SGQ-450D Duplexer - Tune-up and Review

[tweiss3]

I would also be weary of adjusting the power using the input voltage. That sounds dangerous for the long term survival of the circuits. That typically isn't the correct way to adjust a transmitter.

[LeoG]

Manufacturer says the whole setup is Part 95 compliant.  Pretty sure as long as it's designed and built as an all in one unit the output at the connector is what is limited to 50 watts.

 

[marcspaz]

6 minutes ago, LeoG said:

Manufacturer says the whole setup is Part 95 compliant.  Pretty sure as long as it's designed and built as an all in one unit the output at the connector is what is limited to 50 watts.

 

 

I think you are correct, in that what the FCC care about is everything is in one chassis, and what transmit power is coming out of the chassis. Not necessarily the PA output power.

[SteveShannon]

That would be a good thing to send to the fcc in response to their request for regulation simplification suggestions.  I agree that it absolutely makes sense to look at the output of the box, but that’s not how the regulations are currently written.

[LeoG]

And it would make sense.  You can have a 50 watt radio and put all kinds of doodads internally but as long as it all complies with part 95 and is 50 watts or less out the connector they probably don't care.  Btech made a big deal out of it being an all in one unit along with being able to output close to 50 watts.

You know people are always miffed when it says 50 and you only get 40 even though it likely won't even make a difference.  But it's the thought that you paid for that output and it comes up short.  As long as I can make it to my house I'm pretty alright with it.  And I know that 25 watts from my house couldn't punch through the leaves and 50 watts does it in spades.  So power can matter.

[LeoG]

1 minute ago, SteveShannon said:

That would be a good thing to send to the fcc in response to their request for regulation simplification suggestions.  I agree that it absolutely makes sense to look at the output of the box, but that’s not how the regulations are currently written.

Ya, that's not happening.  That's just causing trouble for myself.  I'm sure if there were regulation violations Btech would be the first to know about it.  I'll keep the box output under 50w and it's not going to bother anyone.

[SteveShannon]

7 minutes ago, LeoG said:

Ya, that's not happening.  That's just causing trouble for myself.  I'm sure if there were regulation violations Btech would be the first to know about it.  I'll keep the box output under 50w and it's not going to bother anyone.

Nothing says you have to throw BTech or yourself under the bus to make a suggestion for a rule change.  
Frankly, I don’t think the FCC knows when there are violations.  They have neither the people nor an interest in challenging the certification atteststions submitted by manufacturers unless the problems are so egregious that someone reports them.

[marcspaz]

I found the authorization... it took a few minutes between meetings. LOL

 

What is wild is, the FCC authorization only seems to be valid if the user is operating with a maximum of ZERO dBi gain antenna, unless I am reading this incorrectly.  I mean, it says "should" not "must"... so I don't know the correct answer.  There is nothing in the rules about antenna gain. 

 

Where is my FCC enforcement guy?  We know you read this stuff...  LOL.  Can the FCC legally put a limit on one-off stuff like that without going through a PRM process and an update to the rules?  Seems odd.

 

https://apps.fcc.gov/oetcf/tcb/reports/Tcb731GrantForm.cfm?mode=COPY&RequestTimeout=500&tcb_code=&application_id=MjZkkijyA8IfBeMCZsYVMw%3D%3D&fcc_id=2AGNDGMRSRPT50

 

  

TCB	GRANT OF EQUIPMENT AUTHORIZATION	TCB
Certification
Issued Under the Authority of the
Federal Communications Commission
By:

 

MiCOM Labs 575 Boulder Court Pleasanton, CA 94566

Date of Grant: 12/15/2023 Application Dated: 12/15/2023

BTECH (BaoFeng Tech)

702 N Industrial Ave

Arlington, SD 57212

Attention: Greg Wilson ,

 

NOT TRANSFERABLE

EQUIPMENT AUTHORIZATION is hereby issued to the named GRANTEE, and is VALID ONLY for the equipment identified hereon for use under the Commission's Rules and Regulations listed below.

