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Fringe TV reception and 2 meters (filtering?)

Apr 3rd 2015, 15:04

KD0FGH

Joined: Aug 14th 2008, 10:27
Total Topics: 0
Total Posts: 0
Hi Everybody,
I live in a small town about 3 blocks long where we have 6 hams. Many of us operate on 2 meters from time to time. We are in a deep valley far, far away from the TV stations we receive "over the air" digital signals from. For TV reception, we use UHF yagis with a 116" long boom.

The issue I have a question about involves the signal blanking out on television sets any time any of us transmit on 2 meters. It does not matter who is transmitting. Has there been any success with using a 2 meter "no-pass" filter located as close to the TV tuner as possible? If so, are there certain filters that worked better than others?
73
KDØFGH
Alan Reinpold
Fairview,SD
Apr 3rd 2015, 20:48

WA0CBW

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
What are the frequencies of the distant TV stations? Are you using any amplifiers on the TV antenna? are you using a digital converter box?
I run a 50 watt 2 meter transceiver whose antenna is about 15 feet from my 2-bay "bow-tie" TV antenna with no interference to the TV.
BB
Apr 4th 2015, 06:01

WA9WVX

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Hello Alan,

There is such a Filter available through Microwave Filter Company which is a FasTrap Model # 5KMT-A/H, you and your friends can purchase these 75 OHM Filters and install them either directly into the Input connector of a Pre-Amplifier or if you don't have a TV Pre-Amplifier then connect to your TV 75 OHM Input. I started using these filters in the early 1980s while I serviced 300 W RF Wide Area Radio Paging Systems with remote locations 60 to 80 air miles away from the major metropolitan areas that broadcast the older Analogue TV signals. Most of the time I would interface with the personnel that were taking care of the TV Pre-amps and individual TVs for the customer. Those technicians were amazed once the filter was installed as you couldn't tell if the 300 W Radio Paging station was in use or not.

Years later I purchased several more for my own ham station as I operated 2 m SSB with 1.2 KW Output and living 45 to 50 air miles northwest of Chicago I knew I would cause Front End Over Load to my neighbors TV systems for Over-The-Air Signals. As my neighbors complained, I would take a HT with me, a fellow ham would operate my station. I would communicate back to him to stop transmitting with my neighbor standing next to me, install a filter and then tell my fellow ham to start transmitting again. Again you couldn't tell when my Kilowatt Amplifier was or wasn't in use.

I will admit that there were two different situations that came up, that were impossible to solve. The first was when an individual had a Wideband Pre-amp incorporated into their Winegard Antenna as it clipped into the 300 OHM mechanical antenna feedpoint. If you're fighting that type of situation, there is NOT a filter made to over come that configuration. The second problem was encountered with people that had "Rabbit Ear" Antennas inside their homes. Back in the 1980s even the FCC would not consider "Rabbit Ears" as adequate TV antennas so in essence that's another problem that can't be corrected so keep this in your memory.

They're still making "Bow Tie" antennas with Pre-Amplifiers built into these in house antennas. In this situation all I can do is recommend helping the owner install an outside real antenna with 75 OHM coaxial cable and install one of the filters. Here's Microwave Filter Company's website:

http://www.microwavefilter.com/

Dan
WA9WVX

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