, but in fact it is very functional and fits into the radio shack environment with ease. There are no logos, or fancy knobs here. This is basic functionality at it's HAM RADIO ESSENCE and to the finest degree. In other words, it looks home brew and in fact it should. More on the simplicity later...
The kit consists of small white powder coated cabinet (project box) that frankly is just that. The coating is not professional by any means and there are a few flaws, but it is perfect for the job it has to do.
The parts are packaged neatly and even if it is only one choke, cap or resistor, are identified by small bags (lots of them) with hand written stickers on them. It does not take much time to realize this is not Heathkit we are dealing with. The small parts bags makes this very easy to identify parts and by simply matching them up with the build sheet, you can do an inventory before you begin. I do recommend you do just that. I did not have problems with missing parts. I did have problems with the interface cables and I will detail all of that later.
There is no step by step directions. So if you are not an expert builder, I suggest you consider the pre-built units from FOX DELTA. Check with them for assembled prices.
The project which requires a "bridge unit" will take about 6 - 8 hours to complete. This means 2 - 3 hours for the bridge (you can attach 2) and another 4 - 5 on the meter interface unit. The parts are small and will require a decent solder station that can be adjusted in temperature. I use a ceramic tip unit, but that is not required for this build. However a sharp tip is required because the circuit board is small and busy. However at that point, I must tell you the circuit board is very good indeed. It is easy to read, the hole-thru is neat and all component positions are shown on the board silk screen. I have seen the inside of more expensive units and the quality is no where near these boards.
After completion it only took a few moments to calibrate the bridge and adjust the display. The serial cable (included) that connects the "bridge unit" to the "interface display" is long enough to put the "bridge" anywhere behind the exciter or amp. The "display" can be placed on top of the radio or just about anywhere you desire. Keep in mind that you can connect it to your computer and log the SWR and POWER output on the computer screen if you desire. In fact that was recommended by VU2FD, so we discuss cable interface to computer and the software itself further down this page.
There are 2 LED indicators and 2 PUSH BUTTONS on the face of the "display interface". The buttons toggle through the display functions and they select "A" or "B" bridge units. The "bridge units" are available in 3 distinct models: HF simple, HF dual scale and a 144 MHz unit. Don't be confused by the "bridge" details on the website. If you have a 100/1KW radio room, buy the HF basic, other wise build the dual range bridge if you run up to 2 KW output.
My final take:
It must be understood that I had to make some changes in the kits I built. First of all: The process by which the main board is mounted in the box is poor. If you use the parts shipped with the kit, you will find a problem with the RS-232, DB9 connectors, they simply do not fit correctly. They are pinched into the small box. You will need 4 - 3/8 (#4) nylon spacers, instead of using the grommets that are supplied. The LED indicators on the face are smaller than the holes provided...they need to be enclosed in a 1/4 inch ID (5/16 OD) rubber grommet. It looks better and simply adds a touch of "neat" to the box face, not to mention the LED could be broken or damaged if you are not careful. I have contacted Fox Delta with regards to the small interface cables that are included for connection to the DISPLAY board and LED BUTTON board. These (ribbon) cables are poorly made. They (3 out of 4 total) simply broke at the edge connector. In simple terms these cables must be replaced with something worthy of the rest of the kit. Even if it requires a .95 cent price increase. It will certainly save money in the end. In my words...the cables that are supplied are worthless.
FYI: These cable problems have been addressed. In my case, Fox Delta sent me an entire new base board and a set of cables. This allowed me to make repair to one kit. This was done at their expense and with an apology from Dinesh, VU2FD. He also explained that he would put the kits on hold until the cable problem was resolved. I suggest you contact them with regards to purchasing your kit, or place your name on the waiting list. They are certainly a welcome addition to any shack.
