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Yes, absolutely, Lscott. Equipment needed. -RSSI meter. (Motorola radios have RSSI meters built in, make sure its calibrated, all XPR radios I own are within 0.5 dB of each other, so they are good for the sake of this test) -Signal Generator (use a calibrated RSSI meter to ensure the signal on the display is correct, used the XPR radios here to measure) -50 Ohm dummy load, I use a 50W one, but for the receiver sens test only you don't need anything more than 1W. (for duplexer desense you need the large one) -ISO-tee (directional coupler) Procedure: 1) If you don't have a directional coupler and you don't want to buy one, you can build your own ISO-tee using an old SO-239/PL-259 T-adapter. You need a hacksaw and a file. Unbolt the PL-259 prong from the T-adapter first, cut it with a hacksaw so it barely touches, and then, if needed, gently file it until the measured isolation is around 20-30 dBm. Remember the T adapter already has a 3dBm isolation, and it doesn't take much to file it a bit too much, so, be careful: I ruined two T adapters before getting it right... To measure the ISO-tee isolation I used the XPR6550 RSSI meter with the Signal Generator. You can also install a 20 dB attenuator on one end too I've been told... or you can just go and buy one from eBay... 2) Measure the site RSSI with no signal, this is the lowest signal the radio will be able to hear, for that I used the XPR6550/7550e RSSI meter. This is the best the radio can do, if the noise threshold is -107 dBm, it will never be able to hear a -115 dBm signal... no matter what. You want the radio to be as close to this figure. Perform the ISO-tee tests on several locations to see how different noise thresholds affect receiver. Useful for mobile application. Noise threshold is not receiver desense. Desense happens in addition to the noise threshold. 3) Measured absolute receiver sensivitty and squelch sensitivity on the radio. -Set SQL to threshold. -Connect SG to radio directly with lowest possible signal. -130 is usually a good number to start. -Increase signal dBm until SQL opens. Record this number. -Reduce signal dBm until SQL closes completely. Record this number. -Keep reducing signal dBm until RX led is no longer blinking. Record this number. 4) Connect ISO-tee as follows: -The vertical part of the T-adapter to the signal generator (the one you cut/filed). -The horizontal ends one goes to the radio, the other one to a 50ohm dummy load. 5) Measure dummy load sensitivity. -Set SG signal strength to lowest possible dBm. -Increase signal dBm until SQL opens. Record this number. -Reduce signal dBm until SQL closes completely. Record this number. -Keep reducing signal dBm until RX led is no longer blinking. Record this number. 6) Replace dummy load with the antenna the radio uses and measure sensitivity again. -Set SG signal strength to lowest possible dBm. -Increase signal dBm until SQL opens. Record this number. -Reduce signal dBm until SQL closes completely. Record this number. -Keep reducing signal dBm until RX led is no longer blinking. Record this number. 7) Subtract the RX led sensitivity figure recorded in step #5 minus the RX led sensitivity recorded in 6. 8) Subtract the result calculated in step #7 from the figure recorded in step #3. That is your "effective sensitivity" which can vary quite a bit depending on location. 9) Subtract the result from #7 from the noise level, that will give you the desense relative to noise floor. 10) Now repeat step 7 8 and 9 this for the figures calculated for SQL open and close if you operate in FM, remember to set SQL to threshold, or lowest setting possible. For FM operation Squelch Performance is critical, so you will determine using this test if the radio needs its squelch aligned, tuned... etc. --You can also use this procedure to evaluate duplexer performance and see if you need additional isolation on the RX side if its desensed b/c the transmitter...etc. Once I performed this test on enough of my radios I started to see an emerging pattern, a trend. After all radios were measured, most commercial gear radios I own measured a typical 3-4 dBm "desense" over the noise floor in nearly all my use case conditions, whereas nearly all CCR stuff had an average of -13 dBm desense, in VHF, and about -17 dBm desense average in UHF, again under typical use case conditions. EDIT: Another trend I noticed was that for nearly all CCRs, the higher the antenna gain, the higher the desense above noise threshold, or a decrease in effective sensitivity. Using my base antenna as the ISO-tee antenna, a triple 5/8 collinear at 40 feet up, the desense measured on several CCRs was pretty bad, but honorable supersuck mention goes to all the TYT and Retevis CCR radios tested (GD77, RT52, RT82, TYT MD760) The desense over the noise floor (which was measured at -119 dBm) was on the order of -38 dBm in VHF, and -43 in UHF... so all that gain that my base antenna, all 4.5 dBb, were demolished by the massive -43 dB desense coming from the CCR landfill of garbage... A total winner in my book to buy these pieces of garbage. With the GD77/RT52/RT82/MD760 the base antenna I couldn't hear a 50W mobile beyond 2 miles. With an EVX-539 portable mated to the same antenna I could hear the same mobile, on 25W, talking from 17 miles away. Again, same antenna. G.

