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Ultimate Part 15 AM Installation

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Humor Jokes

So, was the fence grounded?

Carl Blare

I guess so ... I dunno. You'l

I guess so ... I dunno. You'l have to call in to the program and ask ... that is, if you understand chicken ...

I think they should get a new station call letter ID ... KLUX :D

All the best, Ken N. http://fhtinyradio.com/   ken@fhtinyradio.com KF7PLC

Chickens and Part 15 Radio

How does the chicken get the Part 15
signal to get across the road?

He drags a Collins R-390A with an extension
cord attached onto the side of the road.
(This is one strong chicken.)
He plugs the extension cord into an outside
AC outlet on a nearby house. He attaches
a Quantum QX Loop and tunes in the
Part 15 station on the R-390A. It's S3.

Chickens aren't good at making transmitter
antenna loading coils.

Bruce, MICRO1690/1700

P.S. Ken and Rich, thank you very very
much for the test to speech info. I haven't
tried it yet. But, I will very soon!

NOISE AND STATIC RADIO

The Philosophical Mind

Thinking of how chickens are always attracted to roads, it is significant the chicken never follows the road to see where it goes. Instead, it crosses the road until it's over on the opposite side. I would say it imagines there are chicks over there, in the sense of girl chickens.

Girl chickens are swayed by portable radios tuned to a nearby part 15 station.

Egg breakfast, tomorrow.

Carl Blare

Carl, You're Making Me Laugh Again!

I liked the other chicken stories, too.
Bruce, MICRO1690/1700

NOISE AND STATIC RADIO

AMT-5000 installation

First, I was pointed to this thread from one on the ALPB.  I know it's a few years old but I believe I have read the entire thread before posting. Also I am going to rely on the old adage that the only stupiud question is the one un-asked, so please cut me a break if possible. My background - I am a degreed electrical engineer who received his degree 45 years ago but have worked very little in that field. Instead I've been an optical network engineer, later telcom executive, much more familiar with lasers, optical link budgets, fiber characterization (Polarization mode dispersion, chromatic dispersion, optical return loss, etc.). I can say that I was building elecronic kits and other circuits since I was about 10-12, off and on, in my younger years. I still have my working KnightKit VOM I built in 8th grade which was 50 years ago, and for a couple years I was involved in evaluating various wireless solutions such as wireless DOCSIS channel extensions and strand mounted WIFI access points for my employer. So that is a little of my background, but designing, building, operating a Part 15 broadcast station is all new to me. I now have a working SSTRAN AMT-5000. Just running it un-modified from my 2nd floor workshop I've been getting a decent range of about 1500-1800ft. I should mention that my home is about 200ft above street level which I'm sure must help. In the northern direction, which is the direction most of my potential audience resides, I have line of site visibility to the next town which is about 14 miles as the crow flies. No I don't expect my signal to ever reach that far, just trying to describe the lay of the land. Currently, for testing purposes, and I know I must change this to become compliant, I have a 102" whip antenna mounted on a 25ft telescopic fiberglass mast on my 2nd floor deck, fed from the transmitter via 50ft of coax. I am getting no better range with this setup than with the original one with everything inside. I am told this is due to the losses caused by the 50ft of coax. Makes sense to me and my plan is to house the transmitter on the antenna and reduce the transmission line from 50 ft to about 6 inches.That should help tremendously, right? NOW, as to grounding. Currently I have a AWG#12 stranded copper ground run from the xmtrs ground terminal to an 8 ft ground rod that also grounds my home backup generator. It's about 30 ft long. 

GOING FORWARD, I know I should create a system of ground radials.  I have a bunch of AWG#8 solid copper I can use for this. I have the property but not just directly under where the current antenna is located. I am thinking of just daisy chaining a new 8ft ground rod off the existing ground rod about 20 ft away, and then laying about a bunch of 20 ft. radials around the new 8ft ground rod. My property continues to slope upward here so they would not be horizontal on the ground. However the angle they would be at would also be more aimed in the direction of the vast majority of my potential listeners. I figured I would lay them out on the ground and hold them in place with 8" landscape staples so the landscaper would not accidentally hit them with his mower. So far, this would keep the transmitter and antenna mounted on my 2nd floor deck. Does this seem appropriate?  If better, I could move the transmitter and antenna to a ground mount right above the ground radials, although of course I would then have to fabricate extended cables to feed both audio signal and power to the transmitter at the new locations and the antenna would not be as elevated.However I COULD move everything up the hill farther and still have a ground mounted install that is just as elevated as if it was mounted on my 2nd floor deck and 25ft. mast. So far now, I am talking about strictly a 102" whip for the antenna.  I should mention that I ALSO own an ISOTRON 200B broadcast antenna that I also might try, but my intention was always to get some kind of performance baseline before I introduced the ISOTRON 200B. The ISOTRON 200B does also seem to use a base loaded coil. All of your advice, comments, criticisms, suggestions, etc., are most welcome.

