- Posts
Do you think the Rangemaster am 1000 with the recommended
#21-903 Radio shack 102″ whip antenna or the SStran AMT3000
with a part-15 compliant base loaded antenna will broadcast
stronger/further?The rangemaster website dosen’t mention a loading coil
(i assume the unit is designed to have the ouput impendence
roughy that of the radio shack antenna) but you still have
to tune it, and i am assuming that is because the groundingDo you think the Rangemaster am 1000 with the recommended
#21-903 Radio shack 102″ whip antenna or the SStran AMT3000
with a part-15 compliant base loaded antenna will broadcast
stronger/further?The rangemaster website dosen’t mention a loading coil
(i assume the unit is designed to have the ouput impendence
roughy that of the radio shack antenna) but you still have
to tune it, and i am assuming that is because the grounding
will be different depending on where you install it. There
is also no mention of constructing a ground plane for it.
The range they suggest you will get sounds larger in general
to what people seem to average w/ the sstran and a base
loaded antenna(?). Im aware they are selling the product…
The device is fcc certified which is a plus, but
its 8 X more expensive.
What do you think?Thanks
Mark D.
Total posts : 45366The answer to your question lies in what you are using the transmitter for. Are you planning on yardcasting or are you looking to develop a low power community radio station? Are you experimenting or are you providing some sort of service like NOAA weather?
I have had a Rangemaster transmitter for some time. The range of the station is based on a variety of variables, not the least of which is audio processing. I use the Inovonics 222 AM box. My station sounds markedly better than the local commercial stations.
A good ground system is essential to get every bit of signal, you want and need, out of the transmitter. The primary reasons I chose the Rangemaster are: 1) FCC certification, 2) the RF final amp is running well below full capability at 100 mw (less chance of signal distortion) and it’s the only commercially available Part 15 transmitter (that I am aware of) with 600 ohms balanced audio input. All others have unbalanced audio input.
I am aware of a lot of yardcasters who are very satisfied with their SStran transmitters. And a few community stations use them as well. But most of the folks I have talked to who are serious community broadcasters use the Rangemasters. I am sure after some of the folks on this forum read this, they will give you glowing reports for the SStrtan unit as well.
For candid answers regarding the Rangemasters capabilities, contact Keith Hamilton by phone or email…or Ron Erickson at Erickson Broadcast Supply in Madras, Oregon. Both these guys are good resources on Part 15 broadcasting. That’s my 2-cents worth. Good luck.
Marshall Johnson, Sr.
Senior Pastor, President
Rhema Christian Fellowship, Inc.Rhema Radio – The Word In Worship
AM 1660 – FM 101.3
http://www.rhemaradio.org
Total posts : 45366I am attempting to put together a part-15 am transmitter
and antenna for my (very) small college. The whole campus has to
be a 3/4 square mile at the most. So, I figure, If I can put the
antenna near the center i have less than a half mile I REALLY
need to cover, although we’d like to spill out into the surrounding
neighborhoods as much as possible.
The main point of the transmitter/antenna is to get the student
body to be able to listen in their doorm rooms. A few of the dorms
are constructed of concrete block and its unclear what the other
ones are constructed of- I think its some type of faux plaster
made from styrafoam on the outside, who knows what the main
structure is made from. The roof of the unknown structure is
metal. I dont know where they will let me put the antenna,
I may be stuck on the ground pretty far away from the dorms,
I dont know yet.
Budget may or may not be an issue, I have yet to propose
the plans for the transmitter/antenna so I dont know how
excited they are/aren’t going to be about funding the project.
We already have our studio setup and are currently streaming
online, we just want to make the jump from “internet radio
station” to “radio station”.
If we do buy the rangemaster is it true we dont need a coil?
Also, should I follow the guildelines for the ground plane that
are more common from people using an amt 3000?
thanks
markMight work better for the dorms:
Experimental broadcasting for a better tomorrow!
Total posts : 45366I have considered carrier current. The reading I’ve done suggests
to me that we would neet a seperate transmitter for each dorm
building. Also, it seems we would need a professional to couple
the signal into the power lines. I am trying to figure out how
to do this for the least amount of money, its my best shot
at getting the funding. The school will be far more likely to
allocate, say, 350$ for an SStran and the materials needed
to put together a base loaded vertical antenna rather than
3 transmitters and professional installation. Also, Im worried
they wont let me erect an antenna, let alone have me
mess around with their electrical system.
Im hoping to get the most bang for my(their) buck with
one good transmitter and a well functioning vertical radiator.
