http://www.classeradio.org/index.html

About 12 years ago I helped install a Harris 2.5KW (I think) AM transmitter for use on 1350.  I remember PWM.  Can you recall what Class of operation it was/is? The output was solid state.

Regards, John

By far the friendliest and most generous Part 15 Rule is this one

§ 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 quantities
of five 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 § 15.5 apply to this equipment.

The only member I know who has designed and built his own part 15 transmitter is Neil, Radio8Z, unless you count the committee of ALPB Members who designed the Big Talker shortwave transmitter.

Hey everyone

I recently bought  the I AM Outdoor unit. The new one with the white box and the junction box. It came with 75 feet of cat 5 cable. When I got it home I turned it on inside just to make sure everything worked and it sounded great! There was no hum in it and sound was good for that transmitter. I then started putting my transmitter at the location I wanted on the side of the house. I ended up using most of that Cat 5 cable,I am wondering if this could be the cause of the hum? It is stretched the majority of the way. Also I havent hooked it to a good ground yet. This may also be the cause? I do have a wire running from the little lug on the bottom of the box to a nearby faucet right now, until I can get some time to work with it. The noise just frustates me. I am just wanting some other answers to make sure I am not missing something. Any suggestions or help. Thanks everyone. I do not like hum and I would think with it being grounded in the box it should not have this issue??

I'd like some experienced opinions on protecting e.g. a newly constructed AMT 5000 and it's connections, mounted outdoors at the bottom of a custom antenna system, from storms and condensation. What say?

I know it's normalized for 50 ohms but.....

Also 300 KHZ to 54 MHZ

http://www.ohr.com/wattmeter.htm

Today - I am going to test my Procaster, Hamilton AM1000, and Talking House.  My goal is to compare apples to apples to apples. I want to hear the best signal I can from these fcc certified transmitters.  I want to use them in a way that complies with the FCC rules, and without any of the controversial stuff (Talking House ATU is not being used, I am not using ground radials per se, no long grounding, and no synchronizing hamiltons).

My test is purely practical.  No test gear other than the stock radio in my 2013 jeep compass.  

I have the dirtiest airwaves of anywhere I think, given that I do live in an area saturated with the standard AM Broadcast, a huge concentration of Amatuer radio enthusiasts, the companies that are testing various wireless technologies (I am in Sunnyvale, CA).  The cleanest LEGAL band I can find is 1630 AM - 1710 would be cleaner, but I do not know how to attenuate 20db below blah.. so I am not gonna try it.

The testing ground is simple:

MAST: I dug a 3 foot by 10 inch hole in the ground, dropped a 4 foot pole into it, and filled it with quickcrete.

MOUNTING: The transmitters will be mounted to the resulting 1 foot pole, hanging out about 7 inches over the bare ground.

ANTENNA: The antennas are the one that comes with the Procaster, a 102" stainless whip for the rangemaster, and an almost 10 foot 3/4" copper pipe for the Talking House.

GROUND: Just outside of the quickcrete blob is an 8 foot grounding rod.  I will use the shortest bit of 18awg copper wire I can to attach the grounding to the rod.

AUDIO: Behringer 2222 mixer using a computer and Airtime as the music source, mic and cd players will be present, but we will see if I have time to play with all that mess.  

PROCESSING: I do not have a ton of processing gear, so I am still trying to figure out what Ill use.  If I do not have adequite gear for the hamilton and talking house, ill decouple the onboard processing from the procaster to make it as fair as i can.

I'll post results as they happen.

I'm somewhat intriqued by the topic of "long ground leads" and I know it's been tossed about here like crazy.  But from a legal FCC standpoint, what exacgtly defines a "ground lead".

Clearly, in an elevated installation a wire from the ground of the transmitter down to the Earth is generally considered a long ground lead, and apparently not recently accepted.  So, lets say it's an elevated install in the center of a flat roof, and the roof is covered with a hundred radials coming from that ground lead.  At what point do they become radials and stop being ground leads?

