Need Repeater Advice

[Nerumph]

Hello community! I would first like to thank you for taking the time to read through, and possibly assist with, this plea of help I have finally decided to bring to the forums!

So without further adue, here is the situation of a new repeater build I am in need of assistance with!

I have been put in charge of creating a UHF repeater system in place for a fleet of 30 Baofeng UHF radios used during various activism actions here in Cali. The main goal of our organization is to keep both sides of the activism world safe: to keep our activists from unjustly harming individuals and property, and to keep government agencies and radical opponents at bay through non-violent deescalation.

Anyhow, mini unintentional promotion of our org. aside... In order for us to meet all the goals stated above, instant and consistent communication is key; and needless to say our current simplex solution is dismal at best. Apart from the fact that our radios can barely reach different ends of some larger protest marches (something like 5-6 city blocks long at times) which is embarrassing when it occurs, we also use our system in large radius Direct Action protests from time to time, where range from one end to another of a target could be as encompassing as 5 miles in rad.

Needless to say, we are in need of a better solution. And from what I have been finding around everywhere, a repeater seems to be the key!

But first off, here is a quick and dirty diagram I made up for signal and electric pathflow for this duplex repeater:

Keep in mind alot of the descriptive content I added in to help our... less technical understand some basics in the field.

For our signal flow, here is a current list of components we have compiled into the repeater so far:

TX/ RX Transceivers: Baofeng UV-82

Duplexer: Generic UHF mini BR Duplexer (tuned to our specific TX and RX freq. by the ebay seller)

Antenna: Opek Tech UHF base station antenna

Repeater Controller: Surecom DTMF controller (Though we are considering grabbing a Raspberry PI and using ORP Once I can nail down the fundamentals down with the rest of the system.

I won't list cabling specifics in here unless someone absolutely needs it; needless to say I have punched in quite a few patch cables in addition to what is in this diagram (mainly so I was able to insert an SWR meter into the mix).

So now to the fun part. Results from a couple field tests. As far as we were able to tell with these tests, transmission range on the repeater end was not an issue at all, except when our field tester was standing at the literal feet of various skyscrapers in the testing area. The problem we are currently having is every repeater's Achilles heel: RX efficiency.

(And just as a side note, we were able to get an SWR between 1.5 and 2-ish throughout these tests)

So that is where I ask my first question to you all: Just what factors will contribute to RX efficiency? Currently, I know that the RX radio squelch sensitivity, duplexer tuning, antenna tuning, elevation of the repeater, and leadline loss will contribute to or hinder performance to the system. Is there anything else I am missing in the loop?

Is there also a resource to help me do some diagnostics between the above listed dependencies; help me flush out the system so to say?

--------------

And now I get to part two of my plea for help. I certainly am no electrical engineer and do feel like I am in just a bit over my head with wiring this repeater up to a battery system. Regardless, though, I am always willing to learn and don't mind getting my hands a bit dirty with solder. Not to mention we do need this system to be self-sufficient in remote or isolated areas (like on rooftops for instance).

So in terms of components for the electrical side of this repeater, they are as follows:

Battery: 12V, 24AH, 288WH Deep Cycle LA Battery

Solar Panel (for, again, self sustainability): http://www.ebay.com/itm/NewPowa-Hig...ash=item1c42404c56]12V, 20W, 1.6A solar panel

Solar Controller: 20A 12V Controller

TX/ RX Radio Battery Eliminators: 2X Battery Eliminators for Baofeng UV-82's

I have also added the following to the system to help with certain... power issues I came up against when I first tested the system:

Two Stepdown converters for the feeds to each battery eliminator: 12V to 7.5V, 3A converters

One Stepdown converter for the power feed for the repeater controller: 12V to 5V, 3A converter

I also am using 20AWG wire just for future-proofing the system. (adding an amplifier, higher wattage transceivers, etc).

So now some questions: will this solar system be adequate enough to re-supply this system to keep it up for, say, a week constant, with load around 40-50%?
Is the circuitry 'safe' enough to be deployed on someone's roof without deep concerns about fire or explosions?
Any recommendations to help avoid that is the case?

----------------------------

A couple more questions here that have been stewing in my mind over the past few days as I start to re-envision this system. One of which is: I have been looking at amplifiers for the UHF spectrum and have been contemplating adding it into the mix. My question, however, is: would it be better to acquire the amplifier first, or would it be better to go with better TX/RX radios first? Something like the Baofeng BF-9500? I know I would need to get a higher watt-spec duplexer with that for sure, but would it be worth the extra cost for the extra watts? Especially in urban environments?

Another question in relation to the field transceivers themselves. We had recently upgraded our antennas for all units from the standard rubberduck antennas to some high gain Nagoya NA 771 antennas. However alot of our field ops have complained about their... much larger bulk and we have been considering downsizing to the [url=http://www.ebay.com/itm/10x-Nagoya-NA-701-Female-Dual-Band-Antenna-For-Baofeng-UV-5R-F-V-1000-PX-888-/252119458507?hash=item3ab37da2cb:g:3VEAAOxyi3FR20za]Nagoya NA 701 for convenience sake. would this be a worthwhile sacrifice or are we loosing anything at all by downsizing?

---------------

And with that I think I am done for now with my dissertation here, heh. I look forward to hearing from you all to see what you can do to help us out over here. Thank you again for your time and I hope to hear from you soon!

