If what you say is true seankw40, then look on amazon.com and you will see some Chinese transmitters(CZH series) being sold under the name of "Failsafe" which are ready to go right out of box with 500mw power and more, in the US, and not FCC certified.
Why don't they have to stop? I'm sure the FCC can look and see this too. And they CAN"T be set to part 15 levels!
Ramsey kits can be adjusted to operate in compliance with rules.
But please...tell us what meter you got that can measure small enough for part 15 or industry Canada compliance!
Mark
...tell us what meter you got that can measure small enough for part 15 or industry Canada compliance!
Mark, he included info about the meter(s) be bought in his post 32 above.
they in fact do go after those sellers and amazon for selling them but it is like whack a mole for both amazon, ebay and the fcc to go aftet them all.
ramsey and sstran however are usa sellers and they did go after both ramsey and a kit builder for sstran for selling assembled uncertifierd transmitters but have not gone after them for selling kits.
Hi Robert kc8gpd, I knew that Liam Ryan got nabbed for selling transmitters he assembeled from kits to save the buyer the trouble of fiddling with kit constuction, I read about it at hobbycaster.
But I do not know about any action against Ramsey, and I would like to know about what happened to them for their various kits, which still seem to be available?
I'd like to know about that.
Hi Everyone.
Ok I thought we already got the make and model of the meters clear of
what they are. They came from a local radio station and yes the antenna's
do come with them. This will put the meter in alignment with the antenna hooked
to it. The Antenna are not dipoles but a ground plane type antenna. Which gives
the correct impedance to the meter they are providing. The meter is accurate down
to 10 microvolts. I bought the meters mainly to check out the transmitters being
sold on the market such as decade to see how close they are to the 250uv output.
Also to be able to test transmitters that I design and build.
I got a very good deal on these meters and yes most meters are out of the reach
in price for the most people. Like I said the radio station just bought 2 really
advance type meters and I do not know the model on them but I could find out.
They run around $5000 each.
They test must higher field strength but they also test radiation paterns with those
meters to tell which direction most their signal is going out to the public.
I am hoping the meters and antennas they have provided to me will be accurate
enough to tell. I know decade transmitters say theirs is right at the max transmit
level of 250uv. Well I want to buy one of those transmitters and see if the meters
indicate the 250uv @ 3 meters. If they do then I will know these meters are accurate enough to be used.
Please look back in the post of the meter I gave. Now if you are wanting to
know what the $5000 meter is give me time and I will go ask the radio station.
AS most I do not have $5000 just to go and buy a meter,and it just easier to
buy a Decade transmitter from them and ask them to test the transmiter for
power output to be tested before they ship it to you. Since the MS100S runs around
$595.00 well I am sure they will check it for you if you ask them to.
When I bought my TS100 the owner sent me pics of the output power just
to make me happy. I knew what it was doing before it was shipped out.
Then I bought a watt meter that measures 5 to 100mw output in the broadcast
band and it showed exactly what he showed me. That meter new only ran $395.00,but
now I can test all my AM transmitters for output power.
There are several Field strength meters on the market,and I will give one example
of one but it very high also.
PROMAX HD Ranger 2 Touchscreen Field Strength Meter $5800.00
Unaohm EP3000 Professional Field Strength Meter $3600.00
KC901H scalar network analyzer Field Strength meter Sweep Frequency generator
Priced at $935.00
Can be found on ebay.
Anyways I am only trying to be a help to everyone. Sorry it seems like everyone
more upset with what I have talked about more than happy that we are trying to
find a good way to measure FM radio signals. This is one reason why I started out
with the AM broadcast type equipment. By the way if you build your Own FM
transmitter then the 250uv @ 3meters the FCC kind of dismisses it.
Look at this part 15 rule.
FCC part 15.23
Home built devices.
(a) Equipment authorization is not required for devices that are not marketed, are
not constructed from a kit,and are built in quanitites of 5 or less for personal use.
(b) It is recognized that the idividual builder of home built equipment may not
possess the means to perform the MEASUREMENTS for determining compliance with
the regulations !!!!! IN this case, the builder is expected to employ good engineering
practices to meet the specified technical standards to the greatest exent practicable.
