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Retevis 40 watt repeater


WRTZ750
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I picked up a nearly new in the box BTECH AMP-U25D at a local swap for a really good price. This is the one to get. It costs a bit more than the other model but will handle analog plus all the usual digital modes. Here are some documentation I keep in my on-line library for it.

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Internal-Photos AMP-U25D.pdf Review BTech AMP-U25D.pdf Test-Report AMP-U25D.pdf AMP-U25D Users-Manual.pdf

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4 hours ago, Lscott said:

It look like the exact same amp sold by BTECH.

https://baofengtech.com/product/amp-u25/

 

I feel like that goes for a fair number of their products though...ra25 (anytone at779uv/radioddity db20g), rb86 (tyt th-8600), rt9000d (tyt th9000d), rt95 (anytone at778uv, Midland dbr2500) rt99 (vero vnr7500)

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5 hours ago, WRUU653 said:

I guess if you really wanted a Retevis 40w repeater you could add their amplifier to their RT97. They say it's compatable. Non affiliated link below...

https://www.retevissolutions.com/rt91-amplifier#A9132A

I heard a rumor that a GMRS YouTuber will be making a video in the next few weeks showing how "compatible" the Retevis 40W amp is with the RT97 repeater.

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1 hour ago, OffRoaderX said:

I heard a rumor that a GMRS YouTuber will be making a video in the next few weeks showing how "compatible" the Retevis 40W amp is with the RT97 repeater

I am intrigued! I will be tuning in to see how the mystery turns out… Merry Christmas, happy holidays and thank you, you my favorite YouTuber. 🎄 

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May have missed it was me that posted part of an email reply.

Sent: Tuesday, November 29, 2022 9:23 PM
Hello, 

We have plan to make 40W GMRS analog repeater, but the available date is not known yet, once we have update, will public to our SNS, you will see that. If this repeater you plan to use in which application scenario? Like farm, or factory, or ? Thanks! 

Thanks and Regards,

Elsa Jin (Customer Manager)

Web:www.retevis.com

So based on what I was wrote, 40W is coming some time.  No reference to any other product or timeline.  Trying not to post too much, but they clearly wanted to know uses cases. 

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On 12/24/2022 at 6:36 AM, WRUU653 said:

I guess if you really wanted a Retevis 40w repeater you could add their amplifier to their RT97. They say it's compatible 

So it looks like Retevis RT91 amplifier compatible with RT97? Randy has his video up and something to say about that… 

 

On 12/24/2022 at 12:10 PM, OffRoaderX said:

heard a rumor that a GMRS YouTuber will be making a video in the next few weeks showing how "compatible" the Retevis 40W amp is with the RT97 repeater.

I’ll let Randy take credit for posting the link. Go check it out. I don’t want to spoil it for anyone by giving it away. 😀 Thanks for addressing this Randy. 

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1 hour ago, WRUU653 said:

So it looks like Retevis RT91 amplifier compatible with RT97? Randy has his video up and something to say about that… 

 

I’ll let Randy take credit for posting the link. Go check it out. I don’t want to spoil it for anyone by giving it away. 😀 Thanks for addressing this Randy. 

Suffice it to say that Randy was correct. 

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4 minutes ago, WRTZ750 said:

When will this mystery company release more info on a 40 watt repeater?

If you’re talking about Randy’s upcoming mystery company he said it would be the same wattage as the Retevis RT97 which is 10 watts, effectively 5 on output.  I think someone said Retevis was coming out with a higher wattage repeater at some point but hey apparently (as Randy has shown us) they lie sometimes. 😂

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25 minutes ago, WRUU653 said:

If you’re talking about Randy’s upcoming mystery company he said it would be the same wattage as the Retevis RT97 which is 10 watts, effectively 5 on output.  I think someone said Retevis was coming out with a higher wattage repeater at some point but hey apparently (as Randy has shown us) they lie sometimes. 😂


Up above WRVD377 posted the following:

May have missed it was me (wrvd377 in a post above) that posted part of an email reply.

Sent: Tuesday, November 29, 2022 9:23 PM
Hello, 

We have plan to make 40W GMRS analog repeater, but the available date is not known yet, once we have update, will public to our SNS, you will see that. If this repeater you plan to use in which application scenario? Like farm, or factory, or ? Thanks! 

Thanks and Regards,

Elsa Jin (Customer Manager)

Web:www.retevis.com

So based on what I was wrote, 40W is coming some time.  No reference to any other product or timeline.  Trying not to post too much, but they clearly wanted to know uses cases. 

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Ah yes thanks Sshannon, I do remember that now (bit foggy with a cold). Since he said mystery company I thought he might be referring to this…

On 12/23/2022 at 4:17 PM, OffRoaderX said:

The new GMRS repeater coming out in January is very similar to the Retevis RT97 - with the same wattage..

No company mentioned as of yet. I’ll be interested to see what comes out. On both counts. I don’t suppose it would do any good to send Randy one of my mechanical pencils? No I didn’t think so. 🤣

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Putting a 40 watt amplifier on a low budget radio with suspect spec's is the equivalent of putting a 200 HP Nitrous shot kit on your Pinto.  