Jim

Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.

Gounding

The trick you're going to run into, is that to be legal, an AM Part 15 installation can have a TOTAL COMBINED LENGTH of antenna, feedline, and ground lead, not to exceed three meters. Basically, ten feet. 

So if you're going to ground your transmitter it will, for all practical purposes need to be ground mounted over your radials.  If you're running an elevated transmitter, you won't be grounding it (legally).  So if you have a three foot antenna, and three feet of feed line, you've got just enough to get your transmitter a bit more than 3 feet off the ground. 

Basically, add the length of your antenna, the length of your antenna feedline, and the length of your ground lead from the transmitter to the ground attachment, be it a ground rod, water pipe, etc.  If it all adds up to under 10 feet you're good to go. If it adds up to more than that, you're not legal. 

It's the one fact of Part 15 AM that makes it a real puzzle to come up with what works best for you and meets the rules.  Your 30' ground and 50' feedline are not legal. 

Hate to be the one to tell you that, but I guess I got here first this morning

TIB

Part 15 AM Installations

A few added comments ...

The loading coil for a Part 15 AM transmitter system is needed/used to offset the capacitive reactance of the ~ 3-meter monopole antenna.  Otherwise the SWR of the antenna system is so high that almost all of the transmitter power arriving at the base of the monopole is reflected back to the transmitter, and dissipated as heat in its output circuits.

Using a 50-ft length of 50 Ω coaxial cable between the antenna output connector of a Part 15 AM transmitter and the base of a 3-m monopole makes it more difficult to resonate the antenna system using a loading coil included in the transmitter.  It would reduce the r-f bandwidth of the antenna system -- making such adjustment more difficult, and less stable.  Also the length of that coax cable (or "transmission line") must be included in the 3-meter length limit shown in FCC §15.219(b).

The length of conductors used between the transmitter chassis and the point where those conductors connect to buried conductors such as ground rods or buried radials has a great affect on system performance.

This can be seen in the graphic below, for the conditions shown there.

A sensitive AM receive system located in an area of low r-f noise and no co-channel interference might need an arriving field intensity of 100 µV/m or better for reasonably useful reception.

I'm amazed you are getting

I'm amazed you are getting out at all, there is some serious loss for part 15 AM with coax that long and a ground that long is near useless for the transmitter. Above all the setup is exceptionally illegal, you'd be better off ground mounting the thing.

Losses

1.  The attenuation of RG-58/U, 1/4" OD coaxial cable operating in the AM broadcast band is less than 0.3 dB per 50 feet (1:1 SWR).

This means that about 93% of the power applied at one end of that length of cable is available at the other end of that length.

That amount of power loss is negligible in this application.

2.  The graphic included in my previous post here shows that the longer the "ground" conductor between the transmitter chassis and the earth, the greater the field intensity that system will produce (other things equal).

This is the reason why that length is included in FCC §15.219(b).

 

 

i'd like to see

a transmitter challenge involving the various 50 ohm capable transmitters feeding a ground mounted isotron 200 over a suitable ground plane and see how it compares to a rangemaster and procaster under the same scenario. i want to see how the filed strength compares between the setups. my own rudimentary tests on the Isotron using a Chez TS-100 were dismal in performance compared to my procaster but i don't have the area to lay out 32 x 20ft ground radials to get any kind of good performance.

Part 15 Engineer

Hindsight is 2020

I'm not a democrat or a republican, i'm a common sense moderate progressive

 

please don't forget to register and vote

Thanks for the information

Thanks for the information Rich, would a long lead effect the tuning at all?

Tuning

... would a long lead effect the tuning at all?

Yes, it would.  The radiation resistance of the antenna system increases as the length of the "ground" conductor increases -- see the green curve and green vertical scale on my chart.

Radiation resistance is a contributor to the load impedance match that must be optimized in order for that system to radiate the highest possible fields for that configuration.

Coax Transformer

Jim, as Rich stated above the loss in 50 feet of coax at AM frequencies is negligible but there is another characteristic of coax which could be affecting the range.  A length of coax acts as an impedance transformer so the Z presented by the antenna is not what is seen at the transmitter end of the coax, the exception being when there is a perfect match to the antenna. 

