If you are reading this then you are probably a scanner listener. If you are not reading this then just move along. Many of you are also hams, GMRS operators or a user of some other two-way radio in proximity to your scanners. I am or have been all 3 over the years and almost always have a two-way radio (or 3 or 4) installed along with my scanners.
While this is all well and good, there are occasionally issues. The first is the transmitter feeding back into the scanner, either on the same frequency or a different one. Many of us program our scanner for many of the same frequencies we might transmit on, when I was still on the police department, I had all our freqs in the scanner all the time. I just had to remember to lock out that bank when I was working. Same for my ham and GMRS channels. I always have GMRS/FRS/MURS channels scanning and have to remember to turn off that radio or bank when active. While I am a ham I just am not quite as active there and rarely have ham freqs in the scanner, but when I do, I have to lock out those channels or banks.
One thing you may recall on a recent Tale I wrote is that I use CloseCall ALL the time. When I transmit the CloseCall scanner will of course open on that channel or some seemingly random frequency. That random frequency is not really that random; it is mathematically related somehow to the actual frequency, the scanner is so overloaded that it gets confused and hits on something weird. If I cared enough, I am pretty sure I could figure out the mathematical relationship between the actual and displayed frequencies but even I am not that anal.
The more serious issue however is the possible damage to the scanner or the multicoupler that it may be connected to. I use Stridsberg multicouplers in my home shack, I have 4 of the 8-port MCA208M active multicouplers, two of which are in current use and the other two are stored for future use. I also have a couple other active and passive units available as needed. I used to use a 4-port in the car but have added antennas or reduced the number of radios used so each has its own dedicated antenna.
Several times I have had the multicoupler “pop” and stop passing signals. As I understand from discussions with the guys at Stridsberg is that there is a SMD diode that protects the input of the multicoupler from damage caused by nearby transmitters. The problem is that this diode is not user replaceable. Over the years I have had to send a few back for repairs, if the device is still under warranty, they have fixed them for free, otherwise the repairs have been reasonably priced.
A year or two ago 3 of my 8-port multicouplers had gone bad. As they failed, I replaced it with a working unit until I was down to my last working one. I then sent all 3 failed units in for repair. One was still in warranty but the other two were well out of warranty. They fixed all 3 but only charged me for 2 and I got them back in a couple weeks and they all work great. They actually just replaced the oldest unit, it was of an older design, but they only charged me the repair rate to replace it.
I have also had a couple scanners themselves go deaf from overload by my dual bander in the car, most recently a BCD536HP. It was working great until one day I noticed it was not hearing anything. Swapping out the antenna did nothing, so I deduced that the radio was at fault. I opened it up and could not see any evidence of a cold solder joint or damaged BNC connector so sent it to Uniden for repair. The same radio had a display issue unrelated to this, so I had them fix both issues. It cost about $100 including shipping but was well worth the cost, this 536 works as well now as it did when new.
After spending a few hundred dollars fixing radios and multicouplers I looked into ways to avoid this. After looking at a couple alternatives I turned back to my go-to guys at Stridsberg and bought 3 LIM-01WB RF Power Limiters. These handy little devices go between the antenna and radio or multicoupler and protect them from nearby transmitters and electrostatic discharge (ESD) such as caused by wind or lightning. They mention in the documentation that they are not intended for direct lightning hits but can protect from ESD from hits that are nearby.
I put one each on the scanners in the car (BCD536HP’s) and one on the multicoupler at my home shack. At the time I only had one, so I didn’t need to buy any more but of course I have to change things around on a regular basis, so I have another two on order. Unfortunately, they are out of stock until mid-July due to parts availability so I will have to be patient. I suppose I could get a model from a different manufacturer, but I like Stridsberg’s products, and the customer service has gotten better recently. These aren’t really cheap, I paid $130 each for them but I suspect that I would make that up in repairs that I won’t have to make and some peace of mind.
