Motorola vs Chinesium radios for repeater build

[SailorDan]

BLUF: When building a low duty cycle repeater, are the challenges of working with older Motorola radios (software/learning curve) offset by significantly better performance? (compared to low budget Chinese stuff)

Use case: Portable GMRS repeater with ~30W out used to facilitate family connectivity during camping trips. This would be a low duty cycle application with possible battery operation and solar back up.

Discussion: Motorola radios are regarded as premium, commercial quality products - and priced accordingly. Used ones are available, but seem challenging to source programming software for, require archaic operating systems to run said software, and have a steeper learning curve to program (designed for commercial vs consumer use).

Retevis and Wouxun both have GMRS radios (RA87 / KG-1000G) that can link for repeater function, but they are likely not of the same quality as a M1225 or CM200. As a hobbyist, I think the consumer focused radios would be easier to program and adjust. They would probably also be more user friendly if I eventually break up and use a mobiles.

I do have a Retevis RT97 that has worked, but I feel is a little lacking at 5W. Since I am primarily repeating 5W HT transmissions, am I wasting my time/money looking for higher output. I currently use a portable 30' mast with heliax feedline. Would a Motorola option be less likely to desense and improve my receive? (Wouxun claims a receiver sensitivity of 0.3uv - which is comparable to a M1225)

$$$Cost: Would be about the same for both options, with the Motorola option possibly being a little cheaper.

Appreciate your thoughts - Dan

 

[prcguy]

Poor performing, wide band, no front end filtering receivers coupled with transmitters that have high noise floors will equal sh*t performing repeaters with desense you can’t fix. Not to mention transmitters never designed for high duty cycle, even though you call it low duty. You have to consider even if your conversations are brief, the repeater is transmitting whenever anyone talks, so twice the duty cycle of any single radio.

I have tried slapping together various cheap radios and a number of good radios into repeater operation only to find it doesn’t work without a high end Bp/Br duplexer that cost way more than the radios. And a lot of extra shielding and bypassing. Something has to provide really good isolation between transmitter and receiver and if the radios don’t have that inherently it’s gonna be a problem.

And have you seen the guy on eBay selling cobbled together repeaters in plastic tool boxes using old Motorola mobiles with a flat pack duplexer? He gets $500-$600 for those things and they are complete Sh*t. I’ve had several people bring them to me because the range was crap and they had so much defense I’m surprised they got down the block. The idiot that built them had these tiny radios with tiny heat sinks cranked up to 30 watts with crap cables to the duplexer and it was basically a hand grenade waiting to go off.

 

[jeepsandradios]

Personally if the RT97 works I'd keep it. If you want a bit more coverage spend the funds on the antenna system. A real antenna and short chunk of cable and they can work very well for your use. I switched to the Rt97 in my motorhome that was using a GR1225 on Low power (10 watts.) Other than not needing to charge batteries as much I never noticed a difference in coverage. I mainly switched to lessen the power draw on my solar system.

I'm a blue blooded Motorola guy so it was hard to swap the radio but I got it before Midland offered their radio.

 

[redbeard]

Discussion: Motorola radios are regarded as premium, commercial quality products - and priced accordingly. Used ones are available, but seem challenging to source programming software for, require archaic operating systems to run said software, and have a steeper learning curve to program (designed for commercial vs consumer use).

There has never been a better time to get into Motorola radios with more and more people online sharing experiences and resources. Most software is just a Google search away, cables are plentiful from aftermarket manufacturers, and most stuff programs from Windows nowadays. Don't buy a model from the 1980's if you are worried about OS compatibility. As far as learning curve, it's no different than programming a ham rig via PC. Frequency is frequency. Tone is tone. Most software has built-in help to explain a term you may not recognize.

I think this perceived difficulty is nothing more than FUD; Fear, Uncertainty, and Doubt. Perpetuated by OMs who were still clinging to their rock-bound radios who couldn't fathom connecting a radio and computer together. Furthered by the secretive practices of Motorola, gatekeeping the service and programming behind their dealer network and past refusal to work with end users. Those days are long past. An online account is free to setup and for most modern radios the software is a free download from Motorola once your account is setup.

One of the most popular radios to make a small repeater from these days are the CDM mobiles. They still use the iconic 16-pin rear accessory connector with all your signals needed available, program with Windows CPS, and perform well. Many pre-made cables are available depending on what application/repeater controller you plan to use. A pair with a (MM)DVM modem make a great hotspot/repeater for digital radio.

