Subject: [NEXTEL-1] A Question about Licensing

From: [email-masked]
Date: Sat, 07 Jun 2003 13:23:42 -0400

------- Original Message --------
   From: [email-masked]
Subject: Re: A Question about Licensing

Depending on how much power that you need, there are NOW dedicated non-voice
channels for exactly this purpose.  They are the "Group B" channels proposed by
the Land Mobile Communications Council (and recently approved by the FCC).  These
channels are some of the former UHF "offset" frequencies that low power operations
were now supposed to have vacated (and if they haven't they're secondary).

Downside: (1) have the now secondary licensees vacated?; (2) max. bandwidth is
12.5 kHz; and (3) potential interference from adjacent channel wide-band licensees
who haven't narrowbanded yet.

Here's a summary of the Report & Order:
http://www.shulmanrogers.com/450MHzLowPowerFrequencyMandatoryNarrowbandingReportOrdersMarch2003.pdf

Alan Tilles
Shulman, Rogers, Gandal, Pordy & Ecker, P.A.
11921 Rockville Pike, Third Floor
Rockville, MD 20852
www.shulmanrogers.com

In a message dated 6/6/2003 9:52:29 PM Eastern Standard Time,
[email-masked] writes:

> Is there a portion of the uhf band that is set aside for a simplex
> oil field scada?
>
> I have a co-ordinated licensed simplex channel that I just put to use
> but the "skip" interference is causing problems at night and early
> morning hours.
>
> A coordinator has provided me with duplex pairs to listen on in my
> area but I'm finding voice from "skip" stations right now.
>
> I had the uhf equipment dropped on me without benefit of consultation
> and there's very little liklihood that I can switch radios to another
> band right now.
>
> Thanks, BobC

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---

From: [email-masked]
Date: Mon, 09 Jun 2003 00:54:06 -0400

Original Message --------
   From: Robert Schlieman <[email-masked]>
Subject: Re: A Question about Licensing

The term "skip" generally refers to radio signals bouncing of layers in the
ionosphere.

However, there is another phenomenon for extended range communication that does
exist at VHF and UHF, and above.  It is commonly called "ducting" where the
signals are channeled between layers of the atmosphere that have different
dielectric characteristics.  The effect is the same in that you can hear signals
from greater than normal distances.

I don't think you can blame coordinators for such natural weather phenomena.  Just
the same, you might want to get the FCC Call Sign of the "interferer" and look
them up in the ULS to see just how far away they are.  If you have the coverage
prediction tools available, or if you don't contact your frequency coordinator, to
see whether you should be receiving their signals.

Good luck with your transmitter hunting!  Reminds me of  my old 6 meter days when
we did transmitter hunts for sport.

Regards,

Robert Schlieman

wonka12_98 wrote:

> The 25 Watt(UHF)simplex SCADA systems we recently installed didn't
> have any special frequencies assigned by our coordinater. Also there
> is no such thing as SKIP in the UHF band, Thats more common on
> systems that operate in the under 30 mhz HF and Lower bands. Maybe
> someone is just plain interfering with you at night.
>
> \"BobC"
> <bob_c_89431@y...> wrote:
>
>> I have a co-ordinated licensed simplex channel that I just put to
>>
> use
>
>>  A coordinator has provided me with duplex pairs to listen on in
>>
> my
>
>> I had the uhf equipment dropped on me without benefit of
>>
> consultation
>
>> and there's very little liklihood that I can switch radios to
>>
> another
>
>> band right now.
>>
>> Thanks, BobC
>>

---

From: [email-masked]
Date: Mon, 09 Jun 2003 00:58:54 -0400

------- Original Message --------
From: Robert Schlieman <[email-masked]>
Subject: Re: A Question about Licensing

Bill:

When you are dealing with significant over-water signal propagation, the 
dielectric layers are quite broad.  In an example I am very familiar 
with, the Toronto area on the north shore of Lake Ontario has a set of 
paging transmitters on the same frequency that NY State Police has been 
using for years for car-to-station in Troop D.  When the ducting 
conditions were right, those paging transmitters could capture receivers 
200 miles and more, even the receivers in Troop Cars.  Under normal 
conditions the paging signals weren't heard, but when conditions were 
right, it lasted for all during the day for days at a time.  

In your case, along the Atlantic coastline, I am not at all surprised 
that you have extended, if not every day, periods of ducting. 
 Particularly since the Gulf stream flows up the coast with a warm 
current that enhances evaporation and increases humidity.

Regards,

Robert Schlieman

-------------------

Bill Smith wrote:

>As I understand ducting, it is normally heard only in a small area. It went
>in one end and out the other. A relatively small entry and exit area, and a
>small variation in layers would cause a significant shift in the duct
>openings. I could hear these signals when I made the morning trip from my
>shop in RI up to our other shop in SE mass, about 40 miles away. Kind of a
>large duct. I probably shouldn't have been so definite, but I'm very
>skeptical it was true ducting. Ducting would be responsible for the FM
>broadcast DX'er in Chicago hearing my High School 10 watt FM station in
>Concord MA. 
>
>As for the other propagation anomalies or phenomena, they, in my experience
>have been generally bunched together as skip, At least as it related to my
>land mobile experiences. Since I'm not a ham, I don't study the
>characteristics of the various layers and their affect on different
>frequencies. Mostly in my case, Skip is a bad thing. Except listening to LA
>City Fire on 33.70 a few years ago before they pulled the plug on it. :-)
>  
>
and from your previous message:

How do I explain Hearing co-channel systems in Virginia, New Jersey, New
York and Maine here in Boston on our 451/456 channels? It's not ducting.
It's too stable and consistent.