WRXB215

There is a switch.  Immediately below the original question, over on the right, is a pair of buttons. You can choose to sort by VOTES or by DATE.

Like you, I'm dual licensed so I just argue with myself. 🤣

Sorry, this is a little long.  Hopefully not TL;DR long.
This is somewhat Emergency Communications related, but will hopefully answer some questions a lot of new people have about needing a duplexer for a repeater.  I have to say that you need a duplexer if you want to use one antenna.  There is no way around that.  However, you can run a repeater with two antennas if you have the physical space to work with.


 
I have been playing with repeaters for some time.  I have never run a duplexer with any of my repeaters, but rather using two antennas physically separated horizontally.  This is because most of my repeaters are intended to be used in the field during an EmComm event.  So, rather than re-tuning a duplexer while trying to resolve frequency coordination issues in the field, we can simply pick our new frequency pair and carry on.


 
I never really had any desense issues, because I have historically been using two cross-band repeaters, occasionally with as much as 1,000 feet of physical separation and simply RF-linked the two systems.  The space between the two systems resolved any desense issues through natural atmospheric attenuation.  


 
This weekend, I tried doing some testing to see how vertical separation would work, with both antennas on the same mast.  Based on advice from several reliable techs and engineers in the commercial RF world, I figured I would give it a shot.  Unfortunately, my results were not as good as what my research implied it would be.


 
The idea behind stacking the transmit and receive antennas is that there are nulls above and below the axis of the antennas. The more separation, the wider the null in the field gets and the more attenuation you get.  My problem is, with a portable mast, I can’t separate them enough.  I tried clocking the antennas on the mast and had no change in performance worth mentioning, regardless of where they were. 


 
First, only using 5w on 145 Mhz, I stack the receive antenna on the mid-section of the mast and the transmit antenna on the top of the mast.  Both antennas have ground plans.  The initial separation was 40 inches.  The transmitter was splashing the receiver with -4dBm / 0.14 volts.  I moved them to 80 inches apart and it dropped to -57dBm… still not great at an additional 17 dB of attenuation.  Finally, I moved the antennas to 360 inches, a full 30 feet apart.  The splash only dropped to -74dBm, about an additional 23dB compared to 40 inches.


 
As a quick note, I was using LMR400 cable for both antennas.  Swapping the antenna positions made it so the repeater was completely unusable.


 
The next test was using horizontal separation but wired instead of RF linking.  I put the two masts up at 35 feet with the antennas at the top, and same elevation.  The masts were only 130 feet apart from each other.  I placed the repeater in between the two masts for general testing.


 
Testing in this configuration showed that at 20w the transmitter was splashing the receiver at -120dBm… a shade over 38dB of attenuation compared to stacking the antennas at 40 inches of separation and almost 47dB of atmospheric attenuation in total.  At 5w, it was attenuated to the degree that splash was no longer measurable on my SA at the offset frequency.  This is pretty good for what it is, as my repeater’s receive sensitivity is 0.2uv / -121dBm.  This means that at 20w the transmitter is preventing only the very weakest of signals that the repeater could possibly hear from actually being heard.


 
The cable I am using has a loss of 1.5dB per/100’ on 150 MHz.  So, I could increase the physical separation to 340 feet (two 200 foot cables on each feed) and still get 50% of my power to the transmit antenna.  Or, I could set the repeater off-center, closer to the receive antenna to minimize line loss on the receive side, turn the power up to 50W on the transmit side and still have plenty of natural atmospheric attenuation for good performance. 


 
I haven’t performed any testing on the UHF spectrum yet.  However, you need less space for UHF than VHF.  I would suspect that you would see at least another 10dB of attenuation at the distance I tested (130’) or the antennas could be placed as little as 40 feet apart with similar performance.  I will be testing again on 440 MHz, possibly on Thursday.  So, I should be able to confirm.


 
Obviously, having the transmitter and receiver tied together with cables will not provide the low loss and optimal atmospheric attenuation that can be obtained with split-band RF linked systems, but it reduces the amount of hardware you need for radios, power sources and physical security.  As long as you have the 200 feet to separate your two antennas, you should be fine.

Blue Max 49ers has the software for up to Windows 11 and you will need either the Prolific or the FTDI programming cable.

@Taz670 Oh you've done it now! You've entered the rabbit hole and you will never be the same! 😁
Welcome and have fun. 👍

@Taz670 Oh you've done it now! You've entered the rabbit hole and you will never be the same! 😁
Welcome and have fun. 👍

Same.

Dorothy: How can you talk if you have no brain?
Scarecrow: Oh there are lots of people without brains that do a great deal of talking.
🤣
Here is a link to some basic GMRS info. Welcome to GMRS.

@Taz670 Oh you've done it now! You've entered the rabbit hole and you will never be the same! 😁
Welcome and have fun. 👍

@WSAV285 That is where CHIRP comes in real handy. Download from each radio to create a file specific for each. After that, copy the channels you want from one and paste into the other. Good luck.
PS
See here for an explanation of the columns, especially tones.