 

[redbeard]

Plenty of reading at the usual suspects:

Waris - W9CR

wiki.w9cr.net

Repeater Builder

CSF Forums

Batwing Laboratories

W3AXL DVM Modem

Repeater Builder STM32-DVM

 

[prcguy]

I have a repeater build on the bench waiting for some time to complete, so I thought I would share what a PRCGUY portable repeater might look like. This was not really a project driven by need but rather finding something to do with all the junk laying around here.

I had two spare Motorola XTL1500 mobiles not being used in a 450-512MHz split that can go down to 440MHz with modified software. I also have some really good flatpack duplexers and a couple of nice Zero Halliburton aluminum cases. The plan is to assemble a mounting system with aluminum plates and angle stock that will hold the two radios on top of each other up out of the enclosure with front panels angled up for easy access and programming with the duplexer mounted below the radios. I have a small, thin Meanwell 12A power supply that is known to work fine without any VHF/UHF RFI and a Corcom AC line filter ahead of the power supply and those will mount in front of and below the radio front panels. The radios, duplexer and power supply will sit in the box similar to the first picture but higher with front panels angled up. There will be a fold down handle on top of the box and rubber feet on the bottom.

Once assembled the radios will be programmed for 20W on a 440 amateur pair with some jumpers between rear panel connectors making the two radios into a repeater. I also have an MPL list with all PLs and a few DPLs so those can be changed on the fly from the radio front panels. This repeater will be tested on a new hilltop site for a few weeks in the amateur band then will be reprogrammed and tuned on GMRS and tossed back in my garage and probably forgotten about. But it will easily cover most GMRS repeater pairs with front panel selectable PL or DPL codes if needed.

The XTL1500 radios at the heart of this repeater are completely shielded heavy metal castings with lots of heatsink area. I will have a small fan pulling air through the box with RFI shielding over the air intake and exhaust. These 45W radios should work ok for low duty cycle use at 20W, especially with the fan. The really good quality flatpack duplexer along with the fully shielded radio cases in a fully shielded box with double shield RG142 duplexer jumpers will provide good RF performance.

In my opinion this is how you make a portable repeater, lots of shielding, good quality radios, reduced power, good thermal design. I’ll post pictures when completed, hopefully in a couple of weeks when I have time.








Gosh those pictures isolated from the background look great!

 

[nokones]

There is a shielding problem between the CCR junk, especially the Wouxuns that will desense the hell out of the receiving radio unit. I experienced severe desense with two KG1000G + and I couldn't get more than a 1 1/4 mile away with a 50 watt mobile.

 

[ElroyJetson]

Even if they made radios that were up to snuff in all performance and technical standards, which they do NOT, I would still never give any of my money to the chinese communists if there is any alternative that meets my needs. Eventually we're going to be fighting the Chinese, giving them any of my money will only contribute slightly to them being better equipped when that time comes.

I look beyond what's in my wallet at this moment. Unlike some people. A short sighted desire to save money NOW at the expense of my safety and security in the future? Nope. I don't have that.

 

[prcguy]

Even if they made radios that were up to snuff in all performance and technical standards, which they do NOT, I would still never give any of my money to the chinese communists if there is any alternative that meets my needs. Eventually we're going to be fighting the Chinese, giving them any of my money will only contribute slightly to them being better equipped when that time comes.

I look beyond what's in my wallet at this moment. Unlike some people. A short sighted desire to save money NOW at the expense of my safety and security in the future? Nope. I don't have that.

And it’s probably not much more expensive to do it right. In the repeater build I posted above, the 45W UHF XTL1500 mobiles cost me $190 each on eBay. The power/accy connectors cost $5 each at the Dayton Hamvention last year but realistically they run $25 each any day on eBay. The duplexer is about $75 used. The power supply was under $20 new on Amazon. The aluminum enclosure was $20 at a ham swap meet.

All the basic parts cost me $505 and maybe another $50 in future coax, connectors and misc hardware, so about $555 total and my labor is free to me. Compare that to the nearly $600 abortion portable repeaters being sold on eBay that don’t work and need a lot of professional intervention to work.