The provisions of Sec. 15.5 apply to this equipment.
If you do build look at Part 15.19 Labelling requirements
Part 15.5 that they mention is General conditions of opperation.
Anyways as you can see if you make your own equipment and you are not at
250uv @ 3 meters the FCC is not going to bust you. Rule Part 15.23 protects
you if you make your own transmitter because you are building it to the best
of your capability.
Anyways I was just trying to be a help and I say find a field strength meter
that meets what you want. I gave some really good examples.
The ones I did get do have the antenna;s that come with them. This way I can
get a pretty accurate readout.
Thanks
Speaking for myself I am not upset about anything you've presented and as a matter of fact I very much appreciate what you have been sharing and I don't want you to be discouraged by what anybody says.
Since the rules obligate us to maintain very small power levels, we desperately need a way to accomplish that task, and you are working to help us with the problem by evaluating these meters.
Thank you for your contribution Seanwk40.
Hi everyone I do have one meter that was used by the USAF at ont time
for Field Stengths.
The meter is a Blonder Tongue Model FSM-2
Anyways here is what it says when measure strengths with an antenna
Field strength in microvolt per meter (uv/m) may be computed from the following
formula:
uv/m= (freq. in mc / 47.6 ) * meter reading in uv * correction factor.
The correction factor is 1.2 for the folded dipole, and eleminates
the need for incorporating balun and cable losses ( for short lengths of cable in
the measurement. The correction factor for the straight dipole is 1.1
If an antenna other than the ones shown above is used, The figure above should be
divided by the gain of the other antenna relative to the dipole.
The new meters I am getting use different antenna than this one.
Anyways this meters has always done me good if I follow the owners manual for
correct measurement of the transmitting signal.
Thanks
Hi everyone
Let take a reading on the meter of 250uv out at 3 meters.
uv/m=( freq in mc / 47.6 ) * meter reading in uv * correction factor.
Let just use a straight dipole for the antenna with a correction factor of 1.1
uv= uv/3m =( frequen in mc/ 47.6 ) * 250 * 1.1
uv = uv/3m = (88.9 /47.6) * 250 * 1.1
uv= uv/3m = (1.891489361) * 250
uv= uv/3m = 472.8723 * 1.1
uv= uv/3m = 520.15957 ( realize this is at 1 meter away from the transmitter with
the meter only showing a reading on it of 250 uv)but you actually have 520.159 uv
uv = 520.15957/3 ( this is at 3 meters)
uv @ 3meters = 173.3865 uv ( this is what you really have at 3 meters away from the
antenna)
So there is some math involved when taking measurements for the correct level.
Again let go back to the manual .
Field Strength in Microvolts per meter (uv/M) may be computed from the Following
Formula.
uv/M= ( freq, in mc / 47.6 ) * meter reading in uv * correction factor
Thanks
Hi everyone
Where I say this is wrong
Let take a reading on the meter of 250uv out at 3 meters.
This should have said take a reading on the meter of 250 uv @ 1 meter.
Look how the formula works out above.
Thanks
Hi everyone
I really wanted to give a good example.
Ok this formula tells how many microvolts are present at 1 meter from your
transmitting antenne
Straight diploe antenna has a correction factor of 1.1
ok formula
uv/M= ( frequency in Mhz / 47.6) * meter reading in uv * correction factor
Lets say the meter is showing 360 uv using a dipole antenna
uv/M= (88.9Mhz / 47.6 ) * 360 * 1.1
uv/M= 1.867647058 * 360
uv/M= 672.35294008 *1.1
uv/M= 739.588234968 uv ( This is how much uv you really have @ 1meter from the ant.
uv@ 3meter
(UV/M) / 3 = 246.529 uv
This give a rough reading of an FM transmitter @ 3 meters from the antenna
Thanks
Seankw40: wrote: Ok this formula tells how many microvolts are present at 1 meter from your transmitting antenne. ...
The "/meter" part of the microvolts/meter unit of measure does not mean that the measured or calculated value it applies to is the field existing 1 meter from the transmit antenna.
Instead it is the field intensity existing across two points in space that are one linear meter apart, at the physical location and orientation of the receiving antenna.
