FM transmitter of choice...

[radiopilot]

Hello all..

I was wondering what FM transmitter of choice are you using? How does the transmitted signal sound in stereo and or mono? What types of antenna are you using?

I am using the Pico Macom PCFM Commercial transmitter.. it doesn't have alot of power and does not need it to, but the fact that it is a rack mount unit complete with DC regulated power supply, digital display with adjustable audio and RF controls, mono and stereo switch, and excellent construction along with a 5 year warranty makes it very valuable indeed!

Here is the website:

http://www.picomacom.com/macom/products/catalog-A1.htm

My antenna is a Slim Jim design and it's tunned to a particular frequency, and it is mounted 50 feet high... it get's the signal out far and with an excellent sound.

So tell us about your FM stories and any helpful hints...

Radiopilot




<P ID="edit"><FONT class="small">Edited by radiopilot on 11/29/05 05:37 PM.</FONT></P>

 

[oldies1077]

I'm using a EDM 100mw w/a Comet 5/8. But as far as the Pico, I WANT ONE, how much do they cost?????

Thanks,<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>

 

[radiopilot]

> I'm using a EDM 100mw w/a Comet 5/8. But as far as the Pico,
> I WANT ONE, how much do they cost?????
>
> Thanks,
>


Well, there are websites that advertise these units and they range from $162.00 lowest I'd seen up to $199.00.

Try:

http://eenid.us/eenidmarket/pcfm.html

But there are other sites.... try typing in the 'Pico Macom PCFM' in Yahoo or Google.

These are not just amatuer built units but proffesional commercial grade broadcast units built for many years of service for the cable industry.

Radiopilot

 

[oldies1077]

Sold

Looks like i'm buying one. As soon as i make a little cash.

<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>

 

[radiopilot]

> Sold
>
> Looks like i'm buying one. As soon as i make a little cash.
>


You will be very happy with this unit! the stereo seperation and signal to noise ratio is like no other!

Mono on this unit is very quiet and actually better than stereo and it goes out farther too. The unit is on 24/7 and it remembers the station when the power goes out.

I believe that it's got the pre-emphasis set internally for 75us (U.S.), anyway my biggest problem is the audio connectors to the unit are 'cable type' and not RCA type, but not a big deal.

Good luck...

Radiopilot

 

[radiooke]

> > Sold
> >
> > Looks like i'm buying one. As soon as i make a little
> cash.
> >
>
>
> You will be very happy with this unit! the stereo
> seperation and signal to noise ratio is like no other!
>
> Mono on this unit is very quiet and actually better than
> stereo and it goes out farther too. The unit is on 24/7 and
> it remembers the station when the power goes out.
>
> I believe that it's got the pre-emphasis set internally for
> 75us (U.S.), anyway my biggest problem is the audio
> connectors to the unit are 'cable type' and not RCA type,
> but not a big deal.
>
> Good luck...
>
> Radiopilot
>
I am using a EDM10 but soon a EDM100!

What's the specs like for the Pico? (SNR, THD, Frequency Response & Separation)

 

[radiopilot]

> > > Sold
> > >
> > > Looks like i'm buying one. As soon as i make a little
> > cash.
> > >
> >
> >
> > You will be very happy with this unit! the stereo
> > seperation and signal to noise ratio is like no other!
> >
> > Mono on this unit is very quiet and actually better than
> > stereo and it goes out farther too. The unit is on 24/7
> and
> > it remembers the station when the power goes out.
> >
> > I believe that it's got the pre-emphasis set internally
> for
> > 75us (U.S.), anyway my biggest problem is the audio
> > connectors to the unit are 'cable type' and not RCA type,
> > but not a big deal.
> >
> > Good luck...
> >
> > Radiopilot
> >
> I am using a EDM10 but soon a EDM100!
>
> What's the specs like for the Pico? (SNR, THD, Frequency
> Response & Separation)
>



radiooke

Here are the specifications from the PICO MACOM catalog on the PCFM FM Modulator. Comments follow.

FEATURES:

** Frequency Agile
** Stereo or mono operation
** 19-inch rack mount
** 5 year limited warranty
** Adjustable output level

DESCRIPTION: Designed especially for commercial installation, the PCFM provides superior signal-to-noise ratio, separation, and enhanced dynamic range. Switchable mono or stereo capability allows for FM trans- mission versatility.