 

[alcahuete]

You can often pick up XPR8400 repeaters on the bay for $500-$600. I've seen the Vertex model (EVX-R70) for $200. Add a flatpack duplexer and you're good to go. Plugs into the wall, modern programming software, and has battery backup function built in and will charge the battery when it's plugged into the wall. Nice unit in one box, and you don't have to worry about cobbling together the radios and everything else.

 

[SailorDan]

Thank you all for taking the time to share your thoughts.

.... And have you seen the guy on eBay selling cobbled together repeaters in plastic tool boxes using old Motorola mobiles with a flat pack duplexer?

I have sure have - which started my thoughts on maybe I should build myself with a quality used radio vice questionable chinese stuff. Thank you for the feedback on your experience with their performance - or lack there of ;-) And also for sharing your build plan - gives me some information/ideas for researching.

There has never been a better time to get into Motorola radios with more and more people online sharing experiences and resources. Most software is just a Google search away, cables are plentiful from aftermarket manufacturers, and most stuff programs from Windows nowadays. Don't buy a model from the 1980's if you are worried about OS compatibility. As far as learning curve, it's no different than programming a ham rig via PC. Frequency is frequency. Tone is tone. Most software has built-in help to explain a term you may not recognize.

This is good to hear and removes one of my concerns for opening this can of worms. I'm starting to warm up to making this a bigger project, doing it right and learning on the way.

There is a shielding problem between the CCR junk, especially the Wouxuns that will desense the hell out of the receiving radio unit. I experienced severe desense with two KG1000G + and I couldn't get more than a 1 1/4 mile away with a 50 watt mobile.

I have heard a similar account on a youtube video. Gave me pause on dropping the amount of cash necessary for 2x radios.

You can often pick up XPR8400 repeaters on the bay for $500-$600.

I am increasingly tempted to grab a full on repeater, but would like to avoid a 120v requirement.

I think shopping the eBay ads for some used Motorola is in my future.

Thanks again for your inputs.

 

[nokones]

You can often pick up XPR8400 repeaters on the bay for $500-$600. I've seen the Vertex model (EVX-R70) for $200. Add a flatpack duplexer and you're good to go. Plugs into the wall, modern programming software, and has battery backup function built in and will charge the battery when it's plugged into the wall. Nice unit in one box, and you don't have to worry about cobbling together the radios and everything else.

Just don't buy or use a cheap XLT Comm. Duplexer that cost around $150 if you want it to work half-way decent. I believe that duplexer has a problem with plastic inserts in the duplexer ports burning out from the RF passing through.

I am using an EMR Corp. Duplexer with my Vertex Standard EVX-R70 Repeater connected to a Laird FG4605 Omni 5 dB gain Base Station Antenna with LMR400 cable and Amphenol connectors that were not bought from Amazon. My final RF out is around 28 watts. I don't have the battery backup yet. I keep forgetting about it. Also, I need to find the DC electrical connector to mate up with the connector on the repeater.

 

[jeepsandradios]

I am increasingly tempted to grab a full on repeater, but would like to avoid a 120v requirement.

The GR1225 will run off 12volts. That's what I used before the RT97. It worked well and has moved to my barn as a backup to my MTR2000. I believe the XPR also had 12V input. I also run a few Kenwood TKR that run off 12volts. So shop around there are 12V input repeaters. The 1225 was nice but the PA doesn't last long on high power. The issue will be space and sitting amp use if your trying to do this on solar and battery.

 

[alcahuete]

I am increasingly tempted to grab a full on repeater, but would like to avoid a 120v requirement.

I think shopping the eBay ads for some used Motorola is in my future.

Thanks again for your inputs.

It will run off of 12v. You also have the 120v if you need it. And it's all in one box, somewhat modern, an just works. I have one that I use for portable means that I put in a gator case. That holds the repeater, the duplexer, and has some extra room, plus it's on wheels so it can easily be moved around.

 

[JustinWHT]

Fifty years ago we would use Motorola Micors for repeaters. The local Motorola shop was into tower mounted radios. Instead of on-site maintenance, they had me hoist up a complete repeater box replacement.
I pointed out the futility of running a 70 watt repeater transmitter because of asymmetric range.
70 watts TPO + 10 dBd gain (DB420 when Decibel Antennas was still in business in Dallas) = 700 watts ERP.
A 70 watt Micro with 5 dBd mobile antenna would have around 250 watt ERP. In other words the repeater reached out about twice the distance the mobile could talk back to the repeater.