If you do a ground installation and have a hundred radials laying on top of the ground, all connecting at the center to the ground lug on the trasmitter, are they ground leads or ground radials? Are they only radials when buried and are ground leads when on top of the ground? How about elevated radials?

Can the concept of radials even be considered in an elevated installation?

Just tossing this out for comment, no need to get into big hissy fits about what's what.  In the end I believe it's up to the interpretation of the inspector.

Tim in Bovey

So, now that IRC has been on the air for 10 months, and I pretty well know where it reaches, using my car radio, a small portable transistor set, and a boom box, and I've taken actual calibrated field strength readings with the same FIM I use in my "real" radio work, I thought I'd take a moment and map out just how far I'm reaching "as the crow flies" from my antenna.  You can't really measure by driving away unless you can go in a straight line a measured distance!

So I used Google Maps and marked the spots where over the past months I ALWAYS get 100% full, loud signal, that is comparable to the two commercial broadcasters in my area -- the station I work for 5,000 watts about 8 miles from me, and a 10,000 watt station about 30 miles away.  I can sit in the car in these spots and punch between those stations and mine and the volume and signal quality is about equal (actually I'm a bit clearer than the 10,000 watt station 30 miles away).

I have strong, reliable, static free sound at 7100 feet, about 1.35 miles from the antenna.  this holds in virtually all directions.  Remember, I'm in a VERY small town with very minimal interference.  This gives me a circular coverage area of 2.7 miles diameter. 

I can be heard quite a ways past that but the quality varies and I wouldn't expect anyone to listen to it with that much static in the background. At the 7100 foot line that's solid signal in the car, on the $5 portable transistor radio and the cheap boom box. Plus amazing sound on the GE Super Radio. 

This is on the Procaster, using only the built in processing, taking audio straight out of my studio iMac right into the trasmitter. 

I'm quite happy with that. 

Tim in Bovey

Based on Tim in Bovey's 7100 feet, this is what I came up with.  Very impressive, especially being able to cover an entire town. Not knowing his actual location I threw a dart in the middle of town.

I again find myself being temped by this unit:

http://www.radioassociates.com/

Although I have access to a Belar mod monitor, it's not exactly frequency agile and I'd need the matching RF amp, etc to really get much use out of it in part 15 work.

It appears that with the Part 15 module this would not only work, but when used with the IF of a radio could also be used to check modulation of virtually any station, part 15 or full power, which of course makes it useful in my commercial radio as well as part 15 work. it looks to be about a $400 investment with the unit and the Part 15 module. Much cheaper than a more traditional unit.

Anyone seen this in real life? Comments from other engineering types?

Tim in Bovey

Howdy, been a low power bradcaster for going on 2 years on july 3rd. I run "free radio for the free thinker" 92.9 in Haddon Heights, NJ.

Awesome to find a forum dedicated to this form of radio. Can't wait for the great discussion!

73! (yes I am also a SW'ler and dx'er of all the various bands of radio)

I'm putting this post up, but I might

not get back to a computer for a few days.

This transmitter has quite a history - it was

working great a few months ago.  I love carrier

current - it is so interesting.

This is a 3 vacuum tube transmitter from 1971.

A beautiful piece of gear.  All tubes are 6AL11 compactrons.

So anyhow - there is plenty of RF out.  About 6.5 watts.

Just as it should be.  Operating frequency is 1020 kHz -

not a good channel -but clear here during the day.After warm up and audio is fed in -the audio is very

distorted on the radio.  Only a low level can be fed in

- about 10 percent modulation.

Here's the interesting part.

The signal is receivable on 1020 (the desired channel)

and also about 1070 and 970 kHz.  So something is taking

off at about 50 kHz.The crystal is smaller than what is

specified.  (It was all I could get.)  I would like to think that

the crystal is failing and getting unstable.  I like this idea because

another crystal could come along someday.  (It's a fundamental,

which is why getting one is so hard.)

