Lscott
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Posts posted by Lscott
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Just FYI. One of the rv newsletters I subscribe to ran this article on batteries today
Nice article. One needs to understand there are several different Lithium battery chemistries which was not made clear. Some are a bit dangerous and can become unstable under certain conditions. The worse is Lithium-Ion. Lithium-Ion has one of the highest energy densities and why its used in EV battery packs. The protection and monitoring systems built into them is extensive. The other chemistry is Lithium-Polymer which sees use in flying drones where you need the most power and energy storage with the least weight. Those people have to be careful as there have been fires from battery failures.
The reason why Lithium Iron Phosphate is the recommended chemistry is due to it's very high stability. The down side is the energy density, watt-hours per unit volume or watt-hours per unit weight, is a bit lower than for the other types but still much higher than for Lead Acid batteries. Over all for portable use its a good trade off.
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These guys have solar panels, charge controllers and some batteries too. I got a couple of their 50 watt, one 30 watt and four 10 watt mono-crystalline panels. Prices are OK for new.
Example of a nice portable 30 watt panel. Not that large. The 50 watt panels are good but not as easy to carry around. Some people get a couple of panels then bolt them together using a door hinge, with cabinet drawer loop handles on the end, so they can be folded up for easy transport.
https://www.renogy.com/30-watt-12-volt-monocrystalline-solar-panel-new-edition/#prd-specs
If you're lucky you can find used panels at swap meets. Most of the time people seem to want around $1/watt or more, which is a bit much for used panels. What you quickly notice as the panel power goes up the cost per watt drops, for new panels.
If there is no rating for the panel a simple measurement with a meter will give you an idea of approximately how much power you can expect to get out of one. Yeah, I'm one of those guys who at times takes a meter to swap meets.
1. In full direct sun light measure the open circuit voltage of the panel.
2. In full direct sun light measure the short circuit current out of the panel. This will vary depending if the panel is at exactly pointed at the sun or off a bit.
3. Multiply the above two readings then multiply by 0.75 (which is the typical "fill factor" its called, to get the "STC" panel rating. Under typical operating conditions don't expect to get much more than around 75% of the above rating.
For the example panel above you get:
Voc= 22.9 VDC
Isc= 1.7 Amps
Panel Rating = 22.9 * 1.7 * 0.75
Panel Rating = 29.2 Watts (Manufacture lists at 30 Watts)
Real Max Output Power Expected = 30 * 0.75
Real Max Output Power Expected = 22.5 Watts
You can get the Anderson Power Pole connectors at this site, crimping tool as well. I got the big set because I wanted to make a bunch of patch cables.
https://powerwerx.com/anderson-power-powerpole-sb-connectors
Another handy tool is an in-line DC power meter from them. You can keep track of how much power you're producing out of the panels and the amp hours you use from the battery. I got two of these as well, one for the solar panel array and the other for the battery pack.
https://powerwerx.com/watt-meter-analyzer-inline-dc-powerpole
For long cable runs forget the expensive red and black zip cord cable, costs too much. I went to Home Depot, or Lowes, and got a big roll of 12 gauge stranded low voltage direct burial lighting wire, black zip cord type. Then just stick the power poles on the ends after making sure you got the polarity right. With the red and black power poles on the ends who cares what the wire colors are?
https://harriscountyares.org/training/KNW/KNW-120.pdf
You want to use the heavy gauge wire because at low voltage and high current the voltage drop can be significant. The large gauge wire gauge keeps the voltage drop way down even on lower power systems.
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I think this group coined the term "CCR" to mean what it does here.
Hummm... "CCR" -> Ceedence Clearwater Revival. Remember them?
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This is great advice. I would love to get an LFP and it may be next battery. My system primarily runs off of the solar panels and the battery is there to handle heavy draw spikes when I need to use the amp. I think I need a different solar system to switch to LFP.
You likely can use the panels you have now. However you do need a charge controller specific for LFP batteries. I got a couple of the 5 amp ones from the company below, Genasun. They’re good for up to maybe a 50 watt panel more or less. I think you can parallel the controllers. These are the good MPPT, max power point tracking, type, not the crappy PWM ones you typically find on many systems.