I'm running a Ritron UHF repeater with 10 watts at the duplexer output into a 9 dBd gain omni for 80 watts ERP and 20 watt mobiles with 5 dBd mobile antenna for about 70 watts ERP. Nearly a symmetrical match. Repeater is on a 250 foot hill and I get 20 mile radius coverage.

 

[MTS2000des]

I still don't get the ham fetish of cobbling together cheap mobiles, which are not designed for the transmit duty cycle, high RF environments that can overload a receiver, when today used repeaters like GR1225s, XPR8300/8400s, Vertex VXR7000s- can be had for the same money as junk pile radios and are far superior performers.

 

[nokones]

I still don't get the ham fetish of cobbling together cheap mobiles, which are not designed for the transmit duty cycle, high RF environments that can overload a receiver, when today used repeaters like GR1225s, XPR8300/8400s, Vertex VXR7000s- can be had for the same money as junk pile radios and are far superior performers.

And the EVX-R70-G7-40. There are several of these repeaters on eBay and from other sources. I'm glad I bought mine last year. I paid $700 for a brand new unit and all I had to do is get a duplexer and the software and programming cable. It is great unit and performs very well.

 

[prcguy]

Progress update:
Got some time and built a cage thing to hold the two XTL1500 radios and duplexer so they can be removed and serviced from the box as an assembly. Duplexer is tuned and RG-142 radio to duplexer cables are made in a 1/2 electrical wavelength. Power supply and power entry filter are mounted in the box and with a few more tapped holes and one more cable it should be ready for testing.



Aww crap, looks like I scratched up,the wife’s dryer again using it as a picture backdrop. Not sure what I’m gonna do with this thing if it works.

 

[paulears]

So few people have mentioned the critical part. The filters! The little Retevis gets bought by many, and i still have one in stock, but why sell a repeater that encourages people to make it multi channel. That never works! Repeaters that perform are very rarely mobile designs, in mobile cases. They are inside sealed enclosures that make the DC and RF ports the only access point, and can be screened and filtered. Even Motorola repeaters that use ordinary mobile sets are compromised. Many of the Chinese rack mount repeaters contain two separate radios, with that kind of problem, but with external decent filters they can work well. Small 6 cavity filters are always a compromise, but if you take the lid off a 19” rack repeater and find two stripped down and circuit board exposed mobiles or portables with solder tagged interconnects, then things like desense should be expected. Decent repeaters, and i use kenwoods, are still compromised by poor filters. That is where the success or failure is centred. Made worse by leaky short coax links.

 

[prcguy]

So few people have mentioned the critical part. The filters! The little Retevis gets bought by many, and i still have one in stock, but why sell a repeater that encourages people to make it multi channel. That never works! Repeaters that perform are very rarely mobile designs, in mobile cases. They are inside sealed enclosures that make the DC and RF ports the only access point, and can be screened and filtered. Even Motorola repeaters that use ordinary mobile sets are compromised. Many of the Chinese rack mount repeaters contain two separate radios, with that kind of problem, but with external decent filters they can work well. Small 6 cavity filters are always a compromise, but if you take the lid off a 19” rack repeater and find two stripped down and circuit board exposed mobiles or portables with solder tagged interconnects, then things like desense should be expected. Decent repeaters, and i use kenwoods, are still compromised by poor filters. That is where the success or failure is centred. Made worse by leaky short coax links.

Right on point here, many repeaters completely depend on a high quality duplexer or external filter to work, and even then they are compromised. Even some commercially made repeaters like the Yaesu Fusion DR-2X are compromised and could use some attention.

The picture below shows what I did to my DR-2X replacing the cheap internal RG-58 jumpers with double shield RG142 and silver plated connectors. Then a Corcom AC input line filter and lots of ferrites (white cubes) over internal cables between radios and controller, many that are unshielded. This repeater had some slight desense on a service monitor with no duplexer and the transmitter into a load when new. Now it’s desense free on a flatpack duplexer.





BTW, my and probably your DR-2X spews out a lot of transmitter noise when operated on low power 5W and it interferes with its own receiver. Operating these at high power will probable burn up the transmitter, so the only viable power level seems to be mid at 20w. I pad that down to 5w using a high power 6dB attenuator then to a 5w in 85w out amplifier which works well and the repeater runs fairly cool.