Sincerely,

Nerumph

 

[prcguy]

The diagram you show is a typical way to use the specific radios, repeater controller, duplexer and so on to make a repeater. You may run into problems with the radios in a repeater configuration as they have plastic cases and if the antenna is anywhere near the radios the transmit signal can easily get back into the receiving radio and cause desense.

Your duplexer may have adequate isolation like 70dB between transmit and receive frequencies but you may only have 25dB isolation as a system because the radios are known to receive signals with no antenna connected. If you look at an actual repeater everything is inside shielded metal boxes with lots of RF bypassing so signals can't just blast right into the individual radio components and circumvent the duplexer, etc.

Using hand held radios in repeater service means you use them on low power only, otherwise the duty cycle is too high and you will end up killing the transmit radio if the repeater gets used a lot. Think about a repeater vs a single radio where a single radio may transmit for seconds to a minute then rest for at least that amount of time. If you have a half dozen people needing to communicate the repeater transmitter is keyed up continuously for a very long time handling everyone's traffic. I would count on using the repeater transmit radio on low power and accept the resulting reduction in range.

Another problem I've had with a similar setup is the charge controller and similar step down power supplies making a lot of noise on the DC power lines to the radio causing the radios to unsquelch and key up the repeater. This depends on the type of charge controller. I've also had a similar problem with no charge controller where the radio that transmits puts a glitch on the power lines of the radio when it keys and unkeys, and that has caused the repeater to go into a continuous cycle of keying on and off, The easy cure was to put individual batteries on each radio and I finally calmed it down with a very busy choke and large value capacitor filter in the battery eliminators for each radio.

Then you have the problem of the Baofeng receivers being very susceptible to overload from nearby high power radios, so if there are any other repeaters or UHF paging transmitters nearby the Baofengs could have lots of problems in repeater use. This can show up as intermittent weak receive and voices getting chopped up during repeat. Especially with your duplexer being a notch only type, meaning it only tries to remove your transmit frequency from getting back into the receiving radio but it will let all the other local UHF radios in the area into your receive radio causing potential interference.

I would also go with a larger solar panel. A 20w panel will produce about 1 amp at 12v in bright sunlight and that's about what the radios will use on low power transmit. For continuous operation I would go with at least a 50-60w panel if this repeater is going to get a lot of use. BTW your battery is fairly large and should power the repeater for almost 24hrs of continuous transmitting and much longer if the repeater use is fairly low. If you use a more expensive MPPT type charger it can make more use of the panel voltage and you might get up to 1.5A charge current from a 20w panel instead of 1A.

Adding an amplifier to the mix will just exacerbate all the other problems mentioned, plus requiring you to upsize the solar panel and probably the battery too. In my experience, a repeater assembled from all the parts you show can work, but it will be a finicky, unpredictable and frustrating thing that may be fine as an amateur radio toy, but not to rely on for commercial type use.

Then to the obvious problem of legal operation. Sounds like you probably want everything you do to be on the up and up to avoid any legal reason for someone to shut you down. The Baofeng radios are not FCC type accepted for GMRS use and especially for making into a repeater. To be legal, the radios and the repeater must be FCC type accepted for part 95 GMRS. There are lots of handheld radios out there that are GMRS legal but none of them would be legal to assemble into a GMRS repeater. A repeater is FCC type accepted as a repeater out the gate and not necessarily just the radios inside.

Otherwise the Baofeng radios and repeater controller are perfectly legal to use in amateur radio service but it would not be legal for you to conduct your business in the amateur radio service, even if everyone had a license. BTW, everyone in your group has their own required GMRS license, don't they? Even with an actual legal repeater everyone in your group would need their own individual GMRS license (family members excluded) otherwise your leaving yourself and your group open to legal problems.

In my opinion your best solution is to apply for and get a part 90 business license for a low power portable repeater, where all of your group could legally use the repeater. Then get a used low power repeater that is FCC type accepted and have it set up on your licensed frequency. A complete used repeater with duplexer can be had for a couple hundred $$ or less and the seller might even set it up on your frequency for free.
prcguy

 

[K5MPH]

The diagram you show is a typical way to use the specific radios, repeater controller, duplexer and so on to make a repeater. You may run into problems with the radios in a repeater configuration as they have plastic cases and if the antenna is anywhere near the radios the transmit signal can easily get back into the receiving radio and cause desense.

Your duplexer may have adequate isolation like 70dB between transmit and receive frequencies but you may only have 25dB isolation as a system because the radios are known to receive signals with no antenna connected. If you look at an actual repeater everything is inside shielded metal boxes with lots of RF bypassing so signals can't just blast right into the individual radio components and circumvent the duplexer, etc.

Using hand held radios in repeater service means you use them on low power only, otherwise the duty cycle is too high and you will end up killing the transmit radio if the repeater gets used a lot. Think about a repeater vs a single radio where a single radio may transmit for seconds to a minute then rest for at least that amount of time. If you have a half dozen people needing to communicate the repeater transmitter is keyed up continuously for a very long time handling everyone's traffic. I would count on using the repeater transmit radio on low power and accept the resulting reduction in range.