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Did a search but didn't find an exact match regarding what are the characteristics of a good portable battery. I like that this one has Powerpoles already attached and is lighter. Thinking of using my TK-880 in outdoor applications where there's no power other than my truck.
Try looking at battery packs from this company. They do a lot of business with Hams for portable operations. They have pretty good prices considering.
https://www.bioennopower.com/collections/12v-series-lifepo4-batteries
Personally I have the 6AH pack ($80) for portable work with HT's. I have the 40AH ($360) for home use when the power dies. If you get the batteries make sure to buy the charger too. The 6AH LFP weights a lot less than the old 5AH Lead Acid Gell Cell, and with much more usable capacity too.
I don't recommend anybody use a Lead Acid battery unless cost is an extreme concern. Personally I've wreck too many Gell Cell and AGM batteries to want to fool around with them anymore. If you don't maintain them at full charge when not in use they will sulfate and fail. And if you do they still don't last that long.
The other disadvantage is the terminal voltage falls fairly quickly to the point where you're lucky to get maybe 50 some percent of the rated capacity out of them. Most mobile equipment wants to see a nominal 13.8 VDC (+/- 15 %) and when it drops to around 11.75 VDC the equipment misbehaves or shuts down. Then there is the weight.
Using LFP, Lithium Iron Phosphate (LiFePO4), batteries have a nominal terminal voltage of around 13.3/13.4 VDC over most of the full discharge range, which is a good match for mobile equipment. By the time they drop to 12.8 VDC you have used around 90 percent of the rated capacity. The batteries will routinely allow you to discharge them to 80 to 90 percent without damage. Under this kind of use expect to get around 2000 charge/discharge cycles out of the pack. Lead Acid is only good for a few hundred when using just 50 percent, using more the cycle life drops even more.
You can charge up a LFP battery and let it sit for weeks to months without it hardly self discharging. Further for very long term storage you only partially charge them. Sitting around for very long periods doesn't seem to hurt the batteries at all.
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I'm new here so please bear with me.
It would be nice to post a list of acronyms used in this forum. I've been perplexed at some used in threads here.
For instance: CCR = chocolate covered raisins but I know that's not correct.
Can you help?
Tom
It could end up being a rather long list. Here are a few examples. >8-|
http://www.ominous-valve.com/acronyms.txt
https://www.electronics-notes.com/articles/ham_radio/abbreviations_codes/abbreviations.php
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Marc, I'm a technical type myself and I did pick up on the misstatements but I also wasn't going to nit-pick a great analogy apart over what, in the great scheme of things, were fairly minor points. It was, and still is, a great non-technical write-up of a very technical topic.
I agree. For the most part it did what his intended purpose was, a very basic explanation of antenna tuning and gain. Since it wasn't meant as a highly technical article minor errors can slide by without a major loss in the concepts. Great effort.
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That is likely due to capacitance coupling of the ground plane. That is a mag-mount antenna, so the ground plane is not DC coupled at the base of the radiator.
This is a valid point. The antenna impedance is not a simple resistance when off resonance. Combine that with some capacitive coupling in series I’m sure will also generate some weird SWR characteristics.
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For a quarter wave antenna it has some rather odd behavior. There seems to be several peaks and dips in the SWR over the range. I would have expected to see just one dip at the resonate frequency and smoothly rising to either side, which is what I saw with the antenna I built. Also the EZNEC+ antenna simulation I ran for it showed the same thing.
I'm wondering if part of what you're seeing is caused by the UHF (SO-239 to PL-259) adapter used on the antenna analyzer. Of course those adapters are nowhere near a 50 ohm impedance. The simple 1/4 wave i made used BNC adapters which are 50 ohms. Have to be careful because there are 75 ohm versions too and hard to tell apart since the size is very similar.
