Lscott

Looking through the FCC rules there doesn't seem to be any requirements that repeater offsets must be 5MHz. ----------------------------------------------------------------------------------------------------------------------------------------------------------------- §95.1763 GMRS channels. The GMRS is allotted 30 channels—16 main channels and 14 interstitial channels. GMRS stations may transmit on any of the channels as indicated below. (a) 462 MHz main channels. Only mobile, hand-held portable, repeater, base and fixed stations may transmit on these 8 channels. The channel center frequencies are: 462.5500, 462.5750, 462.6000, 462.6250, 462.6500, 462.6750, 462.7000, and 462.7250 MHz. ( 462 MHz interstitial channels. Only mobile, hand-held portable and base stations may transmit on these 7 channels. The channel center frequencies are: 462.5625, 462.5875, 462.6125, 462.6375, 462.6625, 462.6875, and 462.7125 MHz. © 467 MHz main channels. Only mobile, hand-held portable, control and fixed stations may transmit on these 8 channels. Mobile, hand-held portable and control stations may transmit on these channels only when communicating through a repeater station or making brief test transmissions in accordance with §95.319©. The channel center frequencies are: 467.5500, 467.5750, 467.6000, 467.6250, 467.6500, 467.6750, 467.7000, and 467.7250 MHz. (d) 467 MHz interstitial channels. Only hand-held portable units may transmit on these 7 channels. The channel center frequencies are: 467.5675, 467.5875, 467.6125, 467.6375, 467.6625, 467.6875, and 467.7125 MHz. --------------------------------------------------------------------------------------------------------------------------------------------------------------------- I see a lot of newbie questions about repeaters where the "typical" reply states the repeater input frequency is 5MHz higher than the output frequency. However the rules don't require that. Read sections §95.1763 A and C. No mention about a required offset when going through a repeater. It seems so long as the repeater output frequency is one of the 462MHz main channels and the input frequency is one of the 467MHz main channels the FCC is fine with that. Why does that matter? Many people are buying GMRS specific radios that have the repeater frequencies per-programmed into them, with the "common" 5MHz offset assumed by the manufacture and hard coded by the firmware. However if a repeater owner sets up his system to use an input frequency and output frequency that is NOT a 5MHz offset anyone unfortunate enough to own a radio with the repeater frequencies hard coded by the firmware is out of luck. There is noway to make it work short of changing the frequencies. For somebody who wants to keep his repeater "private" with reduced chances of being abused by non authorized users could employ a nonstandard frequency offset. Of course anyone who wishes to use the repeater must have a radio that allows the "non-standard" 5MHz offset to be programmed into it. That leaves for the most part old commercial radios. For a really flexible GMRS specific radio a manufacture should provide a repeater memory channel where the input and output frequencies are selected from a list along with the access tone(s) required. I see enough comments about the Midland radios concerning the tone and bandwidth issues, but nothing about the repeater offsets. If the radios are targeted to be "fully" GMRS rule compliant, sooner or later, the above issue should be addressed as well. This likely also applies to the other GMRS specific radios I see mentioned on the forum.

As a side note there is a story about a Ham who really disliked people using cheap Chinese radios on his repeater. His “solution” was switching to Motorola MDC for access, which they don’t have. Predictably he got a lot of negative comments over the switch, mostly along the lines of being a Motorola radio snob. But it was his repeater if I remember right. https://en.wikipedia.org/wiki/MDC-1200

Some years back I heard a Ham talking to his buddy at Dayton Hamvention one year. He went into the porta-potty. Well his expensive HT slipped off the belt into the big round hole. No guessing what he was shopping for later.

You should key up the repeater, state your call sign, then say something along the lines of "testing...testing". Some people instead of saying "testing" ask for a radio check. Whatever you do the FCC requires you to identify with your call sign. Just keying up the repeater to hear the squelch tail and not ID is called "ker-chucking" the repeater and is bad practice, yet you hear people doing it. Some repeaters have anti ker-chucking protection where the transmitter doesn't key up right away, there is a slight time delay. Others need to detect some real audio before going into transmit mode.