FCC IDENTIFIER:	2AGNDGMRSRPT50
Name of Grantee:	BTECH (BaoFeng Tech)
Equipment Class:	Licensed Non-Broadcast Station Transmitter
Notes:	GMRS Repeater

Grant Notes	FCC Rule Parts	Frequency Range (MHZ)	Output Watts	Frequency Tolerance	Emission Designator
	95E	462.55  -  462.725	46.7735	1.097  PM	16K0F3E

 

Output Power listed is conducted power. The transmitter has maximum duty factor of 50 %. This device is authorized to operate in the following radio services: GMRS (Part 95E). There must be an informational insert inside the box (product package) or the Users Manual must include information that clearly informs the consumer (buyer/owner) when the radio is transmitting on GMRS frequencies, that operation on GMRS frequencies requires an FCC license and such operation is subject to additional rules specified in 47 C.F.R. Part 95. The ant gain used should be 0dBi as max,The device with it's antenna must be installed to provide a separation distance of at least 114cm from all persons. End users and installers must be provided with antenna installation instructions and transmitter operating conditions for satisfying RF exposure compliance.

 

[LeoG]

As long as it doesn't say "shall be".  Should and must can be gotten around legally.

 

[marcspaz]

Also, they are going by what is at the antenna connector of the chassis.  "Output Power listed is conducted power."

 

Conducted Power: This refers to the RF (Radio Frequency) power that is supplied by the transmitter to its antenna, measured at the point where the cable connects to the antenna. This is different from radiated power, which is the power emitted into the air from the antenna.

 

Based on what I read from Cornell, the FCC's definition of "conducted power" primarily refers to the total transmit power delivered to all antennas and antenna elements when the transmitter is operating at its maximum power control level. This is also referred to as "maximum conducted output power."

[LeoG]

Well I'm not putting a 1/4 wave antenna up on an 80' tower.  That would look silly.  LOL

[LeoG]

On 6/26/2025 at 11:08 AM, marcspaz said:

I found the authorization... it took a few minutes between meetings. LOL

 

What is wild is, the FCC authorization only seems to be valid if the user is operating with a maximum of ZERO dBi gain antenna, unless I am reading this incorrectly.  I mean, it says "should" not "must"... so I don't know the correct answer.  There is nothing in the rules about antenna gain. 

 

Where is my FCC enforcement guy?  We know you read this stuff...  LOL.  Can the FCC legally put a limit on one-off stuff like that without going through a PRM process and an update to the rules?  Seems odd.

 

https://apps.fcc.gov/oetcf/tcb/reports/Tcb731GrantForm.cfm?mode=COPY&RequestTimeout=500&tcb_code=&application_id=MjZkkijyA8IfBeMCZsYVMw%3D%3D&fcc_id=2AGNDGMRSRPT50

 

  

TCB	GRANT OF EQUIPMENT AUTHORIZATION	TCB
Certification
Issued Under the Authority of the
Federal Communications Commission
By:

 

MiCOM Labs 575 Boulder Court Pleasanton, CA 94566

Date of Grant: 12/15/2023 Application Dated: 12/15/2023

BTECH (BaoFeng Tech)

702 N Industrial Ave

Arlington, SD 57212

Attention: Greg Wilson ,

 

NOT TRANSFERABLE

EQUIPMENT AUTHORIZATION is hereby issued to the named GRANTEE, and is VALID ONLY for the equipment identified hereon for use under the Commission's Rules and Regulations listed below.

FCC IDENTIFIER:	2AGNDGMRSRPT50
Name of Grantee:	BTECH (BaoFeng Tech)
Equipment Class:	Licensed Non-Broadcast Station Transmitter
Notes:	GMRS Repeater

Grant Notes	FCC Rule Parts	Frequency Range (MHZ)	Output Watts	Frequency Tolerance	Emission Designator
	95E	462.55  -  462.725	46.7735	1.097  PM	16K0F3E

 

Output Power listed is conducted power. The transmitter has maximum duty factor of 50 %. This device is authorized to operate in the following radio services: GMRS (Part 95E). There must be an informational insert inside the box (product package) or the Users Manual must include information that clearly informs the consumer (buyer/owner) when the radio is transmitting on GMRS frequencies, that operation on GMRS frequencies requires an FCC license and such operation is subject to additional rules specified in 47 C.F.R. Part 95. The ant gain used should be 0dBi as max,The device with it's antenna must be installed to provide a separation distance of at least 114cm from all persons. End users and installers must be provided with antenna installation instructions and transmitter operating conditions for satisfying RF exposure compliance.

