Retevis 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 even with the antenna in my office on top of a file cabinet.

I've read elsewhere that many 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 (except COM2) 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 Advanced 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!

 

[K4EET]

<snip> 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!

Unless I am mistaken, all repeaters must undergo frequency coordination through the area coordinator. Just because you think you have a clear frequency, what happens when the frequency coordinator assigns that frequency to a new repeater system? After all, they know nothing about your system since it wasn’t properly coordinated.

 

[K4EET]

Here is the local coordinator:

Indiana Repeater Council – Serving Indiana Amateurs Since 1971

 

[cmjonesinc]

Unless I am mistaken, all repeaters must undergo frequency coordination through the area coordinator. Just because you think you have a clear frequency, what happens when the frequency coordinator assigns that frequency to a new repeater system? After all, they know nothing about your system since it wasn’t properly coordinated.

Amateur repeaters aren't required to be coordinated per FCC rules. Is it a good idea to? Absolutely, but it isn't a law. Repeater coordinators have no authority in ham bands. It's just one of those "best practices" that most people agree to. Personally, if it's a low powered small footprint machine in a radio dead area I don't really see going through the trouble of coordination myself.

 

[kf8yk]

The Indiana Repeater Council has established 'shared non-protected' repeater pairs that are ideal for portable or temporary repeater operations.

IRC Bandplan – Indiana Repeater Council

 

[alcahuete]

It is 100% accurate that no coordination is required. The only caveat is that the non-coordinated repeater owner has the primary responsibility to resolve any interference that may occur.

§ 97.205

(c) Where the transmissions of a repeater cause harmful interference to another repeater, the two station licensees are equally and fully responsible for resolving the interference unless the operation of one station is recommended by a frequency coordinator and the operation of the other station is not. In that case, the licensee of the non-coordinated repeater has primary responsibility to resolve the interference.

 

[N4GIX]

Unless I am mistaken, all repeaters must undergo frequency coordination through the area coordinator. Just because you think you have a clear frequency, what happens when the frequency coordinator assigns that frequency to a new repeater system? After all, they know nothing about your system since it wasn’t properly coordinated.

Now where do you suppose I came up with the primary frequency pair to begin with? In this area coordination with Illinois as well as Indiana.

It is a 10 watt portable repeater that will have no fixed area where it will be deployed within the five counties of District 1 NW Indiana. It will be using a unity gain antenna at around 20', so not in any way a gator-mouth machine...

 

[K4EET]

Now where do you suppose I came up with the primary frequency pair to begin with? In this area coordination with Illinois as well as Indiana.

So you did go through the proper coordination process?

It is a 10 watt portable repeater that will have no fixed area where it will be deployed within the five counties of District 1 NW Indiana. It will be using a unity gain antenna at around 20', so not in any way a gator-mouth machine...

So if you are on Hoosier Hill in Eastern Indiana (for example) at just shy of 1,300 feet AMSL, your 10 watt repeater transmitting into a unity gain antenna will have a coverage radius of approximately how far at UHF? Sorry but I am not familiar with Northwest Indiana to cite a good example...

 

[N4GIX]

So you did go through the proper coordination process?

So if you are on Hoosier Hill in Eastern Indiana (for example) at just shy of 1,300 feet AMSL, your 10 watt repeater transmitting into a unity gain antenna will have a coverage radius of approximately how far at UHF? Sorry but I am not familiar with Northwest Indiana to cite a good example...

Yes, although it was several years ago. I believe that there has been some tropospheric ducting, because I should not be hearing the Attica DMR repeater at all. In fact I haven't heard it at all since around 3pm.

The five counties in which it would potentially be deployed is relatively flat. The highest point in our five county area of responsibility is ~480' AMSL and that being around the La Porte area. The repeater may well never be deployed, in which case it is pretty much a moot issue.

 

[R8000]

Putting the frequency selection aside.....

If you have access to service equipment, how clean is the transmitter ? The china radios aren't known for being spectrum friendly. Receiver selectivity ? Desense ?

You should give it a good test and see if it will be RF friendly to your frequency neighbors.

I saw one of these on a YouTube video awhile back that just had awful desense and the video poster downplayed it. I think the video is gone now.

 

[wa8pyr]

Amateur repeaters aren't required to be coordinated per FCC rules. Is it a good idea to? Absolutely, but it isn't a law. Repeater coordinators have no authority in ham bands. It's just one of those "best practices" that most people agree to. Personally, if it's a low powered small footprint machine in a radio dead area I don't really see going through the trouble of coordination myself.

That might be technically true, but if a conflict arises between a coordinated repeater and an uncoordinated repeater, the coordinated repeater will win. If it gets as far as the FCC, the operator of the uncoordinated repeater could be fined for causing willful interference.

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!

You might want to check all the channels to make sure the duplexer truly works on all of them. Duplexers really aren't intended to be frequency-agile on the fly, and I'd be a bit concerned about the potential for problems, especially if you're using this for emergency deployment. My guess is that it's using a cheap mobile "notch-type" duplexer, which notches out the TX frequency on the RX side, and notches out the RX frequency on the TX side; the farther away you get from the tuning points the worse your performance will be.

