looking for band for temporary/periodic part 15 operation...

What is the maximum range you need in that mix of cities?

Obviously, the best frequencies woudl be the ones that have the highest FS limits, but it also depends on what else might be sharing your frequency. I don't know anything about the 13.553-13.567MHz band. Maybe it's cluttered with other potentially interfering transmissions?

The 902-928MHz and 2400-2483.5MHz bands seem good. Those relatively inexpensive "STL" modules operate in these bands. With a couple of directional antennas you should get exceptional range and signal quality and relative immunity from cordless phones and whatever else operate on these bands. I guess it wouldn't be too cool to have a private phone conversation bleed into a church service! If you can find an STL that operates spread spectrum, then you can pretty much rule out embarassing interference.

Speaking of cordless phones, I wonder if anyone has ever done some serious experimenting with adapting them to directional antennas. I bet the range could easily increase to several miles. Just a thought.

The maximum range I need is about 114 miles or so. (btw, I forgot to add Crestline, CA, to the list of transmit cities, but that would only be once or maybe twice a year, twice a day for a few days. Same thing for Tulare, CA. Mileage before these parentheses do not count Crestline or Tulare.) No matter where I am receiving or transmitting, the signal basically does not need to go south of Chula Vista, east of Alpine, Julian, or Banning, north of San Bernardino or Burbank, or west of Santa Monica.

Also, something I forgot to specify in the original message. Chances are I would not be there to turn the transmitter on and hook it up, so someone else would need to do it. I would basically want to set it up so that all they have to do is plug the mic into the TX, plug the TX into the wall, if necessary extend the antenna or prop it up against the wall, and turn it on. (would it be better if I set up 2 TX's - one to be an STL from inside the building to outside, with the 2nd one being the main TX to my receiving location?)

Also, how much power output is safe / unsafe for people that might be within a few inches or a few feet of the transmitter at various frequencies?
One thing I noticed is that below 9 kHz is not allocated. I would think I could get by on something that would fit in that band. Since it's not practical to put a half-wave vertical radiator at 9kHz inside a building, would a 10kW transmitter into a 2.5 meter antenna get me enough range (because ground losses are so slow to happen), or would it be too unsafe (even for the very low frequency - is it true that higher F/S's are safer at lower frequencies for near-field human exposure?) for people to be close by? Or are there any other radio options I should look at?

I wish I had something more positive to inject, but here goes anyway...

I would say that your best chance would be at 2.4 GHz, or maybe 5 GHz, with high-gain directional antennas (probably dishes) on each end. However:

1. 114 miles is a REAL stretch, and I would say possible but not probable. Some hams in Virginia have gone around 70 miles with wireless LAN gear, but see below.

2. The gear you will find is probably wireless LAN stuff. This has a limit of maybe 12-15 miles, not because of radio range, but because you exceed the TCP/IP ACKnowledge window, so the ends just keep telling each other "I didn't hear you say you got that." That shoots doing VoIP. There is at least one access point card available where you can change the delay time, but that's not trivial.

As far as 9 kHz, I don't know where you will get gear, plus I think you would have a big RF exposure problem in the immediate area. About the lowest frequency in standard use is 60 kHz, which is used by WWVB, the US NIST time station that sets those "atomic" clocks.

13.560 MHz is used for RFID tag interrogation. Unless you have a shipping facility or other user close to your receive site, this could be a possibility with 5 kHz SSB, but I still think you'd need a directional receive antenna (Yagi beam, phased array, etc.).

Finally, you say that this may have to be set up by non-techs. Considering that you are almost trying to squeeze blood from a turnip, you may be asking more than any Part 15 setup could deliver.

Hi everyone,

It seems to me that considering the relatively short times this setup is needed that the most practical way to achieve it is to use a cell phone.

Most church services would be during offpeak hours (if you plan has unlimited off-peak minutes), most include long distance so that's not an issue. And conference calling to multiple numbers could be pre-programmed into the phone (even calling to a landline if desired). There are several adapters on the market to allow a cell phone to accept an audio feed. Nokia phones are easily adapted as we found feeding a 600 ohm line out from a mixer directly into a modified headset plug worked great for live events and the audio quality was quite high. We've found the quality to be best with CDMA digital phones.

The advantage of using the cell phone is that it is easy to use with simple directions and would be reliable as far as getting your audio where you want it.

I just don't think any unlicensed operation can give you 114 miles reliably. With am you would have atmospheric and interference noise and I'm sure just about every frequency where you want to do this is already busy. You would have no protection to your signal.

There are some great microwave products on the market, but I'm sure you would require multiple links which involves finding locations for relays and unless you use digital transmitters/receiver you're going to have some loss of quality with each step. I've seen some higher power 2.4 ghz transmitters online (2 watts) but they are not digital (they use FM) and again have no protection from other users in the band. And even with the higher power you'll still need multiple links.