Since I like Stridsberg’s products I will patiently await the two additional RF Limiters I have on order. I really only need one right now but one never knows so I bought two just in case.
As an aside here: After John Stridsberg (Founder of Stridsberg Engineering) passed away a few years ago his family took over the business. It was a pretty rough time I presume, and things got a bit sideways. Phone calls and emails went unanswered, and orders were delayed. Recently however they seemed to improve and, while not perfect, they have returned calls and provided honest answers to my inquiries. I had talked to John many times over the years, and he did some custom work for me a couple times. He was a good guy for sure!
Back to the Tale:
I have had these limiters in place for a year or so now and have not had any issues. Of course, there is no way to tell if I actually have prevented a radio or multicoupler from popping, but it makes me feel better just the same.
At home right now I have an ST-2 mounted on the side of my house (a topic for an upcoming Scanner Tale). The antenna is connected to a ChannelMaster balun, this goes to an F-to-N adapter, with a 3-foot pigtail connected to a lightning arrester (grounded of course). The main coax then connects that to my office, going to the RF Limiter. This is directly connected to the multicoupler with a double-male BNC adapter, and the scanners are of course connected to the multicoupler.
Both in the car and at home I have compared reception with and without the RF Limiter in place and cannot detect any noticeable difference. While the signal strength meters on the 536’s in the car are not to be relied upon other than as a relative indicator the voice quality and reception of weaker signals do not appear to be affected. At home I have used an Icom R8600 to compare and again I cannot detect any difference with or without the device in line.
There are cheaper devices out there, others have suggested some HP devices commonly available used on eBay. I considered them but ultimately went with the Stridsberg as they are BNC-equipped, the HP’s have SMA’s and would require additional adapters or jumpers Interestingly, when I got my LIM-01WB’s I took the cover off and found they use a Mini-Circuits product as the operative device. See the picture at https://forums.radioreference.com/threads/rf-limiters.474993/post-4026163\
If you have a transmitter near your scanner or the antenna then you probably should use protection. Think of it as a prophylactic for your radios; you will never know if it prevented something bad but it can make you feel better about your life choices.
While this is all well and good, there are occasionally issues. The first is the transmitter feeding back into the scanner, either on the same frequency or a different one. Many of us program our scanner for many of the same frequencies we might transmit on, when I was still on the police department, I had all our freqs in the scanner all the time. I just had to remember to lock out that bank when I was working. Same for my ham and GMRS channels. I always have GMRS/FRS/MURS channels scanning and have to remember to turn off that radio or bank when active. While I am a ham I just am not quite as active there and rarely have ham freqs in the scanner, but when I do, I have to lock out those channels or banks.
One thing you may recall on a recent Tale I wrote is that I use CloseCall ALL the time. When I transmit the CloseCall scanner will of course open on that channel or some seemingly random frequency. That random frequency is not really that random; it is mathematically related somehow to the actual frequency, the scanner is so overloaded that it gets confused and hits on something weird. If I cared enough, I am pretty sure I could figure out the mathematical relationship between the actual and displayed frequencies but even I am not that anal.
The more serious issue however is the possible damage to the scanner or the multicoupler that it may be connected to. I use Stridsberg multicouplers in my home shack, I have 4 of the 8-port MCA208M active multicouplers, two of which are in current use and the other two are stored for future use. I also have a couple other active and passive units available as needed. I used to use a 4-port in the car but have added antennas or reduced the number of radios used so each has its own dedicated antenna.
Several times I have had the multicoupler “pop” and stop passing signals. As I understand from discussions with the guys at Stridsberg is that there is a SMD diode that protects the input of the multicoupler from damage caused by nearby transmitters. The problem is that this diode is not user replaceable. Over the years I have had to send a few back for repairs, if the device is still under warranty, they have fixed them for free, otherwise the repairs have been reasonably priced.