As long as the repeater uses one of the frequencies from the main 467 MHz channels to receive and transmits on one of the main 462 MHz channels and is licensed appropriately, it is a GMRS repeater, even if it doesn’t have an offset of exactly 5.0000 MHz.  
You’re right that most “standard” GMRS radios don’t easily handle an offset that isn’t exactly 5.000 MHz but there are ways around it, especially with radios that have dual watch.

14 hours of continuous operation in VHF & UHF with no issues, but zip going on in the HF bands. 

Yup, I was able to see the Aurora in the Pittsburgh area last night. It was the best Aurora I have seen here. I'm an amateur astronomer and get space weather notifications so I have seen it many times here. 
I took these from my front step. 
 

The HF bands are still dead this morning. 20m is the only band with any decent activity right now. So far VHF and UHF has not been affected.
Here are a few photos I took last night. I used my iPhone 14 to take the photos. I could not see the green with naked eyes.

My wife is actually out taking pictures of the Aurora now, just outside of Phoenix. If she gets anything good, I might post one up. So far all she's sent to me just looks like a giant flood light behind a mountain.

I was on 20M FT8 when the aurora popped up over mid Missouri earlier. I could tell when I started getting a lot of noise show up on my WSJT-X waterfall. I stepped outside and got some good photos of the aurora. I haven't noticed much effect on 2m, 70cm, or GMRS tonight. But the HF bands were definitely affected. 
I did make a few contacts on 6m this evening. Everyones voices sounded digitized and weird.

Nice job! This very thing, making contact on a repeater, is a stumbling block for many new GMRS users. I would say it is one of the bigger causes of discouragement among new users.

I got my GMRS license a few weeks ago and received my handheld radios a few days ago & started setting them up (still learning & trying to set them up lol). Well, I reached a local repeater and made my first contact. It was exciting to me so I just thought I’d share that. Thanks everyone for helping me with my newbie questions. 

If your UV-82 is locked, which it sounds like it is, it will not transmit on GMRS frequencies (or any non-H.A.M. frequencies), and yes, it can still receive and listen to those frequenices.  If your UV-82 is not locked, then it will also transmit on GMRS and other non-H.A.M. frequencies.
The DB20G is a mobile GMRS radio so of the box it will transmit on all of the standard GMRS channels EXCEPT for channels 8-14, so because channel 7 is not between 8 and 14, it should also transmit on channel 7. If it does not, then you are either doing it wrong, you screwed up the programming, or its defective - and i doubt it is defective.

ANY hand-held GMRS radio will talk back and forth with FRS radios.  Any mobile GMRS radio will talk back and forth with FRS radios on channels 1-7 and channels 15-22 .

The UV-82 is a ham radio, so it will not transmit on GMRS frequencies.. To fix this, buy a GMRS radio OR buy a radio that can be 'unlocked' to transmit outside of the intended frequency range.

The DB20G is a GMRS mobile radio and per the FCCs rules, only hand-held GMRS radios my transmit on channels 8-14, however the DB20G should transmit on channel 7, so you may want to re-check that one.

It's weird how some people will whisper on the radio. As if they don't way anyone to hear them. 🤔

It's all nothing more than opinions and guesses until you try it.  Based on my actual experience, actually using the RT97, I would GUESS it will probably be fine, depending on the terrain as already mentioned.
One of the great things about the RT97 vs a "real" repeater (based on my experience using and comparing both types) is the very low power-draw, meaning if you are running it on emergency batteries, it will last a lot longer than a bigger, "better", more powerful repeater.
I would also recommend using a good quality antenna, that is correctly tuned for GMRS, and lightly better quality radios - something simple enough for everyone to use, but at least dust and weatherproof.   I would also recommend making sure everyone has extra batteries and keeps them charged - a monthly/semi-monthly test with everyone would be a good reminder for everyone to charge and rotate the batteries.
EDIT: I forgot the most important part: good quality coax and connectors.. Not just to reduce loss, but to avoid water intrusion.
 

Bingo! Very well said.

Bingo! Very well said.

Fair enough. You do you. I'll do me. Just giving the OP another option so that he isn't disappointed when that $600 antenna might not perform as well as he'd expect.
You can also clear coat a j-pole to minimize corrosion without affecting it's swr/range. I'll take that vs fiberglass that splinters and cracks, or crappy wire antennas encased in PVC. 
As for the j-pole I linked... Not slapped together. Thousands sold, no bad reviews. I'm not a hired sales person, but his j-poles and n9tax's Slim Jim's are well built and perform very well. I own many of both and they outperform dozens of other antennas I've used over the last 35 years. Even my old steel 102" whip still outperforms Antron 99's and the like on 10/11 meter. Some things just work, and I've never had a "dud".