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How to diagnose and resolve an apparent RF issue in my Anytone AT-5555N II setup

TimmyTheTorch

TimmyTheTorch

Well-Known Member
Dec 11, 2022
322
252
73
Northeast Wisconsin
I am told that I have an RF issue in my setup that is causing clipping, distortion and generally a difficult to understand signal even when running low boost or even no boost. I vaguely know in general what it is but to be honest I do not know the proper/methodical way to problem solve this one. I work as a data/BI engineer and while it is a technical profession, the skills are not exactly helpful here.

I have been running between 5 and 8 watts into the KL503HD, radio modulation set between 22 and 30, Zetagi mic modulation between 5 and 8 and the KL503HD anywhere from 1 to 6. I do get decent dead key from the amp given the varying power I put into it.

Here is the setup I have and all of it is new within the past few months:

Anytone AT-5555N II (purchased from and tuned by Scott's Radios, A+ vendor by the way)
Zetagi MB+5 mic and a stock Anytone mic
RM Italy KL503HD
RM Italy 27/586 low pass filter
Powermax PM4-120 power supply
MFJ-941E Versa Tuner II (antenna tuner)
Micronta SWR/Power tester
50 ft of RG213 coax from tuner to MFJ 272, 1.5 KW Lightning Surge Protector (connected to 8 foot copper ground rod)
35 ft of RG213 coax from Lightning Surge Protector to Maco V58 antenna mounted 30 feet in air.
The mast holding the antenna is grounded to a second 8 foot copper ground rod.
New RG8X coax patch cords 1-2 feet long.

There are 3 foot long, 4 gauge stranded cables going from the PSU to a 150 amp bus. The radio and amp both pull power from this bus with the amp using 6 gauge cable and the Q5N2 using what came with it.

Here is the sequence in which I have the items connected:

Anytone AT5555N II radio.
RG8X patch cable from radio to Micronta SWR power tester (so I can tell in general how much power I am putting into the KL503HD)
RG8X patch cable from Micronta to KL503HD
RG8X patch cable from KL503HD to RM Italy 27/586 low pass filter
RG8X patch cable from low pass filter to MFJ-941E Versa Tuner II
50' of RG213 coax from antenna tuner to Lightning Surge Protector
35' of RG213 coax from Lightning Surge Protector to Maco V58 antenna.

I do not currently have a ground cable connected from the PSU chassis to a house ground or any other ground.

I have checked that all the coax connections are tight, except for the one at the antenna base. That'll have to wait until spring and the snow is gone.

Should I just start with a basic setup of antenna connected directly to the radio? I would at least temporarily have a meter in there to make sure the SWR is safe. Or is there a generally-accepted best practice for working through this type of issue?

I do enjoy all of the learning I have been doing here since I re-joined the hobby but I am also looking forward to when I can start paying some of it back.
 

I have never set up a base station, but you seem to have a lot of stuff going on! I would start with just the radio into the antenna. You are aware that the radio has an SWR protection circuit? If all is good with just the radio, add one thing at a time. BTW in my humble opinion that radio is going to be borderline hot for that RM amp! Even turned down they like to swing pretty good!
My two cents......

JD
 
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I guess several questions. What problems are you seeing and who told you you have an "RF Issue" ? What did they mean by this? What mode are you talking on AM SSB? While you do seem to have a lot of stuff hooked up in line it might be as simple as your overdriving that amplifier. Is your SWR good with the antenna? How does everything work with just the radio in line? You have too much unnecessary things in line.

Try this. Radio - jumper - amplifier - jumper - watt meter - antenna.
 
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the way you have your system is dangerous, regardless of any interference you may be experiencing. (BTW you don't really need that antenna tuner unless you are really operating all the way from 12 through 10 meters)

there is an old saying in radio that goes something like "improper grounding is worse than no grounding at all." and it sounds like this applies to your situation.

you see, any and all grounding you do to your radio station needs to be tied in with the AC ground at the main breaker panel going in to the house.

otherwise (and this needs a much longer answer) you could inadvertently make the best path for lightning or voltage surges right through your radio gear.

this is actually part of NEC and if your house took a lightning strike with the way you have your system grounded now, your insurance company could deny your claim.

again, too much here for one forum response, but you need to connect that 8 foot ground rod to the main ground rod for the house electrical system.

you need to provide one, and only one "ground potential".

there are lots of threads on this forum dealing with this issue, and a couple of hours spent searching and reading should allow you to find a good thread that has all the answers you are looking for.

also, if it were me, i would keep the AM deadkey into the amp at 5 watts or below, but that's just me.
LC
 
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Start off with something like this:

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and ground all of your equipment to it. Then use a large single conductor (copper strap/wide braid) and run it to an outside 8' ground rod using as short a run as possible.

Then as LC said, connect that ground rod to your main's ground rod so they are at the same potential.

Use male/male barrel or male/male 90 degree elbow PL259 connectors to eliminate as many jumper cables as you can.

If Scott "cleaned" up your radio and you aren't overdriving the amp, you shouldn't need a LP filter.

And as LC said, you don't need the matcher if you are just using CB channels - your Maco should have a better than 1.5 SWR for the whole CB band. You will actually lose power using the MFJ due to insertion loss.

Unfortunately, you bought just about the worst "HD" amp I have seen. Not saying it doesn't work but, it is actually a low drive amp that has had the input swamped to hell to allow ~35 watts to be dumped into a single RM4 Mosfet that only needs a few watts for full output.

A better "HD" solution is a KL703v. At least with that amp you are dumping ~30 watts into 16 Mosfets - not 1.

Since you may have multiple issues, start trouble shooting using your stock mic since you know it sounds clear.

That should get you started. Good Luck!
 
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Multiple people told me during QSOs that my signal was strong but modulation was clipped/garbed/hard to understand. This was both barefoot plus with the amp on regardless of the amount of power driving the amp. Problem existed with three different mics. It has been diagnosed as ground loop, RF interference, bad radio, bad mic, bad amp, karma... JK on the last one. ;)

I am going to basically start over with how things are setup and do them one at a time instead of the full install I did the first time. I have everything everything unplugged/disconnected at the moment.

I hope the forum does not mind as I work through this here step by step but it may help other newbies / returning folks like me from making the same mistakes/assumptions.

Starting at the Maco V58 antenna itself, it is mounted on a 30-ish foot heavy-duty mast for now.
  1. SWRs were between 1.1 and 1.4 across channels 1 to 40.
  2. The base of the mast is connected to an 8 foot copper rod.
  3. A 35 foot length of RG213 comes down from the base of the antenna into a MFJ 272 lightning surge protector.
  4. The surge protector is connected to a second 8 foot long copper rod.
  5. A 50 foot length of RG213 then goes from the surge protector into the radio room in my basement.
I think the main ground for the house is about 20 feet from the ground rod I have for the antenna mast. It sounds like I need to move the lightning protector wire from the second ground rod and connect it to the same one the mast is connected to, then connect this ground rod to the main ground rod for the house with (4 gauge?) copper ground wire. Is this correct?

Here's what it looks like now:

1674401609305.png
1674402000803.png
 
I would not change a thing until you can verify the setup with a different radio. Both try a different radio in the station, and listen to yourself on a second radio.

Often times where I work, when a big problem develops on a piece of equipment, everyone on the back shifts are doing everything to it. Creating more problems. We will come in and it will take us half a day just to work back to the original problem. It is amazing how the process of elimination will escape the "trained professionals".
 
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