[majortom]

What do you guys think of this? Was lookin in to the VHF noise / interference issues presented by nearby transmitters. And came across this little circuit hams apparently use to knock down TVI caused by their transmitters to nearby TV Antennas. Has anyone tried building one of these Braid breakers? They are designed to be put in place between the antenna and the preamp. Thinkin it might help the static buildup issue also if ya put a high impedance, 5 to 10 Mohm resistor, across it like ya see in a few of them. So it will serve dual duty. Acting as both a Hi Pass Filter to clean up the input of ur preamp,
and a static buildup bleeder, potentially protecting a sensitive preamp from static...drawback is not sure if they're designed to pass VHF HI since seems like they are popular in the UK (a few apparently are though). Dunno their spectrum layout in UK. Googlin Braid Breaker turned up the below links.

http://www.scribd.com/doc/39570693/Antenna-Filter
http://www.qsl.net/g4lna/pages/braidbkr.html
http://www.uksmg.org/content/filter.htm

 

[old sparks]

Assuming you're using a Ruthroff 4:1 balun with your Hoverman, wouldn't there be a DC short between the elements in any case? Shouldn't get too much static build-up if you're DC-grounded.

High-pass filter should help, but you'll want to use low-loss construction techniques if any of your wanted stations are marginal...

 

[Jase88]

I'm pretty sure that's what Tin Lee of Toronto advised that I use for TVI on VHF.

 

[majortom]

Of course i had to make one of these. The first one, as described in the first link.
Need to find a suitable metal project case to install it in, and test it.

 

[ScaryBob]

The combination of a balun and grounding block, with proper grounding, will eliminate static buildup and eliminate most out of band electrical noise.

I've seen lots of gadgets like these. They may help but are limited in their effectiveness. The ones I've seen for TV usually did more harm than good. A tunable notch or narrow bandpass filter is typically better. Modern commercially available filters can be much more effective if they use semiconductors that have significantly better characteristics than coils and capacitors.

 

[majortom]

The combination of a balun and grounding block, with proper grounding, will eliminate static buildup..

I agree, but tell that to the folks whose preamps blew up from static last year.
I think even Jase88 lost one. And in my opinion, he probably has the most professional setup around. I'm not actually trying to fix anything here, just experimenting. BTW, I'm not expecting this to outperform the homemade highpass filter I made to kill the FM Band locally. But it may be easier to build for the hobbiest. I've never heard of anyone designing an RF filter from semiconductors.

 

[ScaryBob]

I was actually referring to ceramic RF filters. They have been used in consumer electronics for several decades now. They are also available for notch/bandstop, bandpass, high and low RF filter applications. The bandwidth plots of coils and capacitors resemble a bell or logarithmic curve. Frequency plots of ceramic filters resemble a square wave and are much more effective. Available types of RF filters include LC Filters, Crystal Filters and Ceramic Filters. Judging by the filter characteristics published by Tin Lee, I suspect they are using ceramic filters.

p.s. Anyone who has used a modern digital radio or a computer media player with an equalizer has used a digital filter made from semiconductors.

 

[majortom]

Looks like this circuit has a little attenuation at VHF-Hi, but it really starts to rolloff just below the FM band. The bleeder resistor is there 'cause with the circuit in place otherwise wouldn't be a path for static to bleed off in to ur grounding system. So, it would be a cheap & dirty fix if a HAM was down the Rd from ya on HF & 6M bands. Definitely simple enough to build one to test if that's what u were suspecting.