Hummm.... 2x Kenwood TK-3180 3x Kenwood TK-380 Motorola HT750 Kenwood TK-3700 3x Kenwood TK-350G Kenwood TK-353G A whole slew of BaoFeng BF-888S and GT1 radios Kenwood TK-880 Kenwood TK-890 Kenwood TK-8360 Here's my list of just HT's, they all work and are programmed: Tri Band: 1 x TH-D74A VHF/UHF tri-band analog/D-Star Digital (MARS/CAP mod) 1 x UV-5X3 VHF/UHF tri-band 128 channel 1 x TH-350 VHF/UHF tri-band 128 channel Dual Band: 1 x TH-G71A VHF/UHF 200 channel 1 x UV-5R VHF/UHF 128 channel 1 x D878UV VHF/UHF analog/DMR Digital Multi Band: 1 x FT817 HF/VHF/UHF (MARS/CAP mod) VHF: 5 x TK-270G-1 VHF 128 channel 1 x TK-2000 VHF 16 channel (International Version) 2 x TK-2170-K VHF 128 channel 1 x TK-2140-1 250 channel (European Version) 2 x TK-2140 US version 250 channel 2 x TK-2160 VHF 16 channel 1x TK-2360 VHF 16 channel UHF: 2 x TK-370-1 UHF 32 channel 4 x TK-370G-1 UHF 128 channel 1 x BF-888S UHF 16 channel 2 x TK-3170-K UHF 128 channel 4 x TK-3160-1 UHF 16 channel 1 x T5720 (Motorola FRS Radio) I have a few dead ones in a junk draw that I may try to fix at some point or use for spare parts. Charger Collection: 5 x KSC-25 1 x KSC-25 (Chinese Clone mod'ed with Anderson Power Pole Input) 4 x KSC-16 1 x KSC-23 1 x KSC-35S Various chargers for specific Chinese and non Chinese Ham radios. Then there are the battery packs, antennas, mobile and base radios too.....

It just proves that if your LOS is obstruction free the distance can be very large. Ham's have been sending signals through their LEO, low earth orbit satellites, and the ISS, international space station, for years using nothing more than a 5 watt HT connected to a small handheld Yagi antenna. I made a few contacts years back using my mobile VHF/UHF radio with nothing more that a high gain vertical on the roof. http://www.arrowantennas.com/arrowii/146-437.html https://www.amsat.org/wordpress/wp-content/uploads/2014/01/Work_FM_Sats-20131010.pdf

The best I can suggest is just simply ask why recommend a different tone from the one you wanted. At least per your post they want to discuss it with you. They may have a very good reason. https://wiki.radioreference.com/index.php/Continuous_Tone-Coded_Squelch_System https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System

Well not for everyone. The law specificity exempts Amateur Radio, those holding a valid FCC license. However what about others that hold a valid FCC license such as GMRS? I guess Hams have better lobbyists and a well organized group, ARRL, to represent their interests.

I assure you the following is true. I've had a few Hams say they do CW while driving. They have a Morse Code key strapped to their thigh. One hand on the steering wheel while the other is sending code. I can't imagine how this can be done without the driver's attention being split between the Morse Key and paying attention to the road. Some people can't even drive and chew gum at the same time. I wonder just how this would be classified? There is no microphone.

"Please note: Use of an HT would still be a violation. The radio must be mounted and the microphone be corded to the radio. Please remember that not all law enforcement officers will be aware of these documents, and may not follow them. Amateurs may still be cited." So what is really the difference between holding a corded microphone or your HT with a pig-tail on it to the roof mounted antenna? These kind of laws are just pain silly.