The interface between the two adapters is likely around 1/2 inch, however due to the velocity factor of that part electrically it looks longer. Teflon has a dialectic constant or 2.1 and the velocity factor is the square root of the reciprocal of the dialectic constant. So for Teflon that works out to 0.69. At 462/467 MHz the RF travels through the connector interface at 69 percent the speed of light, or you can consider the connector looks longer by the factor of 1/0.69, or 1.45 times longer. For a straight barrel adapter, female to female SO-239, I measured the center OD and the shell's ID and using a basic formula to calculate the impedance I got around 28 to 29 ohms.
So if we consider the adapter interface is around 0.72 inches long at 28 to 29 ohms we could use the lossless transmission line equations to figure out what the impedance will be with a given load on the other end. I did that for various frequencies for my own education and the results were "interesting." At the frequencies we are using for GMRS that impedance bump is rather large. I have a PDF of some calculations a while back along those lines just to see how it affected the SWR. If somebody wants them I would have to PM the file. I can't seem to attached anything to my messages in a long while, I keep getting an error that says I only have 666 some bytes left to attach a file. If I could I would.
I know this might be getting a bit deep for some people, but what really counts is the results.
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This will give you an idea about typical usable bandwidth of a stacked phase dual-band VHF/UHF antennas. I will shoot another video with a single band 5/8 wave a little later, so you can see the differences.
This is a Diamond NR7900A 2m/70cm. https://www.diamondantenna.net/nr7900a.html
Very good! We could use more real world info like this. Far better than saying “I can hit such and such repeater x miles away.” I see questions always coming up asking if such and such antenna can be tuned for Ham and GMRS. Nothing like having the measurements which speak for themselves.
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Guys, if you are looking for a super high gain antenna for both Ham and GMRS use, just give it up. There will be a compromise on one end, or the other. If you must use just one antenna for both UHF ham and GMRS, then use a quarter wave tuned to 450.
For a really high gain antenna that is likely true. For a modest gain one the answer isn't so clear cut. I recommended a Comet CA-2x4SR dual band antenna for a friend at work, who got his GMRS license, and looks forward to getting his Ham license as soon as local clubs open up for testing again. You can get it in either a UHF or NMO type mount.
http://www.cometantenna.com/wp-content/uploads/2013/09/CA-2x4SR.pdf
He mounted the antenna on the fender of his pickup truck. It would have been better on the roof but at 40 inches tall it made things difficult going into parking garages, drive thru windows at banks and fast food joints.
I used a Rigexpert AA-1000 antenna analyzer to do an SWR sweep of the operating range.
https://rigexpert.com/products/antenna-analyzers/aa-1000/
On UHF the SWR was OK. As long as the SWR is under 2:1 most radios should have no issues and work OK.
432 MHz - 2:1
438 MHz - <1.1:1
454 MHz - 1.9:1
464 MHz - 1.2:1
467 MHz - 1.6:1
469 MHz - 2:1
The SWR on VHF was even better.
140 MHz - 1.5:1
152 MHz - <1.1:1
160 MHz - 1.6:1
This is close to what the published spec's from Comet are for the antenna. While the UHF band has some notable dips and peaks in the sweep it is still very usable. The antenna was mounted close to the roof pillar. I would guess if it was mounted further away the SWR sweep would have looked a bit better.
You're right about a 1/4 wave having a large bandwidth. I built a couple out of PCB mount type female BNC sockets and some 1/16 inch stiff buss wire for the elements soldered to the center pin and the flange, bent down at 45 degrees for the ground plane. All about 6 inches long. Sitting on a table top the SWR scan showed a max SWR of 1.4:1 at 430 MHZ and 470 MHz after some slight trimming. The minimum of almost 1:1 was at 445 MHz.. I'm using this on top of a bookcase at the office with a handheld UHF radio. It works better than the typical rubber dummy load, called a rubber duck antenna, that the radios ship with from the manufacture.
- ratkin, marcspaz and Elkhunter521
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That depends. The range on UHF is 3 to 5 miles between mobile radios. You can get more range if you can access a repeater. However you will likely drive out of range of the repeater in 15 to 30 or so miles, if the repeater antenna is located high enough. As an example there is a Ham Radio UHF repeater by me with the antenna at 800 feet. The usable range is about 40 miles more or less.