A year or two ago 3 of my 8-port multicouplers had gone bad. As they failed, I replaced it with a working unit until I was down to my last working one. I then sent all 3 failed units in for repair. One was still in warranty but the other two were well out of warranty. They fixed all 3 but only charged me for 2 and I got them back in a couple weeks and they all work great. They actually just replaced the oldest unit, it was of an older design, but they only charged me the repair rate to replace it.
I have also had a couple scanners themselves go deaf from overload by my dual bander in the car, most recently a BCD536HP. It was working great until one day I noticed it was not hearing anything. Swapping out the antenna did nothing, so I deduced that the radio was at fault. I opened it up and could not see any evidence of a cold solder joint or damaged BNC connector so sent it to Uniden for repair. The same radio had a display issue unrelated to this, so I had them fix both issues. It cost about $100 including shipping but was well worth the cost, this 536 works as well now as it did when new.
After spending a few hundred dollars fixing radios and multicouplers I looked into ways to avoid this. After looking at a couple alternatives I turned back to my go-to guys at Stridsberg and bought 3 LIM-01WB RF Power Limiters. These handy little devices go between the antenna and radio or multicoupler and protect them from nearby transmitters and electrostatic discharge (ESD) such as caused by wind or lightning. They mention in the documentation that they are not intended for direct lightning hits but can protect from ESD from hits that are nearby.
I put one each on the scanners in the car (BCD536HP’s) and one on the multicoupler at my home shack. At the time I only had one, so I didn’t need to buy any more but of course I have to change things around on a regular basis, so I have another two on order. Unfortunately, they are out of stock until mid-July due to parts availability so I will have to be patient. I suppose I could get a model from a different manufacturer, but I like Stridsberg’s products, and the customer service has gotten better recently. These aren’t really cheap, I paid $130 each for them but I suspect that I would make that up in repairs that I won’t have to make and some peace of mind.
Since I like Stridsberg’s products I will patiently await the two additional RF Limiters I have on order. I really only need one right now but one never knows so I bought two just in case.
As an aside here: After John Stridsberg (Founder of Stridsberg Engineering) passed away a few years ago his family took over the business. It was a pretty rough time I presume, and things got a bit sideways. Phone calls and emails went unanswered, and orders were delayed. Recently however they seemed to improve and, while not perfect, they have returned calls and provided honest answers to my inquiries. I had talked to John many times over the years, and he did some custom work for me a couple times. He was a good guy for sure!
Back to the Tale:
I have had these limiters in place for a year or so now and have not had any issues. Of course, there is no way to tell if I actually have prevented a radio or multicoupler from popping, but it makes me feel better just the same.
At home right now I have an ST-2 mounted on the side of my house (a topic for an upcoming Scanner Tale). The antenna is connected to a ChannelMaster balun, this goes to an F-to-N adapter, with a 3-foot pigtail connected to a lightning arrester (grounded of course). The main coax then connects that to my office, going to the RF Limiter. This is directly connected to the multicoupler with a double-male BNC adapter, and the scanners are of course connected to the multicoupler.
Both in the car and at home I have compared reception with and without the RF Limiter in place and cannot detect any noticeable difference. While the signal strength meters on the 536’s in the car are not to be relied upon other than as a relative indicator the voice quality and reception of weaker signals do not appear to be affected. At home I have used an Icom R8600 to compare and again I cannot detect any difference with or without the device in line.
There are cheaper devices out there, others have suggested some HP devices commonly available used on eBay. I considered them but ultimately went with the Stridsberg as they are BNC-equipped, the HP’s have SMA’s and would require additional adapters or jumpers Interestingly, when I got my LIM-01WB’s I took the cover off and found they use a Mini-Circuits product as the operative device. See the picture at https://forums.radioreference.com/threads/rf-limiters.474993/post-4026163\
If you have a transmitter near your scanner or the antenna then you probably should use protection. Think of it as a prophylactic for your radios; you will never know if it prevented something bad but it can make you feel better about your life choices.
