++++++++++++++++++++++++++++ See also Monitor Noise +++++++++++++++++++++++++ Date: Thu, 22 Mar 2001 14:44:42 -0800 From: Eric Swartz WA6HHQ - Elecraft Subject: Re: [Elecraft] TVI Hi Scott, Actually your TVI -could- be a result of installing the KAT1, but that may -not- be an indicator of a problem with it. If you were running into a SWR mismatch (even 1.5:1) prior to using the KAT1 the K1 probably was not transferring full power to the antenna. The combination of feed line loss and SWR power reduction by the rig could reduce your power below the threshold necessary for TVI. The addition of the KAT1 will allow your K1 to transfer more power efficiently to the antenna, since the K1 will see a much better match at its PAs. As a result the higher ERP could be overloading your TV. 73, Eric ++++++++++++++++++++++++++++++++++++++++ Date: Wed, 21 Mar 2001 11:21:27 -0000 From: bejones at hursley.ibm.com Subject: [Elecraft] TVI It's amazing how little RF will cause TVI. I had just built a 20m dipole and was testing it with (IIRC) 2W (not the K2 though). My neighbour came and complained I was taking her TV out. The antenna was on the opposite side of my house to hers so I was a little surprised. Expecting wavy lines on her screen I picked up the 2m HT and got my wife to key down while I went next door to investigate (don't panic she's licensed as M0ACL). Wow - completely black screen each key down. Investigation showed she had a dirty TV plug and the centre was unsoldered. Simply soldering the centre cured the problem and 130W from my TS850 now caused the merest (almost undiscernable) flicker. An addition of a high pass filter with braid breaker and full power key down on all bands was unnoticeable. Worth just checking the TV plug for good braid contact and soldering the tip. Brian G0UKB Brian E Jones Centre for Java Technology IBM HURSLEY +++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 21 Mar 2001 17:43:52 -0600 From: "Stuart Rohre" Subject: Re: [Elecraft] TVI Mike, many or most VCRs are prone to RFI. What fixed my VCR in the same room with the shack, was to wind its power cord thru one of the square chokes from Radio Shack. Also used type F inputs and outputs of the VCR to TV with coax, and in extreme case you can use the back to back coax to twin lead baluns to break the coax shield. This is good on a cable TV coax coming into the TV and picking up common mode shield signals. 73, Stuart K5KVH +++++++++++++++++++++++++++++++++++++++++++++ Date: Thu, 22 Mar 2001 01:27:12 -0000 From: "DeniGm3skn" Subject: Re: [Elecraft] TVI TVI from an Elecraft ? I don't think so. Guys let's face it, look to an inadequate TV installation first. Then your own antenna installation. 73, Deni GM3SKN Shetland Islands UK K2 1188 Fists 2817 ARS 827 ARCI 10659 +++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 21 Mar 2001 20:14:40 -0700 From: Larry East Subject: Re: [Elecraft] TVI At 05:43 PM 3/21/01 -0600, Stuart Rohre wrote: >Mike, >many or most VCRs are prone to RFI. > >What fixed my VCR in the same room with the shack, was to wind its power >cord thru one of the square chokes from Radio Shack. Also used type F >inputs and outputs of the VCR to TV with coax, and in extreme case you can >use the back to back coax to twin lead baluns to break the coax shield. >This is good on a cable TV coax coming into the TV and picking up common >mode shield signals. I cured RFI in my VCR using a Radio Shack "VCR/TV/FM Interference Filter" part number 15-579A (not sure if it is still available). It's marked "Hi-Pass Filter, 54 - 900 MHz" but appears to basically a "DC isolator" with a 27pF cap in the center conductor of the coax and some combination of inductance and capacitance connecting the shields of the input and output connectors. (There's no DC continuity between the input and output.) The above suggestion of using two back-to-back baluns would probably be just as effective. Even cheaper would be a homemade isolation transformer with 2-3 turns for the primary and secondary wound on a FT30-61 (or similar) toroid. A small binocular core of the type typically used in TV baluns should also work. (Hindsight is more likely to be 20-20 than is foresight... I bought the "filter" so I use it! Besides, it has nice connectors on it. :-) In a VCR that I previously owned, I