This transmitter has a funny histiry of problems and fixes.

It is somewhat jury rigged.

I love the silly thing.

Anyhow, I guess you guys can ponder this, and if so, I

will respond with more info when I can.

Best Wishes,

bruce (sorry about typos gotta go)

Is the RF ground in the C. Crane FM Transmitter-2 separate/filtered from the power or audio grounds?

I have a C. Crane FM Transmitter-2. I want to put it in a weather proof box up high outside. It would be easiest if I could run a single cable to it. I am thinking either using a coax cable with audio/DC combined or a balanced audio cable with an arrangement similar to phantom power. Either way, I end up tying the power ground and the audio ground together and they get tied to the shield of the cable.

I have thought about the RF ground a bit. If the short antenna on the FM Transmitter-2 wants something to push against, RF could end up on the shield of the combined audio/power cable. I could either suppress that with chokes as close to the FM Transmitter-2 as possible, or I could see if some length of coax between the board I used to split the audio from the power and the chokes gives me more range.

In the C. Crane manual for the FM Transmitter-2 they suggest putting the transmitter over a metal ground plane to make it work better. That makes me think they are counting on capacitive RF coupling between the FM Transmitter-2 and the metal surface. That got me thinking about how I could really work to get the shield of the coax to act as the other half of a dipole for the FM Transmitter-2.

I would make a circuit board the size of the FM Transmitter-2. One side would be a ground plane. The other side would have the capacitors and inductors to split audio from power on the single cable up, as well as a jack for the audio to the FM Transmitter-2 and a cable to run power to the DC jack on the FM Transmitter-2. The ground plane on the circuit board would be tied to the shield on the cable feeding the FM Transmitter-2, it would be tied to the DC ground, and the audio ground. The goal would be to get as much capacitive coupling between the board and the FM Transmitter-2. Then I would put chokes on the cable at the distance from the board that gives me the best signal. As a first guess I would think around a ¼ wavelength of the frequency I am transmitting on.

Then if I got complaints or an inspection, I could pull a unmodified FM Transmitter-2 from the box; all I would have to do is unplug the audio cable from the board, and the power cable from the FM Transmitter-2.

Part of figuring all that out depends on what the FM Transmitter-2 does with RF and ground.

OK troops, I'm about to embark on my own product test.  I have ordered the AMM-SD1 Series AM Modulation Monitor from http://www.radioassociates.com/ .   I will be prepared to test it compared to a freshly calibrated and certified Belar Mod Monitor that I use at the transmitter of the commercial AM I work for.  I will be able to test/compare in three ways -- direct readings from the mod monitor output on a new 5,000 watt transmitter, readings from part 15 transmitter received off a loop sampling antenna near the transmitting antenna, and modulation tests from various stations including my Part 15 utilizing the IF of a receiver. 

this is just one of those setups I couldn't resist trying out and since I'm in a position to test and compare with known professional equipment I can see how it stacks up.  Results may take a while.  The off-air/part 15/receiver pickup is backordered for about two weeks.

Of course I have many other applications for this if it works as advertised with reasonable accuracy. 

I'll keep you posted. 

Tim in Bovey

During the night something got knocked to the floor in the dark by a clumsy radio announcer, but I was too sleepy to find out what had fallen until this morning.

Oh no! The precious TECSUN PL-310 had dropped 2.5-feet to a hard wood floor!

Close physical inspection found no dents or scratches, so we flipped it on and heard rock music at 101.5 mHz.

Oh no! Someone was on my hard-found frequency, maybe a new LPFM or translator. Luckily a generic voice came on identifying the station as KPLA.

A quick search found KPLA, 41kW in Columbia, Missouri, 120-miles away!

Wow, the TECSUN had found a most interesting way of telling me that it was all right and my frequency was still available for local use.

101.5 mHz is used by a Wholehouse 2.0 to send audio editing projects 6-feet to a C.Crane Plus Radio.

