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 Post subject: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Tue 08, 2019 11:25 pm 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
I've subbed another antenna from a Sangean/RS DX440 radio, and I suspect it's much taller (longer) Don't know the ramifications of running it full length. The Sangean antenna ends up 48" from top of cabinet to tip of antenna. So, about 53" ttl. I figured I'd start out with R36 at minimum. This is the 1 watt version, and I sure don't want to get the "sniffers" pounding on my door. Maybe I should eliminate the second transmitter stage. ? Anyone tinkered with this aspect of this transmitter ?


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Wed 09, 2019 12:43 am 
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Joined: Jun Sat 18, 2011 3:36 am
Posts: 2383
Location: Milton, FL 32570
This may answer some of your questions in the antenna section
http://sourcefmtransmitter.com/ramsey-electronic-manuals/FM100-manual.pdf

_________________
Thanks,
Jason
N1EBC


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Wed 09, 2019 5:13 pm 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
.
...Found this addenum for adding parts to make the unit a 1 watt transmitter. This one already is, and it looks factory bilt. Here's a quote out of the instructions - (NOTE: Never use the standard whip
antenna included with the FM100B series transmitters with your FM100BEX.
It
is not rated for the higher power capability of the export unit.) That explains why this rig didn't have the rod antenna
.
.. So, I have to study schematic, and see if I want to eliminate the final stage. Anyone else done this ?


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 Post subject: Transmitter experts
PostPosted: Oct Sat 12, 2019 6:52 pm 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
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...must not visit the transmitter forum much. Hardly a response about my Ramsey FM100B. The number of ttl visits pales in comparison to other forums. I know there's guys with Ramsey knowledge. Solution ?


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 Post subject: Re: Transmitter experts
PostPosted: Oct Sat 12, 2019 7:16 pm 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 791
Did you read the manual, the section about antennas, page 53, has the information you asked for in a previous post.

DM


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 Post subject: Re: Transmitter experts
PostPosted: Oct Sat 12, 2019 9:28 pm 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
.
I was mainly looking for someone that "down-graded" to the legal version. I did read that section. Not much help for my situation, at least I'm not smart enough to decipher the info. LOL :? My transmitter is actually the FM100BWT, which is the 1 watt. (not legal). And the instructions say to never use the whip that is provided with the FM100B.


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 Post subject: Re: Transmitter experts
PostPosted: Oct Sat 12, 2019 10:25 pm 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 791
A simple, yet very effective, antenna for the FM100B consists of a "dipole" (setup either horizontally or vertically) connected to the transmitter RF output jackthrough a few feet of coaxial cable (either RG-58, RG-59 or miniature RG-174,available at Radio Shack and other sources). Correct dipole lengths for majorsections of the 88-108 MHz band are: 88 MHz, each side: 2.7 feet; 5.4 feet total. 98 MHz, each side: 2.4 feet; 4.8 feet total. 108 MHz, each side: 2.2 feet; 4.4 feet total. You can see that there is not a great difference in antenna length from 88 to108 MHz. Some antenna designers have the view that an "approximate" dipolesuch as 2.5 ft. on a side will do fine, while others believe it is worth the effort tocalculate the length for your exact frequency, using the simple formula ofLength (of one side, in feet) = 234/Frequency in MHz.If the dipole is installed vertically, the end connected to the center conductor ofthe coax should be the upper (higher) end. If young children will be around theset-up, a flexible wire antenna is preferable rather than rigid tubing.A "ground plane" antenna can be quite effective. A ground plane consists ofone vertical element (the same length as one side of a dipole) connected to thecenter conductor of the coax. Four "radials" are connected to the shielded sideof the coax at a 90 to 135 degree angle to the vertical element. The dipoleformula is also used to calculate the length of the radial; since radials should beslightly longer than the main element, use 240 rather than 234 in yourcalculations
https://www.manualslib.com/manual/61070 ... e=7#manual

DM


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 Post subject: Re: Transmitter experts
PostPosted: Oct Sun 13, 2019 4:19 am 
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Joined: Jun Fri 20, 2014 7:10 pm
Posts: 1070
The FCC's rules on license-free operation on the FM broadcast band specify a maximum field strength, rather than a transmitter output power. The field strength is 250 uV/meter measured at 3 meters from the antenna. Bringing the output from a 1 Watt transmitter into compliance requires a lot of attenuation. If you were to connect the transmitter's output to a dummy load (which would provide a safe load to the transmitter), even the stray radiation from the transmitter, coax, and dummy load might exceed the legal limit.