also had to install toroid chokes on the power cord (I did it inside the unit) but not on the one that I now have (maybe -- heaven forbid! -- it already has line filtering), but I still need the "isolator" a.k.a. "filter". I also had to make a line filter for my old Primestar satellite receiver, but not the DirectTV receiver that I am now using. I believe that the primary way to keep RF from interfering with entertainment systems consisting of interconnected TV's, VCR's, satellite receivers, amplifier systems, etc. is to discourage RF "ground loops" through the use of chokes on power cords, speaker cables and interconnecting RF cables. Just where to put a choke and what type to use is pretty much a "try and see" situation. Often what seems like a reasonable solution only makes things worse! This RF stuff is all black magic anyway... :-) Just my two (binary) bits worth. 72/73, Larry W1HUE ++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 05 Sep 2001 15:41:25 -0700 From: Jeff Stai WK6I Subject: Re: [Elecraft] RFI in the DVD player hi Tim - I have almost the same antenna, with no known interference, even at 200 W - the difference is that the loop goes to two poles at the back of the house before returning to the roof line. I feed it with ladder line and use a 4:1 balun in the shack, and then tune with the tuner in the rig (K2, K1, etc.). If you feed with coax, maybe a choke balun at the feedpoint would be helpful... There is also the chance that the DVD is defective - you can always try exchanging it to attempt to eliminate that possibility... hope this helps a little - jeff wk6i At 02:20 PM 9/5/01, cyr999 at extremezone.com wrote: >Hi folks - Well I'll be darned. I know that technically I have an RFI halo on my >house since I have a horizontal loop running around the roof - which works >extremely well BTW......but when I got a new DVD player and my wife came up >and said the screen was flashing my Morse code (sent at 5w on my K1) I thought >THIS is ridiculous! > >So......has anybody had this problem? Did you find the DVD case was poorly >shielded or did you put a choke on the video cable? If it was under-shielded - >what >did you use to shield it with? Or did you just throw the silly thing out 'cause >it >interferes with the more important things!!! +++++++++++++++++++++++++++ Date: Wed, 5 Sep 2001 18:22:15 -0500 From: "Stuart Rohre" Subject: Re: [Elecraft] RFI in the DVD player The standard brute force RFI fix is to add a choke near where the AC power goes into the unit. The video cable is already shielded and not likely the fault. Most any plastic cased gizmo can be vulnerable to RF field. The inside of some plastic cases can be sprayed with an aerosol metallic shielding paint, which also must have jumpers to every other case part to fully make it a shield. This may or may not be practical. Other shielding means in small cases is a silver based paint, but again all seams have to be shorted with a conductive strip of metal or foil. Likely the RF choke with a few turns of the AC cord thru it next to the back of the DVD will do the job. If it is common mode conducted RFI on the outside of the shield of the video, you may need a video transformer or back to back balun type set up to break the RF path. Let's hope it is not that, as I do not know if TV balanced to unbalanced baluns also work on DVD video. I guess, however they would if the DVD puts out to TV on channel 3? or 4? GL and 73, Stuart K5KVH +++++++++++++++++++++++++++ Date: Wed, 5 Sep 2001 18:27:55 -0500 From: "Stuart Rohre" Subject: Re: [Elecraft] Re: your mail Nick, here is what I told him to try: core choke like radio shack sells for the AC line right at the device back. A couple turns of AC cord thru it to see if that helps. Also, for coax video out, in, you need the 300 ohm to coax baluns sold for TV sets, and put two back to back so the 300 ohm parts are joined and that breaks any common mode shield signal off the coax. But, try the AC line fix first, as that is definitely an unshielded path. Make sure the K2 is not close or on the same power outlet or fuse/breaker as the TV. Make sure your RF ground is not feeding RF back into the AC green wire. Using balanced (dipole or loop) antennas is usually a lower RFI case. GL and 73, Stuart K5KVH +++++++++++++++++++++++++