Thunderstorms, Persistence, and Remote operation - 3 Questions

Al_NN4ZZ

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

Steve-N5AC

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

Al_NN4ZZ

Steve, Thanks for the reply. In another topic, there is conflicting information for item #3. It indicates the TXCO is on as long as there is power applied. See the highlighted text in this snapshot. Can you confirm one way of the other?

Steve-N5AC

Yes, I was the source of both pieces of information. Initially, the OCXO was to be a module that plugged in where the GPSDO goes. This was later changed and the OCXO goes on the main board. As we characterized the OCXO, we found that the startup time was so fast, it just made little sense to leave it on all of the time. So the amber LED is only for the GPSDO and the OCXO is off when the radio is off. Steve

Tim K8XS

Steve, Along the lines of lightning, forget the direct strike. I don't know of anything that can survive a direct strike unscathed. My concern is near by strikes. I have lost several Ethernet adapters and routers by having long (>10 feet) network cables plugged in during a thunderstorm. Is there any protection on the Ethernet port of the 6000 or is it better to disconnect the Ethernet cable during a thunderstorm? (BTW I have also lost RS232 ports with long RS232 cables attached.)

Al_NN4ZZ

Steve, to summarize: - TheTCXO oven is NOT powered unless the front panel switch is ON - The documentation regarding the AMBER led above is incorrect - There is no benefit to keep power supplied to the radio unless you have the GPSDO option or unless you plan to use the "remote on" ACC feature. (other than the temporary benefit due to the lack of persistence) Is this correct? Regarding the TXCO being on the main board rather than a separate module there may be another factor to consider. On another radio I have the TCXO oven has a fairly high failure rate. The TCXO is on a separate plug in module which allows it to be easily (and inexpensively) repaired by the users in the field. The vendor recommends keeping the radio power on and the oven powered up rather than cycling. There was some feeling that people that didn't keep the main power to the radio on have higher failure rates. Hopefully the TCXO you are using won't have this issue. Should I make this discussion a separate topic? Regards, Al / NN4ZZ

Mike W8MM

I have lost network cards and RS-232 ports from nearby lightning strikes numerous times - same symptoms -> long cable runs. The only sure-fire ;-) prevention I have found is fiber-optic isolation. In my case, I use fiber for the whole run and terminate each end with a cheap fiber-to-ethernet or fiber-to-RS-232 edge device. Some others may promote single-point grounding with transient suppressors, but I like fiber. It always works!!

Steve-N5AC

Al, All of your summary is correct. I am not aware of any failures with TCXOs resulting from power cycling. We use them in our other radios without incident (we use the same brand of TCXO in the FLEX-5000). It up to you whether you make it another topic. I would use the benchmark: do you think this is something others would be searching for (TCXO failure from power cycling) or not? If it's a common problem in the industry and you think others will search for that specific idea, we should address it in a topic. If it is not, it's probably fine being mentioned here. Steve

Al_NN4ZZ

Steve, Thanks for the reply. Your feedback on the use of the same module in the F-5000 is good enough for me. I'll just leave it here and if there are any failures we can always address it later. Regards, Al / NN4ZZ

Al_NN4ZZ

Mike, I like the idea of using fiber but my CAT5 network cabling is in place already. The long runs go from a central server room all over the house. And I use a switch in the shack to connect the computers, printers, and soon the 6700. Do you think it helps to just use a fiber link for the last 5 feet? In other words from the switch to the radio, switch to the computer, etc. Or maybe just one isolator between the RJ45 in the wall and the switch which is about 15 feet and leave the short jumpers from the switch to the computers, radio, etc as CAT5. Do you have any specific recommendations on the fiber optic isolation devices or vendors? Regards, Al / NN4ZZ