In layman's terms, the FCC signal strength limit is very strict. 250 uV/meter is a signal strength that low cost consumer-grade radios can receive, but the reception might not be all that good.


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 Post subject: Re: Transmitter experts
PostPosted: Oct Sun 13, 2019 6:22 am 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
devilsmist wrote:
A simple, yet very effective, antenna for the FM100B


This is not the FM100B, but the higher power version. I'm not trying to get a more efficient antenna, but trying to reduce the power of this 1 watt unit to approximate the FM100B. Again, has anyone "reduced" the power of the Ramsey FM100BWT to part 15? Trying to get totally legal, as the FM band here is real crowded.
.
...Thanks you for the replies so far, btw.


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Sun 13, 2019 12:38 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17725
Location: Utica, NY 13502 (USA)
Quote:
Trying to get totally legal
Even if the power is reduced, the use of this transmitter on the air in the US is legal only if supporting documentation (properly conducted field intensity measurements showing compliance) is prepared by a qualified individual using type certified equipment.

Dave


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Sun 13, 2019 6:16 pm 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
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Dave Doughty wrote:
Quote:
Trying to get totally legal
Even if the power is reduced, the use of this transmitter on the air in the US is legal only if supporting documentation (properly conducted field intensity measurements showing compliance) is prepared by a qualified individual using type certified equipment.

Dave



...So, Dave, where does one find such an individual/ Sounds like it's not worth the trouble and expense. I guess I may have a paper-weight. Maybe a good conservation piece. Such a quality piece, and sounds amazing. Such is life.


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Sun 13, 2019 7:09 pm 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 791
The manual says to adjust R-36 for RF output. Do you have a schematic.

DM


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Sun 13, 2019 9:03 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 17725
Location: Utica, NY 13502 (USA)
oregonwinger73 wrote:
.
Dave Doughty wrote:
Quote:
Trying to get totally legal
Even if the power is reduced, the use of this transmitter on the air in the US is legal only if supporting documentation (properly conducted field intensity measurements showing compliance) is prepared by a qualified individual using type certified equipment.

Dave



...So, Dave, where does one find such an individual/ Sounds like it's not worth the trouble and expense. I guess I may have a paper-weight. Maybe a good conservation piece. Such a quality piece, and sounds amazing. Such is life.
That's the 'gotcha' with the Part 15 rules for FM transmitters. They do not fall under the same rules as for non-certified AM transmitters whose users have the option of limiting their power to 100 mw input to the final amplifier and use a specific length antenna system but do not require field strengths to be measured. It is much more convenient for a user to simply measure the voltage and current then prepare a short document to be kept with the transmitter showing compliance. (I wonder how many people do that?)

I notice that there are a few commercially available low power FM transmitters that claim to be Part 15 FCC certified but only when used with the supplied antenna.

The people who do FM field intensity measurements are often called "consultants" who usually work in the broadcast and related industries. They have the equipment and expertise necessary to conduct these studies and prepare the documents needed.

Dave


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Mon 14, 2019 2:48 am 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
devilsmist wrote:
The manual says to adjust R-36 for RF output. Do you have a schematic.

DM


I have R36 at minimum, and it is very weak with the rod antenna I "shouldn't" be using. Barely reaches beyond the perimeter of house. LOL


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 Post subject: Re: How tall is Ramsey FM100B Antenna, from top of cabinet ?
PostPosted: Oct Mon 14, 2019 3:22 am 
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Joined: Feb Wed 27, 2019 9:51 pm
Posts: 233
Location: Medford, Or.
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...Thanks, Dave. Seems that type 15 is causing a lot of confusion. Typical of gubmn't.


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