marcspaz

Hey folks, we are hosting a get-together on Sunday, July 13th starting at 02:00 PM at Carrabba's Italian Grill in Centreville, VA. We will meet in the main lot and spend some time socializing and working with anyone who may need some guidance on their gear. When everyone is hungry, we can head inside for some ice cold beverages and some food. As always, this will be a family-friendly event. Feel free to bring family and friends. Any questions, just post them below! https://www.facebook.com/events/744340581470568/?active_tab=discussion https://locations.carrabbas.com › Virginia › Centreville 5805 Trinity Pkwy Centreville, VA 20120

Just remember the corner caps are plastic. You should have the mount forward on the hood about 6 or 7 inches for a good ground plane.

Couple quick pics. Ignore the body damage.. it my offroader.

I wouldn't put 2 fuses, but i would relocate the one that came with it to no more than 18 inches from the battery. The closer, the better.

Fiber or fabric roof. That's not an option. For a fiber roof, mounting some type if reflector for a ground plane doesn't work. The material is too thick for it to be inside and it's ribbed up top, which adds a whole new level of aggravation.

If you are mounting an antenna that large, i would drill a hole in the top of the bed rail over the tail light and hard-mount a UHF mount. (Or NMO). The only other option would be to use a lip mount on the hood. Something like this... ot the Diamond version. https://www.cometantenna.com/product/coment-hd-5m-heavy-duty-rs-840-lip-mount-w-dlx-166-coax-gold-uhf-conns/ I'll take a couple pictures of mine in about an hour and show you what I have (both) for GMRS and Amateur Radio

I wonder if being in a metal rack is helping with shielding. Unfortunately that isn't something I can try in the field. At one point, I did run a 3 foot grounding rod and made sure the case of the radio was well grounded, but that didn't do any good either.

Here are a few sweeps of one of my band-pass filters. I'm confident the filter works fine with about -60dB of attenuation on the other bands. The assumption is that key parts of the radio are not shielded well enough. 10m 20m 40m 80m

They don't help with the IC-7300. If there was a radio within a half mile pushing more than 1w and they were on a frequency below me, I couldn't hear anything but that radio. I made two for 20m and ended up buying a third that was a high dollar commercially made and none of them worked. I ever skipped a patch cable and used a double male barrel connector direct to the radio and the filter did nothing. They all looked great on the analyzer, but the radio just lacks the proper shielding in the IF circuits or some other critical part of the system. Never did figure it out. Just started using mt FT-891 for contesting with the group, since it has a native amp keyer.

My two favorite HF radios for newer operators and for people who aren't DX contest junkies are the Yaesu FT-991A and the iCom IC-7300. The Yaesu includes 160m through 70cm (all bands, all modes) and the IC-7300 covers 160m to 6m (all bands, all modes). My personal opinion, the IC-7300 has much better receive sensitivity, but it is more prone to interference because of it. It is almost impossible to use in a group for things like contests or Field Day, but its great if you typically use it at home or with no other operators around. The FT-991A is truly a "Shack in a Box". Good at everything, not great at anything. If you have any interest in 2m or 70cm SSB, its a good choice and one of the few "new" radios that support it. Otherwise you are paying original retail or more for used radios that have been discontinued a decade or more. For example, I have an IC-7000 that was discontinued in 2014. Last known retail price when on sale was $900 from HRO. They are for sale today for between $900 and $1,100 depending on if they have the head separation kit or not.

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."

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.

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.

I can find this stuff... but nothing I can open. Not sure where the actual letter and artifacts are. https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Sum&calledFromFrame=N&RequestTimeout=500&application_id=MjZkkijyA8IfBeMCZsYVMw%3D%3D&fcc_id=2AGNDGMRSRPT50

Steve, the FCC gave the repeater type certification based on the output of the duplexer because the duplexer is inside the chassis and considered and internal part of the radio... part of the design. https://fcc.report/FCC-ID/2AGNDGMRSRPT50 I am trying to find the official FCC cert, but that is the reference I found so far.

Whoa... that is the same issue Leo is having and on the same duplexer.... I may need to withdraw my endorsement.

Hmmm... I can't help but wonder if it is an over-power issue with the duplexer. It's rated for 50w, I tested with about 45w after tuning it, and you're using 70w, which exceeds it's power rating by 30%. Exceeding the rating can cause overheating that can warp/melt internal parts and even cause internal arcing. That will definitely cause detuning and poor isolation, If I was a gambling man, I would say that it was off frequency when I got it, because parts were partially damaged inside (plating damaged, parts warped). I was keeping the power within spec, so I was able to tune and use it with the parts warped to the position that they were in. Now that it's being over-driven by 30% again, you are likely warping parts further, possibly causing plating to peel with excessive heat, which is causing arcing and detuning the duplexer.

Its very possible that the wider configuration of the original notch was reducing power output more than the rated <‐1dB. 70w minus 1dB is about 55w. -2dB would be 44w. Figure the meter probably isn't perfectly calibrated, you probably had -2dB of insertion loss with the wider notch, and -1dB with the more narrow notch. The receive side was/is probably the same. However, -2dB vs -1dB is not really noticeable to the user, even though its measurable. It sounds like the second duplexer they sent you was tuned much, much better that the one that came inside the repeater.

I'm excited to hear how it goes. An additional 8w out was unexpected, but a plus, for sure.