Another problem I've had with a similar setup is the charge controller and similar step down power supplies making a lot of noise on the DC power lines to the radio causing the radios to unsquelch and key up the repeater. This depends on the type of charge controller. I've also had a similar problem with no charge controller where the radio that transmits puts a glitch on the power lines of the radio when it keys and unkeys, and that has caused the repeater to go into a continuous cycle of keying on and off, The easy cure was to put individual batteries on each radio and I finally calmed it down with a very busy choke and large value capacitor filter in the battery eliminators for each radio.

Then you have the problem of the Baofeng receivers being very susceptible to overload from nearby high power radios, so if there are any other repeaters or UHF paging transmitters nearby the Baofengs could have lots of problems in repeater use. This can show up as intermittent weak receive and voices getting chopped up during repeat. Especially with your duplexer being a notch only type, meaning it only tries to remove your transmit frequency from getting back into the receiving radio but it will let all the other local UHF radios in the area into your receive radio causing potential interference.

I would also go with a larger solar panel. A 20w panel will produce about 1 amp at 12v in bright sunlight and that's about what the radios will use on low power transmit. For continuous operation I would go with at least a 50-60w panel if this repeater is going to get a lot of use. BTW your battery is fairly large and should power the repeater for almost 24hrs of continuous transmitting and much longer if the repeater use is fairly low. If you use a more expensive MPPT type charger it can make more use of the panel voltage and you might get up to 1.5A charge current from a 20w panel instead of 1A.

Adding an amplifier to the mix will just exacerbate all the other problems mentioned, plus requiring you to upsize the solar panel and probably the battery too. In my experience, a repeater assembled from all the parts you show can work, but it will be a finicky, unpredictable and frustrating thing that may be fine as an amateur radio toy, but not to rely on for commercial type use.

Then to the obvious problem of legal operation. Sounds like you probably want everything you do to be on the up and up to avoid any legal reason for someone to shut you down. The Baofeng radios are not FCC type accepted for GMRS use and especially for making into a repeater. To be legal, the radios and the repeater must be FCC type accepted for part 95 GMRS. There are lots of handheld radios out there that are GMRS legal but none of them would be legal to assemble into a GMRS repeater. A repeater is FCC type accepted as a repeater out the gate and not necessarily just the radios inside.

Otherwise the Baofeng radios and repeater controller are perfectly legal to use in amateur radio service but it would not be legal for you to conduct your business in the amateur radio service, even if everyone had a license. BTW, everyone in your group has their own required GMRS license, don't they? Even with an actual legal repeater everyone in your group would need their own individual GMRS license (family members excluded) otherwise your leaving yourself and your group open to legal problems.

In my opinion your best solution is to apply for and get a part 90 business license for a low power portable repeater, where all of your group could legally use the repeater. Then get a used low power repeater that is FCC type accepted and have it set up on your licensed frequency. A complete used repeater with duplexer can be had for a couple hundred $$ or less and the seller might even set it up on your frequency for free.
prcguy

Prcguy

is right those radio wont last long a that level of duty cycle,you will burn the radio up if the repeater is being used with very heavy traffic........

 

[N4GIX]

I fully endorse everything prcguy wrote. GMRS is not a good choice as everyone without exception will need their own GMRS license, and at $65 per person every five years can rapidly spiral the expenses!

I recently bought two Ritron RRX-450 repeaters via eBay. They can easily be programmed for 70cm operation in GMRS, business or amateur bands. They are 2u rack mounted, and even include 12 vdc input for "portable" operations. Ritron is an American company located in Carmel, Indiana.

Several weeks ago, there was a custom Motorola repeater installed in a water-proof case for portable operations, and even included an antenna with 40' of cable. Something like that would be ideal for your purpose.

As suggested, were I in your position I'd apply for a business license just to keep everything fully legal. Do realize that if you do so in your own name, you alone assume full responsibility for any infractions in usage.

 

[Nerumph]

Hello PRCGUY, I would first like to thank you for the quick response! You have certainly raised quite a few good points through this and I would like to run down each and get some clarification and maybe even some suggestions on how to improve.

The diagram you show is a typical way to use the specific radios, repeater controller, duplexer and so on to make a repeater. You may run into problems with the radios in a repeater configuration as they have plastic cases and if the antenna is anywhere near the radios the transmit signal can easily get back into the receiving radio and cause desense.

Your duplexer may have adequate isolation like 70dB between transmit and receive frequencies but you may only have 25dB isolation as a system because the radios are known to receive signals with no antenna connected. If you look at an actual repeater everything is inside shielded metal boxes with lots of RF bypassing so signals can't just blast right into the individual radio components and circumvent the duplexer, etc.

This was something I had originally noticed upon alpha testing the unit at my house... and then something that quickly fell to the back of my mind, so thanks again for once raising this concern to me once more.

Back from when I did start noticing it, I decided to use a fat50 ammo box to double as both containment of all needed components and as a first line of defense against exterior noise (as you had said below). I was also contemplating using some lead or aluminum foil to further dampen both internal and external noise, either by coating the interior of the box with it, or wrapping each component in it. Of course mainly it was a question of if that would even do anything to combat RF interfer. and I decided to leave it be.

So would that help at all in keeping out conflicting signal leakage?

Using hand held radios in repeater service means you use them on low power only, otherwise the duty cycle is too high and you will end up killing the transmit radio if the repeater gets used a lot. Think about a repeater vs a single radio where a single radio may transmit for seconds to a minute then rest for at least that amount of time. If you have a half dozen people needing to communicate the repeater transmitter is keyed up continuously for a very long time handling everyone's traffic. I would count on using the repeater transmit radio on low power and accept the resulting reduction in range.