In the extreme, a 1/4 wave length of coax open on the end will present a short at the other end, conversely, a shorted 1/4 wave coax will present an open at the other end.

The best change I made which greatly affected my range was to place 12 10 foot radials at the base of my transmitter/antenna system.  A ground rod makes many folks feel good re lightning but does little as a RF ground for an antenna.

Neil

 EDIT TO ADD  Here's a writeup plus pictures of my experiments with radials which will give you some idea of what I did.

http://www.part15.us/forum/part15-forums/antennas/antenna-field-test-res...

Since the test was a success I permanently installed the system at another location in my back yard with the radials buried and the wine bottle replaced with an isulator.

COMPLIANCE

Tim,

Thanks. I am well aware of all that.Thouight I was clear that this was just a temporary setup to get familiar with the system.  I apologize if I wasn't more clear on these points.I already have an external enclosure ready to house the transmitter and mount it to the base of the antenna, be it the 102" whip or the ISOTRON 200b, OR YET SOMETHING ELSE.  With the current 1700 ft. range I am currently getting with my experimental setup, my signal won't even cross my property line, which is one reason this temp setup is just that, temporary and unacceptable. I already do have 2 other masts (these are aluminum) on my deck which are already grounded. One mast (10 foot) supports my Davis Vantage Pro 2 weather station, the other, a 20 ft aluminum mast supports my GODAR-USA DXR-1000 antenna which is used for DX SW and AM-BCB reception. So I can reach either of these grounds with a very short ground lead, should I choose to do that.My other option,and probably the best one, is to install the radial system in the ground in my  back lot and ground mount the antenna.right on it. Since the hill is high up, the antenna will still be as high as if I mounted it on the 25' mast on my 2nd floor deck.

Jim

Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.

Grounds

... I already do have 2 other masts (these are aluminum) on my deck which are already grounded. ... So I can reach either of these grounds with a very short ground lead, should I choose to do that. ...

Jim:  Unfortunately the top of such masts will not provide an r-f ground even if the bottom of those masts is attached to a very good r-f ground buried in the earth.

So no matter how short is the "ground lead" conductor from the elevated transmitter to the top of that mast, the entire, exposed height of the mast will carry r-f current, and become part of the radiating antenna system of that transmitter.

Below is an analysis of this situation.

The mast is part of ground lead...

Additionally, from a legal standpoint, the FCC will count your mast as part of the ground lead. 

If you put your transmitter on top of a metal mast, and connect the ground lug on the transmitter to the top of that mast, your ground lead is now the 6" wire from the transmitter to the mast, added to the length of the mast.  So if you have a 30 foot metal mast, you now have a 30' 6" ground lead.  There have been NOUO from the FCC issued to several who have had mast mounted transmitters, and those who have had them mounted to other metal structures.  All the metal between the transmitter and the Earth is counted as ground lead. 

I have an elevated installation, however my transmitter is mounted to a 3 foot piece of PVC pipe which is mounted to the side of my wood house. I have no ground lead connected. It is certainly not idea, but fortunately I live in the boonies where there are only two other solid AM stations, and very little noise floor, so I can be heard over a mile during the day.  I can't really do a ground mounted transmitter -- it would be under several feet of snow 6 months out of the year!

TIB

FCC will count your mast as part of the ground lead.

"If you put your transmitter on top of a metal mast, and connect the ground lug on the transmitter to the top of that mast, your ground lead is now the 6" wire from the transmitter to the mast, added to the length of the mast...There have been NOUO from the FCC issued to several who have had mast mounted transmitters, and those who have had them mounted to other metal structures.  All the metal between the transmitter and the Earth is counted as ground lead."

Which absolutely sucks, with additional expletives added. The RangeMaster, I believe was designed to broadcast exactly in that fashion! Then old Keith got the notice...big dent in that idea! Oh well, the thing still is a blowtorch...

Right. ANYTHING to kill the chance of a decent signal at 100mw! For 40+ years I broadcast at 100,000 watts on a full service FM. I was on 5 and 10 thousand watt AMs as well. For the FCC to squash my little 100mw because of the (hyphenated expletive) ground lead? Hell, why bother? 

And everyone wonders why there are so many Pirates...it's this kind of rule! Don't break the Law, but I will damn well complain about it! Does anyone agree with me, or do I need to go elsewhere?

Doug

The Easy Difficult Solution

To reach your target area with a part 15 AM system you must locate the transmitter and antenna at the target location.

Getting the audio to the transmitter could be done in any number of ways, which would be an entire second scientific project we can talk about.