Yeah, until the local PD shows up because you look "suspicious" and won't believe you're just doing a radio range check. Even a few Hams get hassled by the local PD for having a "scanner" in a vehicle and or hearing police radio dispatch calls coming from their VHF/UHF mobile. The recommendation is keeping a copy of the local/state law showing the exception for Hams handy along with your license just in case in the glove box.

Nice radio but it appears not to be certified for FCC Part 95 GMRS use. https://fccid.io/AFJIC-F221S

Well you summed it up right. The mystery is what effect is more dominate in real usage conditions, free space path loss, signal absorption etc. The impressive part is on UHF one needs significantly more power on UHF to generate the same signal strength at the receiver compared to VHF. That’s assuming you keep other factors about the same. In another topic I started I had asked just how much activity do people hear on the license free MURS channels, which are on VHF from around 151 to 154 MHZ. Given the issue of path loss and MURS radios limit to 2 watts I’ll guess it could outperform a much higher power UHF radio.

"www.bccdc.ca/resource-gallery/Documents/Guidelines and Forms/Guidelines and Manuals/EH/EH/Section2Final06062013.pdf"

That would be an interesting test. I often read where VHF tends to reach further because at the lower frequency the RF is absorbed less by tree leaves etc. I'm not so sure that's the main reason. There is another one that could explain it more called "free space path loss" which has nothing to do with signal absorption or blockages. https://en.wikipedia.org/wiki/Free-space_path_loss http://www.sis.pitt.edu/prashk/inf1072/Fall16/lec5.pdf What it comes down to is the signal strength is expressed in "volts per meter" and is independent of frequency but related to transmitter power. "http://www.bccdc.ca/resource-gallery/Documents/Guidelines and Forms/Guidelines and Manuals/EH/EH/Section2Final06062013.pdf" However since one has to use a resonate antenna, or nearly so, the antenna on UHF is roughly 1/3 the "length" of the same type at VHF and thus intercepts just 1/3 of the signal expressed in "volts per meter". Thus the received signal is 1/3 the amplitude, voltage wise, coming out of the antenna. From a power stand point the received signal "power" is proportional to the square of the voltage thus the "power" at UHF would be about 1/9 that at VHF, or in db's, 10*log(1/9), its 9.54db lower. https://www.allaboutcircuits.com/tools/free-space-path-loss-calculator/ Using the above calculator the path loss is 75.962db with the following data input: Distance: 1 KM Frequency: 150 MHz Transmitter Gain: 0 Receiver Gain: 0 And you get a path loss of 85.504db with the following data input: Distance: 1 KM Frequency: 450 MHz Transmitter Gain: 0 Receiver Gain: 0 The difference is. 9.542db lower as expected on UHF compared to VHF for the two frequencies used. The higher the calculated number is in db the higher the loss.

Thanks for the tip. I’ll have to try it the next time. Having the links get messed up sort of ruins things.

A good place to start is some answers to the following questions. 1. Used to communicate primary with just handheld radios? 2. Used to communicate primary with just base radios? 3. Used to communicate with base and handheld radios? 4. Is repeater access required and how far away? 5. Do you need multi-band access, like for Ham and GMRS? 6. What is the terrain like where you plan to operate most of the time? Flat, low rolling hills, mountains, lots of tall building etc. 7. How tall of an antenna can you tolerate? Like getting in to a garage, parking deck, drive through window heights etc. 8. Is a magnet mount needed or are drilling mounting holes in your vehicle OK? 9. How much money do you want to spend? There are a lot of antennas out there from a few inches tall to several feet costing as little as $20 and way up from there. Once you have an idea of what the requirements are people here have some good solid recommendations. Picking an antenna is like going to a buffet. There is too much to choose from.

