Repeater Configuration

[Guest Answer Seeker]

Hello, I am testing two KG1000-G plus with duplexer and receiver range is not what I was hopping for. My question is 

Both radios for GMRS repeater build should be FCC approved or the transmitter radio only?

For example if I use CDM1550ls+ as receiver and  Wouxun KG1000-G as transmitter in new repeater build, would this be conforming to the FCC rules?

Thanks. 

 

 

[BoxCar]

There are no rules regarding what you use to receive with other than it carry an FCC approval. The transmitter though is different and needs type acceptance for the task.

[Guest Answer Seeker]

It has FCC ID AZ492FT4836.

Thank You for quick response. 

 

[gortex2]

What is your expectation ? What antenna, What Feedline ? What duplexer ? Alot of a repeater is antenna and filtering. Granted Id pick anyhting but that radio for a repeater but know guys have been successful with them. I'd look at the rest of the system before I'd worry about a radio

[Guest Answer Seeker]

Thank you for your question. 

Expectation is, two KG1000-G plus in repeater setup would have a better range then RT97 Retevis repeater.  RT97 picks up transmission approximately twice as far as KG1000-G plus. DIY Slim Jim antenna  and  RG213 cables used in testing with 3 different duplexers to insure duplexer is not a problem. 

I will test with CDM once I figure out how to connect it to KG if it all this is possible. 

 

[gortex2]

Still alot of vague info. How much 213 ? Slim Jim is most likely not the best antenna for a repeater. The RT96 should receive just as well as the KG. You will have loss in the duplexer and what ever cables you are using to connect everything. Could be up to 3 db of loss. You really need to do troubleshooting on this. Start with hooking the KG1000 to the antenna with no duplexer. Can you hear the distant location direct ? 

 

[Guest Answer Seeker]

25 feet of 213. Maybe it is not best antenna for repeater but I tried 3 different antennas. With Slim Jim and RT96 I got  best result, antenna SWR was around 1.15, 6 watt out.

Then I took two KGs and test with 3 different duplexers and check the distances, results are not promising.

I did not spend much time to test KG stand alone but it picks distant repeaters the same way as Radioddity GM-30 or Baofeng GM-25Pro handhelds do. KG transmitter is ok too 40 watt output measured by SW-102. 

I don't think there is anything wrong with radios when using stand alone but what it looks like KG receiver in repeater configuration works only around a corner. 

 

[KAF6045]

RG213 has about 5.5dB loss per 100 ft at GMRS frequencies. Call it 6db for computation (and include any connector losses). A 50ft length would then have 3dB loss (50%), 25 ft would have 1.5dB loss.

If I did the math properly, that converts your 40W output to 28W at the antenna. But does not include duplexer losses -- assume 3dB. That means your 40W out is now 20W out of the duplexer, and 14W at the antenna. About 35% actual output.

You say you've tried with three duplexers... Did you bother to put the SW-102 on the OUTPUT of the duplexers.

Oh, BTW: that 35% also applies to /receive/ signal strength. If those distant repeaters are near threshold for the direct radio, they are likely under threshold through the repeater configuration.

 

 

[Guest Guest Answer]

Thank you for your response, 

and thank you for the calculations you have performed  but without looking at the math and comparing two repeaters RT96 (which also has duplexer inside) and two KGs with duplexer using the same cable length, antenna,  handhelds I can reach RT96 twice as far as I can reach KG repeater.

I don't have schematics for KG or block diagram to check but my outdated experience from forgotten hobby building CB transceivers back in 80's tells me that there is nothing else I can do with KGs but try to replace one with different radio for receiver. 

 

[gortex2]

OK. So here are 2 tests you can try.

 

Hook KG10000 to antenna with no other parts. Do a test. It should be similar to RT97 for receive. If so put your duplexer inline. If it drops out thats your issue. 

What jumper cables do you have on duplexer ? more importantly who tuned the duplexer and what is is tuned to ? Do you have model numbers of duplexer ? 

 

[Guest Answer Seeker]

Thank you for your recommendation. 

Jumper cables the same as main RG213 1.5 feet, duplexers sgq-450d tuned to 462.625 467.625, and two sgq-889 tunned to 462.600 467.600 and 467.725 462.725. With sqg-450d I am getting better results then with other two. Duplexers are factory tuned and I can't measure how well they tuned. Testing duplexer tunning will require at least oscilloscope and generator will cost thousands, unless this days there some other cheep test equipment people use to check it.

For now I was checking KG, next thing instead of KG I will test if the another radio plugged in to duplexer gets the signal from the distances worked for RT97 repeater. If another radio receiver perform well then I will look into how to connect to KG. if it does not work well then I will ask for recommendation to replace duplexer. 