The receiving antenna is not required to be 1 meter in length, either. If the antenna used with the field meter is a center-fed, 1/2-wave dipole, then its end-end length for measuring an 88.9 MHz field would be about 1.6 meters.
The antenna factor for any particular antenna when used to measure field intensity normally is provided by the manufacturer of the antenna, or better yet, by the supplier of a complete system to measure field intensity including the receiver, the receive antenna, system cables etc.
The meter came with a supply center fed dipole antenna that could be changed in
length. It ment to be set up 1 meter from the transmitter antenna. The dipole
does go with the meter. That 360 uv was a reading you would see on the meter.
With the formula you do see the intensisity of the field strength at 1 meter ,and
it says if you divide that by the amount of meters you want to find the field
stength at it will be very close. this is why you see me dividing it by 3 ,so I
can get an ideal what would be at 3 meters out from the transmitting antenna.
it give two correction factors one for s straight dipole of 1.1 and the other for a folded
dipole of 1,2. So when the meter shows 360 uv @ 1 meter on it you really have a much stronger field strength.
This is what the formula shows.
Thanks
The meter came with a supply center fed dipole antenna that could be changed inlength. It ment to be set up 1 meter from the transmitter antenna.
A receiving antenna located a distance of 1 meter from an 88.9 MHz transmit antenna would be in the near field of the transmit antenna. So the method you have described to determine field intensity at 3 meters will not produce an accurate answer.
Your interest in making an accurate measurement is very commendable, but the process of doing that may be more difficult to understand and do than it seems.
With more reading and study on this subject I think you'll find that what I have posted about it is accurate.
Also be careful about making measurements at 1 meter. As Rich correctly pointed out, you are in the near-field and your measurements may not be accurate even if you are using a calibrated FSM and applying antenna correction factors. Also, the antenna needs to be raised and lowered anlong with rotating the RF source to maximize emissions.
Hi everyone
this Formula I have had some thoughts and really never tried it.
Ok the for state this
u/M= (Frequency in Mhz /47.6) * meter reading in uv * correction factor
Ok let measure the signal 3 meters out from the transmitting antenna
with a straight dipole which only has a correction factor of 1.1
If we do this and the meter reads 120 uv @ 3 meters out from the transmitting antenna.
Now watch what the formula says we really have at 3 meters out.
u/M= (Frequency in Mhz /47.6) * meter reading in uv * correction factor
uv/M= (88.9/47.6) = 1.8676470588
uv/M= 1.8676470588 * 120 uv ( meter reading)
uv/M= 224.117647056 * 1.1 ( correction factor for the dipole antenna at the meter )
uv/M= 246.529411 uv
So you would have 246.529411 uv @ 3meters
The above would be an actual reading @ 3 meters with the meter only showing
a 120 uv on its scale. This would place you in FCC rules Part 15 for power level.
Now again this is only a theory using the formula an instructions they provided
with the meter.
Take it for what it is but I have tried several ways with this meter and this
is why I bought 2 new meters which should be more accurate but the FCC has
always been good with what I have done .
Please note FCC rule Part 15.23 where if you build your own equipment that they know
you have no way of accurate measurements.
I will write it out again so there is no confusion.
FCC part rule 15.23 states this.
(a) Equipment authorizeation is not required for devices that are not marketed, are
not constructed from a kit., and are built in quanities of 5 or less for personal use.
(b) It is recognized that the individual builder of home built equipment may not
possess the means to perform the measurements for determining compliance with
the regulations. In this case, the builder is expected to employ good engineering
practices to meet the specified technical standards to the greatest extent practicable.
The provisions of sec. 15.5 apply to this equipment.
Anyways if you are trying to take measurements and they are off some the FCC is
not going to care because you are doing the best to your extent with your test
equipment. As they said builder may have no way of getting accurate measurements,
but you have to try your best and if they see that the FCC will not come down on you.
Anyways I am trying to show there are meters that can give you an ideal what you
are transmitting in microvolts. Most meters come with instructions and will help
you find a way to get a field strength reading. This meter I have now not my favorite,
but it does work and that is why I bought 2 meters that should give me a much
more accurate reading.
Thanks