Well the only way to get this to work is copy the whole URL into the address window up to the ".pdf" part. Then substitute the following for the "...ents" part. Then it should work for the long one. resource-gallery/Documents For the shorter one copy the whole URL into the address window up to the ".pdf" part. Then substitute the following for the "....ications" part. Then it should work for the short one. Don't miss the leading period. .za/publications

Dang!! This form's software keeps screwing with the URL's, they won't post right. They cut and past OK but when I post the message they get trashed. I'll try one more time. "https://www.google.com/search?q=field+strength+versus+power&client=firefox-b-1-e&ei=WsY6X4GYI8-PtAaf9JOAAw&start=10&sa=N" "http://www.bccdc.ca/resource-gallery/Documents/Guidelines and Forms/Guidelines and Manuals/EH/EH/Section2Final06062013.pdf"

Hummm. Firefox doesn't cut and past links very well at times. These should work I hope http://www.bccdc.ca/resource-gallery/Documents/Guidelines and Forms/Guidelines and Manuals/EH/EH/Section2Final06062013.pdf http://www.parc.org.za/publications/=Field strength vs radiated power.pdf

On closer inspection the ERP is based on the field strength of the signal. That's the point people seem to miss. A gain antenna increases the "E-Field", Volts per meter. When the tests are performed the location of the field strength meter has to be specified. When doing antenna testing on an antenna test range the "E-Field" is measured at various points around the antenna. There are relationships that you can use to calculate power (ERP) based on the "E-Field" strength. https://en.wikipedia.org/wiki/Surface_power_density The references below gives a bit more info on how the "E-Field" in Volts/Meter works out to power. Note that a number for the antenna gain is part of the calculations. http://www.bccdc.ca/resource-gallery/Documents/Guidelines and Forms/Guidelines and Manuals/EH/EH/Section2Final06062013.pdf http://www.parc.org.za/publications/=Field strength vs radiated power.pdf https://en.wikipedia.org/wiki/Effective_radiated_power There are two ways of looking at this EIRP, effective isotropic radiated power, and ERP, effective radiated power. The two are not the same. For EIRP it's assume the power is spread uniformly over a sphere, which will only happen using a "theatrical" isotropic antenna. The other, ERP, acknowledges that real antennas have some directional properties, thus a higher "E-Field" in some directions verses others. When the "E-Field" is measured then power calculated you will most likely end up with a power higher than what you see at the transmitter's output. That's the antenna's gain.

So by that definition even a high gain Yagi really wouldn't be violating the rules. There is only one driven element (antenna) everything else is either a director or reflector element.

Logically I can't see how limiting the output power will prevent exceeding the FCC's ERP limit. Since they have no idea what antenna is going to be attached it's impossible to set a power level that will not violate the rules, unless it's set at zero. You don't even need to attach a gain antenna. A few people have built a corner reflector and just stuck the radio at the right point which results in a higher ERP than what you get out of the radio, even with a fixed mount antenna. The radio is place at the position where the dipole element would go. Then ran a external headset with a conveniently long wire to the accessory input jack on the radio. https://www.qsl.net/ve3rgw/corner.html While not exactly portable its been done for point to point communications.

The usual rubber duck antennas, stubby antennas, have a negative gain. To get the 0.5 watt ERP the radio would have to produce more than 0.5 watts. Clearly the market for the radio is GMRS. The low power narrow band channels are an afterthought looking at what components were used. The point is anyone who is considering this radio with the idea of using it to talk to FRS radios, or have a real need too, will likely be disappointed. If the radio does what you want that's what counts. At least people know a bit more about the radio's likely performance and can make a better informed choice. That was the goal here.

One point not mentioned much are the gain figures work both ways. That is on transmission and reception. It pays to optimize the losses. A 5 watt radio likely is about as sensitive as a 40 to 50 watt one. You can run into cases where spending more money on a higher power radio to make up for the power loss but it does nothing to increase the receive signal strength. If you can’t hear the other station it doesn’t matter how much power you run. This could be the difference between using a 5 watt handheld with a roof mount antenna, or spending a lot more money on a high power mobile radio. I think enough information is here where choices can be made that fit budget and physical installation requirements. There shouldn’t be any really big surprises how the final system will perform.