There are a few problems with me using a cell phone to do it.
1. It costs me 10c/minute on T-Mobile's prepaid service. (and I wouldn't want to tie up someone else's phone)
2. the audio quality isn't good enough. There are too many compression artifacts, and I'm not confident in its ability to pass frequencies above 4.5kHz or below 27 Hz (the minimum range I want).

What about doing something like...
put wireless FM mic on podium, set for open frequency (or use another band if necessary - signal only needs to get outside building maybe 100 or 200 feet clearly) (this would be like a STL)
plug "STL" receiver into audio input of main transmitter outside building, set up antenna. (not sure if directional antennas can be legally used to focus signal so you have maybe more than the F/S limit in one direction (so long as you have less in other directions and it averages out to being at or under the legal F/S limit), and turn the TX and STL on.
at my end, use a fairly sensitive tuner and high-gain highly directional antenna.
Could something like that possibly work? I'm considering using the 13 mHz band, but should I look at 175kHz, 27MHz, or 49MHz instead?

Also, what are the FCC's rules about using frequencies from 300GHz to above 10^20 Hz?

Hi!

I still think you'd be surprised with the frequency response of a CDMA cellular service. There are several available, some are offering TDMA which isn't going to work as well for you. GSM is gaining some popularity and call quality wise is better than TDMA.

The problem you have is that I don't see any way you can use part 15 equipment and accomplish your range goals. Not only do you have power limitations, but finding an open frequency in your area would be difficult.

The 13 Mhz band is so narrow that it can't carry too many channels, especially if you want good audio frequency response.

The entire 49 Mhz part 15 band shares with cordless phones. 27 Mhz is right next to the CB band and is rather fickle about consistent range.

The 175 Khz frequency is part of what used to be know as the "forgotten band" as it had very little use and almost no equipment made for it. The best range I remember for it was about 25-40 miles during the day and that required building some special equipment for transmission and reception. At night it was almost pure chance with what range you'd have.

Above about 300GHz is infrared light.

There's an interesting chart of frequencies at

http://www.ntia.doc.gov/osmhome/allochrt.pdf

What's the range on 13 MHz like, if for example I use SSB AM with a 5kHz response? It's mostly voice, with some music in which the fundamentals shouldn't be above 4.25 kHz (theoretically high C on a piano is approx 4186.009 Hz, but I like to sample a little above that to account for stretch tuning on the piano (where to have the piano sound in tune with itself (because of string inharmonicity - btw I'm a piano tuner) you have to tune the high treble a little bit sharp of the mathematical theoretical pitches), and some pianos having the high treble tuned excessively sharp, like as much as maybe a note or something like that) or so. (the music is mostly vocals and piano, sometimes acoustic guitar.)

Also, what's the general guideline for exposure to high transmitter powers / RF fields at VLF and below (< 9kHz, which the FCC doesn't have allocated)? I understand groundwave losses are EXTREMELY slow at that frequency, and like I said above, I don't need CD-quality frequency response, but I DEFINITELY want up to at LEAST 4.25kHz (high C on a piano plus a little breathing room explained above) mono. (Stereo would be nice, but frequency response is more important so I'll give up stereo to get frequency response.) I understand there is no specific limitations down there, so I could probably use an antenna around the perimeter of the building or property. I was wondering how much TX power I'd need to have in order to have about a 10dB signal to noise ratio at the farthest normal receiving location I specified (of course this depends on the receiving antenna and radio, but the receiving antenna would probably be only tiny fractions of a wavelength long)?

As for the frequency response (of cell phones and others), I do NOT want any artifacts from having compressed the stream too much. On my prepaid cell phone it's ok for talking to someone for a few minutes, but is unacceptable for listening to something for a couple hours.

From Jon Smicks [u:f5e88fac21] http://home.att.net/~weatheradio/part15.htm [/size:f5e88fac21][/u:f5e88fac21]

13,554.41 (HIFER) "MP", London, ON. Operated by Mitch Powell, VE3OT. On air: June 8, 2001. This station was one participant in the first-ever HIFER QSO on June 15, the other end being Jonathan Jesse's "JJ" (13,557.5 kHz) in Plymouth, MA. That distance is over 540 miles! Mode used was QRSS; a random number (3) chosen by Mitch, and callsigns were exchanged. Update 07/18/01: Both this station and "RY" (13,555.37, see below) were involved in a 12 wpm CW QSO with 100% copy according to Mitch.

