RF interference

General discussion and support for the Peaberry SDR V2.

RF interference

Postby WB8ENE » Mon Jan 26, 2015 6:24 pm

I am running a Peaberry V2 into a Hardrock-50. The antenna is a 135' doublet with open wire feed. The antenna tuner is an MFJ 993B auto-tuner. When I am running 50 watts on 40 meters, I occasionally have a problem where the PB and HR-50 will not exit transmit mode. I have to power down the PB and exit HDSDR. On 30 meters, the problem is much worse. I have problems running more than 10 watts on that band. I am powering the tuner, the PB, and a sidetone generator with the same power supply. When I tried running the PB and sidetone generator off of a battery (using short wires), the problem disappeared, so I tried hooking up a separate power supply in place of the battery, but it was so noisy (electrically) that it was not an option. I used my original (longer) wires to connect to the battery, but the problem came back. I see there is no RF filtering on the DC input to the PB. Should I try to add some filtering to the DC input (I tried snap on ferrite sleeves, but they didn't do much good), keep the DC wires as short as possible to avoid RF pickup, or abandon my open wire fed doublet for tuned antennas fed with coax to keep the RF levels down in the shack? Has anyone else experienced this issue? I really like using the PB, and would like to run 40 to 50 watts output on 20, 30, and 40 meters. By the way, I haven't seen this problem using a coax fed 20 meter dipole.

73,
Art WB8ENE
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Re: RF interference

Postby W4MMP » Mon Jan 26, 2015 7:21 pm

Hi Art,
What does your station grounding system consist of? Are all your major devices (AMP, PS, Tuner) connected to a common point on the station ground? Each individual device should use its own piece of braid (not daisy chained). Once upon a time I had an open line feeding something (I actually forget at the moment), but just to get the feed line out of the shack, I used coax and then a balun connected to the open line. Just a thought.
73
Ron / W4MMP
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Re: RF interference

Postby kz1x » Mon Jan 26, 2015 8:02 pm

The amp key line of the PB is floating, by default, with respect to the PB DC (-) and also to the RF ground (BNC shield).

Check it out on the schematic.

This can be a good thing or a bad thing, but it has to be looked it to see which it is, depending on your situation. It's certainly unusual.

In practical terms, it means the wire for the connection between these two devices (I also have a PB and an HR50) needs both conductors to complete the circuit through the Everlight optoisolator. I have seen iffy soldering on the PB make this keying line less than robust.
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Re: RF interference

Postby WB8ENE » Tue Jan 27, 2015 1:13 pm

The tuner is grounded, but the PB and amp are only connected to ground through the coaxial cables (no ground studs on those devices). The power supply is not grounded either except possibly by the 12V return wire. I'd like to get some ferrite material to choke the 12V DC cable to the PB, but not sure what type of ferrite is best, type 31, 43, 73, or 77. At least the problem is repeatable on 30 meters so I can do some experimenting. Thanks for the replies.

73,
Art WB8ENE
WB8ENE
 
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Re: RF interference

Postby W4MMP » Tue Jan 27, 2015 4:37 pm

Hi Art,

DX Engineering has good chokes: http://www.dxengineering.com/search/dep ... =Ascending.

The prevailing thought is mix 31 is the best for HF work. There are ferrite beads on all my leads (and at both ends) in the shack (power and/or data). This helps eliminate "radiated" RF from entering the devices. However if you have RF ground loops, that will be tough to kill with chokes. By this I mean if there is RF on the shield(s) of the coax between devices (tune - amp), that is a ground loop. This is why ,according to most of the research I performed regarding this subject, highly recommends a separate section of braid from each device to RF ground. You might try placing a ferrite bead (or two) on each of the interconnecting coax.

As for the PB, as I mentioned I have beads on both ends of the power supply leads. Use larger size beads and wrap several turns through them. I even went so far to use twisted pair for the power leads.

Using the combination of beads and RF grounding I have zero RF issues.

Good luck, RF bleed can be a tough nut to crack.
73
Ron / W4MMP
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Re: RF interference

Postby W4MMP » Tue Feb 03, 2015 10:35 pm

Hi Art,
Any progress?
73
Ron / W4MMP
W4MMP
 
Posts: 579
Joined: Fri Jan 03, 2014 3:31 pm
Location: Lovettsville, Virginia FM19EG

Re: RF interference

Postby WB8ENE » Wed Feb 04, 2015 6:48 pm

Ron,

Not much. Been too busy running the snow blower. HI I did get the setup to work on 30 meters while running the PB and the side tone generator off of a 12V battery, but after trying out a different power supply that was extremely noisy, I couldn't get 30 meters to work again with what I thought was the same setup that worked originally. The good news is that 40 meters (my favorite band) seems to be okay. I think I'll go back to the original power supply, and try some ferrite beads at various places. Maybe this weekend. Between keeping up with the snow, babysitting grandchildren, and trying to finish doing my taxes, there's not much time for ham radio.

73,
Art WB8ENE
WB8ENE
 
Posts: 47
Joined: Fri Jan 24, 2014 12:35 pm


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