intermod

But we can get 25 mile range on this portable radio, right?

This is where many groups should really start. The organization can pay for one commercial (or public safety) license for ~$300 (for 10 years) and be assigned one callsign that everyone uses. As opposed to every member having to figure out CORES, FRNs, and pay $35 for a GMRS license. GMRS may have been used originally due to the low-cost radios, but Part 90 radios are just as low cost today. Eventually PII (Personally Identifiable Information) will be enforced for CERT and SAR organizations, and FCC rules permit encrypted transmissions on commercial and public safety channels. And they allow for digital for greater clarity and capacity. And they can be linked easily and without controversy. And have slightly greater protection from interference, particularly if the groups chooses to use public safety catagory channels. Downsides?

I thought I would start this thread as LScott noted elsewhere: "Hummm… This could be the topic for another thread. GMRS seems to be mutating into a hobbyist type service. It seems the original primary intent by the FCC was a radio service simple enough to be used by ordinary people with basically no background in radio communication technology for their personal use, and immediate family members." GMRS traditionally had been for personal use (family, small groups and very small business), in direct or repeater mode. Repeaters were stand-alone (not linked). Large business use was discouraged as the FCC saw this as incompatible with personal communications (which is the main reason the service requires individual licensing). But the number of users have risen dramatically over the past 5-6 years (particularly in the metro areas), and the service is experiencing some growing pains (busier channels, more IX from businesses, other repeaters, etc.). What are the top three causes of this? In no particular order, here is a potential list: General experimentation with repeaters (duplex or simplex), increasing interference in some areas FCC permitting unlicensed 2-watt direct-mode usage Unlicensed 2-watt users operating direct-mode digital (NXDN, DMR, etc.) Entry by new unsophisticated users Linking repeaters using input frequencies (467 MHz; causes interference (IX) to other co-channel repeaters) Low cost (primarily Chinese) user equipment and repeaters Some sporatic use of digital repeaters on GMRS Linking (e.g., Local, Regional, National) Low-cost / long-duration licensing Russia? Other ideas?

Fixed....thanks.

For those who care, MotoSol's current GTR8000 line of repeaters may be replaced with their new "DBR" line. This also means that we may start seeing some GTR8000's repeaters becoming available on ebay soon. Here it is: https://www.motorolasolutions.com/en_us/products/p25-products/astro/dbr-m12-site.html I think a set of two repeaters share a single common power amplifier; specs indicate it allows for two carriers to be spaced as close as 50 kHz. It looks like we are moving back to point-to-point wiring. Equipment staging for these photos must have been performed by an engineer or sales person (or maybe the Human Resources Dept.). Example of DEI? You be the judge.....

I vagely remember this article. Our numbers are a bit differnt - but I dissagree with Jay on the 6 dB degradation. If you reduce the receiver bandwidth by half (25 kHz to 12.5 kHz), the receiver noise floor should drop 3 dB (improving C/I by 3 dB), offsetting his 6 dB to 3 dB. But the rest seems right on the money.

In reality, narrowband effectively reduces coverage by about 3 dB (is this 1/3? 1-2 miles? who knows; depends on the situation). But I would agree its noticeable along the edges. This has the same effect as reducing your transmitter power by half. This was one reason to encourage digital - it can (but not always) replace what was lost with analog narrowbanding. However, the most significant problem with analog narrowbanding was not the coverage impact in an of itself. The interference susceptibility, or the effect of interference, increased by 6 dB. Said another way, interference using narrowband has a much greater impact than it did with analog wideband. With the increase in unlicensed low-power use on the 462 MHz channels, useable range will be reduced significantly in the GMRS service. Interference susceptibility of digital actually improved - this included DMR, NXDN, P25, etc. And, it is even even better than analog wideband (there are just few conditional exceptions). Public safety radio users may not have expereinced as much interference degradation since their channels have less co-channel interference. One Conclusion: if the FCC considers narrowbanding, they really need to permit digital - otherwise range will suffer.

You can with DMR Heck, I don't even say my callsign over the air. Same and callsign is just imbeded in the digital stream....

After you asked this, I re-read the rule section. Maybe the answer depends on the definition of "sharing". There is sharing through "use", but then there is also sharing through ownership and/or control. I am thinking they are referring to "use", in which case a written agreement appears to be needed, along with record retention. Having said this - I know 95% of repeater owners or groups do not comply..... G

I am not completely following what happened - but if its not in the rules or provided in writing, then its not not official and considered hearsay. Although it might be smart to work with the FCC and start a conversation. I hope they did not ask who else uses the repeater; this would be a bit agressive and would warrant a call to your elected represenative (hopefully republican) to have them suggest the FCC back off. But everyone seems to forget this rule: "§ 95.1705 Individual licenses required; eligibility; who may operate; cooperative use. (f) Cooperative use of GMRS stations. (4) All sharing arrangements must be conducted in accordance with a written agreement to be kept as part of the station records." Normally, the best policy in any organization is to keep a limited number (or no) records....but this rule requires something. This is why I have always said that open repeaters may not be permissible unless they meet this requirement.

I was unable to pass them.

Looks like about -119, which is low for VHF. If you have good coax then you are doing better than my area....

You may be one of the few. What does your SDR show for noise floor at 16 kHz bandwidth?

High noise floor, particularly in the metro and suburban areas, can be the controlling factor. This is primarily caused by microprocessors, associated clocks and switching power supplies in electronic products (including many LED light sources). This effectively deafens VHF receivers so that they are no longer as sensitive as they used to be. If you ever get a chance to use 700, 800 or 900 MHz, or even 1200 MHz, it will become immediately obvious. As was said above, while VHF propagates really well outdoors, in some cases the 700-1200 MHz bands can actually do better, except when the signal hits dirt (hill or mountain) or a dense foliage. Another factor to consider in VHF is portable antenna efficiency. Most portable radios are equipped with the 10" flexible helical antenna, versus something that more approximates a 1/4 wave length (18"). The 10" has an effective gain of -11 dBd. That takes a 2-watt MURS radio and degrades it to less than 0.2 watts. And it does the same to reception of signals......so VHF is really being hammered. UHF has become degraded but not as bad. But the antennas (for a given length) are more efficient.

IEEE TECH TALK: IS VHF DEAD? Date: 13 Feb 2024 Time: 05:30 PM to 06:50 PM Online Join link Join Zoom Meeting https://us06web.zoom.us/j/87613850683?pwd=VGhYQmxsU0dlbE5qRnMyS3o2Vmxqdz09 Meeting ID: 876 1385 0683 Passcode: IEEESEA https://events.vtools.ieee.org/m/401815