We also hope to, possibly, one day get a lisense and move
into the majors, so starting w/ an antenna as opposed to
carrier current seems, to me, to be a better start along
that path. I only have 1 year left as GM of the station
and want to get on the air basicly right away. I feel I could
get the rangemaster or sstran going w/in a few weeks whereas
explaining and actually executing carrier current at this school
with its reputation for delays in getting anything done would
make my dream take longer to achieve than I have time remaining
at the college.
That said, any suggestions?
thanks
mark
Total posts : 45366Hi Mark,
It has been many years, but I was involved with a carrier current radio station at a major urban campus. We needed a separate transmitter for each dorm. The university would not allow modification of the electrical system in any way (such as bypass networks across transformers) in spite of quite generous student activity financial support from the university. There was also $$$ involved in getting the audio signals to the transmitters which they did pay for.
One thing you should check is the AM reception in the dorms. My experience is that campus buildings are very noisy electrically and this may limit your effective range as much as the construction materials used. If you can, listen to the reception of weak broadcast stations in the dorms before you proceed and you might get an idea if over the air broadcasting will work.
I know of a local university which wanted to get a LPFM license but were thwarted by the city over zoning regarding putting an antenna on the roof of the building.
Not trying to talk you out of this, just be aware there are many factors to consider.
Neil
Total posts : 45366Neil,
thats a good idea and i will do so this week. The old dorms
are built like fallout shelters and the new ones are all wired with
cable and ethernet and digital phones so I do imagine there will
be some interference. I hope that if i can put the antenna close
to the buildings it will be just enough that you can hear the signal
all over campus. again, campus is literally around a 3/4 mile all told
and a good deal of that is athletic fields and other areas im not
that concerned about covering. we are right outside of a major
city so lpfm lisencing is completely out of the question. I think
our best bet is a part-15 vertical radiator on top of the main dorm.
My main question remains: is a rangemaster w/ the radio shack
whip antenna or an sstran w/ the base loaded 3 meter copper
pipe radiator going to be a better method of over the air transmission?
anyone else care to chime in? i’d really appricate the opinions.
thanks again
mark
Total posts : 45366Just from what I’ve read. I see where time and money is going to be a factor in your proposed operation.
Rangemaster system can be costly. Well over the $350.00 you spoke of. SSTRAN will be about $350.00 with you assembling the transmitter and antenna.
Since you appear to be operating from the stand of a educational “non – profit” organization. You have a studio. Have you considered talking with the cable TV provider, if any, serving the institution?
It is possible to put a FM signal on a Cable TV system for about as much $$ as you mentioned. Also, with many Cable TV systems there is, on occasion, hardware collecting dust in a rack or store room that can do this. If they don’t have it on hand. It’s easy to get from another system “used” for about what you have to spend.
The community I live in has a system where the signal can be “encoded” into the system from anywhere a Cable TV signal can be received. This is done with both audio and video for local football games.
In the 1980’s, on our city’s system. MTV’s Stereo audio was on 92.1mhz FM. Of course you had to be able to receive the Cable Channel for “MTV” and the same cable signal split off to your FM tuner. No special equipment. Just a “Radio Shack” 75 ohm cable TV splitter. a TV and a FM tuner.
Being a “non profit” or educational organization gives you the advantage of bartering from a position where you may actually be doing the Cable Company a favor come tax time.
If your College does its own cable. Your reach won’t be outside of the college.
Might be worth looking in to.
Total posts : 45366That sounds interesting, but it sounds like it involves students
going out of their way to get a cable splitter and to put it
into their tuner (how do you put a coax into an fm tuner?)
regardless, we stream, for free, to all the dorms now via
both the internet and the intranet and the main reason we’d
like to broadcast over the air is the 1# reason students on
campus dont tune in is because “its too much of a hassle”.
so, asking them to modify their stereos to get our station
alone is probally not going to work. Thanks for the imput though.Also, 350 is just what im guessing i can talk them into allocating
for this project. if the rangemaster is truly going to be better
than the sstran then i will try to talk them into paying for that
instead.
Total posts : 45366[quote=markdavis]
1# reason students on
campus dont tune in is because “its too much of a hassle”.SNIP!
Also, 350 is just what im guessing i can talk them into allocating
for this project. if the rangemaster is truly going to be better
than the sstran then i will try to talk them into paying for that
instead. [/quote]From what I’ve read and the technical “specs”. Rangemaster is better on paper. Since I’ve never had the cash to afford one. YET! All I can say is I will own one someday. Right now I’m using the SSTRAN and I’m very satisfied with it’s performance for the price.