13,555.3 (HIFER) "GL", Austin, TX. Operated by KI5GL. Mode QRSS, 3-sec. dots. Operator will QSY higher and can operate higher CW speeds upon request. Power is 1.5 mW into a 1/2 wave Cushcraft R5 vertical mounted 20' AGL. This station was heard in Maryland on Aug. 28 by W3NF; the distance is 1,295 miles.

Two questions right now..

What was the bandwidth of those transmissions?

What's the rule of thumb for converting bandwidths and coverage areas? (for example if something is 1kHz wide and goes 1000 miles before it drops into the noise, how far would something that is 10kHz wide go)

As far as "squeezing blood out of a turnip" for 114-odd miles, just below the 21 meter band isn't a bad choice for QRP ops, really. Propagates best during the day and/or during summer for well over 114-odd miles, but in winter at night, not so much, but it may nonetheless do 114-odd miles handily, maybe. During daylight hours you can expect your signal to bounce off the ionosphere from here to timbucktoo and back. It's a utility band, not a ham band, so it sounds do-able.

As far as "squeezing blood out of a turnip" for 114-odd miles, just below the 21 meter band isn't a bad choice for QRP ops, really. Propagates best during the day and/or during summer for well over 114-odd miles, but in winter at night, not so much, but it may nonetheless do 114-odd miles handily, maybe. During daylight hours you can expect your signal to bounce off the ionosphere from here to timbucktoo and back. It's a utility band, not a ham band, so it sounds do-able.

That's kind-of what I was thinking about its usability, based on the field strength levels (15848uV/m @ 30 meters, as opposed to 10000uV/m at 3 meters for 27 MHz and lower for some other bands (except 900MHz & above)) permitted.
And, based on Ramsey's thing in their FM transmitter manual that field strength voltage drops off proportionately to distance, I calculated that if I had 15848uV/m at 30 meters, I'd have approx 2.6uV/m at 114 miles, which is probably a weak, but usable (for my purposes) signal.

How far would a usable 4.5kHz SSB AM signal go if its upper sideband went up to 9kHz, power output was 5kW, and the antenna was 1/16384 wavelength long? Also, at that low frequency, is that power level safe for near-field (within a few inches) human exposure?

And, about the 13.5MHz - where can I learn more about equipment used on that band?

That's kind-of what I was thinking about its usability, based on the field strength levels (15848uV/m @ 30 meters, as opposed to 10000uV/m at 3 meters for 27 MHz and lower for some other bands (except 900MHz & above)) permitted.

Here's another way to look at it: 10000uV/m at 3 meters for 27 MHz is pretty good by Part 15 rules, but have you ever heard of a 5 watt CB transmitter reliably going more than a few miles under normal conditions. 114 miles is way beyond reality. You might just barely hear the signal at 114 miles under freak conditions, but that's not what you are asking for.

15848uV/m @ 30 meters isn't significantly higher, so you still can't expect a miracle.

Look at http://www.radio-locator.com/ Many high power broadcast stations only go a hundred miles or so.

I think your best bet is to resort to landline telephone (or cellular) for the long runs like 114 miles. If you have some short runs, like 5 or 6 miles, look at the STL modules with directional antennas. Mix and match according to distance. Depending on your telephone service, you might just find telephone to be cheaper in the long run than investing in STL-type equipment that may be finicky and expensive.

I'm not in a position to answer a lot of the questions that were asked, unfortunately, but the chicken band has different propagation characteristics than the 20, 21 meter band. When conditions are right, one CAN pull in good DX on the chicken band. Reliably? No--depends on propagation condistions. So it is with 20 & 21 meters, but it's more reliable with the possible exception of winter nights. It's my understanding that the enterprise isn't intended for constant emissions under all conditions; with respect to propagational conditions alone, the lower end of the 13 MHz band remains a good choice. If the question on 4.5 kHz would have been about 4.5 MHz, I would have said that when paired with operations on the lower end of 13 MHz, all propagational bases would be covered--4.5 for winter/nights, 13 for summer/days.

About using telephone to do it - I'd be willing to shell out a little bit of $$ for the equipment to get started, but I don't want to pay for the airtime / linetime once it's in use. That's why I don't want to use telephone or internet to do it (besides I often wouldn't have internet access at the receiving location so I wouldn't be able to hear it live.)

Ok, so this may not be part 15, but does anyone know if there's any way I could get a permit from the FCC that would basically help me get the range I need? I don't need to use the AM BCB (although 520kHz or 1710kHz MIGHT be an option). If I could possibly get an FCC license/permit for this type of periodic non-broadcast (it's not intended for reception by the general public) operation, what would be a good frequency range to try for (for the combination of best reliable surface wave range, not too much transmitter power (so I don't blow a circuit breaker at the transmitting end or fry someone standing next to the antenna), and short antenna (which may possibly be an indoor vertical radiator whip antenna without a groundplane)? Also how much might I have to pay for the license?