The unit itself, after you have done your magic, a basic test and final calibration...this accessory makes other units look questionably expensive. The Fox Delta unit is the perfect solution for tuning up your tube amplifier or exciter. It is that functional even if you use it for nothing else beyond a tune-up indicator, the SWM2 will save your equipment and the tubes will certainly last longer. That alone pays for the unit. You spend $100 dollars and you will be glad you did. You can buy LARGE SCALE analog meters for twice the price and they will not be as accurate as this little digital unit.
It can be a pain in the ass to build...yes, simply because certain design short-cuts must be overcome by the builder. Without STEP by STEP directions, you tend to find yourself bridging solder and pushing parts out of the way to make room. A "step-by" FAQ page on the website would be a plus and it will not cost the company a dime. I may do one here if I can find the spare time...but in the tradition of Fox Delta, maybe that would be better left up to you.
If I rate the product a 9 out of 10 for functionality, that is because I have done this for 50 years now and building "stuff" is fun for me. If I rate it a 5 out of 10 for build-ability, that is because I have done this for 50 years and after all, I did work for Heathkit. This kit is a great little evening project at a very reasonable price. Don't take my word for it, just buy one, build it and be happy. If you desire, you can buy them assembled, but they will cost you more and certainly you will miss out on the fun.
Interfacing the FOX DELTA SWM2 with your Windows based computer:
This little tutorial will help you set up the SWR / WATTMETER using your Windows based PC. The project, when completed requires a "bridge" unit that connects via a (supplied with bridge) serial cable be connected to one of the inputs on the CPU unit. There are two (2) inputs that are DB9M on the rear of the SWM2, one "A" and one "B". There is also a DB9F (female) connector that you will use to connect the bridge to the computer. This cable is not supplied and you will be required to build, or find one. The pin outs are here:
You will need a 3 or 4 foot (depending) serial cable. DB9F on one end DB9M on the other.
SWM2 DP9F --------- COMPUTER COM PORT DB9M
PIN 1 -----------------> PIN 1
PIN 2 -----------------> PIN 2 required
PIN 3 -----------------> PIN 3 required
PIN 4 -----------------> PIN 6
PIN 5 -----------------> PIN 5 required
PIN 6 -----------------> PIN 4
PIN 7 -----------------> PIN 8
PIN 8 -----------------> PIN 7
PIN 9 -----------------> PIN 9 optional
Shield <------------------------------------------------------> Shield
I am sure the lines indicated in RED are not used, but in a normal NULL MODEM cable, those pins as shown are normal and only PINS 1, 2, 3, 5, 9 are straight through on the cable. If you look at the schematic, you will see that J2-RS232 is the interface and it uses only three lines. Those are 2/3/5 and they are straight through to the computer. If you purchase a M-F straight-thru serial cable, it should work perfectly. Or you can purchase ends, hoods and cable. Any 4 wire (shielded) cable will work, be sure that you ground the shield to both cable connector jackets. If you roll your own, you might add a ferrite RF choke or a snap-core choke around the cable to lower the risk of RF.
When you are ready, plug the cable into your PC and into the SWM2. Now download the software from the website, extract the files and install. This should take a few seconds. The FOX DELTA icon will appear on your desk-top.
The next step is to configure your serial port. The software defaults are 115200 BAUD, 8 BITS, NO PARITY 1 STOP BIT. So set your serial port to these settings. The COMM PORT may be any serial port that is not being used. If you computer comes with only 1 port, you will want to add a port. If you have a spare PCI slot, you can purchase the StarTech 16550 PCI serial interface. They are available at www.STARTECH.com and come in single or dual port models. The KEYSPAN 19HS USB to SERIAL adapter may also be used. Many of us already use this to control our ARCP applications. I chose the StarTech (single port) PCI card. I set this to COMM4 and my parameters inside "my computer" - "hardware devices" - "PCI SERIAL Port" - "properties" - "port settings".
The simple cable posted above works great. I wired 4 conductor with shield - 5 feet long, as above, using the BLUE pins direct. The parts were all available at Radio Shack for about $10.00.