The problem with repeaters used on a long trip are two fold. First you need to know where they are and the channel used. Second most use an access tone, without it you won’t even activate it. Trying to input a tone as you’re driving down the road isn’t recommended. Many of the real GMRS mobile radios require some measure of screwing around to set the tone, that is if it’s even possible. Some you have to use the programming software.
If you’re lucky you may get a contact with a base station, in which case you don’t need to normally worry about access tones. If the base station has their antenna up 30 feet or more you could get 10 to 20 mile range.
Some of the other people here have pointed out in other posts that running a 40 to 50 watt radio mobile didn’t really increase their range much.
I would recommend just using a hand held radio, typically 4 to 5 watt output, connected to a good magnet mount antenna on the vehicle roof. You can buy a hand held GMRS radio for under a $100, some are even less. While you can get a cheap mobile radio for about the same price the output power is about the same. Also the hand held you can use the stubby antenna while out walking around and keep the radio in your pocket when not in use. Don’t even think about trying to use a hand held with the stubby antenna inside the vehicle, you’ll be VERY disappointed.
Your most likely contacts are a few others operating mobile GMRS, some base stations and likely a fair number of people using FRS radios mobile. Remember FRS and GMRS share the same exact frequencies exclusive of the repeater ones. My experience with people using FRS radios mobile inside of a vehicle is the range seems to be no more than 1/2 to 1 mile. In fact the FRS users are likely to hear you well past the point where you will hear them.
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GMRS repeaters do not have to ID. The users of the repeater must ID when they use it.
Unfortunately that's not exactly what the rules really say.
https://www.law.cornell.edu/cfr/text/47/95.1751
Reading the above we have the following:
There are two usage cases that are being confused. One where everyone using the repeater is operating under the authority of the repeater owner (FCC licensee), and the other is when "others" with their own FCC issued call sign use it, either granted permission by the owner or the repeater is listed as "open" for public use.
If the users are all operating under the authority of the repeater owner then yes it doesn't need to self ID. 95.1751 (c1) and (c2) This is the only exception to the repeater ID requirements. This makes sense since everyone operating under the authority of the repeater owner all are using the same call sign. So when they ID the repeater is also properly ID.
However if you read this critically the repeater MUST self ID, as stated in the rules for any GMRS station, if it is being used by anyone else other than stations operating under the authority of the repeater owner. This is the part I think everyone misses. Just because the FCC hasn't busted anyone for this doesn't imply a rule violation is not occurring. Same thing with Part 90 radios being used on GMRS, some in fact have been used for building GMRS repeaters!
In the usage case I had originally mentioned the repeater owner is allowing other licensees to use it and it doesn't self ID with its owners call sign, ever, when in use or otherwise.
I've never asserted that GMRS repeaters must ID if they are not in use. It would be nice if they did. That helped me very late last night, 2AM to 3AM, when tropospheric ducting was going on. A distance GMRS repeater, I caught only part of its CW ID before it faded out, operating on the same repeater channel as the one I use locally, the one that never ID's. No the DX repeater wasn't activity being used so without it automatically self ID'ing I wouldn't have known it was there.
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We are getting off topic here.
GMRS does not have to ID. Period. Per rules. None of mine ID. Commercial Part 90 Repeaters must ID per rules. Alot of Part 90 repeaters ID with no PL/DPL tone so if you have a scanner with PL/DPL enabled you will never hear the ID.
GMRS doesn’t have to ID? What section is that in the rules?
When I’m scanning I have all the tone decoding turned off so I don’t miss anything. I’ve never had it on. Still don’t hear any ID. I do occasionally hear the MDC burst from Motorola radios, but not all of them.
This really isn’t just an academic issue. There have been enough posts I’ve read where users have the same problem, trying to figure out who to contact for permission to use a repeater. The typical answer is listen for the ID, dah, what if there isn’t one? Without something to work with the problem isn’t easy. For anybody thinking about putting one up some thought needs to be put into the decision based on who is going to use it and how is anybody monitoring it on the air going to figure out who to contact.