That was something I had started thinking about earlier in the build (just after I had ordered the parts actually). It is why I started looking at components such as the Baofeng BF-9500 to help out and extend the lifetime of the TX and sensitivity of the RX. Would something like that be a viable choice in terms of duty cycle concerns? It also looks like the casing of these radios is also made of a powder coated metal as well, so I am thinking that may help out in interference negation. Or am I wrong here?

Another problem I've had with a similar setup is the charge controller and similar step down power supplies making a lot of noise on the DC power lines to the radio causing the radios to unsquelch and key up the repeater. This depends on the type of charge controller. I've also had a similar problem with no charge controller where the radio that transmits puts a glitch on the power lines of the radio when it keys and unkeys, and that has caused the repeater to go into a continuous cycle of keying on and off, The easy cure was to put individual batteries on each radio and I finally calmed it down with a very busy choke and large value capacitor filter in the battery eliminators for each radio.

I don't think I have had too much problem with DC noise so far, but then again I have not actually tested the system with the power circuits in place yet; in the beta field area that is. So when you're talking about adding power conditioning through choke and cap, could you give a component example for each? I think I may have found the cap filter online, but I am not familiar with a choke... or I am just really inept at electrical concepts, on or the two, heh.

Then you have the problem of the Baofeng receivers being very susceptible to overload from nearby high power radios, so if there are any other repeaters or UHF paging transmitters nearby the Baofengs could have lots of problems in repeater use. This can show up as intermittent weak receive and voices getting chopped up during repeat. Especially with your duplexer being a notch only type, meaning it only tries to remove your transmit frequency from getting back into the receiving radio but it will let all the other local UHF radios in the area into your receive radio causing potential interference.

Now when you talk about interference here, are you mainly meaning the interference from the Baofeng RX being un-shielded, or are you also talking about the interference coming down the feedline as well? With the former, will changing up to two of those BF-9500 help resolve that issue? With the latter, what can I do to combat that. Is there a portable duplexer out there that will even do bandpass filtering; preferably cheaply as well?

I would also go with a larger solar panel. A 20w panel will produce about 1 amp at 12v in bright sunlight and that's about what the radios will use on low power transmit. For continuous operation I would go with at least a 50-60w panel if this repeater is going to get a lot of use. BTW your battery is fairly large and should power the repeater for almost 24hrs of continuous transmitting and much longer if the repeater use is fairly low. If you use a more expensive MPPT type charger it can make more use of the panel voltage and you might get up to 1.5A charge current from a 20w panel instead of 1A.

Ya, I was mainly considering the solar panel as a supplement to the battery when I was buying it and was mainly considering it as a trickle charger more than a full re-charging system. However with the addition of a different transmitter if that is, indeed what I will be needing for the above issues, I do agree that I would probably need something with a bit more umph; and probably at least one more battery daisychained to the system as well... If I were to add in those different transceivers into the system, what panel would you recommend to keep the system at least in status quo?

In terms of the solar charger, however, is there a difference to the MPPT system that I should be looking for? Like a specific spec or just all around better performance. Would [url-http://www.ebay.com/itm/12V-24V-20-30A-Auto-Switch-MPPT-Solar-Panel-Battery-Regulator-Charge-Controller-/111821595240?var=&hash=item1a09162268:m:mDT4BvQI5sOYw6fRkkwUBbg]something like this[/url] be something to consider then?

Adding an amplifier to the mix will just exacerbate all the other problems mentioned, plus requiring you to upsize the solar panel and probably the battery too. In my experience, a repeater assembled from all the parts you show can work, but it will be a finicky, unpredictable and frustrating thing that may be fine as an amateur radio toy, but not to rely on for commercial type use.

I did kinda figured the amp would just seem a bit extreme for a tiny system such as this for now. I do have to ask, though, would the amp be of any use if I were to install those 50W TX/RX units? As in, would the wattage stack (50W in 100W out), or would it simply be 50W in, 50W out?

And as for it being an amateur system, that was kind of the start of it. We had considered other options and were almost about to give up given the expense of a full repeater system ("in the thousands" is certainly not in any activist's budget ). I had stepped up as both a proof of concept for the team as well as a stride into a long-desired hobby of mine. So I suppose this is a bit of a muscle flex for my limited electronics skills in a way.

Then to the obvious problem of legal operation. Sounds like you probably want everything you do to be on the up and up to avoid any legal reason for someone to shut you down. The Baofeng radios are not FCC type accepted for GMRS use and especially for making into a repeater. To be legal, the radios and the repeater must be FCC type accepted for part 95 GMRS. There are lots of handheld radios out there that are GMRS legal but none of them would be legal to assemble into a GMRS repeater. A repeater is FCC type accepted as a repeater out the gate and not necessarily just the radios inside.

Legal is awesome and we are great supporters of the process... usually. When said process takes upwards of $1,000+ to get fully part 95, prebuilt systems, however, we will take a look at other means to get there. I am not saying I will not do my best to bring the system to FCC spec, but with the funds we have at our disposal, there could be some... adjustments made in lew of cost. Maybe being the key word there...

Regardless, I am fully open to suggestions on transceivers under 150$ to put into the system that would make it closer to spec. Preferably ones that we can program without Motorola admin codes.

