MTR3000 Repeater

[zerodayjames]

Hmm this Comprod is almost identical to the Sinclair I was looking at. Little bit lighter, pole is slightly smaller and also more affordable. I was digging having a Sinclair duplexer/antenna combo though..

Comprod Communications, Inc. - 406-512 MHz 8dB Quad 1/2 Wave Dipole Antenna - 774-70TM-1/2 - Tessco

COMPROD's 774-70TM-1/2 406 – 512 MHz quad dipole antenna 8 – 8.5 dB bi-direct gain. 450 W. Includes harness with N Male termination. Internal to mast. 1/2 wave spacing. ORDER MOUNTING CLAMPS SEPARATELY.

www.tessco.com

Very similar to

Sinclair Technologies - 406-512MHz 4-Dipole 10.15dBi Antenna - SD314-HF2P2SNM (D00) - Tessco

SINCLAIR's SD314HF2P2SNMD00 406 – 512MHz UHF 4 – dipole antenna 10.15 dBi offset with N Male connection. 8 dBd with bi-directional pattern. 0 deg. downtilt. SD314 – HF2P2SNM (D00)

www.tessco.com

 

[zerodayjames]

Finally got my Motorola account squared away and connected the MTR3000. Lookin good!

 

[kayn1n32008]

Hmm this Comprod is almost identical to the Sinclair I was looking at. Little bit lighter, pole is slightly smaller and also more affordable. I was digging having a Sinclair duplexer/antenna combo though..

Comprod Communications, Inc. - 406-512 MHz 8dB Quad 1/2 Wave Dipole Antenna - 774-70TM-1/2 - Tessco

COMPROD's 774-70TM-1/2 406 – 512 MHz quad dipole antenna 8 – 8.5 dB bi-direct gain. 450 W. Includes harness with N Male termination. Internal to mast. 1/2 wave spacing. ORDER MOUNTING CLAMPS SEPARATELY.

www.tessco.com

Very similar to

Sinclair Technologies - 406-512MHz 4-Dipole 10.15dBi Antenna - SD314-HF2P2SNM (D00) - Tessco

SINCLAIR's SD314HF2P2SNMD00 406 – 512MHz UHF 4 – dipole antenna 10.15 dBi offset with N Male connection. 8 dBd with bi-directional pattern. 0 deg. downtilt. SD314 – HF2P2SNM (D00)

www.tessco.com

Comprod and Sinnclair are both high quality manufacturers. Miles ahead of the Commscope DB antennas.

 

[kk6rq]

When they work, they work extremely well. I still have a few MTR2000's laying around but the RSS won't run on modern 64 bit computers so you have to keep a bit of an older machine around to work on them. Quantar RSS does support 64 bit operating systems...

Free VMWare Player with 32bit Windows works excellent and buys you back all those 32bit-only programs (MTS/MCS, Astro Saber/XTS3K/Astro Spectra, MTR2K, etc.). Mind you, VMWare was recently bought by one of those equity firms that buys up companies and sells them off for parts, so you may need to change to Proxmox or VirtualBox at some point. Been using this setup for over a decade and the ONLY problem I ever ran into was not recognizing an i-Button, and that was VMWare Fusion on a Mac.

 

[kk6rq]

Again, dont get hung up on 100w. You're not going to gain much unless you are dealing with combiner losses when combining multiple repeaters to a single antenna.

Encryption capabilities were in the fore thought of the P25 spec, as is security of the key.

Encryption on DMR was an afterthought. Only Kenwood(and possibly Tait) need key loaders to load AES/DES/ARC4(EDP/ADP) keys.

Kenwood and Tait both have software keyloaders available, though I'm not familiar with the criteria/requirements...but they definitely exist.

 

[PreferredCustomer]

Seems like a lot of new GMRS users and new hams want to put up a repeater, when a couple of 50 watt mobiles would meet their needs.

 

[mastr]

Seems like a lot of new GMRS users and new hams want to put up a repeater, when a couple of 50 watt mobiles would meet their needs.

You forgot part of your statement- "as long as someone else furnishes a repeater".

A "couple of 50 watt mobiles" won't reliably talk halfway across the county I live in.

 

[PreferredCustomer]

You forgot part of your statement- "as long as someone else furnishes a repeater".

A "couple of 50 watt mobiles" won't reliably talk halfway across the county I live in.

I see a lot who want to do it themselves.

50 watt radios, used as a base station, with a good quality antenna at a decent height should certainly be able to make it across an average county. A repeater won't be any different, unless the antenna is a few hundred feet in the air.

Maybe not vehicle to vehicle, but base to base.

 

[jeepsandradios]

Maybe on a flat dessert that may work. I have a DB404 60' in the air hooked to a LMR base radio. On UHF I cannot get to my closest town 14 miles away to a mobile radio. I dont live in the mountains but hilly countryside. Sadly folks post I can talk 50 miles all the time then new users get frustrated when there baofeng and jpole can't talk that far. Manage expectations. Yes some cases may work but on UHF there is alot to think about.

 

[MTS2000des]

Yep, here in hilly and foliage infested north Georgia, a 50 watt UHF mobile may get you 3-5 miles of usable range, if you have good 5/8 over 5/8 antennas on mobiles, and a decent base antenna with quality feedline. That's why not having a hog sucking up every repeater simulcasting all over three states is a problem here.

 

[zerodayjames]

Yeah my use case definitely requires the repeater...

So I've made a ton of progress on this project. Got the MTR 3000 programmed and tuned the depluxer. I threw in a couple shots of what I've done.

I am now trying to dial in the duplexer tune. From what I have found I was able to get an average of -36 dBm on the rejects and -1.5 dBm on the passes when the cans are tuned separately. Once I connect everything in series and test that way, I am getting a -69 dBm reject and -3.5 dBm pass. I haven't done any additional tuning while they are all connected, only tuning to each can individually. From what I've read and been told is that I should be able to get at least a -100 dBm out of these Sinclairs. Any suggestions?