Not everyone has access to expensive for pay database services. Not every GMRS, for that matter Ham, repeater is listed in commonly available on line databases. That’s been another complaint here as well. The database on this site has repeaters listed that no longer exist, repeaters that exist but the owners choose not to list it, I know of a few of those too where a buddy lives, and just plain wrong info on some that do exist, like the one I tried tracking down.
When somebody asks about putting up a repeater it isn’t just about do you need one. There is the engineering aspect and the regulatory requirements too. The repeater doesn’t live in a vacuum, it has to coexist with other stations and users so going a step beyond what the letter of the rules require could be well worth the effort. All are important IMHO when asking about advise.
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What I wrote is all required by law to put up an antenna tower. It doesn't matter who owns it or what service/band its on. Even if someone puts up a Rohn 45 in their backyard, all of the things I wrote are required by law and FCC rules. If private owners choose not to, they are in violation of federal law.
If someone has a private use repeater at their house or business and its mounted on a building not more than 10' high from from top of the roof, then I suppose it would not go through any of that... but it wouldn't be much of a repeater, either. I guess it would be okay for their HT's while around the house/neighborhood, but that would be about it.
As far as finding a station (and owner) that does ID, that is actually really easy. There are free, online RF detection centers all over the globe. Especially here in the US. Once you have the address, you can lookup the land owner and you're done.
I have a local UHF broadband repeater that started causing issues around here. I was able to find the repeater in just about 15/20 minutes. It happened to be owned by the local FD, so it was easy to find out who to talk to.
The repeater I was trying to locate turns out it’s on the top of a building that’s listed as the roof top at 206 feet above ground level. So per your points it wouldn’t have been required to be registered with the FCC.
There is also a Ham repeater on the top of what is now GM’s headquarters. That’s only 14 to 15 miles line of sight from my house.
http://www.gmarc.org/wp/wp-content/uploads/2020/05/RenCen-repeater-qsl-compressed.jpg
There is also another Ham repeater just a mile or so from the GMRS one on top of another building at 300+ feet. Both of which are just under 5 miles to the west of my location.
Both Ham repeaters do self ID.
Since the above are not on a tower, and the antennas are mounted close to the roof top there is no legal requirement they be registered with the FCC?
I was not aware of any FCC requirement to register if you’re on a tower however. That’s new one for me. Thanks for educating me on that.
I also monitor the security frequencies from two local malls. It was rather interesting when the police protesters showed up by the one in Sterling Heights a few weeks back. Both use repeaters. Nether one self ID’s that I can tell from several years of monitoring them. Both are listed in a well known on line scanner database.
https://www.radioreference.com
In that one of the two shows the call sign for the repeater. There is nothing listed for the other one. Again doing an FCC GEO search on either the input or output frequencies yielded nothing that makes sense. A search of just the frequencies used for the city, where I’m guessing the repeater is located at the mall, didn’t yield anything useful either. How would one use freely available sources to track down the owner, and the call sign, of the non ID’ing repeater?
So for the two malls how can they operate with out either the repeater nor the hand held radios used ID? Is there a specific FCC rule that allows this or are they in violation?
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Repeater sites are (or at least should be) registered with the FCC. In order to put up a tower, there has to be permits issued, an environmental impact evaluation, an FAA Risk/Impact evaluation and a RF exposure evaluation, determining RF exposure health risk to people/animals in the area... and all submitted to the FCC as proof that you are in compliance with all applicable laws. Plus the FCC regularly does site inspections.
These systems don't cover a tremendous amount of real-estate and there are not many of them in many areas. If a machine starts doing something stupid or is non-compliant, I promise you, unless the owner has completely ignored every single law and requirement, they know who owns what machine and where to find both the machine and its owner.
What you said is true I’m sure for commercial systems, public safety etc. I don’t recall seeing anything in the FCC rules requiring a GMRS repeater to be registered with the FCC. Neither are Ham repeaters, but you do work through a local frequency coordination body which is not part of the FCC. The only requirement is each station must ID, so as long as only qualifying family members use the machine it doesn’t need to self ID. Each qualifying family member when they ID satisfies the requirements. However if non qualifying family members use it then it’s impossible to determine who is the owner unless it self ID’s.
