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I need some input on this:
I need some input on this:
First if you keep up with wpdy 95.7 fm youll know we are part 15 and have a hard to please landlord. Antennas are permitted here but with few options as to how we can mount antennas in our small yard .
(currently our fm is transmitting on a indoor antenna in a mobile home)I want to broadcast wpdy on am also, my question is this.
Can a suitable signal be transmitted thru leaky coax that is tacked along the wall close to the ceiling? If so what would be my expected coverage and how much power can i use on leaky coax and stay legal.If i understand part 15 rules, 100mw to 30 watts maybe transmitted thru leaky coax on a.m…… is this correct or is 100mw the limit?
I maybe thinking of the campus radio setup wich might not apply to wpdy’s situation.
It’s been awhile since i worked in radio and that was as a dj not an engineer.Thanks
Total posts : 45366From your descripton of your situation, I see no advantage to using leaky coax over just a simple wire with a loading coil. Without refreshing my memory about this by reading the rules, I recall the rules for leaky coax are based on field strength and not power. You might search part 15 rules about this but usually the field strength limits, in addition to being difficult to measure, result in less range than the 15.219 provisions regarding power, antenna, ground, and transmission line lengths.
The use of carrier current is intended for campus systems and are also field strength limited. The advantages for a campus which you will not enjoy is that the field strength is specified at the boundary of the campus allowing a pretty strong signal on campus.
Here, I use a SSTRAN feeding a coil loaded antenna tuned to resonance mounted to the ceiling of my basement horizontally. My home is primarily stucco and the hardware cloth and foil faced sheathing underneath form a pretty good Faraday cage, yet I still can hear a strong signal on a cheap portable out to about 150 feet or so (1000 feet on a car radio). Your home may be a better shield than mine so it is not possible to predict what you will experience. A tiny wire extended out one of your windows may perform well.
Keep in mind that many common yard items (patio umbrella poles, poles for bird feeders, clothes lines, etc.) can be used as antennas. I don’t know what leeway you have but maybe you can get some ideas from this. Also, search this site for stealth antennas. There have been many posts here on this topic.
Neil
Total posts : 45366as far as i know there is no reason why he could use carrier current. it would just need to be 15uV/m @ 47,515/(frequency in khz) = meters from any power lines and from the building where the transmitter is.
Thank You,
Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.orgModerator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree
Total posts : 45366I think radio8z has your answer. A coil loaded antenna will produce the highest output. This alone would not be enough except that you can create a pseudo carrier-current system by NOT grounding your transmitter. As long as there are no RF chokes in the path to your power feed, a significant amount of RF will feed through to the building wiring. This may be enough to enable others in your building to receive a strong signal. This is true for the SSTRAN transmitter because the wall adapter is just an AC transformer, which has a low pass-though impedance for RF. Other types of power supplies may not have a low impedance for RF.
Leaky coax is only good for a small range along the length of the coax. You would need to run leaky coax all through your building for it to be effective.
PhilB
Total posts : 45366Ok,
I am in a mobile home park, the trailor would act as a sort of faraday cage, (after all its thin walled and metal skinned). I would have to go with an indoor antenna since i have not really even brought this up with the management of the park.I have spoken with maintainance and they are giving me the sense that even tho the rules say we can have antennas here, they dont seem to enthusiastic about helping me install one.
So i believe at this point it would be best to install yet another indoor antenna using the coil design with *sigh* dare i say no ground system? It pains me to say this but even though i seem to have a good potential audience here, (100 mobile homes i think) moving to a better location may solve all my broadcast troubles.
But i am willing to try out the loaded coil antenna if anyone has any plans or suggestions, i would be willing to see about adding a part 15 a.m. station to Rock 95.
Although im not too excited about the price of a rangemaster. Im on a fixed income here and this is after all a hobby, besides…. we have a baby on the way ! lol So naturally she will come first.
Thanks in advance for any help in the future.
Rock 95 Seven
Total posts : 45366Rock 95 Seven,
I recall that you are in a mobile home park and that is why I suggested some ideas about a stealth antenna. Unless you actually try it, I don’t think it is going to be possible to predict your range with any indoor antenna. My indoor here gives about 150 feet with a cheap portable radio. I can provide details if you are interested. The loading coil design is probably not going to be the “magic bullet” you seek but it may be worth a try.
Do I read between the lines correctly that you may not be able to do any external antenna work yourself? I need to make a few assumptions here. One is that your power in your home is of the three wire variety. That’s your ground; the screw on the cover plates. The second is that there must be a way to extend a 3 meter wire out a window to get your signal out of the “cage”.
Congratulations on your baby and keep your family your first priority.