The 12VDC required can be any "wall wart" that delivers 500 MA or better with the center pin positive 1/4 inch connector.
Now try it out...you should see this on your screen if every thing goes as planned. If you do not, you will have to configure the setup. That is choose a COM PORT, set the BAUD RATE as above and test again. The unit will display the meters as shown here as soon as you are connected. The GREEN LED will flash if connection is completed.
Note that there are three (selections) you can make on the SCALE PANEL input box. "SET", "CMD" and "LOG"; these each have a specific function. If you click on the "LOG" selector, the LED changes to YELLOW and you are now LOGGING your SWR to a .CSD file that can be read in an Excel spreadsheet. You can PLOT your SWR using this function and then GRAPH the results. Very nice for working on antennas. If you do not have Excel or are not familiar with it, you can read the CSD data using "Notepad" in Windows. I will elaborate on this function in a tutorial some time in the future.
The "SET" selection is where all the deep dark secrets are hid, but if you select "CMD" you can change the interface display functions from the computer. That is to say, the "CMD" dialog box is the same as pushing the buttons on the SWM2 front panel. All the functions of the PIC IC are available from this panel. It is helpful if you are running strictly from HRD or FLEX and you need more information from the bridge unit. This would be in line after the AMPLIFIER and before the TUNER if you have an amplifier in line. If not the bridge should be after the exciter and before the TUNER or the ANTENNA. See the SEND COMMAND screen grab located to the left. Mode will control the SWM2 display and SCALES (A or B) will set the bridge units for proper power levels. I suggest you start with "AUTO" for all selections, the PIC will display as soon as you make a selection, all changes are completed upon request. To close the panel, click "EXIT".
The "SET" is your configure panel for setting up your interface and how it handles the bridge information. Below is the "SET" basic program panel. You can find the DATA LOG file location here and change it elsewhere if you need to. You can set the display and of course, change CHANNEL NAMES as I did here. You can test the interface from this panel if you are having problems. More on the "TEST" application further down the page.
Above is the SET PANEL ADVANCED settings. This is where you control the options that are displayed on your computer and on the SWM2 display window. Any change you make will require an "APPLY" before they can be programmed into the PIC controller.
The SWR defaults to 3:1 on the interface. Anything above 2.9:1 will display as "HIG" in the controller and the RED LED will light. You can increase this reading by setting it higher as above for 4:1 or whatever you need. In general 3:1.1 will shut most exciters down to a minimum of output. If you have an internal tuner, you can overcome this power reduction, but you may have a fault in the SWM2 that will display a "HIG" indication even though the exciter is tuned to 1:1 SWR. So, to over come this increase the SWR alert to 500 (5:1) and the fault will not display...however, remember that an extremely high SWR will counteract in the antenna tuner as heat. Don't fool yourself into thinking all is well. I know of a few operators who like the "sweet spot" method of tuning an antenna. This is foolish simply because a 3:1 SWR will shut the radio down. Trying to find the "sweet spot" while reading the SWM2 will not give you an accurate reading. You must use a different method and one that certainly is more accurate then spinning the dial at full power key down. Do you get a kick out of creating QRM all over the band?
You can set the scale MIN and MAX from the advanced panel. If your amplifier is capable of 2KW you can set this for one scale, while leaving the exciter scale to 100 (or 200) watts. Remember the the screen above is for the DUAL CHANNEL bridge. Each channel must be calibrated properly and the relays inside the bridge unit will "click" as they ramp between scale settings. If you chose the HF BASIC BRIDGE, your screen above is very simple and does not display dual range. The REFRESH times can be adjusted also, or you can select FAST-MED-SLOW for refresh. Click the DEFAULT button and all settings will revert back to default, select APPLY or CANCEL.
One more item: Note the "COMPACT" hit box, this box, when highlighted will simplify the digital readout according to your settings MIN-MAX. This is useful for INPUT / OUTPUT settings when you use two (2) bridge units in your RF path from exciter to amp and from amplifier to tuner. This may also come in handy while you tune up your amplifier.