This was EXACTLY the problem I had trying to identify the local repeater I’m currently using. No self ID, nothing shows up of any use when doing an FCC GEO search on the exact frequency over a limited range of 50 miles. I finally tried contacting the owner because it was listed on this site’s repeater database, by shear luck and I still wasn’t really sure. But even then the info was wrong because the owner died and the listing wasn’t updated for a few years. Months went by and no response to my emails, unknown at the time they were going to a dead guy’s account. Then when it was updated everything got worked out really quick. If it had ID’ed with the current owners call sign a simple lookup of that in the FCC license database would have given me the contact info I needed and saved me a lot of screwing around.
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Per 47 C.F.R, Part 95 Subpart E, §95.1751 ( c ) states that the repeater doesn't need to ID itself if... (2) The GMRS stations whose communications are retransmitted are properly identified in accordance with this section.
So, even if the license holder is not using the machine, if people that are using it properly ID, the the repeater is considered in compliance with ID requirements.
That doesn’t make any sense to me. The point of ID’ing is so the owner of the repeater can be contacted in case of a problem. I don’t own the repeater I mentioned and I’m sure the FCC won’t be knocking on my door, nor anyone else using it with their own call sign, if there are issues. Without a proper ID how would they know who really is in control of it? It’s a lot less work to get the call sign of the owner from the on-air self ID, look them up in the FCC database then contact them directly. The other choice is having the FCC pull the plug then wait around to see who shows up to check the system out wondering why their repeater quit. If nobody shows up, the repeater is off the air problem solved anyway. Might even pack it up and take it with them on the way out the door. If their nice they could leave a nasty note taped to the empty rack.
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I’ve looked at those cheap repeater controllers. Those are the ones you connect two radios together using the mic/speaker jacks and key the other radio using VOX. The main complaint I have with using one for a quick throw together repeater is the lack of an ID function. I have looked at the “ID- O-Matic” which has it but you need a COR it seems to make the thing work, which of course an modified radio doesn’t provide. So that brought me back to the first option about hacking the hardware to add an ID function.
The cheap controllers without the ID could be used in two cases. The first is a half-duplexer repeater, which has the limitations you pointed out previously, and used exclusively by the licensed user. The second is with GMRS, but only if qualified family members use it exclusively since everybody ID’s using the same call sign.
All other cases the repeater needs to self ID. The strange thing is the one GMRS repeater by me, which I have the owners permission to use, along with a few friends, I have NEVER heard it ID yet. How the owner is getting away with it beats me other than the FCC doesn’t want to bother with it. It doesn’t get much use so unless you know it’s there you wouldn’t notice.
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Not disagreeing there, but there are serious limits to crossband repeaters. They do have their place though. I have a complete X-Band repeater system that will work with any two bands, covering 10m, 6m, 2m and 70cm. Including antennas, a battery, diplexer, solar charger and the radio... it was about $700 for support of 50% duty cycle, 24x7. It is almost exclusively used for me, personally... not others.
The model you discussed is known as ITDR, or Indirect Transmit / Direct Receive. An example of some problems you will experience with these types of solutions are limiting the users to only people you make aware of it (compared to known offsets for same-band), many times the repeater antenna is too close to the ground and other obstructions for any significant increase in coverage, and your receive is significantly hampered by the fact that you are listing direct on an HT.
My gear supports ITDR and ITIR (Indirect Transmit / Indirect Receive). ITIR helps with both the ability to transmit and receive, but now significantly restricts who can use the repeater, normally being used/usable by a single operator to extend their TX/RX range.
In general, they can be a great individual solution for Hams and (if planned in advance) be a marginal solution for a group of Hams with the correct / compatible gear, but not ideal for a true repeater service and definitely not legal in GMRS.
I think his was a full cross band, duplex, design. The two radios are cross connected. He did his initial testing with the antenna on his tower.
He is also the main radio tech for a local city’s transportation department. He done some tower climbing and repeater installs. Many of his comments are similar to yours.
The one I remember most is a story where another tech went out to check the repeater equipment in the shack at the tower base. Opened the door only to discover a huge hornets nest inside. By the time help arrived he was passed out on the ground from all the stings. Luckily he survived.