 

[Guest Keasbeynj700gmrs]

On 11/7/2022 at 2:22 PM, gortex2 said:

What is your expectation ? What antenna, What Feedline ? What duplexer ? Alot of a repeater is antenna and filtering. Granted Id pick anyhting but that radio for a repeater but know guys have been successful with them. I'd look at the rest of the system before I'd worry about a radio

Hopefully your using a meter to read your output etc .....

[Guest Answer Seeker]

Hello, your guest name suggests that my future repeater on 700 can interfere with yours unless Roosevelt Park tries will interfere and disrupt the signal. lol. 

I have mention above in the posts what I have and what I am planning to test next. In summary I will connect CDM1550ls+ as receiver to KG as transmitter and compare with RT87 repeater KG+KG repeater and CDM+KG repeater and expectation is to get better range than with RT87 

But looking further I have question. At bare minimum I need recommendation on  what specific (device names) equipment should I have in order to be able check tunning on my duplexers. 

 

 

[DONE]

The SPECIFIC equipment that you need to check a duplexer is a tracking generator and spectrum analyzer.  And the knowledge on how to run it. 

You can also use a VNA including those cheap little ones but they are not going to be as accurate as a better quality piece of equipment.

 

Now there are other ways of doing it that don't involve as much expensive gear.  A GOOD watt meter can get you close on the pass. 

You would place the watt meter in the line BEFORE the duplexer and then connect a dummy load (not an antenna) to the antenna port on the duplexer. 

Transmit and check your forward and reflected power.  If you have more than 1 or 2 watts of reflect, the duplexer is probably not working or tuned right.

Then place the watt meter between the duplexer and dummy load.  You are looking for LESS than 2 dB of loss.  So if the radio is doing 10 watts, expect 7 to 8 watts out. 

If you are getting 6 or less, then again there is an issue. 

Now for the RECEIVE side.  Program the radio to transmit on the INPUT frequency of the repeater.  Connect it to the HIGH side of the duplexer and do the same test. Again you are looking for 2dB or less of loss.  At NO POINT should you try transmitting the wrong frequency through the duplexer.   The reflect from doing so is higher than having an open coax and WILL blow the finals in the radio you are using to test.  And you are also advised to turn the power down on the radio to 10 watts if your watt meter has a setting that it's close to full deflection at that power level.  But the lowest setting creating the greatest deflection on the meter is the way to go with this.

DON'T try tuning the duplexer with this test method.  Doing it wrong will tune the notch across the transmit frequency and again, blow the radio. 

[Guest Answer Seeker]

Hello and thank you for recommendation. Assuming if I understand correctly, we want to measure wattage loss across duplexer high and low using dummy load and utilizing watt matter, reduced transmitter power and important to be the same frequency the duplexer tuned to, otherwise it is possible to blew up the final transistor on the transmitter. This is for testing only not tuning. 

I was looking at the equipment found this on Amazon. is this OK SSA3021X-TG  for duplexer tuning? Do I need anything else?

Thank You. 

[WRFP399]

So. If I understand this all correctly you have two repeaters. One is made up two KG1000s and the other is an RT97. The KG repeater is not receiving the same signals that the RT97 can receive.  If the antenna and feedline are the same between the two, and in the same location, than that indicates there is a problem with either the duplexer or the receiver of your KG repeater.  

We can start with simple problems starting with the squelch levels of the receiver making sure they aren't set too high.  Try swapping the KG's around to see if one works better than the other at receiving. If that makes no change take a look at the duplexer or take it somewhere to have it looked at to ensure it is tuned correctly. 

[Guest Answer Seeker]

Thank you all for your time reading this and your recommendations you have provided. 

I tested two repeaters comparing to RT97. Three repeaters in total. Two others repeaters tested with the same cables, antenna, duplexer and handheld and tested one after another. 

1: KG  receiver + KG transmitter

2: CDM1550LS+ as receiver  and KG transmitter.

I stopped in 5 locations and check if I can reach/open repeater. Sad but old CDM radio receiver was able to receive transmission from all test locations but new KG did not. (squelch levels also checked)

CDM+KG would be a candidate for repeater configuration instead of RT97. Also reading recommendations I order NanoVNA-H4, I will need spend some time to learn how to use it, to see  if I can squeeze more range out of my cables/antennas.

Also if you have any recommendations related duplexer, antennas, tuning equipment that works, please share part numbers or names.  

Thank You. 

 

[gortex2]

Do you have a license ? If so register and we can help more. 

I would definately get duplexer checked out. 

 

[triode]

Last message did not show up for some reason, I am registered now. Thank You for invite.