The PIC16 TEST function is the best way to see just what your SWM2 and the bridge are actually doing. Each scale is listed and if you have a bridge connected to one, or another or both, the results of the samples will be displayed here and a basic pin interpretation of each of the PIC16 functions. If the bridge is functioning as it should, there should be active information in all the GREEN boxes. Again I emphasize this is "bridge" dependent. The image here displays the "DUAL BRIDGE" unit. In the SCALE boxes, BIG AL for instance you see "FWD Watt" (white box) and "REF Watt" (white box). The values in these boxes are a direct relationship to your calibration of the bridge. If you did your job, and you have a good antenna system, The "FWD Watt" will display your RF output to the load and the "REF Watt" will display the RF reflected back to the bridge. The PIC does the MATH and displays the "SWR" for each scale (yellow box).
This mode "TEST" is where you want to be when doing those final calibration settings. This screen will show voltage at load, sample rates for both forward and reflected range. There is a lot more here than meets the eye, so take a moment and look around. Use this screen often to check the validity of the PIC16 data you see displayed on the SWM2 main display. BTW: The refresh rate above the graphic should be + or - 1% of your computer clock (60 mS = 1 second tick).
One more item, before you exit the TEST page, click the "SET" button again and go back to the "SET" page and choose the type of interface you want displayed on your computer. Making the selection will un-check the "TEST" bullet. Now click apply and follow directions...that simple.
You may also refer to this information as you continue to the CALIBRATION section.
Special thanks to VU2FD for great support and all the helpful input.
BUILD IT...it will work !!!
The SWM2 kit is a nice little break from the usual kit building routine. First of all there are no directions.
That is right, you get a carton with all the parts, a small project box (white) and a parts check off list. Everything else you will need is on the website. You will need the schematic, parts layout sheet and a few pictures of the completed unit. All this is available in .PDF form on the website. Unless you are an expert at reading schematics, you will need the following .PDF files:
(1) 2CHWM-v1.10.pdf (operation manual)
(2) SWM2-CPU-SCHEM-parts.pdf (required build)
(3) BRIDGE-hf-simple.pdf (required build)
(4) BRIDGE-hf-dual scale.pdf (required build)
(5) SWM2-calibration.pdf (see noted below)
(6) 2chWATTMETER.zip (software for Windows PC)
(7) 2chWMv1.10.zip (PIC16 Firmware)
All the above files are available from the FoxDelta website. The contents of all will certainly help you build and setup your unit.
Please read the CALIBRATION information attached in this document.
Lets take a "home brew" approach to the build...
Your parts list will be used to build the unit. Each small parts bag is marked for identification. The actual part value is written on a small sticker and placed on the bag. You need only match the part type and value with that on the check list sheet. You take a small bag, open it, verify the part, check it's location on the PCB chart, verify that with the board image and insert in into the board and solder. That is all it takes, but you can get in trouble if you do not pay attention.
The DUAL BRIDGE unit shown here. Looks rather simple to build. This is not a hard kit to assemble and if you follow some simple steps you can't make a mistake.
The kit comes complete with all parts and the serial connector that will be used to connect the bridge unit with the SWM2 PIC16 circuit board and PC interface. (As noted earlier, no cable to the PC is supplied, roll your own.)
If you look carefully you will see 2 small DIP relays, 5 small mini-pots, 1 variable tuning cap and the current transformer.
The current transformer must be wound, and the entire unit with a small piece of coax is in one bag. The small torroid with wire, that you will wind 30 - 32 turns on the core. I suggest you wind as many turns as possible, keeping them neat and close wound. The result will leave you about 2 inches of left-over wire. This you should do first. Now mount the COAX connectors, and follow with the relays, pots (watch them for correct location) and the DP9 connector. The rest is simply open the bags and insert the HOLE THROUGH parts.