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Good post... Nice read to let new-comers know what the reality is.
As far as "mobile repeaters" go... to do it right, its much more expensive and difficult than a fixed-station repeater, with nowhere near the performance advantage. I built a portable repeater system for a government emergency response team. It cost a bit over $16,500.
The antenna alone was a massive project. It was on a 10' tall tripod (mast mount centered half way up) with a 30' fixed mast and a 30' crank extension, for a total of 65' of elevation. The equipment and batteries were extremely heavy and had to be installed in vented enclosures to keep them dry and cool. The repeater had to be trucked to a location and dropped at a high-point. Setting up the portable tower took a huge amount of labor and real estate to get it stood up and staked out so it was straight and wouldn't fall over in 20-30 mph winds.
And unless you have a babysitter, you need self-contained GPS tracking and local alarm on the transceiver in the event that some knucklehead finds your repeater and decides to leave with it.
That all depends. I have a Ham buddy who built a special event repeater, for local marathons and bike runs, really cheap with some used radios and a good power amp. The way it was done is using cross-band repeating so the expensive cavity filters get ditched. Most Ham HT’s can be programmed to do split band operation. You RX on one frequency on one band, say VHF, and TX on another, UHF, when you press the PTT button. For Ham radio this usually ends up being the 2 meter and 70 cm bands. On the repeater side a simple diplexer is enough to work the VHF and UHF radios into and can be had for $50 to $75 new.
Then he takes advantage of the local high rise buildings. Through his contacts he has access to the roof tops. No need for an expensive tower and feed line. When you’re on top of a 10 to 15+ story building you get some decent coverage. Since the repeater can be located close to the temporary antenna you don’t need expensive feed line. And what you do use is fairly short thus keeping the losses down and thus the TX’er power required.
Granted his conditions are not the general case but if one looks around and takes advantage of the local resources you can save a huge amount of money and effort.
However if one wants to build an in-band repeater, then yes it gets more complicated and likely expensive as you pointed out.
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Wow... That is in NO WAY legal for use in the USA.
The 463 (and 468) MHz band is reserved as National Interoperability frequencies for Medical Emergency communications - ambulance and hospital two-way radios.
The 409-414 MHz band is for US Federal Law Enforcement, and "Federal Incident Management - Tactical Interop Communications" - whatever that is, I wouldn't want to mess with it.
By the way, there are 20 channels in the 409 MHz band that are known as the "CB" band in China, and they are legal to use there.
The usual non compliant consumer marketed Chinese wireless crap being sold in the US. Some years ago there was a problem with “high power telephone wireless handsets” that claimed 1 mile plus range. Turned out they were operating on the Ham 2 meter band. After a series of complaints to the FCC the issue was addressed.
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Unfortunately data transmissions are allowed on any MURS channel. While the FCC requires monitoring for activity before transmitting I seriously doubt for automaticity operating stations they employ “busy channel lock out” and just key up regardless.
Even with a max power output of 2 watts and a simple antenna a data transmitting station can ruin a given channel for a 1 to 2 mile radius with frequent use. With only 5 channels it doesn’t take many stations keying up automatically to ruin things for MURS in an area.
I remember driving through a particular area near me frequently and could always count on picking up a data burst every few minutes on one of the channels. That went on for months. Eventually I locked it out of the scan list in my mobile Ham rig. Like you I found it very annoying. Lately about the only thing I do hear is the local Walmarts, Sams Clubs etc. and seldom at that.
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Still a no go for me. Not sure why. I didnt realize the URL was outside the US. Most of my contracts are US DOD and Federal Law Enforcement. We're not allowed to use foreign resources (with extremely limited exceptions). Likely I never have.
That's very strange. I just tried it again and it works for me. Maybe you have some security limitations on your computer.
Anyway here is a snippet of what is there. It is a radio propagation modeling program using publicly available geodata. I this this would along the lines of the for pay service you use but for amateur radio, or other radio service, uses.
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Calculations
The hart of every RF simulation tool is the prediction model. There are many models that predict RF propagation but the most known is the 'Hata-Okumura' model. This model is 'the mother of all models'.