Good luck to you guys and for what it my opinion may be worth. I believe, from what little commercial radio experience I have, the reason why most college students don’t tune to AM is because there’s nothing there that they are interested in. When you change that by bringing your programming to the air. Your “lazy listeners” won’t be “hassled” and will seek you out.
Keep it fun!
Total posts : 45366Hi all,
The fact that the Rangemaster is “certified” needs to be discussed. The reports of substantial range may well be grounded in truth, but to my understanding there are two things to consider.
First, FCC certification means the device was found compliant with the FCC part 15 rules under defined and disclosed laboratory conditions. It appears to me that this means the input power was less than 100 mW. and the out of band signals were less than the rules specify. I have searched and have not found the laboratory test conditions for this unit.
Second, the Rangemaster web site illustrates the installation of this unit using a long ground wire in apparent variance from the FCC rules regarding antenna, transmission line, and **edit correction** ground length requirements. This may account for the claimed long range of this unit since the ground lead is an intentional radiator.
The device is certified but I ask under what lab conditions and is it certified when installed with the prescribed grounding system as shown on the manufacturer’s website? Certification does not absolve the user of responsibility for the use of the device.
I would welcome comments from Rangemaster or other knowledgeable persons regarding this.
Neil
Total posts : 45366Hello all,
We get this question almost daily, we address it at length on our website at http://www.am1000rangemaster.com/groundlead.html
Total posts : 45366[quote=Hamilton]… we address it at length on our website at http://www.am1000rangemaster.com/groundlead.html [/quote]
Here are two statements from the paper linked in the quote above:
[i]1. To me the Part 15 law is clear enough, 3 meters for the antenna and ground LEAD. That clearly means to me that the ground lead is the connection from the transmitting circuit to ground.[/i]
[i]2. This is similar to how we recommend our systems be setup for a rooftop installation in that a massive wire is run from the dirt to the transmitter on the roof, we call the massive wire “Ground”. So “Ground” extends to the tip of the massive wire from the “dirt’ “Ground”.[/i]
Physics shows that the upper tip of a “massive wire” leading from a dirt “Ground” as you describe does not [b]at all[/b] behave as a ground at radio frequencies.
In fact, grounded shunt-fed vertical structures sometimes themselves are used as radiators in commercial AM broadcasting. The bottom of such a radiator is buried in the earth, and electrically bonded to a ground system of 120 buried radials each 1/4-wave long.
Once this shunt-fed vertical structure rises any height above the earth it begins to function efficiently as a radiator. The same will be true of the “massive ground wire” you describe, whether it is enclosed in a “grounded” conduit or not (the conduit will radiate, also).
The electrical function of the ground LEAD you are describing does not end at its connecting point to the “massive ground wire.” The entire conducting path (ground lead plus ground wire) will not have the r-f characteristics of a real earth ground at radio frequencies until that path enters the earth. Until then, BOTH of them radiate, and in many cases, will radiate more field strength than the 3-meter “antenna,” itself.
Keith, I hope you will research this topic further. Part 15 users refer to your website for guidance, and no doubt you want it to be technically accurate, and not based on supposition.
//
Total posts : 45366Hello Keith (user name Hamilton…hope that is you),
Thanks for your reply and the link in response to my previous post.
I still have some questions that you perhaps can answer. Was your transmitter certified compliant with part 15.219 and not part 15.209? If this is the case, 15.219 appears to address only the final input power and the spurious emissions (plus radiator lengths which I will not repeat here) and can be done without an antenna and ground. Is this true? Was your unit tested for part 15.209 compliance?
Were any field strength measurements done for the FCC certification of your unit under the installation conditions mentioned in your link?
Since the responsibility for compliance in operation rests with the user, I think the user should know what certification conditions and restrictions apply before they blindly assume certification assures acceptable operation.
Your response will be appreciated,
Neil
Total posts : 45366Yes our unit was certified under 15.219, the FCC was aware that our unit exceeded 15.209 limits (as many transmitters do under the 100mw, 3 meter limitation), the field strength readings were in the lab report. The lab gives detailed measurements on the intentional frequency level on a calibrated test range and the first 10 harmonics.
The reason for certification is so the user (and an inspecting FCC agent) can be comfortable knowing that the transmitter complys with FCC rules, certification requirements are available on the fcc.gov website.
On another subject, the antenna ground issue, I would like to point out to folks that I seem to get singled out for recommending that our customers ground the antenna circuit for lightning protection, when as far as I know, every other certified Part 15 AM transmitter manufacturer out there does their antenna the same way! For general safety and the quality of our unit we never considered not including lightning protection and for the lightning protection to work the antenna circuit must be properly grounded, same is true with all the other certified transmitters out there.
- You must be logged in to reply to this topic.
