Subject: [NEXTEL-1] indoor amplified TV antenna

From: [email-masked]
Date: Mon, 19 May 2003 21:41:24 -0400

------- Original Message --------
From: [email-masked]
Subject: RE:indoor amplified TV antenna

Hi Eric,
	We've had several of these cause problems. I've never had anyone say
no after replacing it. 
	Those amps are usually made very cheaply. I've tested a couple and
it was difficult to find any reason why the thing would oscillate. Often
just placement of the UHF and VHF antenna close together would cause it to
oscillate.
	Code of Federal Regulations Title 47, Volume 1, Part 15.5 General
Conditions of Operation (b): "Operation of an intentional, unintentional, or
incidental radiator is subject to the conditions that no harmful
interference is caused and that interference must be accepted that may be
caused by the operation of an authorized radio station, by another
intentional or unintentional radiator, by industrial, scientific and medical
(ISM) equipment, or by an incidental radiator. (c) The operator of a radio
frequency device shall be required to cease operating the device upon
notification by a Commission representative that the device is causing
harmful interference. Operation shall not resume until the condition causing
the harmful interference has been corrected."

	Technically he doesn't have to stop using the device unless notified
by a Commission representative. Which begs the question: Who are Commission
reps, employees of the Commission and/or licensees? Anyway, I have contacted
the FCC regarding issues like this one and as you are probably aware, it is
the user of the device responsible for ceasing operation. I guess in your
case, lets just hope he doesn't use it near another site.

Bryan

-----Original Message-----
From: eric995us [mailto:[email-masked]]
Sent: Monday, May 19, 2003 8:28 PM
Subject: indoor amplified TV antenna

I just got finished tracking down another interferer to the local
cellular system.  It was a Phillips MANT-300 indoor amplified TV
antenna.  It was 7/8 of a mile from the cell site and was, on the cell
site antennas, -105dBm on 831.1 +/- MHz.  

We (my company) got him another antenna after telling him (verbally)
that we would like to have the old one.  When we went back to his
house, he took the new antenna and when I asked if I could have the
old one, he said "No, I'm going to use it at my trailer up north.  You
have my word I won't use the old one here." He thanked us and closed
the door, leaving us standing on his porch.

I was hoping to get the old unit and see what it was like inside and
see if I determine what exactly was happening to make it oscillate.  

Oh well.

I'm going to try to get the company legal dept to write a letter
thanking him for his cooperation in fixing the interference and
mentioning that the FCC has legal responsibility for finding these
things and if they were to find it, they would be a lot less pleasant
than us about wanting it....in other words, please don't use it....

The characteristics of this interference was a 50KHz or so wide FM
modulated signal with 120Hz hum on it.  The frequency was fairly
stable, only drifting around 100KHz or so.  Based on the signal levels
I measured adjacent to the device while it was powered up, I would say
the thing was doing as well as my signal generator when I get +10 to
+20dBm out of it.

Has anyone managed to get their hands on one of these and determined
the cause of their failure?  Is it a failure within the "antenna"
itself, a bad piece of coax between the "antenna" and the TV, or
signal leaking out of the TV, back into the "antenna"??????

Eric

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---

From: [email-masked]
Date: Wed, 21 May 2003 17:29:12 -0400

-------- Original Message --------
From: Jack Daniel <[email-masked]>
Subject: Re: indoor amplified TV antenna

Eric,

Similar problems have been posted in these forums for avor a year.

Phoenix area seems to have a lot of these problems for some reason;
maybe it's a combination of a lot of RV/Campers in and our of the area,
high temperatures and 'camps' near major tower sites.

In addition to the absolute TRASH televison products (I hear Wineguard
even redesigned some of their stuff because of oscillations) wireless
distributors continue to sell cheap cellular boosters to anybody with a
few bucks and no skills or training. 

One brand of BDA has had been reported here as causing 'spurious'
problems repeatedly in the Phoenix area.

We all need to get used to it because there is no penalty for screwing
up a band anymore and increased 'noise floors' is being encouraged by
FCC's current 'new unlicensed technology' spectrum policy.

But I may be wrong......
Jack Daniel
=================================
 
eric995us wrote:
> 
> I know I'm replying to my own post, but have any public safety folks
> had fun with these things yet?  I put out a poll within my own
> company and we've had 6 of the things come to our attention in
> Cleveland, OH and "several" in the other markets.
> 
> The problem with these antennas seem to be well known within
> government circles--to the point that the US Coast Guard has issued
> warnings about the amplified antennas.  The link below points to one
> of the warnings.
> 
> http://www.uscg.mil/hq/g-m/moa/docs/11-02.htm
> 
> I've also found four of these (as a ham), messing up the 420-450MHz
> band, so the frequency agility of these antennas is quite awsome.
> 
> I was hoping to get ahold of the busted unit from the last one that I
> found, but alas......  If I had to guess, I would say the thing
> contains one of those MMIC "gain blocks" that goes from DC to 2GHz
> so, with 30dB or so of gain.  If so, that would explain the wide band
> over which their problems can appear.
> 
> What I'm hoping here is, if the public safety community also has had
> problems with these things, the combined voice of the Coast Guard,
> cell phone companies and public safety might get the FCC to begin
> considering how to go about thinking about how to decide how to begin
> figuring out what to do about these things...before they become the
> next nightmare.
> 
> Even one of those public notices from the FCC the describes the
> problem and the person's responsibilities would probably be helpful.
> At least we could hand the notice to the person with the antenna.
> 
> Most people don't believe that these things can cause problems and
> want compensation (in one case a big screen TV--which I declined)
> before dealing with the problem.
> 
> Eric