Practicality of 600-800 watt amplifier use in SMALL RESIDENTIAL TRACT??
Hi All. Having got my great-grandson interested in our hobby I have been inclined to help him along with obtaining equipment a bit sooner than his pocket-book might allow. "Spoil 'em if ya' can" is not always bad! He's a great young man. I digress - sorry.
He lives in a RESIDENTIAL NEIGHBORHOOD in the ever popular TRACT HOME configuration. Lots are separated laterally by perhaps 25 or 30 feet at most then the next home begins. The BACK YARDS are approximately 100 feet deep where they then abut only a retaining wall and ANOTHER LOT begins; CLOSE PROXIMITY indeed!
My blessing and curse: Since I have always lived in some form of 'wide open space' I have never had to contend with RFI except to my own non-amateur radio related equipment. I was blessed to be able to run the legal limit and never really worry. HOWEVER, this limits my knowledge of the problems encountered in TRACT NEIGHBORHOODS when any amount of power is utilized.
IF I help the young man out and present him with an amplifier in perhaps the 600 to 800 watt range ...... will I perhaps be creating a great number of PROBLEMS for him DUE TO HIS CLOSE PROXIMITY TO OTHERS in this TRACT HOME location?
This is one time where I wish I had a bit more knowledge from first-hand experience in "operating while keeping neighbors happy" - but, I have virtually none and do not want to create issues that might disrupt or diminish my great-grandsons liking for his new-found hobby.
Thank You in advance guys and gals,
Don -- WD5JOY (still avoiding the 'SK' addendum)
Last edited by WD5JOY; 05-26-2012 at 12:35 PM.
Reason: My gawd-awful spelling!
My lot is 72-feet wide and 130-feet deep and the house sits basically in the middle of the lot. Houses on each side are approximately 20-feet away and my across the alley neighbor's house is less than 75-feet away. At present, I run up to 1400 watts output on 80 through 10-meters (I haven't completed my amplifier that will do a full 1500 watts output), 850 watts output on 160-meters (would run more but have to get a better high voltage transformer). I run lower power on 50 MHz, 144 MHz, 222 MHz, and 432 MHz.
In the 40-years that I have lived in this house, I have had 1 true RFI complaint. That was a couple of weeks after I moved in and I was running a Heath SB-200 linear. A neighbor, 2-houses "down" the alley, was getting RFI in his stereo. Putting 0.001 mfd capacitors from the speaker terminals to the chassis on his amplifier fixed the problem. My next door neighbor, to the west, is a computer consultant and often has 10, or more, computers running at the same time. He has 1 amplified speaker that I "get into" from time to time. I have offered him ferrite cores, capacitors, etc. to eliminate any possible interference. But, he told me that on the few occasions that I do get into the speaker he just disconnects it.
Everyone's station and situation is going to be different. You really can't be sure what RFI problems you may encounter until you give it a try.
Amplifiers are nice to have but decent antennas are way more important.
"Oh what a tangled web we weave when first we practice to receive."
-Otto Watt Sept. 5 1925
You do have to have a RF exposure survey done. The neighbors are in the Uncontrol Environment catagory. Doing a quick calculation of the limits at the 80 meter band and the 10 meter band shows that at 3.5Mhz you're okay. At 29.7Mhz you're not, but this calculation is for continous transmission and full carrier. Using the duty cycle you can reduce this distance to find it as an exceptable distance from the antenna.
The possibilities of RFI certainly are present and that would actually depend on the equipment the neighbors have. They are just as likely to cause interference to the amateur station as you would be to them.
I lived in an apartment and operated at 600W and never had a single complaint. I would worry about RFI as it comes up. There are folks out there that are so sensitive about the presence of an antenna that they will start blaming everything that is having problems on the amateur station. To weed those out what you would do is put the antenna up and tune it, then do nothing for a couple of weeks. Just have the antenna disconnected from the rig. You will soon find the persons that have a problem with an antenna and think you shouldn't have one. They will produce a lot of silly complaints about what the antenna is doing to them, their family, their dog or cat and anything else they can blame on the antenna. You will know who to ignore and you may want to go out of your way and them about your little truth seeking mission.
BTW the backyard is large enough to accommodate a vertical with plenty of radials. Just an idea for the future.
Hope this helps
Last edited by KO6WB; 05-26-2012 at 05:02 PM.
Back when I was on HF all the time, I used an AL-1200 in a similar setting. I had *zero* problems, and I didn't have to do anything special with grounds, bonds either. I used wire antennas and never once had any trouble with the neighbors or their electronic "toys". So, give it a try - if it doesn't work out, simply quit using the amplifier.
And what is this RF exposure survey? Never did one and don't care. Sounds like some big-gubment overregulation to me...
Also, K7MH said:
"Amplifiers are nice to have but decent antennas are way more important."