When all parts are mounted, verified and compared with the build sheet information, you can complete the coil assembly. Use a sharp blade and carefully remove 1/2 inch of insulation from each end of the coax. One end will be your ground (the antenna side). Note as in the image, the shield is soldered to the small ground lug that is attached to the COAX CONNECTOR machine bolts and nuts. The small 4.7pF cap is then connected to the center of the connector and soldered to C13 on the PCB. The coax is then passed through the torroid core and soldered to the INPUT coax connector. The shield should be removed and cut away at this end. The image shows a small insert the looks like a piece of insulation, there is no such part in the kit. Pass the coax through the torroid and use a small amount of RTV (clear or black) to hold the coil in place. Solder the one end of the XFMR to "A" and the other lead to "B" on the PCB.
This is the parts layout sheet that is available in the .PDF build files I listed above. This basically is the only build sheet you receive, so you will need to pay attention to the parts list and verify the placement of the part using this drawing.
I have colored 5 of the MINI-POTS. These are very important and you must place them properly on the board.
Keep this reference for later on when I explain the calibration. The .pdf file for calibration is rather technical and if you follow it as written, you will make a mistake. There is an error that will frustrate you until you figure it out. Like most puzzles, we have the answer here. Follow our calibration format and you will do just fine. Above all be sure you install RV1-RV5 correctly. Note the screw positions and the values. Install RV1 (10K) first and then follow up with RV2,3,4 and 5 (100K)
If you chose to build the BASIC HF bridge unit, you will find the coil build kit is similar to the DUAL unit. However there are no relays and you will have only three (3) pots to mount. The HF basic is a simpler, less expensive bridge unit. I will be building one of these soon. I will have all the details for you here when completed.
Check your board and prepare to build the the SWM2 display unit.
This is the completed SWM-2 PIC board and project assembly.
The layout and parts list that is supplied with the kit must be downloaded from the website. I suggest you print out the layout sheet and the main board picture so you can follow along with the build. The step will be to separate the 3 boards in the kit. You will want to build the BUTTON and LED board first and then prepare the LED screen PCB by soldering the 16 pin edge connector on the PCB. Now mount these boards in the project box and set it aside. Note: You can mount the BUTTONS on top rather than on the bottom, this makes it easier to set when you use the unit. Place a small 1/4 in. rubber grommet over the LED before you install the PCB. This looks better and protects the LED. If you do not like the WHITE box, sand it with 400 wet sandpaper and shoot any color you desire.
You can begin on the main PCB by installing the IC sockets, be sure that you match the socket DIMPLE with the screen on the board. Now mount and solder the edge connectors, DC source plug, and the DB9 connectors (2 MALE and 1 FEMALE, note their locations). Next you want to find and solder the XTAL for the PIC16 and install it with the correct small pF caps (all in one bag). Now install the VOLTAGE REGULATOR and then the DISPLAY VOLTAGE TRANSISTOR (this is the only SMD component you have to install). Now mount and solder the "contrast pot" and prepare to install the small components. I suggest you solder the transistors and insert the chips last; so find these bags and set them aside. Begin with the mylar caps and then the tantalum caps (note the, + lead is the longer lead). Move on with the all the resistors and finally the chokes and diodes. Following in this order, it will be easier to find the part and match it up with the build sheet and the layout sheet. When all components are finished, insert the chips and solder the transistors to the board. Match the board screen with the transistor orientation. Note the images in the .PDF and be sure your board looks similar. Check your work...
Upon completion, check all connections under a magnifying lens. Look for solder-over and runs. Be sure that all components are soldered properly. Look over the DIP SOCKETS for bridged solder and be sure your work is clean and neat. Check all diodes and tantalum caps for orientation. Be sure that the IC's are installed properly.
The basic test for the completed unit is nothing more than inserting 12 VDC to the power connector. The center pin is positive. As soon as you apply voltage the screen will light for a moment and then display the basic setup.