Otherwise the Baofeng radios and repeater controller are perfectly legal to use in amateur radio service but it would not be legal for you to conduct your business in the amateur radio service, even if everyone had a license. BTW, everyone in your group has their own required GMRS license, don't they? Even with an actual legal repeater everyone in your group would need their own individual GMRS license (family members excluded) otherwise your leaving yourself and your group open to legal problems.

In my opinion your best solution is to apply for and get a part 90 business license for a low power portable repeater, where all of your group could legally use the repeater. Then get a used low power repeater that is FCC type accepted and have it set up on your licensed frequency. A complete used repeater with duplexer can be had for a couple hundred $$ or less and the seller might even set it up on your frequency for free.
prcguy

Now as I was saying above, the prices we were looking at for used repeaters with duplexer and 10-25W were upwards of 1,000-1,500$ used. This was after many searches through the Ebay listings, Cragslist and other radio surplus sites. Maybe we were looking in different places than we should have? If you have any suggestions for something under 350$-ish (as that is just above what we paid for this prototype) then we would certainly consider it, so long as it had the ability to jack in to a DC system for us to use off grid.

In terms of that Business license, just how would that work if our ops location changed from day to day? Though we do have a few demonstrations in the metro area here, we also do bring our 'pony show' elsewhere to different cities and even countryside when the job demands it. Does the P90 allow for roaming or would we have to re-apply every time we decided to pick up shop and re-locate? Also, what are we looking at in terms of pricing for that? 100$? 1,000$?

---------------------

I also have a couple more questions to bring up while I have you here. One of which is a re-request of a point I brought up in my earlier post; about the different dual band antennas:

We had recently upgraded our antennas for all units from the standard rubberduck antennas to some high gain Nagoya NA 771 antennas. However alot of our field ops have complained about their... much larger bulk and we have been considering downsizing to the Nagoya NA 701 for convenience sake. would this be a worthwhile sacrifice or are we loosing anything at all by downsizing?

As well, in the case which we are using this system in large direct action movements and we need alot of surface area, what is your recommendation for a temporary antenna mast? I was thinking of using 3/4 inch well drilling pipe cut to 5' segments coupled together to form something around 25ft high. It would be rooted in a large drum of concrete and tied down with carbon-hardened bailing wire. Just how would that work in the P90 business license if we were so inclined to go that route?



Again, though, I would like to thank you for your response! You have really helped pull some important factors to light with this!

I hope to hear from you again soon!

Sincerely,

Nerumph

 

[Nerumph]

I fully endorse everything prcguy wrote. GMRS is not a good choice as everyone without exception will need their own GMRS license, and at $65 per person every five years can rapidly spiral the expenses!

We certainly are considering other options at this time. Right now GMRS is just the most accessible band for us to graft on to until we can root out some other options. That does sound pricey and not where we want to go considering we have many different people coming in contact with our equipment on any given movement.

I recently bought two Ritron RRX-450 repeaters via eBay. They can easily be programmed for 70cm operation in GMRS, business or amateur bands. They are 2u rack mounted, and even include 12 vdc input for "portable" operations. Ritron is an American company located in Carmel, Indiana.

The price does look... reasonable enough, but what do you get with that price? Is it a full system with duplexer or just a TX/RX unit?

Several weeks ago, there was a custom Motorola repeater installed in a water-proof case for portable operations, and even included an antenna with 40' of cable. Something like that would be ideal for your purpose.

Any specs on that? Article? Video? Ebay site? Who was it that made that up?

As suggested, were I in your position I'd apply for a business license just to keep everything fully legal. Do realize that if you do so in your own name, you alone assume full responsibility for any infractions in usage.

I do realize that; and that is why I am fortunate enough to not be the actual ops leader and would not be applying for it in my name.

 

[KC4RAF]

Everything the above posters have written

is on the money. Those transceivers aren't going to last long at all, the lack of metal housing will cause problems as well. You need to think long and hard about investing your money into quality transceivers. Otherwise you're going to be spending more and more just to get it all to work correctly. Just a word to the wise.
edit:
You may want to check into MURS transceivers. They usually will work up to 5 - 6 city blocks. Usually. Do some research about the MURS.

 

[mmckenna]

I agree, unless -every- user is going to get their GMRS license, then this isn't the place to do it.

No reason to give law enforcement a reason to bust you. While it's ---extremely--- unlikely that you'd run into any legal issues, it'd be much easier to do this right in the first place.

Trouble with GMRS is 2 fold:
-every family needs a license.
-Most urban areas have at least a few active repeaters. I know the San Francisco Bay Area and Los Angles have several high site repeaters on all frequency pairs. You won't find an unused pair. You might have to have several pre-programmed channel pairs set up with different PL/DPL tones to make this work across the state. Each and every city would have different active frequency pairs and tones.

Most police departments are smart enough to do a quick search of the FRS and GMRS channels to hear what's going on with the protesters. Nothing wrong with that, but none of your traffic will be secure, and you'll have to deal with other people possibly transmitting on the channels you'll try to use.

GMRS wouldn't be a good choice.

Also, over a few city blocks, you shouldn't be having issues with simplex communications. Sounds like you'd need to look at your whole system first before trying to build a repeater system. Using 4 watts on UHF should be working quite well in that sort of environment.

