Thunderstorms, Persistence, and Remote operation - 3 Questions

  • 2
  • Question
  • Updated 4 years ago
  • Answered
Thunderstorms, Persistence, and Remote operation - 3 Questions
There have been some posts about leaving the radio on 24/7 to get around the persistence issue. That may be a reasonable short term option for some. An FRS rep suggested it's fine and he does that himself.

Question 1 - We get a lot of thunderstorms here and even with the antenna disconnected I don't like to leave radios powered up. Is that a valid concern to protect the front end?

Question 2 - for remote operation, is it okay to leave the radio on 24/7 (given the lightning concerns) or is this a case where the "remote on" feature via the ACC connector is the FRS recommendation?

Question 3 - In the long run (after persistence is working) I'm planning to leave the radio powered 24/7 for the TXCO oven. Is it correct to assume that when the front panel switch in the off position, power is ONLY applied to the oven? Or are the processor and the RF front end circuits also powered up and susceptible to lightning induced surges?

Regards, Al / NN4ZZ

Photo of Al / NN4ZZ

Al / NN4ZZ

  • 1710 Posts
  • 581 Reply Likes

Posted 5 years ago

  • 2
Photo of Steve - N5AC

Steve - N5AC, VP Engineering / CTO

  • 1030 Posts
  • 1001 Reply Likes
Official Response
Al,

#1, the radio front end is "reasonably protected." With the preamp off, the radio overloads at +9dBm. Damage occurs at about +24dBm as I recall. There is a relay to disconnect the antenna from the ADC at +17dBm. Lightning could easily cross the relay and cause damage as in all radios. If you believe you could be struck by lightning, I would advise disconnecting the radio from the antenna -- I would.

#2, The remote on is really designed to provide a way to power up the radio or power it off to save current, reset the radio, get it off the network, etc. Lightning concerns are independent of the remote on functionality.

#3, With power off (power switch off or remote off), the OCXO or TCXO are not powered. They will quickly return to the correct frequency. With a GPS module, you have the option of leaving the GPS on or off when the radio is off. The GPS module employs a TCXO that is disciplined by GPS.

When the power is off, only the supervisory processor (a Cypress PSoC) is powered, not the FPGA or TI DaVinci main processors. Lightning won't care about any of this, however. As it works its way through the radio it generally feels plenty capable and free to jump tracks, run across components that are not supposed to conduct, etc. It is probably "better" to have the radio off than not if lightning strikes, but I would bet there would not be a big difference in the outcome from a direct strike.

Having said all this, there are two main boards in the radio -- the MBTRX with the processors, FPGA, ADCs, etc. and there is the MBPA100 board with the PA. ANT1 and ANT2 are on the MBPA100 board. I would bet it is harder for lightning to move from one board to the other. The MBPA100 board is much cheaper to replace should it need to be replaced. So if I was going to take a lightning hit of any kind, I would prefer it be on the MBPA100. Not sure if this helps...

Steve