Retevis RT97S Repeater and RF Power Amplifier

[lawenforcement]

I recently purchased a Retevis RT97S Portable Repeater through the Mygmrs.com website. After viewing products on the Retevis website I noted that they sell this repeater in a package that includes an external RF power amplifier that's installed between the repeater's output and the antenna feedline in order to increase the repeater's output wattage. Does anyone know how this configuration could possibly work? It seems to me that once the RF power amp is keyed up, it would cut off the input to the repeater / duplexer. The power amp can't possibly be passing the incoming frequency to the repeater / duplexer's antenna input while the external power amp is keyed up so the repeater's receiver would effectively be without an antenna connected during transmission. Retevis responded to me by saying they have customers who are successfully using this product combination  BUT they did not say they have tested it themselves. 

 

[TNRonin]

TNRonin,
Youre getting good advice from radio professionals about the best antennas and feed line. That’s great if you really want the best. If that’s the case simply ignore the rest of this post. 
If you’re still reading you might be a hobbyist who’s just interested in “good enough“ and the financial savings that implies. 
You already have LM400 feedline. 
I think you already have a J-pole. 
A short run of LM400 will have nearly no discernible incremental losses compared to hardline. Just make sure you seal the connectors against moisture. 
A better antenna will make a difference, but how much is that worth to you?  
Hook up what you have and try it. It won’t cost you anything but your time and I guarantee you’ll learn from the experience. Then, if it doesn’t work like you want, you can always try a different antenna (or perhaps raising the j-pole). You can always upgrade the feed line as well. 
I would hate to see your enjoyment of the hobby diminished because you’ve been convinced that what you have isn’t good enough when the actual incremental improvement is only measurable to professionals. 
Don’t let the best stand in the way of the good enough. Lots of people use LM400 and j-poles with inexpensive repeaters and do just fine. In the end elevation and location are the most important factors and all the money you have cannot overcome that. 
 

Good info. Thanks.

Sent from my SM-T860 using Tapatalk

[SteveShannon]

2 hours ago, gortex2 said:

The issue in the end is not money or lack there of. Its location. If your repeater is on a 5000' mountain then inferior equipment is made up for height. Most folks are installing a repeater on a garage or house in town. IF you look at the true loss of cables and adapters you will see noticeable differences and may sour the hobby taste. Very few folks are on sites that have LOS to hundreds of square miles but I guess on youtube anything is possible. 

The repeater in question is about 5-7 watts leaving the antenna port. 25' of LMR at 460 is about .75 db of loss. Now add .50db for each adapter you use. Your rapidly up to 3db which is about 1/2 your power. So when your repeater on your garage is only transmitting 2-3 watts then folks ask why they handheld inside the house can talk to another and not thru the repeater. 

But I digress I keep forgetting the hobby is about doing it as cheap as possible as hams do in this new age. BTW you can grab 1/2 LDF jumpers on ebay for under $50 if you do some searching. I just sold 6 1/2" commscope superflex jumpers for $30 each with N (M) on both ends. So you can find some decent stuff if you look. 

He has (or will have) a repeater with an SO-239 connector.  He already has an antenna that has an SO-239 connector. He has LM-400 feedline that has PL-259 connectors that will mate directly to the antenna and repeater, no adapters needed.  In terms of loss through connectors, that’s the least he can make it, regardless of whether he uses hardline or anything else.  If he gets a jumper with N connectors on both ends he would have to add N to PL-259 adapters, which (using your numbers) would add 1 dB loss and negate the 0.75 dB difference (your numbers for the loss through 25’ of LM-400) in losses through the feedline. 

But what are the losses through 1/2 “Commscope?  The losses per 100 ft (according to the Commscope website) are 2.342 dB or about 0.55 dB for 25 feet.  So, by using Commscope Superflex and two adapters, the losses are 0.56 + 0.50 +0.50 or 1.56 dB So now he’s 0.8 dB negative compared to using what he already has.  

Yes, he might decide that he doesn’t have the coverage he wants and decide to buy an antenna with more gain.  He still has that as an option. 

“But I digress I keep forgetting the hobby is about doing it as cheap as possible as hams do in this new age.” 

Way to lash out at both hams and those who have already stated they don’t have deep pockets.  

[gortex2]

LDF4-50A CommScope 1/2" hardline is 1.4db of loss at 450mhz.

LDF4-50A

I said before use the LMR and the ham radio antenna and find out how bad it works. Then either leave the hobby disappointed that it doesn't do what everyone on here says a repeater can do or go spend funds on he proper stuff to do it right. 

I'll leave this topic and go back to real radios now.

[OffRoaderX]

6 hours ago, gortex2 said:

I'll leave this topic and go back to real radios now

Thank you.

[WRUH615]

lawenforcement,  am using a simplex repeater that can be used with an amplifier, which is a great affordable way to do range/antenna/coax testing before buying the expensive stuff.   LATNEX RC-S120 Simplex Repeater Controller

[BoxCar]

  LATNEX RC-S120 Simplex Repeater Controller cheaper at Newegg.

[WRUH615]

On 9/17/2022 at 8:15 AM, OffRoaderX said:

For most normal people, GMRS is not a hobby.

I put it another way: 

GMRS, like many of the other things I do, are not a "Lifestyle" or "Identity" activities.   Radios are a tools.   
(That's the same way I look at firearms and motorcycles.). I don't need "stuff" for people to know who I am.
I don't wear corporate logos on my back. My tools let me do what I want to do. I don't wear free advertising.

Edited November 28, 2022 by WRUH615
Spelling

[Lscott]

14 hours ago, WRUH615 said:

I don't wear free advertising.

I have the same feeling when I see those license plate frames with the dealer's name on it. They were going to stick one on the new 2023 Mazda CX-5 I just got and told them no. Worse is when they "brand" your ride with a dealer's name decal stuck on the paint of the shinny new car you just paid a ridiculous amount of money to buy.

[BoxCar]

2 hours ago, Lscott said:

I have the same feeling when I see those license plate frames with the dealer's name on it. They were going to stick one on the new 2023 Mazda CX-5 I just got and told them no. Worse is when they "brand" your ride with a dealer's name decal stuck on the paint of the shinny new car you just paid a ridiculous amount of money to buy.

I ask how much are they willing to pay me for carrying their advertising. 

[WRB891FRANK]

On 8/30/2022 at 12:06 AM, Ian said:

I was wondering about that scenario a couple days ago.  It says on the Baofeng 40-watt amp description that the analog models pass RF passively when the amp is off, and I was wondering if I could get away with a cheater repeater like this.

 

Short answer?  Not without replacing the duplexer with a fifty-watt model, sounds like.  That's another hundred bucks on Amazon…

That can't and won't work its physics . it does say that on the web site . amp must go into duplexer .so you must buy pass the internal duplexer