Also, a repeater, to be useful, needs to be in a good central location. That might be difficult to do. Making sure it's secure and recoverable might be a bigger part of the task.

I'd suggest either licensing one of the itinerant UHF channels for simplex use, or simply using cellular phones.
We get a protest or two here every year. I work at a University and it's kind of to be expected. Our PD knows to listen for coordination on FRS and GMRS, hence most protest organizers simply use their cellular phones for coordination.

Even if your intent is to be completely peaceful, there is always "one in the crowd". Having all your coordination out in the open where anyone can listen in might not be the best idea.

 

[12dbsinad]

Now when you talk about interference here, are you mainly meaning the interference from the Baofeng RX being un-shielded, or are you also talking about the interference coming down the feedline as well? With the former, will changing up to two of those BF-9500 help resolve that issue? With the latter, what can I do to combat that. Is there a portable duplexer out there that will even do bandpass filtering; preferably cheaply as well?

To address you on this part, Baofengs are VERY cheaply built as far as the receiver goes (and transmitter for that matter). These can become "overloaded" or unusable even when just using it with the stock antenna around any type of mild RF environment. A commercial grade radio on the other hand would have no problems in this type of environment because of a much better receiver design. Now, throw on a higher gain external base antenna and you have just increased this probability of it happening with ANY RF present. There is extra filtering that can be installed (bandpass and notch filters) but, you probably wouldn't achieve the desired results given that the receivers are so poor.

I would follow the advise given here, for legality, cost and performance.

 

[WA0CBW]

Keep in mind a repeater doesn't necessarily improve your coverage unless:
(1) it is located in the center of the area you want to cover.
(2) it is located high enough to be "line of site" to all of the users in the area you want to cover.
Remember that each user has to be able to access it from their location.
BB

 

[jim202]

To address you on this part, Baofengs are VERY cheaply built as far as the receiver goes (and transmitter for that matter). These can become "overloaded" or unusable even when just using it with the stock antenna around any type of mild RF environment. A commercial grade radio on the other hand would have no problems in this type of environment because of a much better receiver design. Now, throw on a higher gain external base antenna and you have just increased this probability of it happening with ANY RF present. There is extra filtering that can be installed (bandpass and notch filters) but, you probably wouldn't achieve the desired results given that the receivers are so poor.

I would follow the advise given here, for legality, cost and performance.

I would not bet the store on commercial radios not having overload problems. As time has progressed, the quality of some of the commercial radios has gone way down. It would take some careful homework to pick out the better quality commercial radios. Even some of the off the shelf lower cost Motorola radios are not what you got 10 or 15 years ago. Quality of these receivers has really taken a nose dive with time. Even some of the top dollar costing radios do not perform that well.

Putting it in simple words, even the public safety agencies are finding out just how the quality of radios available today have gone down hill.

Another point that has not been brought up is the temptation to take a mobile radio and turn down the power to reduce heating the transmitter up. This is not a good idea to try to go below about 50% of it's rated power output. The solid state transmitters today become unstable if you go much lower in power. It is best to look at the transmitter spectral purity using a spectrum analyzer. This way you can see if the transmitter has started to generate any spurs that shouldn't be there.

Another issue with trying to use a mobile radio for a transmitter is that the heat sink is only rated for a 5 or 10% TX duty. A fan blowing on the heat sink can help the heat problem. But the driver stage will get really hot if additional heat sinking isn't added to it. Many people don't know enough about transmitters to know about the driver heat issue.

One other area that is of concern is the cables between the radios and the duplexer. These really need to be made with double shielded coax cables. This cuts down on signal leakage. As others have mentioned, shielding of both the transmitter and receiver is very important.

Bottom line in trying to make a repeater out of a couple of portable radios is just not in the book of working. Just about anyone in your position that has gone before you can attest to not spend the money or time effort. Your chances of failure are about 99%.

The suggestion of being able to change frequencies of your radio package are a good thought. But the duplexers are a fine tuned device with very narrow bandwidth of operation. Bottom line in using a duplexer, you can't change frequencies without a total re-tune of the cavities. Depending on how far you may have to move, it might also cause the jumper cables between the cavities to be changed to a different length. These jumpers are a critical length to the performance of the duplexer.

These comments are not what you want to hear, but that's the facts of radio physics. Been working with radios and repeaters a very long time. There are no short cuts you can take or cheap radios that will work.

You might want to take a step back and evaluate what your really trying to do and why. Maybe a better solution would be to have a simplex operation and put up a base station on a building to cover the range you want. Just don't use a high gain antenna as it will cause a cone of silence right near the building. It will give you range, but cause near in problems. This way you could obtain a commercial business license on an itinerant frequency or two.

Use the station like a dispatcher and control the activity of the other portable radios out on the street. Using a simplex frequency, the radio units closer to each other can hear the transmissions. Those further away won't always hear what is being said. If it is important, then the dispatcher could relay the message.

Jim

 

[nd5y]

One more thing nobody mentioned. Even if Baofeng radios had good receivers, were well shielded and had enough heat sink for 100% duty cycle, they still don't have COS output on the external connectors and that junky Ebay repeater controller doesn't have a COS input. Any FM repeater that relies on VOX to key the transmitter will never work properly.