SPECIFICATIONS:

** Frequency range: 88.0 to 107.9 MHz
** Frequency resolution: 200 KHz
** Frequency stability: / - 15 KHz
** Audio bandwidth: 30 Hz to 15 KHz
** Audio S/N: > 60 dB
** Audio Separation: > 30 dB
** RF Output Level: 45 dBmV
** RF Level Adjustment: 10 dB
** AC Power: 110 VAC or 220 VAC (optional) @ 400 mA
** Dimensions: 19" long X 3" deep X 1.75" high
** Weight: 6 pounds / 2.7 kilograms

[all specifications subject to change without notice]

Very stable transmitter in it's class...

Radiopilot

 

[oldies1077]

what is 45dbmV equal in terms of milliwatts????

all the charts i found said 35dbmV equals about 0.1xx milliwatts. this does not seem right though.<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>

 

[radiopilot]

> what is 45dbmV equal in terms of milliwatts????
>
> all the charts i found said 35dbmV equals about 0.1xx
> milliwatts. this does not seem right though.
>


45dbmV = 79 millvolts and 84 microwatts which is the legal FCC limit for this unit, if you need the signal to be stronger you use the FMS Single Channel Amplifier shown on the Pico Macom website and it'll push the FM transmitter beyond
1 watt but it's good to know you can adjust the PCFM and the FMS amplifier to legal part15 output. I've not had a single complaint as the PCFM has double bandpass filters and the FMS amplifier has double filtering as well, remember these units are built to withstand TV interference as that was it's main purpose, my TV is clean, no ghosting, no hass, no nothing!

Every other FM transmitter I've used I had to scrap, or put away as they caused too much interfence and that is your major FCC complaint.

Radiopilot

 

[carlvanorden]

I'm using the EDM 100...

> > > Sold > > > > > > Looks like i'm buying one. As soon as i make a little> > cash.> > > > > > > > > You will be very happy with this unit! the stereo> > seperation and signal to noise ratio is like no other!> > > > Mono on this unit is very quiet and actually better than> > stereo and it goes out farther too. The unit is on 24/7> and> > it remembers the station when the power goes out.> > > > I believe that it's got the pre-emphasis set internally> for> > 75us (U.S.), anyway my biggest problem is the audio> > connectors to the unit are 'cable type' and not RCA type,> > but not a big deal.> > > > Good luck...> > > > Radiopilot> > > I am using a EDM10 but soon a EDM100!> > What's the specs like for the Pico? (SNR, THD, Frequency> Response & Separation)> Although it is "illegal" as far as wattage goes, my situation is kind of strange: I have two antennas: the one I use the most is the simple wire it came with, and it is TAPED up against the outside of my metal trailer! I have another one, a rubber duckie tuned to my frequency sitting about 20 feet up in a tree, but connected via RCA wire.>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>I live in the mountains, and I'm high up, but not the highest up, therefore I have great signal on my plain and below me, but not above.>>>>>>>>I get very loud FM quality stereo 2 miles solid in just about every direction no matter which antenna I use, however what is strange is the simple wire seems to do a better job with the signal. Other than studio equipment, I have no processors connected to it; for the money, the size, the flexibility, the EDM 100 is killer!!Carl<P ID="signature">______________
[email protected], [email protected],[email protected]</P>

 

[radiooke]

> > what is 45dbmV equal in terms of milliwatts????
> >
> > all the charts i found said 35dbmV equals about 0.1xx
> > milliwatts. this does not seem right though.
> >
>
>
> 45dbmV = 79 millvolts and 84 microwatts which is the legal
> FCC limit for this unit, if you need the signal to be
> stronger you use the FMS Single Channel Amplifier shown on
> the Pico Macom website and it'll push the FM transmitter
> beyond
> 1 watt but it's good to know you can adjust the PCFM and the
> FMS amplifier to legal part15 output. I've not had a single
> complaint as the PCFM has double bandpass filters and the
> FMS amplifier has double filtering as well, remember these
> units are built to withstand TV interference as that was
> it's main purpose, my TV is clean, no ghosting, no hass, no
> nothing!
>
> Every other FM transmitter I've used I had to scrap, or put
> away as they caused too much interfence and that is your
> major FCC complaint.
>
> Radiopilot
>
I never experienced any interference with my EDM10

 

[radiopilot]

Re: I'm using the EDM 100...