It must be understood that the .pdf file that illustrates the calibration has 2 errors. I will explain them for you, but first you must know how this works. On the DUAL DISPLAY unit you have 2 relays that function as HIGH and LOW output. One set (RV2 and RV3) controls the FORWARD reading, and likewise (RV4 and RV5) control the REFLECTED value. Calibration includes setting 100 W levels for LOW and HIGH FORWARD and likewise LOW and HIGH REFLECTED. The PIC16 program does the math and calculates FORWARD vs. REFLECTED RF, using these values it produces an accurate SWR reading for your display. The HI-LO scale relays are controlled by the PIC16. The controller changes the relays as required/desired. You can hear them "click" if you listen closely while you change the settings.
The scales on the SWM2 DISPLAY are "A" and "B" and each has it's own setting. If you do not connect the serial port to your PC, you will be limited to a 100W MIN and 1KW MAX reading. This is why it is so important to follow these instructions listed here.
First, if the display unit functions as displayed in the instructions file, you may continue. Connect your BRIDGE unit to "A" or "B". Connect your exciter to the INPUT CONNECTOR and your dummy load to the OUTPUT connector (you may use your antenna for the basic tests). Key up your exciter in CW mode with 100W output. The scale should respond. This is pre-calibration test and the value on the display is not important. If you see no indication, reverse the IN and OUT coax connectors and try again. You should see some output or "HIG" on the SWR SCALE.
If you have any indication that the unit is working, it is time to connect to the PC. Refer to the cable wiring information that was given earlier in this document (Interfacing the SWM2 with your computer). When completed you should see the WATTMETERS on your PC SCREEN. This is a good indication that the unit is ready for calibration. If you are having problems, refer to the "TEST" program that will indicate if your PIC is functioning as programmed (see TEST PIC V1.10 above). The green LED should be flashing at a rate about 1 second interval. NOTE: If you cannot connect to the serial port of your PC you will not be able to set the PIC above 1KW. The software must run in order to set the HIGH and LOW scale range. Otherwise, use the HF BASIC calibration.
I will show you exerts from the .pdf file and I will explain the differences.
If you have not become familiar with the buttons on the SWM2, I suggest you take a minute and play. You will figure it out in no time. remember that push while holding in the LEFT button for a few seconds, will set the unit to SCALE MODE.
The .pdf file on the website (calibration.pdf) will help you set up your SWM2 interface, but the changes I write about here are the latest information regarding the BRIDGE unit and how to properly set up the calibration.
You should have the unit up, running, connected to your PC. All preliminary testing must be completed. You should have a copy of the ACROBAT FILE "calibration.pdf" on your screen or in print so you can follow along here.
Attach a 50 Ohm DUMMY LOAD to your BRIDGE UNIT. Attach your exciter output to the bridge and apply 12 VDC to your SWM2 interface. Be sure the BRIDGE to INTERFACE cable is plugged into SCALE "A" and the CABLE from the PC is connected to the interface. Open up the DUAL BRIDGE and prepare to calibrate. Complete steps 1, 2, 3, 4, 5 and 6.
(step 7) The ACROBAT file, in this step you are directed to adjust RV1 for .65 volts across the TP1 test point to chassis ground (see STEP 6). Do not adjust the DVM for .65 volts. Adjust RV1 for minimum on the DVM. The diodes do not require BIAS and it is important that you remove any BIAS voltage on this TEST POINT.
The above adjustment may cause problems during reading cycles. You do not want the diodes to CUT-OFF so remove the BIAS on them. Turn the screw on RV1 till the DVM reaches "0" or as low as possible.
(step 8) You are directed to connect the PC to your SWM2 (interface) and "set" both scales for 200W and 2KW settings. this step is important and must be done before you continue. Please note the settings are changed by using the "SET" button on the PC software, and the "ADVANCED" settings panel. You can review this information above in the "INTERFACING" portion of this page.
