Retivis RT97 Portable Repeater

[n4gix]

I finally received my shiny new RT97 portable repeater yesterday. I chose to have them program it in the ham portion of the UHF band, since they don't charge extra for it, nor for tuning the duplexer. I do have the service equipment here in case I ever need to retune the duplexer.

 

So far I'm very pleased with it's performance even though currently it's connected to a tri-band NMO mag mount antenna on a 14' diameter pie pan. I was able to hit the repeater full quieting about 3 miles from my 40 watt mobile. 

 

I've read elsewhere that many (including our very own Rich!) have had problems getting the programming software configured properly. After several attempts, I finally discovered that Retevis only allows COM1 through COM20 in their software. On my development computer all COM ports 1 through 22 (save one) are already in use, so the system assigned COM23 to the Prolific programming cable!

 

I noted that COM2 was not already in use, so I had to use the Advance option to re-assign COM23 to COM2. Bingo! Now the darn thing will connect and will allow for read/write operations to take place.

 

I note that the RT97 has 16 channels that may be programmed. Evidently the duplexer they are using will allow +/- 500kHz to pass through adequate signal, so they have pre-programmed the other 15 channels accordingly! This has proved to be a blessing since my primary channel (#1) is 442.975/447.975. The closest repeater on that pair is in Attica, Indiana, nearly 120 air miles from me so I thought that was clearly enough separation to cause no problems, especially since I chose to use 141.3 CTCSS for the input/output tone. Unfortunately, Attica is a DMR repeater and the analog 'machine gun sound' has been coming in loud and clear! So I've moved up 12.5kHz (channel #2) to eliminate the nasty sound...

 

I am intending this portable repeater to be used primarily as part of our ARES group here in NW Indiana, and am anxious to get this outdoors for some range testing!

 

[Extreme]

"...and am anxious to get this outdoors for some range testing!"

 

Me Too!  

[gortex2]

Another advantage of 16 channels is you could put different PL DPL combinations in each channel with the same frequency. In GMRS that can be good.

[Lscott]

I finally received my shiny new RT97 portable repeater yesterday. I chose to have them program it in the ham portion of the UHF band, since they don't charge extra for it, nor for tuning the duplexer. I do have the service equipment here in case I ever need to retune the duplexer.

 

So far I'm very pleased with it's performance even though currently it's connected to a tri-band NMO mag mount antenna on a 14' diameter pie pan. I was able to hit the repeater full quieting about 3 miles from my 40 watt mobile. 

 

I've read elsewhere that many (including our very own Rich!) have had problems getting the programming software configured properly. After several attempts, I finally discovered that Retevis only allows COM1 through COM20 in their software. On my development computer all COM ports 1 through 22 (save one) are already in use, so the system assigned COM23 to the Prolific programming cable!

 

I noted that COM2 was not already in use, so I had to use the Advance option to re-assign COM23 to COM2. Bingo! Now the darn thing will connect and will allow for read/write operations to take place.

 

I note that the RT97 has 16 channels that may be programmed. Evidently the duplexer they are using will allow +/- 500kHz to pass through adequate signal, so they have pre-programmed the other 15 channels accordingly! This has proved to be a blessing since my primary channel (#1) is 442.975/447.975. The closest repeater on that pair is in Attica, Indiana, nearly 120 air miles from me so I thought that was clearly enough separation to cause no problems, especially since I chose to use 141.3 CTCSS for the input/output tone. Unfortunately, Attica is a DMR repeater and the analog 'machine gun sound' has been coming in loud and clear! So I've moved up 12.5kHz (channel #2) to eliminate the nasty sound...

 

I am intending this portable repeater to be used primarily as part of our ARES group here in NW Indiana, and am anxious to get this outdoors for some range testing!

 

I would be interested in knowing how deep the notches are for the duplexer. The typical cheap Chinese ones they use are spec'd for around 70db and that's at a very narrow bandwidth. To get a 500KHz bandwidth I suspect the notch depth is rather poor, traded off notch depth for bandwidth, leading to poor performance, i.e poor off frequency rejection and RX desense from the TX side.

 

My understanding is the TX side of the notch filter should be tuned for the exact RX frequency for maximum notch depth while the RX side of the filter should be tuned for maximum notch depth at the TX frequency.  

[gortex2]

Agree. Id be worried how far from center I'd go. I normally tune my flatpack style ones dead center of GMRS band so it can go up or down a channel or 2. Much more it does show issues the further away from center.

[n4gix]

I would be interested in knowing how deep the notches are for the duplexer. The typical cheap Chinese ones they use are spec'd for around 70db and that's at a very narrow bandwidth. To get a 500KHz bandwidth I suspect the notch depth is rather poor, traded off notch depth for bandwidth, leading to poor performance, i.e poor off frequency rejection and RX desense from the TX side.

 

My understanding is the TX side of the notch filter should be tuned for the exact RX frequency for maximum notch depth while the RX side of the filter should be tuned for maximum notch depth at the TX frequency.  

 

You are absolutely correct. Were this portable repeater going to be in continuous use its current parameters would be an issue.  However, its intended usage is to be deployed anywhere within our ARES five counties for emergency coverage likely no more than two or three days, it shouldn't be much of a concern.

 

Our plan is to use a unity gain antenna no higher than 20' to reduce any chance of interference with other 70cm operators. I just got it two days ago and haven't had time to bench test yet. I may in fact wind up tightening up the notches on the duplexer if it proves to be a problem. There's a lot of testing yet to be done!

 

EDIT: I have determined that the interference from the Attica repeater was a result of tropospheric ducting. I've not heard the digital 'noise' since around 1500 CST yesterday afternoon.

[WRFP399]

I have one of these operating up on a remote mountain side here in Alaska. It uses a SLA battery that is solar re-charged. I get a range of around 25 miles or so when coupled with handhelds such as Vertex VX-231s and/or Motorola PR400s. It probably can go further but I run into the inlet and can't test it further.

 

Out at 25 miles it starts to get a bit noisy in the signal but the message is readable. I attached a photo of looking in out from where it's located at.

[n4gix]

Wow, that's terrific performance for ~5 watts!  It certainly proves the claim that "height make right..." 

[mbrun]

I have one of these operating up on a remote mountain side here in Alaska. It uses a SLA battery that is solar re-charged. I get a range of around 25 miles or so when coupled with handhelds such as Vertex VX-231s and/or Motorola PR400s. It probably can go further but I run into the inlet and can't test it further.
 
Out at 25 miles it starts to get a bit noisy in the signal but the message is readable. I attached a photo of looking in out from where it's located at.

Very, Very Nice.


Michael
WRHS965
KE8PLM