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What is this AM antenna?

J

jlehmann

These antennas have been popping up all over Eastern Massachusetts on pirate (maybe Part 15?) stations, mostly on the high end of the dial.

Here's one that I took a picture of today. I've been searching around online to see if I could find what these antennas are, but I've found nothing so far. All of the ones I've seen have been mounted on top of houses/buildings.

Anyone know what it is?

antenna.jpg
 
> These antennas have been popping up all over Eastern
> Massachusetts on pirate (maybe Part 15?) stations, mostly on
> the high end of the dial.
>
> Here's one that I took a picture of today. I've been
> searching around online to see if I could find what these
> antennas are, but I've found nothing so far. All of the ones
> I've seen have been mounted on top of houses/buildings.
>
> Anyone know what it is?
>

Looks like it could be an antenna for a TIS (traveler's information service) installation.
 
I'm not 100% sure, but it looks like one the antennas made by Morad, Inc. out of Seattle, Washington for (licensed) Highway Advisory radio stations. Originally made for marine comms in the old 2-4 MHz band, Morad modified them for use in the AM broadcast band by licensed travelers information station users. I've installed a number of them. They are very well build and they work very well but if I remember correctly they are quite expensive ($1000+). Their web site is under construction at the moment, but I believe they are at http://www.morad.com/

Remember that using one with a part 15 transmitter would be illegal unless perhaps you reduced transmitter power to maintain the field strength requirements.

John

PS: My favorite Highway Advisory installation used a 10w Radio Systems transmitter with one of these Morad antennas on 530 kHz. The antenna was installed on top of a large flat-roofed warehouse and because the roof was covered in copper the signal was tremendous and could be heard for 10+ miles. We had to reduce the power down to something like 0.25 watts in order to stay within the legal field strength for T.I.S. stations.



> These antennas have been popping up all over Eastern
> Massachusetts on pirate (maybe Part 15?) stations, mostly on
> the high end of the dial.
>
> Here's one that I took a picture of today. I've been
> searching around online to see if I could find what these
> antennas are, but I've found nothing so far. All of the ones
> I've seen have been mounted on top of houses/buildings.
>
> Anyone know what it is?
>
 
as long as the antenna is not longer than 3 meters and you mount the transmitter right at the antenna, i doubt that it would violate part 15 when using 100mw input. i can't tell from the picture. I had one that(just sold on ebay) was less than 3 meters long made of fiberglass and helicly wound and had a special matching circuit to match 50 ohm transmitters and tuned .500 - 2mhz







> I'm not 100% sure, but it looks like one the antennas made
> by Morad, Inc. out of Seattle, Washington for (licensed)
> Highway Advisory radio stations. Originally made for marine
> comms in the old 2-4 MHz band, Morad modified them for use
> in the AM broadcast band by licensed travelers information
> station users. I've installed a number of them. They are
> very well build and they work very well but if I remember
> correctly they are quite expensive ($1000+). Their web site
> is under construction at the moment, but I believe they are
> at http://www.morad.com/
>
> Remember that using one with a part 15 transmitter would be
> illegal unless perhaps you reduced transmitter power to
> maintain the field strength requirements.
>
> John
>
> PS: My favorite Highway Advisory installation used a 10w
> Radio Systems transmitter with one of these Morad antennas
> on 530 kHz. The antenna was installed on top of a large
> flat-roofed warehouse and because the roof was covered in
> copper the signal was tremendous and could be heard for 10+
> miles. We had to reduce the power down to something like
> 0.25 watts in order to stay within the legal field strength
> for T.I.S. stations.
>
>
>
> > These antennas have been popping up all over Eastern
> > Massachusetts on pirate (maybe Part 15?) stations, mostly
> on
> > the high end of the dial.
> >
> > Here's one that I took a picture of today. I've been
> > searching around online to see if I could find what these
> > antennas are, but I've found nothing so far. All of the
> ones
> > I've seen have been mounted on top of houses/buildings.
> >
> > Anyone know what it is?
> >
>
<P ID="signature">______________
Oldies 1610 AM Stereo

"Proud User of Chris Cuff's Alfredo Lite 100mw"

http://www.part15.us
Largest Part 15 Website in the World</P>
 
> > These antennas have been popping up all over Eastern
> > Massachusetts on pirate (maybe Part 15?) stations, mostly
> on
> > the high end of the dial.
> >
> > Here's one that I took a picture of today. I've been
> > searching around online to see if I could find what these
> > antennas are, but I've found nothing so far. All of the
> ones
> > I've seen have been mounted on top of houses/buildings.
> >
> > Anyone know what it is?
> >
>
> Looks like it could be an antenna for a TIS (traveler's
> information service) installation.
>

The stations using these are not TIS stations. Most of them broadcast in Haitian, and cover reasonably well. I highly doubt they are legal Part 15s. It's strange that I've found 5 of these stations I think, and they all are using antennas like this.
 
> as long as the antenna is not longer than 3 meters and you
> mount the transmitter right at the antenna, i doubt that it
> would violate part 15 when using 100mw input.
_____________

Don't forget that the entire length of the conducting "ground lead" path from the Part 15 AM tx chassis to a true r-f ground at/on physical earth also is part of the radiating structure of a "Part 15" AM antenna.

So an elevated "3 meter" section of tx+radiator as described in this application may be substantially longer than that as a result of its installation, and therefore not in compliance with Part 15.
 