Follow steps 9, 10, 11, 12, 13, 14 and 15. In step 16 you are directed to set your exciter to 28.4 MHz. I suggest you set your exciter to the band you operate the most. If you operate 20 meters, set the exciter to 14.2 for SSB or 14.1 for CW operation. You are looking for accuracy and if you do not operate 10 meters, why calibrate for that band? (HINT: Look up DUMMY LOAD on the Internet. If you do not have one, there are several designs and schematics for building one that will handle 100 WATTS.)
Step 17 is important, but read carefully. Do as directed. RV-3 is the BLUE indicator in the image here. Skip steps 18 thru 27.
Follow along here for the next calibration steps, then when completed as directed here, continue with step 28 and complete the ACROBAT file.
Continue from step 17...Return to the "scale mode" and and select the 2KW HIGH power for SCALE "A". Key the transmitter again at 100W output (CW) and adjust RV2 for 100 WATTS on the display. You may not see anything on the scale, so back out the screw 3 turns and key the radio again. If the display shows a reading, continue. if not turn the screw in 5 or 6 turns and read again. I suggest you "key up" only after making adjustments. Do not adjust with the exciter full 100W output for more than a few seconds. You should now have a 100 watt reading for each scale range selection. Now reverse the cables so that the exciter is connected to the "antenna" side and the dummy load is connected to the "exciter side" of the coax connections. This is "reverse" or "reflected" power setting. Follow the same directions as above, however for the 200W "reverse" reading adjust RV4 GREEN mini-pot for 100W and in the 2KW setting adjust RV5 for 100 WATTS. Essentially you are adjusting 100W reading from the SWM2 no matter which direction RF is flowing through the BRIDGE. If 100W is "FORWARD" and 100W is "REFLECTED" the PIC16 program will handle the math for your SWR display.
Now mechanically connect your BRIDGE as close to the final RF device as possible. This step is important for any "current XFMR" device that monitors RF voltage via RF current. Before you cover the bridge, check the readings, if there is more than 1% difference (+ or - 1 watt @ 100W scale) You should recalibrate. If you are of by 2% or greater, your SWR readings will not be accurate and could mean the difference of 1.1:1 and 1.3:1. These readings are Ok, but in my shack, not acceptable. (HINT: Use a 50 OHM dummy load with a coax jumper as short as possible.)
That should wrap it up, now read the remaining steps in the ACROBAT file and you should be set to go.
As a quick reference...
(1) Adjust RV1 for "0" volts on TP1
Connect the exciter and the load to the proper connectors on the bridge unit..."forward power"
(2) Adjust RV3 for 100W in the LOW SCALE
(3) Adjust RV2 for 100W in the HIGH SCALE
Reverse the cables in and out..."reflected power"
(4) Adjust RV4 for 100W in the LOW SCALE
(5) Adjust RV5 for 100W in the HIGH SCALE reading.
Connect the PC cable to the INTERFACE and using the "CMD" mode set the scale to RF/POWER and watch the meters climb. Note the multiplier in the meter window. You don't get this with those analog meters you paid big bucks for. If you have a reasonable computer (P4 or greater) the meters will swing fast and accurate.
CLOSING STATEMENTS and REVIEW COMMENTS:
Ok here are some tips and FAQ's...
First let me say that there will be a new version coming soon. The SWM-3 will use USB and have a few more bells and whistles that it's predecessor. Also there will be an software upgrade by I2TZK that will enhance the graphics and offer a higher resolution meter and readout. Note: Even the big guns in the business don't offer many upgrades for firmware or software.
There is more to this unit than meets the eye. The entire PIC16F877 microprocessor tutorial can be found here: Microcontroller and a .PDF located here: Embedded Systems at CS-UOHIO.edu. There are several other links that will help you understand the PIC16. The program software is available here: IC-PROG and HELP FILES simply select the downloads from an index. You can search many links on your own, these chips are very inexpensive and yet they can be designed to do many small applications when it comes to serial or USB communication with outside devices. It should be noted that a PIC PROGRAMMER can be purchased from Fox Delta. The latest USB programmer supports Microchip PICkits. The Fox Delta FD-UPP will cost you 40.00 plus shipping.