Best bet is to pick one frequency and tune the duplexer to that, then program the repeater for two other frequencies 12.5 kHz away on either side of the primary. Leave it at that and you'll probably get acceptable performance from the two alternates. Much more than that would be a stretch.

 

[vagrant]

@N4GIX It would be wise to use 441.500 as your repeater output and 446.500 as the repeater input. That pair is listed as shared non protected for Indiana and Illinois in each respective coordinating body band plans. This will allow you to tune your built-in notch duplexer to the exact frequencies and avoid additional losses during transmit and receive if using a different frequency. Additionally, you may want to enter those same input/output frequencies in each of those channel selections to avoid additional TX/RX losses by using a different frequency.

 

[N4GIX]

@N4GIX It would be wise to use 441.500 as your repeater output and 446.500 as the repeater input.

That is likely what I'll wind up doing as soon as I can schedule some time to do so, although I will still likely add two channels +/- 25kHz as close alternative frequencies. Several years ago when the coordinators approved me using the pair I had instructed the techs to use for the programming, this 441.500/467.500 wasn't set aside for this purpose.

For those who don't know, this is not a case of "two HTs" in a box. The transmitter is totally separate and very robustly shielded, and the receiver is likewise separate and well shielded.

 

[vagrant]

By the way, have you connected a meter and observed the actual watts coming out of the box? If so, what was that number? Thank you.

 

[N4GIX]

By the way, have you connected a meter and observed the actual watts coming out of the box? If so, what was that number? Thank you.

Not yet I haven't. Even though I'm officially "retired" I still seem not to have as much free time as I'd expected!

Okay, I've just checked with my trusty Diamond DX-600 meter:
VSWR 1.1
PWR 6 watts

 

[kayn1n32008]

That might be technically true, but if a conflict arises between a coordinated repeater and an uncoordinated repeater, the coordinated repeater will win. If it gets as far as the FCC, the operator of the uncoordinated repeater could be fined for causing willful interference.



You might want to check all the channels to make sure the duplexer truly works on all of them. Duplexers really aren't intended to be frequency-agile on the fly, and I'd be a bit concerned about the potential for problems, especially if you're using this for emergency deployment. My guess is that it's using a cheap mobile "notch-type" duplexer, which notches out the TX frequency on the RX side, and notches out the RX frequency on the TX side; the farther away you get from the tuning points the worse your performance will be.

Best bet is to pick one frequency and tune the duplexer to that, then program the repeater for two other frequencies 12.5 kHz away on either side of the primary. Leave it at that and you'll probably get acceptable performance from the two alternates. Much more than that would be a stretch.

A mobile duplexer can easily be tuned to pass 250KHz of spectrum. BTDT with a LMR portable repeater. 13 channels with the repeater TX @ 153.xxxxMHz, repeater RX was 5.26MHz above using a Sinclair mobile duplexer. TX power was adjusted to give about 5w out of the duplexer.

 

[paulears]

I got one of these a few months back and the small size duplexer fitted is not that sharp at all. On the analyser it's quite simple to tune and has nice locks that don't drift much as you tighten the lock nut, but I could get pretty decent rejection on the Uk frequency split on the band I'm using it in (business, not ham) 453 TX 459 RX. Performance was pretty acceptable, the transmitter is quite clean, just a few low level spurious outputs but not much different to the Kenwoods we use normally. However, the frequencies I have available are not in 12.5kHz channels next door to each other. We have quite randomly allocated channels, and the next one available to me is too far for the duplexer without retuning - so for UK use we can't have hams with their own repeaters ad hoc. Portable repeaters are allowable with permission only. On the business hire channels they're fine, but it means I really have just one channel without retuning the filter. In honestly, it's not unexpected with the size of it. I suspect many people making the videos either have not got the test gear or knowledge to align the filter or have specified a frequency for the order and just assumed they can move away from it more than it's pass band allows.

It's too expensive really, but is a neat simple device. It will sit on the shelf I guess. Nobody is likely to want to buy it!

 

[vagrant]

What was the notch, 40 dB?

 

[kayn1n32008]

You might want to check all the channels to make sure the duplexer truly works on all of them. Duplexers really aren't intended to be frequency-agile on the fly, and I'd be a bit concerned about the potential for problems, especially if you're using this for emergency deployment. My guess is that it's using a cheap mobile "notch-type" duplexer, which notches out the TX frequency on the RX side, and notches out the RX frequency on the TX side; the farther away you get from the tuning points the worse your performance will be.

Best bet is to pick one frequency and tune the duplexer to that, then program the repeater for two other frequencies 12.5 kHz away on either side of the primary. Leave it at that and you'll probably get acceptable performance from the two alternates. Much more than that would be a stretch.

The two attached photos are of a Sinclair 6 cavity BpBr ResLoc duplexer, that a group I am involved with picked up this past weekend. As you can see, it is factory tuned to pass, 1.0625MHz of bandwidth. Pretty sure the 6 cavity ResLoc is spec'd at 85dB isolation, 1.2dB insertion loss, with a 1MHz pass band. In my experience, Sinclair duplexers will easily exceed isolation and insertion loss ratings.