 

Went to the website and found this.

 

And then found this about the HDG antenna

 

So much for the informational insert inside the box

[LeoG]

If at first you don't succeed, try try again...

[LeoG]

New duplexer from Btech.  Same one that's in my repeater with the same tuning.  Marc said he's going to try it out as is and get a base level to compare to.  I haven't put this one in my repeater at all.  Had it in my possession for about an hour before it was on it's way to Marc.

The 1st trial was from the repeater that was replaced by Btech and it exhibited the same reception problem I had with it originally that the one they sent me to replace it solved.  Marc said on his system it worked nearly as well as what he was running for a duplexer currently.

All just experiments to see if I/We can improve on my system.  The only thing that should improve is less desense in the system letting weaker signals in without interference.  Just how much....

That's why we experiment.

 

[marcspaz]

Okay folks...  Leo sent me a new SGQ-450D duplexer.  We gave this one a tune-up and it's looking good.  I am very impressed.

 

First, I swept it while it was factory tuned.  It looked really good and if it was mine, I probably would have left it alone.  On the transmit side, we had a good notch removing the receive frequency at almost -80dB.  On the receive side, the notch looked even better at -85dB.

 

 

 

 

Leo asked me to see what I could squeeze out of it, and I have to say, I am impressed with how well it tuned.

On the receive side, we got the transmit frequency notch out -95.5dB.

 

On the transmit side, I was able to notch out the receive frequency -95.5dB.  Very well balanced.

 

I recorded a quick video of the sweep showing notching as deep as -100.2dB, which is fantastic.  The video demos the benefit of a hi-res VNA (mine goes to 1024 points), the sweep results, and the SWR at power.

 

On the receive side, I was at 35 watts, but when I switched frequency to demo the transmit side, I forget to turn the power down.  That SWR reading was at 50 watts, even though I said 35 watts.

 

 

 

I really hope this helps someone on the fence about buying a B-Tech repeater or the SGQ-450D duplexer. 

 

@LeoG, can you share your opinion on the real-world results?

[Lscott]

This is the kind of detailed real world data that's useful. 

[LeoG]

I'll just say that there are many flavors of the SGQ 450D duplexers out there and this particular one came directly from Btech and who ever they use to manufacture them.  The original one that came with the repeater had the same numbers but it definitely wasn't made in the same place.  The replacement they sent me and the one I purchased are the same.

 

Thanks again for all your hard work tuning these for me Marc

[LeoG]

So far real world results comparing the wideband tune and the single channel tune aren't vastly different.  My neighborhood is a mix of hit or miss when I'm walking around with my Tidradio H3.  I have certain "stations" I stand at and do my repeater testing specifically so I can do comparisons.  Time of day and day to day make a difference in my area.  I am in LOS but have at least 1.6km of heavy treed areas in the way.  My repeater antenna is only up 13m at its center radiating point which puts it in the thick of the leaves.

That night when I put it in I did notice the transmission from the repeater seemed a bit more smooth, meaning the background hiss was much more mellow and it seemed like better quieting.  It is by no means anywhere near full quieting.  I have my base station and I use a digital recording app to record my tests.

And just like any night it will vary.  I have tests that are LOS and testing areas that are not.  Most of the tests last night were comparable to the last couple of tests except for my last station in front of my house.  That one usually is nice and it cut out this time.  I had other tests that are usually not so good come in better than usual.  So like I said it varies.

Today when my wife called me on the radio from the home base (50 watt, CA712EFC, 13m high) it came in much better than usual.  That was one time and only about a minute of conversation.  That too can vary from time to time.

So far I can say that the single channel tuned is doing at least as good as the wide band tuned.  Was hoping for better, but given my circumstances it's understandable that the 5 watt has a tough time getting through the trees.  On the original duplexer I couldn't make it at all, I could trip the repeater but almost never get audio through.  The wide band replacement usually gave me acceptable audio and the single channel tuned duplexer does about the same.

I still need to do some farther out testing which I haven't done in a while.  The goal is to reach my family one town down and that's going to take more height.