The problem with the whole concept of teaming up with an amateur radio club is that some amateur radio operators despise people with a lower level license than them. There's no way they would accept somebody from the gmrs service as deserving of their time. I have a general class amateur radio license. I am what is lovingly referred to as a no code General Tech. It's a dig that General and extra class license holders use to insult General class license holders who did not have to pass the morse code requirements. I have literally had dozens of experiences where General class license holders who passed their Morse Code test and extra class license holders who have passed there Morse Code test found out that I was a no code General and stopped talking to me in the middle of a conversation because I wasn't worthy of their time. While there is a good amount of people in the amateur world who are absolutely amazing at Radio stuff and love to share their knowledge, there are way more people who are just grumpy old sour pusses who would rather cut a finger off than help someone who isn't "worthy of their time."

Maybe the word oscillation is whats got me. Oscillation is usually internal to the repeater due to a failure. Or if the separation and isolation are not good, you can end up with a transmit loop if the input and output tone are the same. You won't have any oscillation. If you have a short tail, the repeater transmit may cut in and out as the receiver cuts in and out. I usually set mine to 2.5 seconds. You will hear the remote station drop out and come back in, but the transmit stays open for 2.5 seconds after the last drop.

Hmm. I'm not sure what you are describing is all that unusual. Every radio that is on the ragged edge of a repeater can cause that 'oscillation' condition if the duplexer is not tuned correctly. There really isn't anything you can do beyond a properly tuned duplexer. Now when I am testing, I do run repeaters with the receive input not connected to anything, a dummy load on the transmit side and no duplexer. I have never had a transmit signal from the repeater desense my test HT to the point where there was a failure to operate correctly. I'm not sure you can create that condition unless something is horribly wrong somewhere.

It stands for "Oh, Shit! Over!"

It's a Smith Chart SWR Circle. It's a circle that is drawn centered at the origin frequency, passing through the plotted impedance point. This circle represents a constant SWR through the range. The value where the SWR circle intersects the positive real axis (right side) of the chart indicates the SWR. The closer the red dot is to one of the lines radiating from the right side, the closer to 1:1 the SWR is on that frequency. I tried the TinyVNA and it did not work. It was way off... very inaccurate. A friend of mine (who is a retired RF engineer) uses a SAA-2N VNA when he is in the field. He has great results with it, which is why I went with that specific VNA. It's "good enough" that I would not encourage people who are doing this as a mild hobby to buy a commercial Signal Analyzer. If professionals are using it, the SAA-2N VNA is good enough for me. I have not compared mine to a commercial grade SA, but I have tuned 5 duplexers (UHF and Commercial VHF) with the SAA-2N VNA since I bought it and have had amazing results. With a 2m repeater only having a 600KHz offset, accuracy is extremely critical. My 2m repeater is covering over 8 miles with 5w handheld radios and well over 25 miles with 50w mobiles, and the antenna is only 100' above the ground, 200 feet above average terrain. Those numbers are both further than the theoretical/calculated RF LOS. So, I personally have confidence in the SAA-2N VNA.

To answer question about tools used and how to adjust a duplexer, here is a quick overview. Tools I used: Windows PC SAA-2N VNA VNA View software Box Wrench Screw Driver Brass Brush To tune the duplexer, you have to follow a couple of steps. Calibrate the VNA for the frequency you are testing (via the PC or on the VNA, depending on if you are using the PC or not) I typically set the center frequency to the frequency I am tuning for, with a 10MHz spread. From there, we are going to tune either the low side or high side, separately. For this example, we can start on the low side. Connect the S11 cable to the "antenna" port. Connect the S21 cable to the "LOW" port. Put a dummy load on the "High" port. Refer to Image 1. Set the Trace 1 format to S21 Thru. With a mobile UHF cavity duplexer, you can disable the other traces, but if you want to track your SWR at the same time, set Trace 2 format to S11 SWR, and then disable the remaining traces. Adjust your scaling so you can see at least -110dB Adjust each adjustment screw to create the deepest notch possible, to the transmit frequency. In this example, 467.600MHz. only adjust one tuning screw at a time, loosen the jam nut with the box wrench, just enough to allow the tuning screw to move, and while making adjustments, hold the jam nut with the wrench. Typically, once you set the screw to the proper depth, it can be a bit tricky to set the jam nut without turning the screw a bit at the same time. A trick I learned is that I put the screw just a few degrees off, counter clockwise, so as I tighten the jam nut, it snugs the tuning screw into the correct location. See Image 2 and Image 3 From there, switch the S11 cable to High, and the dummy load to the Low side. Repeat the tuning steps for the high side, but tuning the notch to the receive frequency. In this example, 462.600MHz. This guy has a great video on using a VNA to adjust a duplexer. I have no idea who he is, but it it's good content. The only thing I would add is, he stated he is using 200 sweep points. I would use the highest sweep setting you can that provides a good enough resolution of the frequency spread you are tuning. On the VNA itself, I use 401 points, but on the PC, I use 1024 points. https://www.youtube.com/watch?v=TbEK4v_3Xuo With this duplexer, specifically, the tuning screws are brass. Either the manufacturer or B-Tech spray painted the tuning slugs. I had to spend a bit of time cleaning the paint off the screw threads and heads with a brass cleaning brush to make it so the duplexer could be tuned. If you have a situation like this and want to repaint the screws for cosmetic reasons, be sure to use non-metallic paint, such as Krylon Fusion for Plastic. It must be non-metallic, polyurethane free, and lead free. I am including a few extra pictures displaying the results. Image 1 Image 2 Image 3