Although it is "illegal" as far as wattage
> goes, my situation is kind of strange: I have two antennas:
> the one I use the most is the simple wire it came with, and
> it is TAPED up against the outside of my metal trailer! I
> have another one, a rubber duckie tuned to my frequency
> sitting about 20 feet up in a tree, but connected via RCA
> wire.>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>I live in the
> mountains, and I'm high up, but not the highest up,
> therefore I have great signal on my plain and below me, but
> not above.>>>>>>>>I get very loud FM quality stereo 2 miles
> solid in just about every direction no matter which antenna
> I use, however what is strange is the simple wire seems to
> do a better job with the signal. Other than studio
> equipment, I have no processors connected to it; for the
> money, the size, the flexibility, the EDM 100 is
> killer!!Carl
>


Carl,

The EDM transmitter seems to be a good transmitter, but.... it's not FCC certified, second it's way too much power and if the fines don't seem to hurt anyone, the 'pirate lable' is not easy to shake off if you ever want a LPFM or LPAM license in the future.

The PCFM is solid, has everything in it's place, ie. power supply, metal case, etc. and it's not that much more than the EDM, for a much better unit... see for yourself...

I actually would invite the FCC agent to my place and have them look at all my equipment knowing full well they will not have any need to close me down.

Anyway, back to why the wire transmits better is the signal does not deteriorate due to the length of your wire, as soon as you use the longer wire to your rubber duckie, the signal is attenuated, try using LM400 cable, it's very low loss cable and if used less than fifty feet, you'll not lose more than .5db of signal....

Radiopilot

 

[simcha]

Link to fm transmitter info

I have found an interesting link talking about the transmitter as well as some other fm transmitters. In additon he talks about remaining faithful to part 15 in connection with the antenna etc
http://global-cm.net/distribu.html

 

[radiooke]

Re: I'm using the EDM 100...

> Carl,
>
> The EDM transmitter seems to be a good transmitter, but....
> it's not FCC certified, second it's way too much power and
> if the fines don't seem to hurt anyone, the 'pirate lable'
> is not easy to shake off if you ever want a LPFM or LPAM
> license in the future.
>
> The PCFM is solid, has everything in it's place, ie. power
> supply, metal case, etc. and it's not that much more than
> the EDM, for a much better unit... see for yourself...
>
> I actually would invite the FCC agent to my place and have
> them look at all my equipment knowing full well they will
> not have any need to close me down.
>
> Anyway, back to why the wire transmits better is the signal
> does not deteriorate due to the length of your wire, as soon
> as you use the longer wire to your rubber duckie, the signal
> is attenuated, try using LM400 cable, it's very low loss
> cable and if used less than fifty feet, you'll not lose more
> than .5db of signal....
>
> Radiopilot
>
"I've not had a single complaint as the PCFM has double bandpass filters and the FMS amplifier has double filtering as well,"

But if one uses the pico with the add on FMS amplifier it won't be FCC approved anymore. For part15 you are not allowed to add any amplifiers to a part15 device.

 

[rfry]

> what is 45dbmV equal in terms of milliwatts????
>
> all the charts i found said 35dbmV equals about 0.1xx
> milliwatts. this does not seem right though.
________

Probably this spec defines tx power rating. The actual power level in milliwatts that it represents will depend on the load impedance across which that voltage is measured (which load impedance the mfr hasn't stated).

If that impedance is 50+j0 ohms, then 45 dBmV = 177.8 mV. As P = E^2/R, then 177.8 mV across 50 ohms is about 600 microwatts.

A power level of 600 microwatts far exceeds the ~11.4 nanowatts needed to radiate the legal Part 15 FM field of 250 uV/m as measured 3 meters in any direction from a simple 1/2-wave dipole antenna. And not much more is needed by a short "whip" antenna.
//

 

[rfry]

Re: Link to fm transmitter info

> I have found an interesting link talking about the
> transmitter as well as some other fm transmitters. In
> additon he talks about remaining faithful to part 15 in
> connection with the antenna etc
> http://global-cm.net/distribu.html
_________

I don't know who wrote the text on that URL (partial clip below), but they are WAY off the mark as far as what Part 15 allows for systems in the FM broadcast band.

Part 15 does NOT allow a "100 mW maximum limit" for Part 15 FM systems. That is a Part 15 AM Rule.

A radiated power of only ~11.4 nanowatts is needed to generate the maximum legal Part 15 FM field from a simple 1/2-wave dipole. Ramsey, EDM and the "Pico" units all are rated for _far_ more power than necessary for legal Part 15 FM operation at the maximum legal field strengths.

+ + +

PARTIAL CLIP from global-cm.net

"RF output level of about dBmV translates to just under
100 microwatts of power. This is about 20 dB less than that found
on the typical Ramsey FM 10, which is close to the legal power limit
in the United States, under 10 milliwatts ( dBmV). Adding an
amplifier to match the ballpark legal limit of 100 milliwatts
( dBmV) is somewhat difficult for the layman to calculate. It is
correctly described as 250 microvolts received on a 1-meter dipole
antenna, distance at 3 meters from transmitting antenna. A very
efficient antenna when connected to the Ramsey units can actually
put you over the legal limit. Their FM-25 unit when set to the
"export" output position and coupled to ANY antenna will exceed
the FCC limits. Do at your own risk, but be well aware of the pen-
alties, should you be so unfortunate as to be made an enforcement
example.