> > > These antennas have been popping up all over Eastern
> > > Massachusetts on pirate (maybe Part 15?) stations,
> mostly
> > on
> > > the high end of the dial.
> > >
> > > Here's one that I took a picture of today. I've been
> > > searching around online to see if I could find what
> these
> > > antennas are, but I've found nothing so far. All of the
> > ones
> > > I've seen have been mounted on top of houses/buildings.
> > >
> > > Anyone know what it is?
> > >
> >
> > Looks like it could be an antenna for a TIS (traveler's
> > information service) installation.
> >
>
> The stations using these are not TIS stations. Most of them
> broadcast in Haitian, and cover reasonably well. I highly
> doubt they are legal Part 15s. It's strange that I've found
> 5 of these stations I think, and they all are using antennas
> like this.
>

Here's another one. This one is located on top of an approximately 5 story building.

antenna2.jpg
 
You are Correct This is a morad Model SF-1610
The inductor is 612 microhenry.
It has a 10ft base pipe 49 inch tip base pipe.
7 1/2" tip base pipe.
and uses 12 75foot radials.
I have the entire spec sheet including smithchart if anyone want's
to Build one.

Rich
 
> > as long as the antenna is not longer than 3 meters and you
>
> > mount the transmitter right at the antenna, i doubt that
> it
> > would violate part 15 when using 100mw input.
> _____________
>
> Don't forget that the entire length of the conducting
> "ground lead" path from the Part 15 AM tx chassis to a true
> r-f ground at/on physical earth also is part of the
> radiating structure of a "Part 15" AM antenna.
>
> So an elevated "3 meter" section of tx+radiator as described
> in this application may be substantially longer than that as
> a result of its installation, and therefore not in
> compliance with Part 15.
>

The antenna in the first picture clearly had coaxial cable running down off the roof into a garage, so I guess it is clearly not a Part 15. I can receive them here at my house about 5 miles away, during the day, with not much difficulty.
 
> You are Correct This is a morad Model SF-1610
> The inductor is 612 microhenry.
> It has a 10ft base pipe 49 inch tip base pipe.
> 7 1/2" tip base pipe.
> and uses 12 75foot radials.
> I have the entire spec sheet including smithchart if anyone
> want's
> to Build one.
>
> Rich
>

Most of the ones that I've found are in areas that there would be no chance of having room for 75 foot radials. They just appear to have coax feeding them at the base, with no other wires clearly visable.
 
Hi Rich,

Can you email that info to [email protected] ???

Remove "nospam"

> You are Correct This is a morad Model SF-1610
> The inductor is 612 microhenry.
> It has a 10ft base pipe 49 inch tip base pipe.
> 7 1/2" tip base pipe.
> and uses 12 75foot radials.
> I have the entire spec sheet including smithchart if anyone
> want's
> to Build one.
>
> Rich
>
<P ID="signature">______________
Oldies 1610 AM Stereo

"Proud User of Chris Cuff's Alfredo Lite 100mw"

http://www.part15.us
Largest Part 15 Website in the World</P>
 
> > You are Correct This is a morad Model SF-1610
> > The inductor is 612 microhenry.
> > It has a 10ft base pipe 49 inch tip base pipe.
> > 7 1/2" tip base pipe.
> > and uses 12 75foot radials.
> > I have the entire spec sheet including smithchart if
> anyone
> > want's
> > to Build one.
> >
> > Rich
> >
>
> Most of the ones that I've found are in areas that there
> would be no chance of having room for 75 foot radials. They
> just appear to have coax feeding them at the base, with no
> other wires clearly visable.
>
 
I Tried to send some pics of the Instruction sheet
and the email bounced.

Rich
 
Hello Rich,

I'm interested in this antenna as well. My e-mail address is [email protected] Thank you very much for making the specs on it available. -- Jason

> You are Correct This is a morad Model SF-1610
> The inductor is 612 microhenry.
> It has a 10ft base pipe 49 inch tip base pipe.
> 7 1/2" tip base pipe.
> and uses 12 75foot radials.
> I have the entire spec sheet including smithchart if anyone
> want's
> to Build one.
>
> Rich
 
Hi Jason

I Think this is the one I sen't you in the mail
about a year ago.
there is also a 530Khz version.

Rich
 
Hi Rich if you send me the info i can post it on part15.us email [email protected]

> Hi Jason
>
> I Think this is the one I sen't you in the mail
> about a year ago.
> there is also a 530Khz version.
>
> Rich
>
<P ID="signature">______________
Oldies 1610 AM Stereo

"Proud User of Chris Cuff's Alfredo Lite 100mw"

http://www.part15.us
Largest Part 15 Website in the World</P>
 
> Hi Jason
>
> I Think this is the one I sen't you in the mail
> about a year ago.
> there is also a 530Khz version.
>
> Rich

They were on the hard drive of my old computer, which died. :-( -- Jason
 
> You are Correct This is a morad Model SF-1610
> The inductor is 612 microhenry.
> It has a 10ft base pipe 49 inch tip base pipe.
> 7 1/2" tip base pipe.
> and uses 12 75foot radials.
> I have the entire spec sheet including smithchart if anyone
> want's
> to Build one.
>
> Rich
>

I found a website that has what looks to be the antenna, and it's not a Morad. Maybe they just use the same design? The picture isn't very good, but if you click on antennas on this site, you'll see it:

http://www.lpbinc.com/CDv2_0/TIS HAR.html
 
LPB Resales a lot of items.
like The LPB AM2000 was the USI-AM100.
and if you notice the antenna says SF model.
same thing, they like to rename for some reason

Rich
 
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