Ok, Great questions and while I am half asleep I'll try to get a reasonable answer to you. Channel 8-14 are limited to .5 watts power and 12.5kHz bandwidth due to them being close to the repeater input channels. By limiting TX power and narrow banding those channels, it reduces the chance of interference with repeater users. FRS is narrow band (12.5kHz) all the way through, and most bubblepack radios will be set up this way. GMRS uses wide band (20kHz.) They can talk to one another if on the same channel, though there will be some degradation of audio (narrow band transmissions will sound quiet on wide band channels, and wide band transmissions may clip or sound over-modulated when heard on a narrow band channel) Bandwidth is the total amount of frequency space a signal is allowed to take up. A 12.5kHz signal can take up as much as 6.25kHz of frequency space on either side of the center frequency. A 20kHz signal can take up to 10kHz on either side. So when a wide band radio is listening to a narrow band transmitter, it is expecting a 10kHz signal on either side of the center frequency, however since the narrow band radio only sends out 6.25 on either side, the audio output becomes quieter. On the flip side, a narrow band radio is expecting a 6.25 signal on either side of the frequency, however when it receives a 10kHz signal, the radio is hit with an extra 3.75kHz of signal and will either over-modulate, or overload the front end (in rare cases however usually worse when very close to one another.) I'm sure some of the other radio heads could explain it better, but thats the fundamentals. Narrow band and wide band radios can talk to one another which a few minor issues, but will work in a pinch. and the .5W TX power is simply to help prevent interference with repeater users.

The issue is with the importers and manufacturer’s taking liberties that are counter the FCC regulations either explicitly or implicitly. The FCC establishes technical criteria for devices that are intended to be used in only certain radio services, to maintain the integrity of the service and to serve the best interest of the people. Without this the service falls apart, quality/reliability degrades, and the service dies. Without it, the people are not happy. I will avoid all debate on how well they do it. Each service is established with frequencies, emission types, power level limits, and how they are to be used and by whom. The radios manufactured are intended to be used in and for that service only, and intended to be operated by persons or organizations licensed to use them. Depending on the service, the persons may or may not be required to have any technical knowledge. It used to be it take a certain physical hardware design to achieve this. Certain models for certain services. This is all with the intent of making the service most useful and effective for the parties for which the service is intended to serve. Technology has evolved. Current hardware design now makes it possible to design a radio that is technically capable of operating on wide range of frequencies, all types of emissions and wide range of power settings and of various qualities. That is great, as it makes it possible for a manufacturer to perhaps use the same radio innards to serve different purposes, a cost benefit to the manufacturer and consumer. The problem comes in when the radios are not locked down to and limited to the service for which they are intended and the radios are available to persons that have limited or zero knowledge of the various services. A person gets a radio learns how to operate it and suddenly they transmitting on frequencies that adversely affect public service. Suddenly a person changes a setting and now digital communications is happening on frequencies reserved for FM. Radio only works well for for the masses when standards, rules and guidelines are followed. Yeh, isn’t it cool that now any person can afford to buy a radio that costs only $25 and that can play havoc on the amateur frequencies, public service frequencies, GMRS and FRS frequencies, etc... all in one. As a responsible licensed GMRS and Amateur Radio operator I want order on and to the airwaves. I want standards and I want the rules followed. Why, because it is this order that makes the airwaves useful when lots of people are using them. So the issue ultimately is that some manufacturers are skirting the intent of the FCC regs and selling radios that can configured by the user to operate in services that they are not certified for and at a cost that makes proliferation of the products into the hands of the neophyte easy and for nearly nothing. I reiterate a comment I made earlier. I own a recently FCC certified part 95e radio using just product supplied by the manufacture for that radio I can cause it to be suddenly have the ability to transmit on Amateur, public services, and private land mobile frequencies and at higher power than is allowed on some. Will I do it, no. Would others do it? Without a doubt. The point being, that should not be possible for a current generations GMRS radio without internals modification. This is where the manufacturer’s should be held accountable. Sadly, the offending manufacturers are all seem to be Chinese based and we do not have the ability fine them or shut them down. Then you have importers like Rugged Radio that appear to be complicit and take advantage of and propagate the weakness. Sadly, it is cost prohibitive to enforce the rules at the end-user level. We, the tax payers cannot afford that. Instead you need to go to the source of the problem - Manufacturers and Importers. Hope this helps. Michael WHRS965 KE8PLM Sent from my iPad using Tapatalk

Uh... has this topic been discussed beyond death yet?

... and as usual, the topic has been sidetracked, the OP has disappeared never to be seen again, and we're left arguing minutia of the meaning of poorly written rules that aren't enforced anyway. <sigh>.

Sigh... wasn't letting me add the JPG. https://i.imgur.com/mVih2uV.jpg