 

[12dbsinad]

I would not bet the store on commercial radios not having overload problems. As time has progressed, the quality of some of the commercial radios has gone way down. It would take some careful homework to pick out the better quality commercial radios. Even some of the off the shelf lower cost Motorola radios are not what you got 10 or 15 years ago. Quality of these receivers has really taken a nose dive with time. Even some of the top dollar costing radios do not perform that well.

Putting it in simple words, even the public safety agencies are finding out just how the quality of radios available today have gone down hill.

Jim

Jim, we are talking about Baofeng radios here. I wouldn't compare these to the cheapest of Motorola's. I am old school, working on Micors and Mastr II repeaters and voter receivers back in the day. I consider those to be built like a tank to anything made today, but the bar has to be set, and it's way above a Baofeng!

 

[cmdrwill]

Ultra mickey mouse.....

 

[quarterwave]

Nothing wrong with the direction of thought...but don't reinvent the wheel. This has been done a million times before. Trying to use 2 of those cheap handhelds will be nothing but trouble.

The best thing you can do is invest in a real repeater.

 

[Project25_MASTR]

Your group or org could probably apply for commercial itinerant licensing (they do have repeater pairs available) on a statewide or nationwide basis (a few hundred dollars here versus individually licensing everyone).

Location often means more than power does. I've seen some interesting little low power (5W or less) repeaters being built with mid-tier (not from the big 3) mobile or data radios (total cost is around $200 per radio). Personally I'm fond of the idea of using data radios but I've never actually looked into what would need to be done for additional heat sinking.

 

[NDRADIONUT]

The Repeater Builder's Technical Information Page™

 

[prcguy]

Sorry, I didn't see this response until now.

On your questions, shielding the hand held radios from each other and the outside world would be good RF practice for assembling them into a repeater, including bypassing all audio and control lines to each radio to reduce the chance of the transmitting radio interfering with the receiving radio. That may not be practical but its the proper way to do it. The Baofeng mobile radios are probably better shielded than the handhelds.

The other problem is the receivers in Baofeng hand helds are bottom of the barrel for signal overload and your type of duplexer will not keep out nearby high power transmitters on nearby frequencies coming down the feedline. Repeaters used in dense urban areas with lots of radios around need to have very good receivers to combat overload and other problems.

The 50W Baofeng radio may or may not have a better receiver and you could never use them at 50W in repeater service because they will burn up. With a heat sink used on the 50W Baofeng your might be able to run them around 10W but probably less for repeater service. 50W is probably at the limit for your duplexer and the higher power you run on a small notch only duplexer, the more chance you have of your transmitter interfering with your receiver with the limited amount of isolation your duplexer has.

You have to consider the same problems when using an amplifier, it may not be rated for continuous operation and you might actually degrade repeater performance going to 50W or more with your duplexer.

To get an idea of what size battery and solar charger you need, measure what the repeater system uses in receive mode and transmit mode. Estimate how much transmit time it might have over 24hrs, then triple that because you will always underestimate these things. Then add up how many amps over 24hrs and I would choose a deep cycle battery double the amp hours you add up.

It probably takes about 1.5X the amount of power to charge a battery compare to what you have used, and you have to estimate how much usable sunlight you have on an average day. An MPPT type charger will make better use of the solar panels compared to a regulator or simple on/off type, but the MPPT is notorious for introducing noise into the DC power system. It takes a bit more to calculate an appropriate battery/solar system for a repeater so consider what I said as just some discussion.

Another thing is most solar panels for 12v systems put out around 19 to 21v open circuit and at rated output they are well above 12V, which means you can't calculate their current capability at 12V. Otherwise a 60W panel sounds like it can make 5A (60W / 12V = 5A) but in reality it makes maximum power at maybe 18V so its really 60W / 18V = 3.33A and unless you have a buck boost MPPT type controller all you will get is 3A from a 60W panel charging a 12V battery.

You might shop for a used Motorola R100 or similar repeater. I believe these are FCC type accepted for GMRS (you better check) and I don't think they do narrow band, so there should be lots of them around cheap, like $200 or maybe $300-$350 with a small duplexer. I even have one or two lost in my garage someplace. However if they don't do narrow band then they would not be usable with anything other than GMRS these days.

In the end it sounds like you really need a part 90 itinerant business license. You might not even need a repeater and VHF may suit your needs better than UHF. You might find a way to range test both bands under worst conditions and you might be surprised at the range without a repeater.
prcguy

Hello PRCGUY, I would first like to thank you for the quick response! You have certainly raised quite a few good points through this and I would like to run down each and get some clarification and maybe even some suggestions on how to improve.



This was something I had originally noticed upon alpha testing the unit at my house... and then something that quickly fell to the back of my mind, so thanks again for once raising this concern to me once more.

Back from when I did start noticing it, I decided to use a fat50 ammo box to double as both containment of all needed components and as a first line of defense against exterior noise (as you had said below). I was also contemplating using some lead or aluminum foil to further dampen both internal and external noise, either by coating the interior of the box with it, or wrapping each component in it. Of course mainly it was a question of if that would even do anything to combat RF interfer. and I decided to leave it be.

So would that help at all in keeping out conflicting signal leakage?



That was something I had started thinking about earlier in the build (just after I had ordered the parts actually). It is why I started looking at components such as the Baofeng BF-9500 to help out and extend the lifetime of the TX and sensitivity of the RX. Would something like that be a viable choice in terms of duty cycle concerns? It also looks like the casing of these radios is also made of a powder coated metal as well, so I am thinking that may help out in interference negation. Or am I wrong here?