Mike W8MM

Al, I, too, have long CAT5 runs all over the house. I have a conduit from the basement to my shack and it was easy for me to pull out the CAT5 and pull in the fiber. I can't remember what the edge devices are, but a quick Google search for "fiber media converter" will produce tons of hits. Happy shopping ;-) The main benefit of a fiber link is to disrupt currents trying to flow through the equipment induced by the lightning pulse. Any long conductor attached to the equipment is either a capacitance probe or a 1-turn transformer as far as lightning is concerned. Disrupting the impromptu current path is the goal. As long as the the fiber run is long enough that the induced pulse can't flash across the gap provided by the fiber, even a few feet will help a bunch. I should mention that the media converter power supply on the CAT5 end of the run is a potential lightning failure point because of the current path from the CAT5 "antenna", through the media converter, through its power supply, to the house wiring mesh, and ultimately ground. That is another reason that I pulled out the CAT5 to the shack and replaced the entire run with fiber. That way the non-conducting fiber cannot form a lightning antenna that induces currents anywhere!

Al_NN4ZZ

Mike, Thanks, it's not as easy to replace my long runs but I like the idea of adding a 15 foot fiber link between the shack switch and wall jack to improve my chances of surviving an induce spike. And as someone mentioned, with a direct hit all bets are off anyway no matter what you do. So I'll do some shopping to see what I can find. Regards, Al / NN4ZZ

Gerald-K5SDR

Al, I agree with Steve that TCXO failure has been a non-issue. We have been using this part since 2006 with very few problems.

W0QKL

Al

I would just like to add my two cents to this question. I had a thunder storm move through the area a few weeks back and the tail end of the storm was some 25 to 30 miles away so I decided to power up my 6500 and make a few contacts, after getting back on the air there was a VERY Powerful SINGLE clap of thunder very close to my location and the rig lost about 20+ dB of gain on the front end of the transceiver. I verified the loss of sensitivity using the Drake TR-7 transceiver, as I have compared both the 6500 and TR-7 on very week signal several times in the past. After the thunder clap I needed the pre-amp on max just to come close to the sensitivity on the drake. I sent the rig in and Flex replaced IC-73. I now keep the antenna disconnected if there is even a hint of thunder in the area. 

Regards,

Bob - W0QKL

Al_NN4ZZ

Bob,
Thanks for sharing your experience.  I have a disconnect on my coax coming into the shack for this reason.  It is an Array Solutions ratpack switch that grounds all of the antennas when it is not energized.  (of course in the event of a direct hit. all bets are off).

But it brings up the whole question regarding the RISK of operating remotely.   If you live in an area that is susceptible to thunderstorms like Florida, Georgia, etc,  you know they often come up quickly and unexpectedly.   And if you are operating remotely (even just across town) you won't know when one is in the area.

Even with the ability to remotely power down the station (radio, amp, antenna switches, etc)  how will you know when the weather requires that?   I wonder what others do or are planning to do for remote operation. 

Howard / KY6LA,
I know you operate remotely a lot, are there any special precautions you take or is your CA QTH pretty immune to thunderstorms ?   

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com

   

KY6LA_Howard

Simple answer I live in San Diego. We get 320 days a year of sun and 45 days of clouds/fog. I put a new roof on the house in Oct 2012 and the first time it saw rain was Feb 2014. In all my 30 years in San Diego I don't recall ever hearing thunder or seeing lightning. Hence I do absolutely nothing to protect my equipment

Al_NN4ZZ

Howard,
Well that makes sense --- your QTH is a very good one for remote operation from the lightning perspective.  For those is us not so lucky, we'll have to figure out something.  By the way here is a link to a site to monitor lightning strikes in real time.  

http://www.lightningmaps.org/realtime?lang=en


Here is a snapshot from this afternoon around 2200 UTC.  It shows our area in Georgia....every yellow dot is a strike.  They fade over time.   The blue and green lines pop up for a second when there is a strike and triangulate its position from several listening stations.  You can zoom in or out to cover your area or the whole country.  In the snapshot below you can see the storms in Alabama that are headed our way.  

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com

W9OY

If it jumps the 20,000 ft gap between the anvil and the earth any gaps in the radio, relays or even cables laying on the floor are trivial. The only recourse is single point entry of all cables and ac. W8JI has pretty good info on his site 73. W9OY