Part 15 FM "Voice of the Microcosm."

Is carrier current AM possible under part 15?

I've seen posts about using hardware to do it, but never any mention of enforcement.

AspiSys sells their ASMAX series which I may have to buy if someone else doesn't offer an alternative. I currently use Radio Systems' I.AM.Radio transmitter and ATU. I like both of them and will continue to use the ATU as long as possible. Although I'm still looking at AspiSys' DRMAX series of DRM transmitters, I'm having great difficulty communicating with the company since they don't sell their DRM transmitter openly. Personally, I'd like other alternatives for a Part 15 DRM or AM stereo transmitter anyway.

Maybe the builder of the SSTRAN can add AM stereo capability to his transmitters?

Radio Scientists:

I have a question that some of you may have some experience with. I have a short horizontal antenna in my attic which I have loaded with a variable loading coil.

This antenna is feed by a RG 59 coax from the basement. The antenna tunes very well and I get very good range. The problem is the amount of hum I get on the radios in the house when listening.

The hum is also present but to a lesser degree some distance from the house, but it is still there if you turn up the volume, more than what I would like to see.

I have tried all sorts of polarizations of the long wire antenna including moving it to different parts of the attic and running it along the rafters up and down (semi vertical) and horizontal along the part where the rafters join together at the peak of the roof. I also tried running the antenna wire up and down in from the top of the roof to the ceiling joists and back up  to get a vertical pattern. I was trying to get the least amount of coupling between the house wiring and the antenna

My loading coil at the coax end is grounded in the attic. I have also tried different ground routes which all connect to a copper pipe in the attic which connect to the cold water main pipe. I checked it out with an ohm meter to make sure the pipe is connected to a solid ground.

I use the standard Talking House power supply. I have also tried to isolate the hum by using a 12 volt battery and that made no difference so it’s not a power supply issue.

I have tried ground loop isolators on all sources and even made a dummy grounding plug which I used on the input of the TH5 Aux input, to make sure the hum was not originating from any attached gear.

Using the grounding plug on the input of the TH 5 AUX input made no difference the hum was still there on dead carrier.

I went up in the attic and tried all sorts of antenna variations and configurations.

Nothing really made a significant difference.

To test further I turned the transmitter on and used a 12 volt battery to power it, so I didn’t need to rely on AC power to power the transmitter and had no connection to the house wiring. I didn’t apply any audio to the transmitter because I wanted to test hum levels.

I then set up a battery powered portable radio near the circuit breaker box where I was going to turn breakers on and off. With the radio on and tuned to the TH5, I took one breaker at a time and switched off, I went through the entire panel till I got to the last breaker. As I went thought the process sometimes turning a breaker off made the hum less some time more.

The next test I did was pulled the main disconnect on the breaker box to turn everything off at once… ok finally no trace of  hum in the carrier, so with all power disconnected to my house and no AC flowing in the wiring  there was no hum, just a perfect carrier on the radio.  I had to pull the main disconnect to get a clean carrier, with all breakers off, I still got some hum but pulling the main switch, all hum was gone.

Personally I feel since there is a lot of electrical wiring in the attic that the RF is mixing with the magnetic fields of the 110 volt power lines.

If this is true and anyone can explain to me how this happens I would appreciate it! 

I think the only real answer is to this is an outside antenna mounted a distance from the house. I do have an outside antenna now on one of my AM transmitters and that is much more hum free, that transmitter I run off batteries when I use it but wanted this other transmitter for general purpose use, like I said everything is good but the darn hum.

My knees are worn out from moving around on the rafters, I tried every possible antenna configuration. The test with the breaker box confirms my beliefs that on this one there is not much of a way out but turn off all the power in my house I suppose if I want a pure signal!  Bit of overkill but at least it was nice to hear that absolutely clear carrier. Any help anyone can come up with I would appreciate it!

Sad Radio Joe