I don't think I have had too much problem with DC noise so far, but then again I have not actually tested the system with the power circuits in place yet; in the beta field area that is. So when you're talking about adding power conditioning through choke and cap, could you give a component example for each? I think I may have found the cap filter online, but I am not familiar with a choke... or I am just really inept at electrical concepts, on or the two, heh.



Now when you talk about interference here, are you mainly meaning the interference from the Baofeng RX being un-shielded, or are you also talking about the interference coming down the feedline as well? With the former, will changing up to two of those BF-9500 help resolve that issue? With the latter, what can I do to combat that. Is there a portable duplexer out there that will even do bandpass filtering; preferably cheaply as well?



Ya, I was mainly considering the solar panel as a supplement to the battery when I was buying it and was mainly considering it as a trickle charger more than a full re-charging system. However with the addition of a different transmitter if that is, indeed what I will be needing for the above issues, I do agree that I would probably need something with a bit more umph; and probably at least one more battery daisychained to the system as well... If I were to add in those different transceivers into the system, what panel would you recommend to keep the system at least in status quo?

In terms of the solar charger, however, is there a difference to the MPPT system that I should be looking for? Like a specific spec or just all around better performance. Would [url-http://www.ebay.com/itm/12V-24V-20-30A-Auto-Switch-MPPT-Solar-Panel-Battery-Regulator-Charge-Controller-/111821595240?var=&hash=item1a09162268:m:mDT4BvQI5sOYw6fRkkwUBbg]something like this[/url] be something to consider then?



I did kinda figured the amp would just seem a bit extreme for a tiny system such as this for now. I do have to ask, though, would the amp be of any use if I were to install those 50W TX/RX units? As in, would the wattage stack (50W in 100W out), or would it simply be 50W in, 50W out?

And as for it being an amateur system, that was kind of the start of it. We had considered other options and were almost about to give up given the expense of a full repeater system ("in the thousands" is certainly not in any activist's budget ). I had stepped up as both a proof of concept for the team as well as a stride into a long-desired hobby of mine. So I suppose this is a bit of a muscle flex for my limited electronics skills in a way.

Then to the obvious problem of legal operation. Sounds like you probably want everything you do to be on the up and up to avoid any legal reason for someone to shut you down. The Baofeng radios are not FCC type accepted for GMRS use and especially for making into a repeater. To be legal, the radios and the repeater must be FCC type accepted for part 95 GMRS. There are lots of handheld radios out there that are GMRS legal but none of them would be legal to assemble into a GMRS repeater. A repeater is FCC type accepted as a repeater out the gate and not necessarily just the radios inside.

Legal is awesome and we are great supporters of the process... usually. When said process takes upwards of $1,000+ to get fully part 95, prebuilt systems, however, we will take a look at other means to get there. I am not saying I will not do my best to bring the system to FCC spec, but with the funds we have at our disposal, there could be some... adjustments made in lew of cost. Maybe being the key word there...

Regardless, I am fully open to suggestions on transceivers under 150$ to put into the system that would make it closer to spec. Preferably ones that we can program without Motorola admin codes.



Now as I was saying above, the prices we were looking at for used repeaters with duplexer and 10-25W were upwards of 1,000-1,500$ used. This was after many searches through the Ebay listings, Cragslist and other radio surplus sites. Maybe we were looking in different places than we should have? If you have any suggestions for something under 350$-ish (as that is just above what we paid for this prototype) then we would certainly consider it, so long as it had the ability to jack in to a DC system for us to use off grid.

In terms of that Business license, just how would that work if our ops location changed from day to day? Though we do have a few demonstrations in the metro area here, we also do bring our 'pony show' elsewhere to different cities and even countryside when the job demands it. Does the P90 allow for roaming or would we have to re-apply every time we decided to pick up shop and re-locate? Also, what are we looking at in terms of pricing for that? 100$? 1,000$?

---------------------

I also have a couple more questions to bring up while I have you here. One of which is a re-request of a point I brought up in my earlier post; about the different dual band antennas:



As well, in the case which we are using this system in large direct action movements and we need alot of surface area, what is your recommendation for a temporary antenna mast? I was thinking of using 3/4 inch well drilling pipe cut to 5' segments coupled together to form something around 25ft high. It would be rooted in a large drum of concrete and tied down with carbon-hardened bailing wire. Just how would that work in the P90 business license if we were so inclined to go that route?



Again, though, I would like to thank you for your response! You have really helped pull some important factors to light with this!

I hope to hear from you again soon!

Sincerely,

Nerumph

 

[RFI-EMI-GUY]

Licensing

Ditto on this group needing Part 90 licensing instead of GMRS. Your group will stand out by operating in GMRS and unlikely that your operation will be legal per FCC unless all participants cough up the $65 for a license.

 

[RFI-EMI-GUY]

You can license itinerant frequencies for a repeater (FBT) throughout the US. You have no need then to obtain a license when roaming.

"In terms of that Business license, just how would that work if our ops location changed from day to day? Though we do have a few demonstrations in the metro area here, we also do bring our 'pony show' elsewhere to different cities and even countryside when the job demands it. Does the P90 allow for roaming or would we have to re-apply every time we decided to pick up shop and re-locate? "