OOPS! Darn reflector software got me again. This was meant as comments to
the originator.
Sorry folks.
73
Bob, K4TAX
----- Original Message -----
From: "Robert & Linda McGraw K4TAX" <RMcGraw@Blomand.Net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, May 28, 2005 9:47 PM
Subject: Re: [TenTec] ORION BCI
> Eric:
>
> Were you able to determine if the 160M / BC interference from the stations
> was fundamental overload or IM?
>
> I've found both to exists however, many times the source is external to
> the
> radio and thus is IM as a result of non-linear devices in the field of RF
> from multiple sources.
>
> In one case I solved, the interference was the result of transmitter IM
> being from 5 different sources mixing in the PA of a VHF paging TX. Took
> some good software to find this one and lots of listening to figure which
> 5
> TX's was on the air when it happened. They were communications sources
> which were of dispatch nature and thus only transmitting briefly. A
> circulator was placed in the output of the offending TX and the problem
> was
> solved.
>
> These guys complain about BCI and IM. To that I say HA! My ORION is at a
> 5KW AM TX site. The 75M center fed antenna is tied to one end of the AM
> radiator with the end insulator about 45 feet from the tower. To add
> insult
> to injury, there is a 50KW SW AM station is about 2 miles away. It
> operates mostly near the 40M band. Needless to say, there's a good bit of
> RF around the ORION which is located about 30 feet on the desk from the
> BC
> TX. NO BCI exists, no external filters required.
>
>>From my perspective, most hams don't have a clue as to what a "clean site"
> actually is and most are very poor RF technicians with even a poorer
> understanding of good engineering practice.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message -----
> From: "Eric Rosenberg" <wd3q@starpower.net>
> To: <tentec@contesting.com>
> Sent: Saturday, May 28, 2005 8:21 PM
> Subject: Re: [TenTec] ORION BCI
>
>
>> I've been following the thread on BCI to the Orion with both interest
>> and amusement.
>>
>> I live in Washington, DC proper, 5.5 miles from a 50kw AM station
>> operating at 1500 kHz (signal measured a -10 dBm with a lab-grade
>> spectrum analyzer on my inverted-L), and another relatively high power
>> AMer at 1260 kHz.
>>
>> From my roof I can see (and have photos of) all of Washington's TV
>> (NTSC and HD) and FM broadcast towers, not to mention the plethora of
>> US and foreign government, commercial and other point-to-point
>> transmitters and repeaters that operate into the microwave bands and
>> seemingly beyond.
>>
>> Regardless of the number and size of cavity filters, weak signal and
>> amateur satellite operations are difficult (I used to operate on AO-13
>> and to a lesser degree the pacsats) or impossible.
>>
>> And the intermod/overload on 160 is pretty amazing, regardless of the
>> radio I've used... be it Kenwood, Icom, Yaesu or Ten Tec.
>>
>> For the past 5 years, I had an Omni-6+. For the past year, an Orion.
>>
>> The solution? Well designed and built BCI filters. I spent as lot of
>> time researching what was available in the amateur radio
>> world. Neither the ICE filter (402X), W3NQN, Top 10 Devices or anyone
>> else's worked for me. In the end, I did find one, not (yet)
>> commercially available filter that worked so well for me that I had my
>> best score ever in the CQ 160 contest! If and when it becomes
>> available, I'll post information here on the reflector.
>>
>> A great resource for locating the broadcast (AM, FM and TV) stations in
>> your neighborhood is AMSTNS and TVFMSTNS by Bob Carpenter,
>> W3OTC. Bob's software was invaluable to me in identifying the local
>> broadcasters to better understand who and where and to what degree the
>> offending stations might be. An overview of the software is available
>> at http://users.erols.com/rcarpen/INFO0227.html while the latest
>> versions of the software are available at
>> http://home.earthlink.net/~lvehorn/ For best results follow the
>> various links!
>>
>> The bottom lines is that if you're close to a broadcaster and suffer
>> from intermod and overload problems, don't blame it on the
>> radio! External filters are the only solution.
>>
>> GL!
>>
>> Eric W3DQ
>> Washington, DC
>>
>>
>>
>> --
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>>
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>
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