Here are pictures of my completed project:
Because I wanted to match my station, I painted the small project box prior to completing the boards.
The boxes are powder coated in appliance white, so you will have to rough up the surface with 400 wet sandpaper. Then shoot with you favorite finish. Late model Kenwood radios use a cast finish gray. I used a matt-black with a coat of clear for the case cover.
The buttons are installed "upside down" for ease of use and the LED indicators have a small rubber grommet on them to fit the hole. Rubber feet are from Radio Shack. The hardware I used are all small computer machine screws. The interface cable was home-brew, all parts are available at Radio Shack.
FOX DELTA TIPS: FAQ
PAINTING THE PROJECT BOX
The project box comes in appliance white. This may be attractive in your kitchen but it does not blend well in HAM SHACK. All FOX DELTA devices and projects are white. Some are painted and some are an inexpensive powder coat. If you want to change the color, you should rough up the surface with No. 220 automobile finish paper. First dry and then before paint, wet. An inexpensive primer can be used before you finish the box. You will notice the display is brighter and easier to read if the box color is a darker contrast. This where you add your personal touch to the project. Have fun !!!
SWR READING V1.10
Some of us are experiencing "no SWR indication" (1.0 on the SWM-2) when using the V1.10 software.
TIP: I have also seen the problem but after a few minutes I went into the SET/ADVANCED dialog box and checked the settings. Everything looked fine, but still no SWR indication. I reversed the coax cables to test my bridge and found it was working fine. I set the exciter to 50 watts and slowly de-tuned the antenna tuner, the reflected power displayed indicated all was correct. So I decided to RESET the PIC settings by clicking "default" on the setting panel. That set the scale settings and all other settings to DEFAULT. I then set the scales (1 & 2) back to 200W and 2KW, as explained in the calibration instructions. I tried the SWR again and this time it works perfect. You can watch your SWR on your radio and compare it with that of the SWM-2. It should correspond between both radio and SWM-2 readout. If you de-tune the tuner out of resonance (3:1 SWR) the "HIG" should flash on the display and the RED LED will light.
NOTE: If you do not have your SWM-2 connected to your computer your SWR reading may not be accurate.
USING THE V2.02 SOFTWARE
The new version of SWR software has been released with the latest PIC chip V2.02. You can check the version your PIC firmware is using by turning on the SWM-2 and read the BOOT-UP screen. This screen indicates V1.10 or V2,01 or 2. In either case, if you have 2.0 or higher, the new software will function perfectly. When calibrating your bridge for either version, the same rules apply. You may follow along in our tutorial for the "dual bridge" calibration. Remember that you must set the SCALES 1 & 2 using the software before you adjust RV2, 3, 4 and 5. Otherwise, all calibration results will be 1/2 the power applied.
NOTE: Make sure you connect to the SWM-2 using the software (either version) before calibrating the bridge unit.
The new software will search for the COM PORT that you have selected. If it finds the PORT the program executes. If it does not find the SWM-2 board, you may try to force the serial port setting.
Downloading the software you need
You should download all the required software for Version 2.01 of the SWM-2 unit by visiting the Fox Delta Website. I recommend that you go to the site often because there are always updates there. The latest version of the unit is coming soon. The SWM-3 is a USB version of the same great device and yes it operates even better because the USB version id powered by the USB 2.0 interface. No need for the 12 VDC (serial) power supply.
Get all the software and SWM-3 details here
NOTE: THIS IS THE DETAIL PAGE WHERE ALL SOFTWARE DOWNLOADS RESIDE. USE THE SLIDER ON THE RIGHT SIDE OF THE PAGE. SOFTWARE, TECHNICAL ARTICLES and PRICE INFORMATION IS LOCATED NEAR THE BOTTOM OF THE PAGE.