Have I hurt my radio?...

Mike Agnew

Greetings! I have installed the Electraft KPA 500 amp to my 6300 and I fear I may have hurt something before I got everything sorted out and settled in. The issue is that on 40 meters (and only this band) I get this strange spike of noise while the amp is in STANDBY but it completely disappears when I change it to OPERATE mode. If I change the TX on that slice to another, it is still there, but not quite as bad. This is what it looks like:

I would really appreciate any advice or suggestions before I open up a Helpdesk ticket, as I know the guys are full-bore trying to solve bigger problems for more people than just me.

Many thanks and 73, 😕

K1UO Larry

First, try disconnecting leads from the Amp one at a time to see if that spike is connected with one of the leads from the amp to your 6300. From your description, something is being switched on/off internally on the Amp itself when you change from STBY to OPERATE. A few well placed ferrites may just fix that for you.

Mike Agnew

Thanks Larry. I tried that this afternoon...one at a time till there was none! Even with the amp completely offline, no cables, no power, nothing, I still have this anomaly. Anything else to do, or should this be a ticket?

Many thanks!

Patrick

Could be T/R switch problem in the amp. Also do all testing into dummy load. Do the radio, no amp in line direct to dummy load, see if you see a clean signal. Into dummy load you should see on RX -150 to -160 dbm. If that is Ok put amp back in line with dummy load see if problem is there. Do put into op, then do some drive to push the amp output power up. Check forward and reflected power or SWR. Make sure it is reasonable. If you see the noise. On standby then it is most likely a T/R switch problem. Means a call to elecraft.

Mike Agnew

Hi Patrick, no I mean I have the amp completely and I mean completely disconnected from the radio, and from the world. There are no cables connected between the two, and the power is off. In fact, even the power cable is unplugged on the amp after all that.

Perhaps I don't understand?

KD0RC

Hi Mike, One last thing to try if you haven't already, is to do a factory reset. Be sure to export your profiles first. I would test for the problem after the reset, and if it is gone, re-import your profiles and test again. If the problem recurs, then you can be fairly confident that you have a corrupt profile.

If the reset does not cure the issue, then you should submit a help desk ticket.

Stan VA7NF

I have seen similar situations with my 6700 - Mostly involving the wide band noise blanker. Running with WNB on, then turning it off elevates the apparent noise in parts of the spectrum.

Also strange happenings when listening to VLF (below the broadcast band) and raising to rf gain up to +30 and 40db. This causes the gain to drop significantly with some strange artifacts.

The WNB is relatively new but the rf gain since initial purchase (running pre V1 SMARTSDR)

Mike Agnew

Thanks Len, I just now did the factory reset. After the reset, I'm getting the same "AM splatter" even before I import any profiles. Listening to the signals on these splatters I hear, I think, fuzzy Latin music. The only way I can get my receivers to act and hear "normal" is to have my amp connected and on the "OPERATE" mode. Attached is a document with the screenshots of what I see under various conditions noted:

Flex and amp conditions.docx

What do you think?

Thank you so much!😕

KD0RC

Ah! That may be the clue! It sounds like AM broadcast from a close station. When you select operate on your amp, the bandpass filters are in place, filtering out the broadcast interference.

I am not sure, but I am guessing that the 6300 does not have the bandpass filtering of the 6400 or 6600.

There are BCI filters available that can be used between transceiver and amp. Just be sure to get one that can be used with a transmitter running 100 watts.

While I can't be 100% sure that this is the issue, I do think it is pretty likely.

Mike Agnew

Strange that I have never heard or seen before these big splattering signals before. I'm nearly certain I over-drove the amp with my radio at least once (before I figured things out) and somehow the feedback to the radio blew some things up? Right at that point I noticed these issues.

This is my first go at having an amp, probably obvious?

KD0RC

I don't think it is very likely that you damaged anything. The KPA 500 shuts down and protects itself very quickly when overdriven. Overdriving the amp will not feed back to the radio in any way, so you should be safe there.

I believe that it is just coincidence that this happened at the same time you overdrove your amp.

Mike Agnew

Thanks Len. I appreciate it.

John KB4DU

I had the same aha moment. The original post was on 40M, and these are on 80M and 20M. What is happening on 40M now? What does it sound like?

Mike Agnew

Latin music. Lots of instruments and singing. Kinda fuzzy, sounds out of tune, distorted, and far away. What are you getting?

John KB4DU

This could be a short wave broadcast station. They generally inhabit the freqs above 7200, and stronger at night. The first screen shot shows LSB,I can’t tell about the 80/20 bands. Have you tried listening to the 40M signal in AM mode?

KD0RC

Mike, it sounds more like BCI to me. To verify that, tune to the offending station on 7,200 on one panadapter, then open a second panadapter and tune it across the AM broadcast band until you hear the same station that you hear on 7,200. If you find it on the broadcast band, that will confirm the source.

It is also possible to be a shortwave station, but not likely one in the 40 M band. Do you see anything similar around 3,600 KHz?

Since the bandpass filtering of your KPA 500 knocks out the offending interference, it is likely to be coming from out of band.

Mike Agnew

Well, this is interesting. May be too small to read? I'm hearing the same exact AM station on every one of these!

Screenshot.docx

KD0RC

Yep, it looks like frontend overload from a very strong local station. Have you looked at the AM broadcast band yet? I would bet that there is a broadcast station very close to you causing all of this.

David Decoons, wo2x

About 5 air miles from me someone put up an illegal broadcast radio station (city of Paterson, NJ) that was spurious. You could see their signal on some of the ham bands. The FCC finally tracked it down to a 2 family home and shut it down. It was Spanish music and talk radio. There is a large Hispanic population there. We operated Field Day last year from a site looking down into Paterson and we could tune the broadcast band and found at least 4 illegal transmitters.

Low power transmitters (AM and FM) are popular with real estate agents ("talking houses"). Some of those can cause issues.