Until your repeater has a decent receiver with good sensitivity and selectivity you haven't done anything to improve the performance of the system. No matter how much horsepower you think you just gained.

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On 1/7/2023 at 9:20 AM, Radioguy7268 said:

Putting a 40 watt amplifier on a low budget radio with suspect spec's is the equivalent of putting a 200 HP Nitrous shot kit on your Pinto.  

Until your repeater has a decent receiver with good sensitivity and selectivity you haven't done anything to improve the performance of the system. No matter how much horsepower you think you just gained.

Well they never said how they would do it in the email.  I wonder if it is this.

Retevis AR30 Full Duplex Repeater FARM TRACTOR BUNDLE | retevis.com

 

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1 hour ago, gortex2 said:

That does not appear to be a GMRS repeater but a part 90 repeater built out of mobile radios. (Part 90 is guessing as they don't list it on the site).

The usable frequency range of the transmitter covers the Part 90 spectrum.

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I'm still trying to translate what they mean by "Forwarding sensitivity decreases" under the last "Duplex" heading. I'm thinking that they actually measured receiver desense - and they're spec'ing it at 3dB.  But then I'm thinking, no - they wouldn't advertise that. Or, would they?

For the rookies - a 3dB desense (reduced receiver performance when the transmitter is keyed) is somewhere close to unforgiveable. Not to mention unworkable. You basically took every 4 watt portable & made it perform as well as a 2 watt portable.

 

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1 hour ago, WRTZ750 said:

So who wants to buy it with their own monies and try it?  Not me but am curious.

Or just stick with Motorola or Vertex?

*Directed at WRTZ750* A commercial repeater will always be superior to these things. 2 moto MCS2000 series (or similar, Kenwoods are easier to program) with a repeater controller and proper vertical+horizontal separation of TX and RX antennas (the dB amount of isolation is cumulative) will get you started. Save up for a good duplexer. Used is fine. Then you can reclaim an antenna and the coax for another installation. Who doesn't want more antennas in the yard (besides the wife)?

*No longer directed at WRTZ750* No one who uses GMRS thinks. Not "thinks about *insert subject*", just thinks. These briefcase repeaters are for very close range, portable applications. For tower (stationary) repeaters these things suck. Never even used one and I can tell you, they suck. Here comes the thinking part, so prepare yourselves. Quick note since people will bring it up: I was a cellular/pager/RF comms tower tech for United Radio in Syracuse, NY before I changed fields to IT. I have seen installations and test equipment Sad Hams could only dream of touching. I DO NOT have a HAM license, but if there are any Sad Hams who wish to deem myself as unqualified, please find the nearest short pier and talk a nice long stroll off of it.

UHF Things To Know™:

Height is king. LOS is required.

Coax line loss is huge in the UHF bands. The higher you go, the more picky the RF Electricities get.

Any duplexer that can fit in a briefcase that small WILL NOT WORK. $200 Chinese duplexers DO NOT WORK.

OK knowing this lets take a look at a conservative situation. You antenna is 30ft up. Your coax run is 50ft of LMR400 (LMR is fine for duplexer connections from the ANT port to the antenna ONLY) to be able to reach the 40W briefcase repeater.

Type: LMR400

Length: 50ft

Frequency: 464.500MHz (middle of band)

SWR: 1:1 (being generous)

Pwr In: 40W (These are 40W because of shitty duplexer insertion losses BTW, actually a 50W xmitter)

Matched Loss: 1.37dB

SWR Loss: 0dB

Total Loss: 1.37dB

Real Pwr to ANT: 29.2W

So your 40W repeater is really a 29W repeater in this case. Bump that up to a more typical 100ft run and it's a 21W repeater. This stuff is all calculated for and mitigated on a real tower. Simplest way to overcome this is with a decent dB gain antenna.

Example:

Cable Loss per 100 ft at Operating Frequency = 2.73 dB

Cable Length = 50 Ft.

Calculated Loss = 1.4 dB

Power into Cable = 40 Watts

Power out of Cable = 29.2 Watts

Gain of Antenna = 3 dBd

ERP of Antenna System = 58.3 Watts

See? Now you're more than a 40W repeater. A decent antenna costs more however. The gain covers both TX and RX so no need for a preamp. Most antennas use dBi as the measurement because the numbers are bigger. They are not real, however. Subtract 2.17 from any dBi rating and you have the actual dB measurement. 

Now from looking around on here and reading the stickies, I cannot discuss how all of this can be easily and cheaply mitigated with a nice 100W commercial UHF radio for xmit on your repeater. There are many calculators that will show you what your xmit power will be in the situation above though and/or my inbox is open.

Other options awarded to you with used commercial radios is the remote control head style radios. Most of those simply use an RS232 style interface. This can easily (fairly) and cheaply be modified to use CAT6 cable to extend the cable connection to up to 125ft. You could then mount the xmit radio much much closer to the antenna to shorten your coax run while also moving the transmitter farther away from the receive radio thus reducing desense more.

GMRS can be great for you if you just do your research and think.

 

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