Neil
Total posts : 45366Fun stuff, and congratulations on the new family member.
A couple of things to consider:
Carrier Current (through the park’s wiring accessed via your unit) might give some results. In addidtion to what PhilB noted about the Carrier Current effect of the power supply, you could try wiring the antenna output that way too.
Probably should look at the Neutral Loading Option illustration and also the first few links in our PDF Reading Room, which get into Carrier Current in depth.
The Low Power Radio Communications (L.P.R.C.) Tech Page has several items on Carrier Current as well, including Carrier Current Part 1 and Carrier Current Part 2 and Carrier Current Techniques
You would still use a loading coil, but you would be loading the portion of the wiring that ran between you and the next step down transformer from the utility company. That would give you the physical presence of an outdoor antenna without installing one. If there are no transformers between you and the other units (not too likely, unfortunately) then you would have a park wide Carrier Current system.
Two obvious cautions – watch out for the hazards of working around mains power and remember that everyone else is in a Faraday Cage too, and will have a difficult time tuning AM in their boxes.
One way to mitigate the latter might be to make and give away instructions for the Easy to build AM receiving antenna for your radio
Experimental broadcasting for a better tomorrow!
Total posts : 45366Neil,
I apolagize if i offended you in anyway.
I could do the antenna work myself or rather with help from maintainance since they seem to have their own way of doing things.I asked awhile back why the park rules limit antennas to extend only three feet above a trailor, their reply was to cut down interference from ham/cb radio’s. they said there have been cb’ers here before that caused tvi and the antenna height limitation was for cutting down on the tvi.
I have been a cb’er for almost 20 years and know that even a station that was 100% legal (4 watts a.m.) could cause tvi and can be worse if the antenna was at a low elevation. I even explained that to them but i feel like it was shrugged off as a silly notion.Tvi is not my concern here so ill get off that subject.
My fm seems to do just fine despite the fact that the whip antenna that came with the fm25b is mounted on the transmitter and the transmitter is inside the home. We cover the park pretty well although we tend to get a picket fence effect when driving thru the park due to the trailors being so close together and the metal reflects our signal in many directions. Neil it dawned on me that we have cable tv wired to our home and the holes drilled in the floor are a bit wider than the rg-59 coax. I wonder if i would be over stepping the 3 meter rule if i could ground to the chassis of the trailor by running a wire thru the hole the catv used. I am using the screw for the 3-wire as a ground for the f.m. even tho i see no difference to the fm i know it would make a big difference to the a.m.It is funny how well our f.m. is doing broadcasting out of a metal can.
As for using a wire out the window, that maybe the only way to get my signal out of the home and into the street. Of course it would have to be insulated since the metal windows would ground the antenna.Time will tell . Thank you for the input.
Rock 95 Seven
Total posts : 45366Rock95,
You did not offend me in any way and I regret that something I posted might have given that impression.
SCWIS has posted a lot of food for thought. You might want to check his links.
This is going to take some experimentation and you should try the easy stuff first.
Good luck,
Neil
Total posts : 45366I’m not sure whether to post here or start a new thread…
But I hear you talk about coil base-loading a wire antenna for the SSTRAN in a basement above.
I just built my first SSTRAN…or even first radio kit for that matter.Is this something that can be used with the regular wire antenna?
Or does this take a special antenna to use with it?Also – I was looking at the external antenna on the SSTRAN site.
I don’t have many places to really put up an external antenna…but one place is behind my garage.
However, there isn’t hardly any room to run the wires for the ground plane (not sure if that’s right term).
Only a few feet wide by mabye 10 or 15 feet long for the run. Also a big tree nearby.Any thoughts???
PS – I’m getting about 75 feet with my transmitter.
The transmitter is on the 1st floor of my house with the wire antenna on the floor by the wall.
I tried taking the wire out the window and up to the 2nd floor with no real increase in range.
I also tried grounding the black wire to my computer case without any real difference there either.
I would like a little stronger signal in my garage. (or covering the rest of the city for that matter – haha)I’m thinking about trying FM next. (Ramsey 100B with external antenna??? Legal??? Range???)
May be easier antenna to install and keep if it is compliant.Brian
Total posts : 45366Hi Brian,
Welcome to this board. I know you from another board so I have a bit of background information about what you have so far.
The 75 foot range you report is a bit shy of what I would expect with a stock SSTRAN with a wire antenna. This could well be due to the receiver that you are using for your tests. Have you tried a test drive using a car receiver? You should be getting several hundred feet.
You mentioned that you extended your antenna out the window. The exterior materials of your house could have an effect (aluminum siding, stucco). The reason that your range did not change when you grounded the tx. to your PC is because it was already grounded through the audio cables.
