Yes, I thought of that. I carefully examined them, I have good stock of RP-SMA to SMA adapters and I have been bitten by that before! I also used an ohm meter to verify that the center conductor was continuous all the way back to the PCB where you can just probe the tab of U.FL connector on the Microchip module. I also verified it was not shorted to ground. But you are correct, it is about the right amount of signal loss you would expect from that.
I was looking at some GitHub issues and there are some complaints about the things gateway suddenly losing range. It seemed like it was more of an issue of sudden deafness and not reduced output power though. Do you think there is a possibility that it ever transmitted with no antenna installed? They always make a big deal about never powering up the SX1276 module with no antenna connected, but I don’t know why it would ever transmit without bring commanded to do so. Regardless, I follow their advice with all the node thingys that I’ve been working with and so far, it all seems to be working. I am using a Rak831 based gateway with a raspberry pi. That may be something you wish to consider if you’re going to start over. I think you can get a module from Amazon for a decent price, though you’ll likely have a hard time locating the adapter if you want to stack it straight on top of a raspberry pi without buying a whole kit that includes the pi.
I suppose I can’t rule out that it transmitted into an open circuit, although as an RF engineer I am usually very careful about that. Yes, the module does seem to be very deaf, I think I have established that. I am in a high lightning area and although there hasn’t been a strike close by in the last year or two, I suppose there could still have been enough of a transient induced on my antenna to damage the unit. I have a big external Laird antenna about 10m up in the air. I will re-check its swr before I connect anything new up to it.
Was your setup difficult to get going? I want to try and focus on applications rather than spending a lot of time getting a gateway functional. Originally I also wanted to help TTN with their Kickstarter campaign, I think they are trying an amazing venture. But I am a bit worried about the ruggedness of the gateway now.
Sounds like a lot of coax between the gateway and the antenna, what are you using for feedline? Getting me neither up and running correctly took longer than I wanted, but most of that time was learning curve as I’m new to the LoRa thing. It would appear that their (RAK) latest installation script might make things easier for a newbie because it factors in the intended region. Since I bought the US915 “kit”, I was a bit surprised to find it preconfigured for EU spectrum.
Most of the tutorials you find seem to make the same assumption. The whole key is getting the global and local json files right, and I can help you with that. I ended up not using the SD card that cane with the kit, so I had to download raspbian stretch light and go through that process. You gotta get the reset script toggling the right gpio pin too.
Kersing has a GitHub repo with a modernized packet forwarder, but I haven’t experimented with that yet. It helps if you have some Linux command line skills, but I’ve been using Linux for over 20 years, so… I think there are some other forks of the semtech stuff that have good setup scripts that ask questions helping you get everything right.
Once I got it figured out, it’s really pretty simple. You have basically two processes running, an interface to the gateway hardware and a somewhat abstracted packet forwarder. The install script sets them up to start as a system daemon.
I had the same intentions of concentrating on nodes, not getting the gateway working. In retrospect, I’m glad that I went through the pain as it helps me understand how all this works. I’ve played with a couple of different types of nodes now. I’ve gotten a bsfrance lora32u4 working and the Rak wisnode successfully sending and receiving. You’re going to find that’s not quite as straightforward as you’d think. I believe the firmware for the wisnode has been upgraded to better handle a us region, mine set the wrong channel mask, so it was way off frequency. I’ve only done activation by personalization (ABP) so far. I’m ready to step up to OTAA now, but I’m still experimenting, so ABP is easier for me. To get OTAA working, you have to have transmitting and receiving working, but ABP will let you get packets to the application without struggling with reception initially.
Using a Linux based gateway let’s you monitor the log files which helps a lot. I also recompiled the software with more debugging messages enabled.
Problems I had with the bsfrance board included having to struggle with the bootloader when trying to upload sketches (it likes to use two different com ports in windows), soldering up DIO1 (the default solder pads are fine, but most people seem to be obsessed with moving it to D6 instead of just jumpering the pads). They have reasons, but it’s not important enough to me to worry about it; I don’t mind losing Serial1. I will start using ISP from now on though as I’m tired of trying to time pushing reset at just the right time to get an upload via the bootloader working. As for the wisnode, don’t jump to the “obvious” conclusion that it’s an Arduino shield. You can use it that way, but you have to fiddle with jumpers every time you want to upload to the Uno or use jumper wires to get Serial debug messaged out. I’ve only used it by typing AT commands manually. It does work, but it’s not a panacea when you want to hook it to an Arduino Uno. It seems that most of the LoRa/Arduino boards have unique quirks to get them working. You almost always have to find some manual way to hook DIO1 to a pin before it will receive packets. I’m digressing, so I’ll likely get chastised for being off topic by discussing nodes in the gateway area, but I sure wish I’d have been able to find this information all in one place when I was learning it the hard way. 
Well, that’s quite a bit to chew on! I will have to think if it mightn’t be easier to get another TTN gateway and see if it is any different from my current one. That has some attractive features, because I could move the Microchip board from one to the other, I guess. But having control of the code would be nice. What I would really like is some sort of test mode where the gateway chirped on each of its channels in turn so I could measure the power.
As for the coax, no, the gateway is right up in my walk-in closet! The coax goes pretty much straight through the dry wall to the gateway. So there is about 2m of LMR400 coax. (plus a gaggle of adapters to get from the N on the coax to the RP-SMA on the gateway!).
So far I’m satisfied with the rak831 based gateway. It might be overkill to have a raspberry pi dedicated to driving it, but I’m thinking that will come in handy with the new TTN V3 stuff coming. I’ve been completely satisfied with it’s reliability. It was up almost 3 weeks straight before I rebooted it because it wasn’t showing up in the console, but that turned out to be a problem with the web interface, not my gateway. It was forwarding packets to the application just fine.
There are some utilities included with the software, but I haven’t played much with them. One, I believe, is for doing what you mentioned, forcing the transmitter to put a signal out.
Rak has some new stuff out that looks appealing. One is a kit for outdoor use. It’s waterproof and has a LoRa module that appears to put out a more powerful signal.
I find their web site a little hard to navigate! I don’t think it will work, it looks like they require a physical LAN connection. From where my gateway is I need it to connect via wifi, which the TTN gateway was able to do with no problem. In fact, their web based setup was super easy. So I am leaning with going with another TTN one. I was looking, it has actually been two years since I put it up first. Time flies.
I would like to hear how your flood project goes. My email is w0run dot gordon at gmail dot com.
The raspberry pi 3 and 3b+ have WiFi built in. I’m currently using a wifi connection for my rak831 based gateway. When I mount it in a weather resistant box and move it outside, I will be using power over Ethernet for it. I’m going the route of no feedline rather than trying to make up the loss with a bigger antenna. My only concern is heat, those rak831 modules get pretty warm.
I ordered and received a second TTN gateway. This time I am being particularly careful not to transmit without an antenna or other load. In fact, I have a 20dB attenuator in line, and a directional coupler.
I deleted my application (it looks like you cannot edit device EUIs), and created a new one. I registered a new device, and I got my device eui using lora.mac(). I made sure everything is set for the US 915 MHz band.
I have copied the code from several examples, I think it should be good. It just sits in the endless loop printing “Not joined yet”.
I am new to this and have recently set up a LoRa gateway and a end node on LoPy.
I have put in the appkey and appeui as required and can see the device as online on the console. The gateway is also sending and receiving packets correctly as expected.
However the LoPy is stuck in the “while not lora.has_joined()” loop. I dont know how to debug this can anyone please help?