Does LimeSDR have input ESD protrction against static when connecting an antenna? If so, are there any protection diodes or is this realised differently?
Also, can anyone confirm that the max input (rx) power (before damage) is really 12dBm?
I just want to be careful and not damage my future SDR with my 10W ham radio station.
All the inputs to the LimeSDR are transformer coupled from the U.FL connectors and there’s a fair amount of conditioning and decoupling post-transformer. I’m attaching a schematic that shows this. I would think it’s going to be nearly improbable that any ESD would propagate to the LM7002 to cause damage.
There is a 50W PA that I just purchased and took delivery on from EBay that accepts 0dBm (1mW) and provides +47dBm (50W) of power output. Here is the link to that PA:
The LimeSDR outputs +10dBm (10mW) so you’ll have to attenuate the output of the LimeSDR to obtain the 0dBm input requirement to the 50W PA, but that’s easily fixed with a small SMA attenuator like this:
That’s how I’m going about getting the LimeSDR up to power. All this also considers that you have a Low Pass Filter at the output of the PA very much like the TAPR LPF that will eliminate any transmitted harmonics from going over the air because of any non-linearities of the PA to the feedline and antenna.
Also, this assumes that you’ll be running the LimeSDR in the HF band. If you’ll be running the LimeSDR in the VHF, UHF or SHF band, there are comparable RF amplifiers out there for those services that you can find reasonably cheap, too.
Let’s say someone wanted to put some ESD protection on just in case. What would the part be called? An attenuator? A limiter? Can you recommend some parts?
This is my device schematic, used like standard HF input for all SDR RX
Can be useful from 400 kHz up to 130 MHz but best performances are 1,8 to 50 MHz http://www.helifor.eu/hrs/download/file.php?id=39
diodes are 1N4148
optional
Bourns 2057-07 Series Light Duty 2-Electrode Miniature Gas Discharge Tube (75 V)
That’s actually the PA that I purchased, but they offer it with a heatsink attached and that’s the one I purchased (assembled and with a heatsink). I’ve yet to strap it to a LimeSDR because I’m waiting for transmit to come along for Single Sideband (SSB, as in USB and LSB voice…There are no apps that support that yet).
More to follow on my results as I have that - stay tuned,
@9a4db
Will follow those links down. How would one apply tx power to rx1 or rx2? Does that require a physical connection or is that possible in software/firmware/gateware?
@hTo137
typical case can be when you connect RX1 to SDR and RX2 to any other transceiver.
Press to PTT (TX on, transmit) means end of life to SDR on RX1.
Therefore sometimes when I use for example FT817 with some of my SDR, mic or CW key
are physically disconnected from FT817 unit.
The best lightning protection is removing the antenna from the radio or the card itself that i always do when there is thunderstorm or lightning i dont trust anything else since voltage current or lightning can jump even its 1 inches apart.
Indeed. On the equipment I have permanently connected to external antennas I use N-type surge arresters. However, as with IT security, the best defence possible is to disconnect
@ancer this one wants to make the disconnect automatic. Works at night or when one’s away.
@andrewback from the hackaday description it sounds like they’re in a high lightning area so seems like they want to disconnect although they mention alternatives. Disconnect is what I do with equipment plugged in.
Back to static, seems like something inline is the best way.
It really is the only way to protect against lightening, the spike itself is so short and intense that any device based protection will only blunt the worst of a nearby hit.
Direct hits are death to anything connected no matter how you protect it.
Lightening? Unplug the antennas, preferably at the mast.