How to get the PCFM up to near the legal power level? The cheap
and "dirty" way would be to connect an inexpensive VHF distribution
amplifier to the output of the PCFM, and then to an antenna system.
The PICO TA-25 will get you within 5 dB of the 100 mW maximum limit.
Just over dBmV is a pretty respectable power level, if you are
on a restricted budget."
//

 

[radiopilot]

> > what is 45dbmV equal in terms of milliwatts????
> >
> > all the charts i found said 35dbmV equals about 0.1xx
> > milliwatts. this does not seem right though.
> ________
>
> Probably this spec defines tx power rating. The actual
> power level in milliwatts that it represents will depend on
> the load impedance across which that voltage is measured
> (which load impedance the mfr hasn't stated).
>
> If that impedance is 50+j0 ohms, then 45 dBmV = 177.8 mV.
> As P = E^2/R, then 177.8 mV across 50 ohms is about 600
> microwatts.
>
> A power level of 600 microwatts far exceeds the ~11.4
> nanowatts needed to radiate the legal Part 15 FM field of
> 250 uV/m as measured 3 meters in any direction from a simple
> 1/2-wave dipole antenna. And not much more is needed by a
> short "whip" antenna.
> //


Rfry,

The impedance of this transmitter is 75 ohms owing to the fact that this unit is built for the cable industry so using the formula above gives far less wattage and that is what the FCC has certified no more and no less...

This unit is in compliance and as long as too high a gain antenna is not used, I can't see the FCC blowing smoke over, like I said any visit from the FCC will not cause any trouble... however using some other equipment may cause some problem.

Radiopilot

 

[rfry]

> The impedance of this transmitter is 75 ohms owing to the
> fact that this unit is built for the cable industry so using
> the formula above gives far less wattage and that is what
> the FCC has certified no more and no less...

That's no great help, as you'll see. Using the equation I posted earlier in this thread, 177.8 mV across 75 ohms is ~400 microwatts -- still many thousands of times higher power than the ~11.4 nanowatts that needs to be radiated by a simple, 1/2-wave dipole or whip antenna to generate the maximum, legal Part 15 FM field of 250 uV/m at a 3 meter distance.

> This unit is in compliance (etc)

Tx power rating is not the issue here. A Part 15 FM tx system cannot be "compliant" without defining the field strength produced by the antenna connected to it.

Engineering realities for these systems prove that the power levels provided by the Ramsey, EDM, and "Pico" FM transmitters are far higher than required to produce the maximum, legal Part 15 FM field of 250 uV/m at a 3 meter distance even from a simple 1/2-wave dipole or whip antenna.
//

 

[radiopilot]

Re: I'm using the EDM 100...

> "I've not had a single complaint as the PCFM has double
> bandpass filters and the FMS amplifier has double filtering
> as well,"
>
> But if one uses the pico with the add on FMS amplifier it
> won't be FCC approved anymore. For part15 you are not
> allowed to add any amplifiers to a part15 device.
>

Radiooke,

Just to clear the air, I don't have the FMS amplifier, I'm just using the PCFM, the reference is for those wishing to up the signal, that the amplifier also carries the filters... I should have made it more clear, but you are correct in your statement about adding power amplifiers to any Part15 device... the only way to use the any amplifier is to be certified with the system by the FCC.

Radiopilot

 

[radiooke]

Re: I'm using the EDM 100...

> > "I've not had a single complaint as the PCFM has double
> > bandpass filters and the FMS amplifier has double
> filtering
> > as well,"
> >
> > But if one uses the pico with the add on FMS amplifier it
> > won't be FCC approved anymore. For part15 you are not
> > allowed to add any amplifiers to a part15 device.
> >
>
> Radiooke,
>
> Just to clear the air, I don't have the FMS amplifier, I'm
> just using the PCFM, the reference is for those wishing to
> up the signal, that the amplifier also carries the
> filters... I should have made it more clear, but you are
> correct in your statement about adding power amplifiers to
> any Part15 device... the only way to use the any amplifier
> is to be certified with the system by the FCC.
>
> Radiopilot
>

Sometimes people think if they have a approved type FCC transmitter they can add a approved type FCC amplifier and that it would still be approved!