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I can find this stuff... but nothing I can open. Not sure where the actual letter and artifacts are. https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Sum&calledFromFrame=N&RequestTimeout=500&application_id=MjZkkijyA8IfBeMCZsYVMw%3D%3D&fcc_id=2AGNDGMRSRPT50

Steve, the FCC gave the repeater type certification based on the output of the duplexer because the duplexer is inside the chassis and considered and internal part of the radio... part of the design. https://fcc.report/FCC-ID/2AGNDGMRSRPT50 I am trying to find the official FCC cert, but that is the reference I found so far.

I’m not sure why you think regulations are different if the transmitter and duplexer are packed into an enclosure. The regulations very clearly state that the transmitter output power must be limited to 50 watts, not that the all-in-one box output power must be limited to 50 watts. You obviously understand the difference because you clearly distinguished between the transmitter output power and the duplexer output in your earlier post. But that was really the least of my concerns. The fact is that the transmitter is putting out 71 watts, which is harder on the circuits. That’s 40% higher power than designed.

This is compliant with part 95. Because it is sold as an all in one unit the output at the antenna connector is limited to 50 watts max. It has nothing to do with the internal components. But if you had this same transmitter and hooked it up to an external duplexer it would be against regulation. It's just like buying a 50 watt mobile radio. The output of the radio is 50 watts (or less) at the antenna output which falls within part 95. The duplexer needs to be inside the system and specifically designed to be an all in one system to comply. I think it's a 65 watt transmitter. I can't get it to go below 60 watts with the voltage on the power supply dialed down to 11.5 volts and I think it went up to about 71 when it was dialed up to 13.8v. I've never had it higher than that. This is what I bought, not something I made.

So far my wideband duplexer is working fine. Maybe the out of tune lets you throw more power at it. IDK. Looks like Btech will let me purchase another one of the newer Duplexers. It's the one I'm currently running and has been able to take the 70 watts in so far for about a year with no degradation. Not sure if they'll send it tuned to my spec or just send me another wideband. In which case I'll get it tuned. I have to go to their link they made specifically for me because the duplexers aren't in their catalog to sell.

The excessive RF power will take a toll on the circuitry of the transmitter as well as being non-compliant with GMRS regulations. I would suggest adjusting the RF output down to 50 watts at the transmitter output, before the input to the low side of the duplexer. Many times repeaters are run at reduced power levels to prevent early failure.

Whoa... that is the same issue Leo is having and on the same duplexer.... I may need to withdraw my endorsement.

This was the duplexer that came with the repeater originally. It was suppose to work with the transmitter power they had but obviously they were mistaken because they had to replace them. The duplexer they replaced it with seems to have the same power rating but has been working well since I replaced it. Most of the ratings I've seen on duplexers have a range rating and then a listed rating like this 40w-80w (50w). Before I toss it I'm going to pull it apart to see if there's any scorching of the internals. I don't expect anything to be wrong on the high (receive) side but on the low side there might be issues.

Everyone should review this old thread.

Hmmm... I can't help but wonder if it is an over-power issue with the duplexer. It's rated for 50w, I tested with about 45w after tuning it, and you're using 70w, which exceeds it's power rating by 30%. Exceeding the rating can cause overheating that can warp/melt internal parts and even cause internal arcing. That will definitely cause detuning and poor isolation, If I was a gambling man, I would say that it was off frequency when I got it, because parts were partially damaged inside (plating damaged, parts warped). I was keeping the power within spec, so I was able to tune and use it with the parts warped to the position that they were in. Now that it's being over-driven by 30% again, you are likely warping parts further, possibly causing plating to peel with excessive heat, which is causing arcing and detuning the duplexer.

Swapped the wideband duplexer back in and did my test loop. Pretty much back to normal. I think yesterdays test was slightly better but not by much. Had trouble in my usual spots. But I had trouble in a reliable spot too. Looks like for now this duplexer is staying put.

Well the news is anything but exciting. Reception is markedly worse. I only had one spot in my loop that I was able to communicate through the repeater. The rest of them either kerchunked it or didn't register. Very disheartening. I thought this would be much better than the other duplexer and right now it's looking like it is reacting like it was when I first got the repeater. I can contact it with my 50 watt. And I have a guy 2 towns up that I was communicating with before with good clarity, R7 and now he's barely an R5. Lots of background noise and very low modulation. Worked but you had to concentrate to hear what he was saying and even then it was hard. Since tomorrow is a bust for things to do at work I'm going to swap out the duplexer tonight and make the rounds again. It's always possible it's atmospheric and not the single channel duplexer. Or maybe it just can't handle the 65 watts in like the 2nd one they sent me. Either way it's getting swapped out for now. Thank you very much for the effort Marc

Oh it absolutely was. Noticeably so. I wasn't able to contact the repeater from my area with the original duplexer and when they sent me the newer one I was able to connect somewhat reliably. Still pretty iffy and right on the fringe. But communication was acceptable.