That's very true, but good luck with that when you're on a very small lot - especially if you want to go below 40M. These antenna companies out there are making a killing selling "compromise" antennas, many of which are nothing more than large, cumbersome dummy loads. Sometimes you need something to get yourself past the compromise that is your antenna...
If I could type I wouldn't have to edit so much.
RF Exposure is just a bunch of HOOEY!!!! No one is going to be MICROWAVED by someone transmitting a signal on HF. I have been around high power RF all my life and am not "INJURED" by it. My brain isn't BAKED!!! HOOEY!!!
BUt what U DO hafta worry about is miserable cordless phones and stereo systems. THERE you can get some RF into the lines and get Audio Rectification where they will hear U on the device and complain. Of course, just some well-placed ferrite chokes will fix it all up, but they might not want to allow U to do that. THEIR answer for it is for U to GET OFF THE AIR!!!!!
So I don't like close living quarters. There is always atleast one CRANK somewhere that will whine and whimper that you are JAMMING his listenning to "AFTERNOON DELIGHT" or "MUSCRAT LOVE"
You can do an exposure calculation at the following URL:
That method utilizes the approved FCC / OSHA calculation procedures. You are required, by law, to make these calculations if your power output exceeds the following levels:
in MHz Peak Envelope Power in Watts
1.800 - 2.000 500
3.500 - 4.000 500
7.000 - 7.300 500
10.100 - 10.150 425
14.000 - 14.350 225
18.068 - 18.168 125
21.000 - 21.450 100
24.890 - 24.990 75
28.000 - 29.700 50
50.000 - 54.000 50
144.000 - 148.000 50
222.000 - 225.000 50
420.000 - 450.000 70
902.000 - 928.000 150
1240.000 - 1300.000 200
2300.000 and higher 250
There are "fudge factors" that have to be applied to the transmitted power when doing the calculations. The first is the actual accepted effective power of a particular emission. For SSB this factor is 0.2 (20-percent). For CW this factor is 0.4 (40-percent). For AM, FM, data, etc., this factor is 1.0 (100-percent). As such, if the peak output power of a linear amplifier is 800 watts, for SSB the power entered into the equation would be 160 watts. For CW it would be 320 watts. For the other modes it would be 800 watts.
However, that is for a continuous transmission. The area that has to be considered is divided between "controlled" and "uncontrolled". Controlled means, basically, your own home since you have control of the transmitter. Uncontrolled means areas outside of your home over which others have no control. For the controlled area a total time frame of 6-minutes is considered and for uncontrolled areas the time frame is 30-minutes. You have to take into consideration the amount of time spent actually transmitting during these periods. For most amateur operation, that time is usually less than 50-percent of the time while operating, often much less. As such, the effective power level has to be reduced by at least 50-percent. In the case of the 800-watt peak transmitter that would make SSB as 80-watts, CW as 160-watts, and the rest 400 watts.
Next, you have to figure the distance above ground of the antenna in determining the exposure. For example, a yagi 50 feet above ground already starts with a distance of 50-feet. The distance to the uncontrolled area is the square root of the following: Distance above ground squared plus the distance from a point directly under the antenna squared. For example, if the antenna is 50 feet above ground and the neighbor's house is 50 feet away, the effective distance would be the square root of ((50^2)+(50^2)) = square root (2500 + 2500) = 70.7 feet.
Plugging the linear's 800-watts peak SSB output at 28 MHz into the site gives a result of 5.086 feet as being the "safe" distance from the antenna for the controlled area and 11.3107 feet as being the "safe" distance for the uncontrolled area. As such, anything outside of that distance is considered perfectly safe.
The truth be known, the "safe" exposure levels allowed by the FCC /OSHA are at least one-tenth of the actual level that might even cause any harm and are probably even less.
What I have done is to calculate these levels for every band that I operate and for every mode that I operate at the highest power levels that I can transmit and for every antenna. I then printed out the results and put them in a loose-leaf binder. That way, if anyone happens to question the exposure levels (including the FCC or OHSA) I can immediately show that person that I am in compliance with the regulations. Depending on how many modes, bands, and antennas you have, the entire process takes less than 15-minutes and becomes a permanent record.
The requirements to perform these calculations are contained in 47 CFR Part 97 Sections 97.13(c)(1) and 97.13(c)(2).
Yesterday was concrete pour day for my new/first tower. When the cement mixer driver queried, "So you're one of those guys who interfere with my TV?!", my response was, "Yes -- proudly". In the near future, I expect to be causing even more QRM!
Originally Posted by WA6MHZ
The last amateur exam I took was in 1990. I know alot has changed since then, including the introduction of this RF exposure stuff. I do believe it's a bunch of nanny goverment garbage, I mean, if RF exposure was so bad all my elmers wouldn't have lived into their 80s...some lived past 90!
I never did an exposure evaluation, but I would like to know if the FCC ever actually "pinched" anyone for lack of one...?
If I could type I wouldn't have to edit so much.