The “talk about a basement antenna” is probably in reference to a few post where I have described my setup. Mine is far from ideal, but it works for what I want to do which is cover my yard. Even though it is in my basement mounted horizontally I get a good signal on a cheap receiver out to about 150 to 200 feet, and on a car radio out to about 1000 feet.
There are many others here who have devised very clever antenna systems. A search of this site may give you some ideas, and better yet, others may add their experiences to this thread.
It is my opinion that any FM system that exceeds about a 200 foot range is asking for trouble. You might consider an inexpensive FM tx. such as the Ramsey FM-25B or FM-30 unless the bells and whistles of the higher end models appeal to you. Others are welcome to comment on this.
The next quantum leap for your station in terms of range will probably be to use a coil loaded antenna and, if possible, a ground radial system.
Keep experimenting and keep asking questions here. The more you do this, the more you will learn, and the more range you will achieve. The best you will probably do with a car radio is a range of 1/2 to 1 mile. Table top radio range will be a lot less.
Neil
Total posts : 45366One of my friends got interested in FM transmitters from my setup. He doesn’t have much technical background, and I had to explain I couldn’t build him a kit. I suggested he try one of the “whole house FM” transmitters since they’re FCC approved and not real expensive.
So He bought one, decided after running it for a week or so he wanted to mount it outdoors. So he put it in a tupperware sandwich container, drilled holes for the antenna and cables, a little silicone sealer to keep water out of the holes and some lithium grease on the antenna so water wouldn’t seep into the telescoping sections. No tweaks, no extra gear. Fastened it to a wooden window frame on an attic window.
He gets a little better range than I do, and doesn’t have to keep adjusting the tank circuit to compensate for drift. Mine is mono, he gets a bit better range with stereo. Not hugely better, but maybe 50 ft or so more than I do (or the “cheap portable” he used to test that is better quality than mine. LOL). Testing with his car radio, about 3 blocks before it becomes unlistenable, and there’s some noticeable fade and hiss starting at about 2 blocks.
But it’s no muss, no fuss, no bother, no soldering, no adjusting. It’s an FCC approved unit and I doubt he’ll run into any trouble. He says it sounds good through the house and yard and a friend who lives next door can listen with no problems.
Me, I like tinkering, soldering, calculations, taking meter readings and etc. But if I was doing it all over again and wanted to be sensible? I’d definitely consider buying one and slapping it into a tupperware container as an option.
My range to “good car radio” is about a block less, but that’s most likely because there are a lot of trees, and houses are closer together here. Interestingly, I found the “car radio” range is more when starting at the house and driving away, and a bit less when coming towards the house from several blocks out. Not sure if it’s more due to the metal body of the vehicle giving the antenna a bit of a gain pattern or because the reciever “holds on” to a signal better once it’s gotten it. But I found it kind of entertaining as a concept that it makes a noticeable difference.
Daniel
Total posts : 45366Daniel,
You wrote:
I found the “car radio” range is more when starting at the house and driving away, and a bit less when coming towards the house from several blocks out. Not sure if it’s more due to the metal body of the vehicle giving the antenna a bit of a gain pattern or because the reciever “holds on” to a signal better once it’s gotten it.
I think you are correct on both counts. It is well known to amateur radio operators that on VHF the favored direction is toward the long dimension of the roof metal from the antenna. If the receiver has a frequency agile LO locked by a phase locked loop, the “capture range” is narrower than the “tracking range” in terms of bandwidth which would explain why a receiver may not lock onto a weak signal which it can track once locked.
Neil
Total posts : 45366————————— quote from Neil
The 75 foot range you report is a bit shy of what I would expect with a stock SSTRAN with a wire antenna. This could well be due to the receiver that you are using for your tests. Have you tried a test drive using a car receiver? You should be getting several hundred feet.
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Answer…
The radio I use in the garage is pretty good….but my vehicle is getting about the same range. It starts getting weak at 75 foot. In fact, I think the receiver in my garage is picking up better than my 99 Tahoe.—————————-quote from Neil
You mentioned that you extended your antenna out the window. The exterior materials of your house could have an effect (aluminum siding, stucco). The reason that your range did not change when you grounded the tx. to your PC is because it was already grounded through the audio cables.
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Answer…
I have aluminum siding.
I’m really torn on the base loaded antenna…how important are the ground plane wires. I have VERY LITTLE room behind the garage for the wires since they go on the ground and it’s in a walking path a few feet wide.Not sure what to do next or which way to turn….but the FM 25 and FM 30 are looking pretty good…I can use my portable mp3 player to pick up fm only.
I”m trying to get my e-mail account working here…somehow my new password didn’t take correctly. I can post…but not check e-mail.
BD
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