Technical Topics > Equipment

Lex dealing with RFI and home misfortunes

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Zane:

--- Quote from: Sealord on September 16, 2022, 0021 UTC ---Don't sell the Palstar; I still have my R30CC (mine is an early version w/12v option on the coax) and will never part with it.  I know the radio has mixed fans, but it's a great receiver for what it does.

--- End quote ---

Agreed!

Z

SL!

Pigmeat:
Didn't Drake make the Palstar line? I remember seeing them advertised and thought, "Boy, look at the tuning knob on that baby!"

I read an article about the Villard Loop in a ham mag years ago. The guy was a CW op and lived along the Gulf Coast. He built one on cardboard that he used with a portable receiver to copy other op's. His had two modifications, it used copper foil and he used a tuning capacitor. He had a wire out the window he used for the QRP rig he ran on 30 meters.

He spoke of how well it worked in the summer static and storm season, mentioning that he was so engrossed in making contacts one night that he didn't know a thunderstorm was on top of him until he saw lightning flashes out the window.

The lesson with this loop, if you're a ham, is don't use those big ear muff headphones. This is a quiet loop.

Just like Al to buy an antenna when he could have made his own. He was the Little Lord Fauntleroy of DX'ing. He knew real radios though. Refined tastes.   

Zoidberg:

--- Quote from: Pigmeat on September 16, 2022, 0129 UTC ---Didn't Drake make the Palstar line? I remember seeing them advertised and thought, "Boy, look at the tuning knob on that baby!"
--- End quote ---

I chatted with Paul Hrivnak on the phone about 10-12 years ago, after first getting the Palstar receiver. I was curious about some design details, including what appeared to be a doodad inline with the Hi-Z antenna input to reduce the risk of static shock in real longwire antennas, particularly in dry summers in windy areas.

If I'm recalling correctly, Paul was an engineer for RL Drake for awhile and (again, if I'm recalling correctly) was also involved in the design of some of the smaller portable Lowe receivers (HF-150?) that were popular in the early 2000s-2012 or so. Later, Lowe also basically rebranded a Palstar, with permission from Palstar.

But the Palstar was a totally independent design from Drake. When the two are compared they aren't similar in size, build, or diversity of features. The Palstar has only two filters, no AM sync, etc., but rock solid AM performance on MW and HF and seems immune to overloading or images. I seem to recall some minor legal kerfluffle between Drake and Palstar about 10-15 years ago over some design issues, but I can't find those references online now. If I'm recalling correctly the dispute was over Palstar's use of the same metal speaker cabinet used by Drake for its optional external speaker. the Palstar just reoriented the cabinet/grille differently in essentially the same cabinet. I think Palstar later switched to its own speaker cabinet design.

I haven't kept up with the industry in the past decade and might be misremembering some details.

Zoidberg:

--- Quote from: Pigmeat on September 16, 2022, 0129 UTC ---Just like Al to buy an antenna when he could have made his own. He was the Little Lord Fauntleroy of DX'ing. He knew real radios though. Refined tastes.

--- End quote ---
I think Fansome was enamored of the miniature beer cans attached to the RF Systems EMF antenna.

Seriously, though, IIRC, the "magnetic transfer" canisters on the various RF Systems antennas were some sort of impedance transformers intended to physically shorten a wire antenna, and reduce some manmade RFI. RF Systems sold these in the EMF and a Windom style.

ChrisSmolinski:
I like to divide received RFI/QRM/etc. into two categories:

1. Signals flowing on the transmission line / coax cable shield - common mode signals.
2. Signals actually "in the air" so to speak, being picked up by the antenna.

The first case is where common mode chokes (aka ferrite cores) on the transmission line can help. They can reduce or eliminate currents flowing on the outside of the shield. It's almost always worthwhile to give this a try as it's pretty easy, and due to the proliferation of computers, switching power supplies, etc. in the house it is inevitable that you have at least some common mode issues.

You do need to pick the right kind of core material to use, with enough turns of the coax through it, to be effective. There's other posts here on the HFU detailing what to use. I've *never* found the simple clamp on ferrite cores to help. Never. Not on HF anyway.

For the second case, no number of ferrite cores or other magic is going to help. Radiated RFI that is being picked up by your antenna looks exactly like a signal from a radio station. The ferrite does not know the difference.  Special coils or inductors or transformers or what not in the antenna aren't going to do anything either. There are a few things you may be able to do:

If you can make the antenna directional, you can null out, or at least reduce the intensity of, the offending signal. Of course this is more difficult on HF than VHF/UHF due to the wavelength size. And if you've got RFI from several directions, or it is the same direction as the station of interest, you are out of luck.

Antenna placement can also help. Get it as far away from the house (or your neighbor's house) as possible, as well as power lines (both for RFI and safety reasons).  Try a few different locations / orientations and see what works best for your stations of interest.

Use coax cable to feed the antenna, and possibly start feeding the antenna further from the house. Yes, this means a smaller antenna, but a smaller antenna that picks up a lot less RFI wins.  So rather than run your long wire directly from the shack window, maybe start it from a nearby tree, and run coax from the shack to the tree.  And of course properly feed the antenna with an appropriate transformer and ground it correctly - see other posts, for example: https://www.hfunderground.com/board/index.php/topic,74042.0.html

And of course try to identify any RFI sources and deal with them. If they're in your house, you can fix them. I find this tool to be excellent for fixing RFI generators. Usually only one application is required:

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