Its very possible that the wider configuration of the original notch was reducing power output more than the rated <‐1dB. 70w minus 1dB is about 55w. -2dB would be 44w. Figure the meter probably isn't perfectly calibrated, you probably had -2dB of insertion loss with the wider notch, and -1dB with the more narrow notch. The receive side was/is probably the same. However, -2dB vs -1dB is not really noticeable to the user, even though its measurable. It sounds like the second duplexer they sent you was tuned much, much better that the one that came inside the repeater.

I still go outside during sever weather so I can make accurate reports to the Sky Warn Net. But I sure am not going to go chasing any storms. And I will head for cover if I see a tornado heading my way.

If it gets you the distance and clarity you want, it's a good setup. "Good enough" is a valid concept.

There may even be one or more on this forum who has participated in it. A long time ago. When I was they were younger and more reckless.

Good information. See? I knew somebody here could answer that question.

There's a company that makes custom lengths of 7/8" heliax to order. Their prices seem pretty reasonable when I looked, but might still break your budget. I'd go with the best cable you can get for the main run. Use whatever connectors the antenna uses (no adapters at the antenna end). Then a lightning protector. Then 400 ultraflex to get into the house and to a base station, or a single adapter to a skinny coax with the matching ultraflex on one end and SMA-F (usually) to connect to a hand-held being used as a base station. My preference for outdoor connectors (and in general, actually) is N connectors. I wrap the completed, tested connector assembly in Scotch 88 electrical tape and then slide one of the heat-shrink tubes from a local Home Depot/etc. underground splice kit onto it and shrink it. That makes it watertight (you don't want water getting into your nice new cable). The heat shrink tubing and hot melt glue inside it will make a watertight seal, and the electrical tape means the connectors won't get gunked up with glue if you ever have to go into that connection again. This way you can upgrade your antenna at a later time without worrying about your cabling robbing power. If you use a commercial installer (not on your budget) you should get a PDF or hardcopy of an SWR sweep across your intended working range. Otherwise you can probably find someone with a SW-102 or similar to give you power and SWR readings. At the other end of the spectrum (pun intended) you can go all-out. My plan is 7/8" heliax from the lightning protector to a 20' mast on the roof, then a DB420-B (if the price ever becomes sane again - prices have tripled and Andrew is quoting 4-5 month lead time) antenna . The ground field is eight 8' long ground rods 16' apart connected with a continuous length of #4 copper and bonded to the power entrance. From the lighting protector to the repeater inside the house, I'll be using 400-class ultraflex. If you were in the NYC area, I'd give you a short reel of LMR600 - I end up with anywhere from 50' to a few hundred feet I can't use, on giant (table-size) reels. This is stuff left over from other RF work where LMR600 is preferable. That stuff is so thick and stiff that I made a walking stick out of an N connector on a length of LMR600. It was the end of the day and a storm was rolling in, so I just put connectors on the too-long cables to connect them to the protector bank. 2 days later I came back and cut the lengths down to the proper size, hence the leftover.

Ya, I have one of those 97S repeaters. More of a bug out repeater.

Sounds good LeoG. I fear that Retevis made a mistake when they upped the TX power. They either didn't have enough isolation in the duplexer, or choose to allow more insertion loss to get a high isolation. Either way is makes for poorer RX sens. I hope I'd dead wrong though and it's good. According to the spec sheet, the 97S is 0.20uV, which comes out to -121dBm. Many years ago when I worked on a project that had a full duplex radio I modified it (in a kludgy way) with a 1dB NF preamp and custom bandpass filter to protect the low NF preamp. The resultant RX sensitivity was about -123dBm, which is as low as you can go in the real world on a 25KHz channel BW. So the -121 of the RT97S is pretty darn good for a "mere" consumer grade repeater.

One fellow regularly hits 200 miles. Then again he is a legend in his own mind.

Well I was wondering about that but never asked the question. Since the wideband was tuned flat(ish) I was wondering if it might restrict the power. Just another compromise when doing this type of system I guess. Was pretty shocked to see 70 watts out of the transmitter. Thought maybe 60 at the most. Hopefully the receive will give me the same boost as the transmit.

I'm sorry you're experiencing the grief that you are, in your area. I Wish I could share some of the diversity of the folks here. Most of our Hams are discussing future antenna projects, current projects, ways to help the younger crowd get started with their stations, and even our local Gmrs guys are discussing antennas, tech projects and ways to improve their hobby ! A growing number of our hams are becoming licensed for Gmrs, and vice versa, with our Gmrs crowd seeking out classes for their Tech and General licenses. Most behave and conduct themselves as adults, and try to help fellow operators.