(meteorobs) ICOM PR1000 + FM Antenna on Channel 6 = No resultsyet

Tue Jun 12 01:15:28 EDT 2007

My take on this URL is that their site is central to a circular array of 
channel 6 transmitters almost all equally distant. Under that condition it 
is possible there is no PREFERRED direction to aim the antenna to receive 
all of the stations reflected signals equally....

(But I do have a problem with that personally). I would not aim vertical, 
especially with 1 or 2 stations in a specific direction, because it covers 
only an area overhead whereas an aiming point lower toward those 1 or 2 
stations would cover a longer distance & a larger section of the sky area 
tho' the signal strength would be diminished from the greater distances. But 
that is open to experimentation.

Apparently the receiver has selectable upper and lower offset. They appear 
to be using the negative(?) side and about 700 Hz offset. I am not clear as 
to why they think the doppler effect is occuring in only one direction when 
it could occur with the meteor going away or approaching. Approaching would 
give a stronger signal might be their thinking.

 Anyway maybe someone else has better info. I am doing a lot of second 
guessing here.

----- Original Message ----- 
From: "Siddhartha Jain" <siddhartha at siddharthajain.net>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: 2007/06/11 15:07
Subject: Re: (meteorobs) ICOM PR1000 + FM Antenna on Channel 6 = No 
resultsyet

> On 6/11/07, stange34 at sbcglobal.net <stange34 at sbcglobal.net> wrote:
>> Not sure what you are doing now.
>>
>> I thought you were interested in the FM band.
>
> Yes, I started with that but after discovering that the FM range is
> completely cluttered in my area, I was forced to give up on it.
>
>>
>> Channel 6 if it is in the frequency of 83 mhz is far below the maximum 
>> gain
>> frequency of the FM-6.
>>
>> The URL data I sent you earlier shows an increasing LOSS of antenna gain 
>> at
>> the low end of the FM band(88 mhz) with a FM-6.
>>
>> You are operating apparently well below the antenna's FM design.
>
> That is what I understood as well but being a newbie with radio-stuff,
> I just wanted to confirm that it is the antenna that seems to be the
> biggest culprit here.
>
>>
>> Not sure why you have a "splitter" in the system. Splitters decrease 
>> signal
>> strength
>
> Yes, will remove that. The split was feeding the FM radio. But that's
> no longer required and can go away.
>
>>
>> The CW filter should probably be set toward 15Khz. The 2.8Khz (3.0) may 
>> be
>> too narrow for the audio spectrum of meteors. Not sure myself of where 
>> the
>> meteor sound spectrum is most prevelant. Others may know.
>>
>
> I tried to find the URL earlier before posting this message but
> couldn't find it. Here it is now the reason I chose the CW mode with
> the 3khz default filter.
>>From http://www.spaceweather.com/glossary/nasameteorradar.html
> "The antenna we use [pictured left] is a 6-element Yagi; it is a
> commercially available cut-to-frequency channel 4 TV antenna sitting
> on the ground and pointed straight up," says Dr. Rob Suggs of the MSFC
> Engineering Directorate. "We use the CW demodulator on our Icom
> PCR-1000 so that 67.250 MHz (channel 4 zero offset) appears at about
> 700 Hz. This also inverts the passband so that the doppler shift of
> meteor echoes is reversed (frequency increases rather than decreases
> to the 'zero' frequency of the trail echo). The filter is set to 3 kHz
> bandwidth and the AGC is turned off."
>
>
>> I assume from your language the antenna is not truly straight up, but is
>> aimed at a distant zenith(60 miles up), MID-WAY between you and the
>> transmitting station.
>>
>> I do not engage in RF meteor detection so this is ONLY my opinion of the
>> whole thing you are doing.....
>>
>>
>
> Thanks for your comments, Larry.
>
> - Siddhartha
>
>
>> ----- Original Message -----
>> From: "Siddhartha Jain" <siddhartha at siddharthajain.net>
>> To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
>> Sent: 2007/06/11 12:59
>> Subject: (meteorobs) ICOM PR1000 + FM Antenna on Channel 6 = No results 
>> yet
>>
>>
>> > Hi,
>> >
>> > My setup:
>> > A Radioshack FM-6, connected to a RG6 cable via a 300-to-75ohm
>> > transformer, into a splitter, then connected to a ICOM PR1000 with a
>> > RG59 cable and F-to-BNC connector. The antenna points almost straight
>> > upward towards the zenith/south (There are a couple of Channel 6
>> > stations located southwards in Santa Barbara and San Diego)
>> >
>> > The PR1000 is tuned to 83.25Mhz (Channel 6) and set on CW mode (filter
>> > 3khz). The audio output goes into the soundcard of a pc and recorded
>> > thru audacity.
>> >
>> > So far all I have is a straight line when I look at the waveform of
>> > the recorded audio.
>> >
>> > Any suggestions to improve my chances of observing meteors? Or am I
>> > missing something here? Do you think its absolutely necessary to
>> > upgrade to a TV antenna for this purpose?
>> >
>> >
>> > Thanks,
>> >
>> > - Siddhartha
>> > ---
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>> >
>>
>>
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