TX - 440.050
RX - 444.050

Transmit - Low Pass
Pass: 440.050
Reject: 444.050

Receive - High Pass
Pass: 444.050
Reject: 440.050

Can 1
TX Low Pass
Pass 440.050
-1.56 dBm
Reject 444.050
-36.56 dBm

Can 2
TX Low Pass
Pass 440.050
-1.51 dBm
Reject 444.050
-36.21 dBm

Can 3
TX Low Pass
Pass 440.050
-1.49 dBm
Reject 444.050
-36.89 dBm

Can 1
RX High Pass
Pass 444.050
-1.62 dBm
Reject 440.050
-36.12 dBm

Can 2
RX High Pass
Pass 444.050
-1.56 dBm
Reject 440.050
-37.87 dBm

Can 3
RX High Pass
Pass 444.050
-1.61 dBm
Reject 440.050
-36.56 dBm

Final Readings series of cans:

RX High Pass
Pass 444.050
-3.40 dBm
Reject 440.050
-69.71 dBm

TX Low Pass
Pass 440.050
-3.80 dBm
Reject 444.050
-70.12 dBm

 

[Ubbe]

I am getting a -69 dBm reject and -3.5 dBm pass. I haven't done any additional tuning while they are all connected, only tuning to each can individually. From what I've read and been told is that I should be able to get at least a -100 dBm out of these Sinclairs. Any suggestions?

It's only a 4MHz split and the MTR can handle that 69dB rejection just fine.
Are the harnes between cans adjusted in lenght to the 440Mhz frequency to get a proper 50 ohm impedance?
If they are not then the cans adjustments are compensating for that and will loose some performance.

/Ubbe

 

[zerodayjames]

It's only a 4MHz split and the MTR can handle that 69dB rejection just fine.
Are the harnes between cans adjusted in lenght to the 440Mhz frequency to get a proper 50 ohm impedance?
If they are not then the cans adjustments are compensating for that and will loose some performance.

/Ubbe

These are the specs of the duplexer. Do I need to change out the lengths of the harness depending on the tune even if it's within the range?

average input power max (W)	250
connectors	N-Female
frequency range (MHz)	420 to 450
impedance (Ω)	50
insertion loss max rx to ant	2.2
insertion loss max tx to ant	2.2
number of cavities rx side	3
number of cavities tx side	3

 

[Ubbe]

These are the specs of the duplexer. Do I need to change out the lengths of the harness depending on the tune even if it's within the range?

That 420-450 range are +/-4% of the frequency so should be fine for a harness to cope with that frequency range if it was originally cut for it.

/Ubbe

 

[WA0CBW]

Normally ham UHF repeaters are 5 Mhz split. Normal UHF radios will need a custom split programed to access the repeater.
Bill

 

[zerodayjames]

Tried tuning back to factory specs. I still feel like I can do better...

TX: 430.000
RX: 435.000

TX Low Pass

Can 1
Pass 430.000 -1.41 dBm
Reject 435.000 -38.50 dBm

Can 2
Pass 430.00 -1.49 dBm
Reject 435.000 -39.10

Can 3
Pass 430.000 -1.26 dBm
Reject 435.000 -39.00 dBm


Final - All cans connected
Pass 430.000 -2.69 dBm
Reject 435.000 -69.8.26 dBm

 

[Ubbe]

Maybe just some leakage in coax/connectors/Rigol?

If one duplex filter manage to reject 40dB and the next also 40dB it would be a 80dB rejection and if the third also can do 40dB it would be 120dB. When a signal generated that close to a measured signal 100dB down it will be very difficult to avoid that signal leak out from the generator and goes into the measured signal. It will be the same situation at the site.

/Ubbe

 

[zerodayjames]

Okay thank you that's what I figured. The rejection is supposed to be the sum of the cans.

Someone mentioned in another forum that I may be limited to the noise floor of the Rigol. This would make sense because when I turn off the tracking generator, the floor sits at around -69 dBm. I probably have it tuned to -120 dBm rejection, I just can't get a reading of it. Is there a way to adjust the noise floor of this Rigol? Again, this is the first time I've ever even heard the term "noise floor" but it sounds like it might be the cause of the problem. I attached a picture of the Rigol with the tracking generator off.

 

[ramal121]

The dynamic range at that span is not that great. To get a better idea of how low the notch goes do this:

Set freq to the notch
Set span to 1 MHz or less, you want the pass off the display, just the notch
Input attenuator to 0, RF preamp on
Set your bandwidth (RBW/VBW auto) to 3 kHz. Slower the better
Tracking generator level to 0 dBm then normalize the display
Have at it
If you want to take the "hair" out of the bottom of the notch try changing the trace to power average and wait a bit.

Remember that span and bandwidth are your friends as far as sensitivity is concerned. You'll want to do the notch last then go back to a larger span to just eyeball how it all looks.

You are using a dummy load on the unused duplexer port and attenuators on the analyzer ports to soften any impedance mismatch, right?

 

[Ubbe]

I usually didn't have access to a $10,000 instrument for fine tuning duplexers down at the noise floor so I used a radio programmed to receive the TX and RX frequencies and connected that and then had a signal generator and tuned the rejection to max while keeping the radios reception with a little background noise, increasing the signal generator level gradually and having a very weak tone modulation as a pilot to not tune for any false carriers. As soon as I touch a coax the signal strength usually went up even when using double shielded coax when the rejection starts to go over 60dB. It's difficult to shield everything when reaching a 60dB isolation. Then used the radio again to tune for best bandpass signal.

/Ubbe