Over the years new models have been developed where the growth of commercial cellular networks like GSM UMTS, and now WiMAX are the main drive. These networks operate in th UHF and SHF bands (450 to 2400 MHZ). Other frequency's are used for broadcast of Radio and TV (VHF and UHF, 50-800 MHz) and a small portion for PAMR and PMR networks. Their focus is in the VHF and low UHF frequency's (50-500 MHz).
The prediction models used for these networks are devided by coverage distance. For GSM, DCS and UMTS (900-2400 MHz) these models are limited to predictions over a short range. Due to the nature of broadcast the distance over wich predictions are made is extensively bigger than for cellular networks.
The difference in range for the model is devided in to two main categories:
2-way communication or 1-way communication.This choice is influenced strongly by the en-user terminal. A if a uplink is required, a hand held terminal will limit the coverage because these devices have limited transmit power and poor antenna performance. In the case of broadcast A Radio receiver does not need to talk back to the broadcaster so bigger powers do no harm to the link budget.
When prediction over small distances are required to be accurate it is important that the influence of local buildings (clutter) is taken in account. when predictions are performed over bigger distances the dominance of clutter decreases and eventually can be left out of the calculations. This simplifies the formula for calculating RF propagation.
Accurate RF predictions require detailed clutter and height data bu this data is generally expensive and only affordable when income out of the exploitation of a radio network is high. For amateurradio, emergency services, and students for example it is not realistic to have this accurate data available. Therefore low budget and easy accessable data must be accessed. Radio Mobile uses geodata that is available on the internet for free.
Based on the Hata model many other models have been derived. Also models have been improved for their specific purpose. But some general models have been almost the same and available for free. On very well known model is the Longley-Rice model. This model is accurate over a wide range of frequencys and over various distances. Based on this model the US Institute for Telecommunications Science (ITS) created a propagation prediction model know as the Irregular Terrain Model or ITM.
Radio Mobile uses the ITM model.
To understand the operation and limitations of the model I have collected information about the Longly-Rise and ITM model on this website.
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The link below is for the "on-line" version. Maybe you'll have better luck with this link.
http://radiomobileonline.pe1mew.nl/
This is the snippet from the link above.
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Welcome
To the website dedicated to Radio Mobile Online.
Radio Mobile Online is the online version of the popular RF propagation tool Radio Mobile by Roger Coudé.
Radio Mobile Online can be found at: http://www.ve2dbe.com/rmonline.html
Radio Mobile Online is a radio wave propagation prediction tool dedicated to amateur radio.
It uses digital terrain information and a mathematical model to simulate radio transmissions between two fixed sites (radio link) or between a fixed site and a mobile (Radio coverage).
The digital terrain information comprises two databases: Elevation and land cover. Those databases are located on the server and represent a total of 198 GigaBytes.
Radio Mobile is a popular tool for RF studies. Between 2012 and 2015 663304 studies have been performed and 26198 accounts have been made. More information? Follow this link: RMW Online popularity.
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I don't recognize the URL and the page won't load o my PC or phone. So, I can't really say for sure.
You might want to try it again. The website is in the Netherlands. I tried earlier today, no luck. Tried again just a few minutes ago and now it seems to be working. All I did was click on the link in the post using Firefox on my laptop.
GMRS on a Road Trip?
in General Discussion
Posted
I would recommend you use the official Kenwood software to program the radio. I’ve had problems with Chirp and the TK-270G/370G wide/narrow band 128 channel radios, VHF and UHF. For the older TK-370 wide band only 32 channel radio it seems to work OK. Reporting Chirp bugs is fine, just don’t hold your breath waiting for them to get fixed. Seems some never do get addressed.
One of the main problems with Chirp is not all of the radio’s features are accessible. That’s why the manufacturers software is necessary. Before I even consider buying a used radio I’ll search for a downloadable version of the programming software. Second is getting the programming cable. If I can’t get both I won’t buy the radio.
I don’t know about other people but I’ve had much better luck finding the above for Kenwood radios verses Motorola radios.