I’m new to this site and not sure where to post this, so please forgive and redirect me if needed.
In a Correctional setting, I am experiencing multiple instances of inmates being able to pick up facility/officer radio traffic on Sony SRF-39FP Walkman type radios.
If anyone has experienced this, or similar anomaly, please share.
Thank you.
If you are transmitting in the clear on FM - especially VHF, then the problem is simply signal strength and a wide open receiver, with very little out of band resistance built in. Usually the problem is worse when there’s a maths link between TX frequency and the FM broadcast band.
Yes, it is clearly poor/little/no shielding on the receiver (SRF-39FP). How to prevent it from picking up the VHF signal is my quandary.
How close are the radios? You can improve it a bit of you are willing to wreck it. The trouble is that it involves screening. The process isn’t too difficult. You can use guitar cavity screening foil, or paint on shield - but this of course wrecks the MW internal antenna performance.
Modifying the SRF-39FP’s is NOT an option.
Perhaps my identifying myself as a Dept. of Corrections Radio Tech has not communicated the broadness of this situation.
The anomaly is occurring in multiple facilities, in multiple locations across the entire State, and over multiple frequencies. The “receivers” involved are personally owed by incarcerated felons, and number into the hundreds if not a thousand plus. The VHF signals being heard are of the Corrections staff.
In that case, your only option is to swap out the radios - digital being the obvious move. I didn’t realise the radios belonged to the inmates!
VHF is just too close. Which band are you transmitting in (roughly). I’d have thought that security wise, digital is the only real solution - especially as these kinds of radios can be tweaked to make them even more responsive to the out of band signals. Digital just makes a nasty noise.
The SRF-39FP has been around since the 90’s and, as I stated before, there are hundreds if not thousands of them throughout the system. There are digital radios available for inmates to purchase as well, but the SRF-39FP is much cheaper, and many of them get purchased used from inmate to inmate. I agree the “easiest” option is to just pull them and replace them…however government just doesn’t work that way lol. We can’t just force a system wide change when it come to prisoner property.
The way I see it, there are only two solutions: Replace the radios in the hands of the inmates with something else or replace the Correctional Officer’s radios. The latter would seem to me to be the better solution as it would give you the opportunity to move to a higher band (900 MHz) or move into a digital mode.
That’s what I meant too - I assume these radios are with the long term prisoners, and maybe passed on to new ones? Seriously though, I’m surprised that security in this day and age is treated so casually? The inmates can listen to the staff? This should be sorted by the powers that be urgently. In the UK for a long time our fire and police services used channels inside the FM broadcast band. Everyone listened to them. Eventually they moved out. Digital radios for the staff are now cheaper and offer more features than ever before, and security wise, so much better.
Thank you for your input and concern. However, the cost of equipment alone for a project on the scale you suggest would be into the multi-millions. The anomaly is occurring on a VERY limited basis. There have only been a handful of reports from a couple of facilities. Add to that, that it is neither consistent nor continuous (a prisoner doesn’t hear more than a few words at a time, not whole transmissions).
I know that if I were a correctional officer and knew the inmates could hear what I was saying on the radio, I’d be going to the union because it’s a safety issue. Whether the inmates are hearing just a few words, or whole transmissions is irrelevant. The situation will change when a CO is seriously injured, or worse, killed because of the problem.
I’d make this report to your superiors and suggest they make a change to the type of equipment the inmates can buy. Yes, it isn’t an instant solution; but one that will take years to take effect. At least is is doing something. Until your state upgrades its communication system to a modern digital trunking system, there really is little else that can be done.
The wheels of progress turn slow. We have begun lifecycle replacement with digital capable equipment a couple of years ago.
The minute you work with compromised radios, your bosses have put you in a position that is unacceptable. Who runs the prison, the inmates?
Unbelievable, and somebody should ask your union to sort it out - putting you all at risk like this!
People complain the UK is always behind, but our prisons and police have been secure and digital for quite a while now!