I have 6 M7Es. The resistors have been reworked to allow for use of the external antenna. I am providing power though a USB port on a computer. I am using the Universal Reading Assistant program and using all the same settings for each reader. The antenna is the Sparkfun UHF RFID Antenna (RP-TNC). I tested each M7E using the same wires, which included a RP-SMA U.FL cable and a RP-TNC to RP-SMA (1-m) cable to the antenna cable. I tested the read distance with UHF tags and some antennas picked up the tags from farther distances (easily 5+ feet), while two antennas only read tags within 1-3 inches of the antenna (no readings near the reader, just the antenna), and one antenna did not detect any tags near the antenna, no readings near the reader either. I tested the RF power with a power mapper (Vulcan) switched to the 0dBm setting to make sure the tags were not an issue. I am not experienced with the power mapper, but tried to do a simple test. I measured out a few distances up to 2 ft and held the mapper in the same position for each test. Within 2 feet, the 3 working antennas were off the mapper, over 100 (not sure the units, the top numbers on the mapper). The 2 partially working readers were around 18-20 watts at 2 feet and increased as it approached the antenna to 100 at the antenna. The reader that did not pick up any tags was 5 at 2 ft and 53 next to the antenna. All the reworks look good, like they would all provide strong connections. Could the rework still be the issue? Is there a way I can test to rule out the rework as the issue? What else could be causing the differences in power output?
looks like you have 7 M7E boards and 7 antenna’s. If so, it should not be be that difficult to find out whether the issue is with the M7E board or the connected antenna.
Just take a good working combination, then exchange with one antenna that is not good working. see what happens.
The resistor you have moved to a different place on the M7E is a zero ohm. Maybe check with ohm meter.
Sorry, I may have made a mistake in the text. I have 6 M7E boards and I tested them all under the same conditions and with the same external antenna - I did not test multiple external antennas. As far as testing the resistor, I did not do the rework and won’t be able to remove the resistor myself to test, I’ll check with the person that moved the resistors for me. Thanks.
Thanks for the clarification.
instead of moving the resistor, one could also make a bridge with a small wire on the 2 soldering points of the resistor.
As you use the URA, make sure the read /write power is set the same everytime and antenna 1 is selected.
When you set a high power (e.g. 2700), the M7E will get hot quickly. When too hot it will bail out, then just wait a couple of minutes for it to cool down.
Thanks for the suggestions! Here’s where I’m at now.
I tested all the boards with a multimeter. The 3 that were not working well, were not soldered well enough to the pads, the other 3 had good connections. I may fix those with a wire as suggested.
I also tested the connection from the pad where the resistor was newly connected (external antenna pad) to and the u.FL center pin. I don’t have tips that are very fine, so I connected the cables and placed the other probe inside of the RP-TNC end. I tested all the readers and they all read OL. Should some resistance be registering with this connection? To see if there was an issue with the cables, I tested the connection between the RP-TNC end and what I am pretty sure is the trace on the coaxial connector (if the C port is on the bottom, I tested the right tab by the coaxial connector) and did get resistance readings of 0.2 on all the boards. Because of this, I do think my tips are connecting well in the RP-TNC end, though I am not sure.
From this information, can I conclude that the cable connection is good, but there is a break somewhere between the coaxial connector and the external antenna pad with the resistor? I may be placing the probes incorrectly and they are kind of bulky, so I am not sure if I have an issue or not. The 3 that have been reading are still reading, but I haven’t tested them at any further distances (beyond 3 ft) or evaluated anything related to reading consistency. I was surprised to learn that the 3 readers that had no measurable connection between pads where the resistor was located could still read tags with the external antenna, so I’m a little suspicious that the good readers could be jumping gaps somewhere too. But maybe it is nothing and I need to try again with some finer tips.
your cables look fine. Should be (very close to) 0 ohm.
Clearly the issue to fix is the soldering.
Keep in mind the need for strong cooling when you use high power values, the M7E will get hot soon. One other aspect is the strong power supply that can handle bursts. It needs good capacitors. A typical wall-wart will not do it. There are many articles around that on this forum