Re: SDR's and ESD Damage.


If you have a transmitter involved this system will "work" but it is not optimum. Ideally the TR switching should have a aafe sequencing, which may clip off the first syllable of a word when using VOX.

To transmit
First the antenna "relays" must switch to the safe TX position, and then the transmitter power amplifier can become enabled.

To receive
Disable the transmitter PA and then switch the antenna "relays" to the RX position.

Alas, without modifications to most transceivers won't work. The can be made to work with an external TX switch that handles VOX for SSB folks (perhaps with a couple syllable audio dealay).

The last I looked at it the Signalink line was missing two critical features. It needs to feed out an antenna switch interface control and a separately timed transceiver control. It also needs a computer controlled TR switch signal for very fast switching signals such as ALE. (Using VOX trims off enough of the first transmission that one of three redundant signals is missed reducing performance under poor conditions.)


On 20180409 03:25, David Salomon wrote:
Harry -
I put one of these ( in front of my receive antenna splitter/amp, which goes to all my HF radios.  It protects all the attached devices from coax induced ESD and signal overloads.  It will cap the signal level to a safe level so you don't have to worry about cooking the front end of the radio from a transmitter that is too close.  In my case, my receive antenna is only about 15' from one of my transmitting antennas, so it's a lifesaver for my radios.  It is also a switch that will cut the antenna connection to the radios on transmit.  This particular one isn't sold anymore. However, DX Engineering (and many other ham radio suppliers) have other devices ranging from fairly inexpensive to moderately expensive.  Note that this is ONLY for receive antennas - you can't use it on a connection that will be used for transmit.
I'd rather blow up a $200 protection device than thousands of dollars of connected equipment.
73 - David, AG4F

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