Carl Blare

From Keith Himself

I got this from HB. Under Psrt 15 Transmitters, there is a thread discussing the RangeMaster at ground level and above groun d level. I am claiming FAIR USE here quoting him:

[Edit Notification   Part15.us administrators have received notice from Bill DeFelice at HobbyBroadcaster that the copied post is copyrighted and that if the post is not removed a complaint will be filed under the DCMA  with the site hosting provider, therefore it is gone but here's the link to the original post:

https://www.hobbybroadcaster.net/community/index.php?topic=728.msg32842#msg32842

end edit]

Basically your ground wire cannot be an antenna. Use engineering practices to prevent it from radiating; An interesting topic is that it seems to be OK with the FCC to use the Earth of the electric system for this connection. Note that the million or so talking house transmitters that are out there connect directly to the building earth ground, I assume this was approved in their certification?"

I am glad I ran across that post. I feel a bit differently now. I hope this develops discussion. It sure shines a light on some important issues...

Doug

Rich:

Your turn.

Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.  

Grounding

Tim,

No problem I am well aware of the rules. When I set  up my permanent installation the antenna will be ground mounted above the radials and still be just as elevated as if I had it on one of my 25 ft towers on my second floor deck, as my back lot is a good 40-50 ft higher than the ground level of the house.

Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.

Let's Keep This Proper, Shall We?

Dugger, to keep things civil, "Fair Use" does not apply here. Attorney David L Amkraut, in an article for TheBookDesigner.com, says Fair Use consists of "limited and reasonable uses of copyright–protected work." Large copy-and-paste reprints from a source identified by the murky acronym "HB" does not qualify.

To keep things respectful and legal, the proper thing would have been to ask the author for permission to use excerpts, with links to the original piece. Luckily, actions like yours only cause friction and raw feelings between Part 15 groups on the Web. Elsewhere in real life, it can be cause for copyright infringement and assessed damages.

I've been in publishing for 28 years and can tell you that merely claiming "Fair Use!" does not make it so. Seek out the "Four Factor" test to see why. But more importantly, I'm sure you would not like seeing entire blocks of your own work appropriated without proper credit.

Darsen the III

THE DMV

Installations (RE: Reply 83)

... When I set  up my permanent installation the antenna will be ground mounted above the radials and still be just as elevated as if I had it on one of my 25 ft towers ...

Jim:  Just to note that other things equal, the groundwave fields produced by "Part 15 AM" systems greatly depend on the r-f power they radiate -- not from their elevation above local terrain/AMSL.

An elevated tx+whip system using a 25-ft mast/conductor to connect to an r-f ground most likely will produce higher fields at the same given distances than a transmit+whip system installed at the same elevation AMSL, but using a much shorter conductor to connect to an equivalent r-f ground.

The reason for that is due to the added radiation from the 25-ft conductor from the tx to earth r-f ground, for the system installed at the higher elevation AMSL.

My Failed Attempt.

Darsen, you said:

"...the proper thing would have been to ask the author for permission to use excerpts, with links to the original piece."

Good grief. The man posts in a public forum. I gotta ask permission to quote him? Not a chance. I just will be more selective. Too much of this friction and raw feelings between Part 15 groups on the Web. 

Oops! Now I'm quoting YOU! I'm done.

Doug

One More Thing

Mods:

Feel free to delete post #81 if there has been some "violation".

Doug

Jim you might want to invest

Jim you might want to invest in a rangemaster or procaster before you spend too much trying to get this system to work the way you want it. 

I've been there and spent 3 or 4x what the Rangemaster goes for by trying to get the lower cost transmitters to get the same range. In the long run it might be cheaper to save up for the higher priced gear and get the coverage you want. I was dissapointed for several years until I bit the bullet and got a used Rangemaster.

Not saying good coverage isn't doable with your gear, in fact its very possible, just be prepared for a headache and some choice cursing as you work on it. (Which arguably can actually be very fun and educational)

That's not the rule

Basically your ground wire cannot be an antenna.

This is incorrect. The rule is the combined length of your antenna, feedline and ground lead cannot exceed 3 meters.  The FCC doesn't care much about the rest. 

And when you want to know about what may or may not be included in a certification, look it up on the FCC web site!

TIB

Rangemaster

Mighty,

Thanks very much for the suggestion.  While I am happy with the SSTRAN AMT-5000, I am now also looking at the Procaster and the Rangemaster.

Jim

Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.

Quoting vs. fair use

Seems to me that is someone makes a public post in a public forum, and then someone replies and quotes the original post, there is no issue since the original poster has been fairly attributed.

Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.

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