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The RF Workbench / 11 meter / 27 MHz Beacon Project
« on: April 21, 2017, 0421 UTC »
Hello all,
I'm about to move out of my current residence but my soon-to-be-former roommate (and landlord) has agreed to let me keep some radio equipment here. Included in this list of equipment is an 11 meter dipole antenna installed in the attic of the house [roughly 35-40 feet above ground level]. I was thinking about purchasing one of the RadioShack pager transmitters models 17-6020 and 17-6023 (which are crystal controlled and put out 4-7 watts carrier power), re-crystalling it, dropping the power down, and wiring it for non-stop transmit as a beacon of sorts. These on-site pager transmitters operate on CB channel 23 - 27.255 MHz. [parts list: http://support.radioshack.com/support_phones/doc52/52327.htm]
Another option would be to acquire an old R/C transmitter (which, of course, would drastically reduce both my required power to run the transmitter and the actual transmitted power itself).
I have a bag of 26-27 MHz crystals for the following frequencies:
26.540 MHz
26.670 MHz
26.740 MHz
26.995 MHz [RC Brown/Channel 3A]
27.090 MHz
27.125 MHz [Channel 14]
27.140 MHz [I have 3 of these!]
27.195 MHz [RC Green/Channel 19A]
27.220 MHz [Right between channels 21 and 22]
27.225 MHz [Channel 22]
27.255 MHz [Channel 23] - also the default frequency for RadioShack pager transmitters
27.270 MHz [Right between channels 26 and 27]
27.320 MHz [Right between channels 31 and 32]
27.545 MHz
27.675 MHz
27.725 MHz
27.775 MHz
If you take the in-band [26.965-27.405] frequencies out of the question, that leaves 26.540 MHz, 26.670 MHz, 26.740 MHz, 27.545 MHz, 27.675 MHz, 27.725 MHz and 27.775 MHz. 27.090 MHz is too close to 27.095 MHz (another R/C channel), as is the case with 27.140 MHz (too close to 27.145 MHz, not only heavily used for R/C purposes but also wireless computer mice, etc). 27.225 MHz is a heavily used frequency locally and I fear using it (or 27.220 MHz) would result in somebody DFing me pretty quickly.
In a perfect world, I'd have somebody build me a dozen or so transmitters that I could place throughout the city I live in various places using various frequencies and various output power levels/antennas.
eBay has various other frequencies (usually sold in pairs for transmit/receive, the "receive crystal" being tuned to 455 kHz below the indicate frequency - so a crystal set for 26.995 MHz contains a 26.995 MHz crystal and a 26.540 MHz crystal).
Anybody have any thoughts on this? The 4-watt RadioShack pager transmitters are available for cheap-ish on eBay and can apparently easily be re-crystalled. Dropping the power down to 1-2 watts or should be easy enough as well. While a secondhand R/C transmitter would certainly be cheaper, it wouldn't give me nearly as much TX power.
I'm about to move out of my current residence but my soon-to-be-former roommate (and landlord) has agreed to let me keep some radio equipment here. Included in this list of equipment is an 11 meter dipole antenna installed in the attic of the house [roughly 35-40 feet above ground level]. I was thinking about purchasing one of the RadioShack pager transmitters models 17-6020 and 17-6023 (which are crystal controlled and put out 4-7 watts carrier power), re-crystalling it, dropping the power down, and wiring it for non-stop transmit as a beacon of sorts. These on-site pager transmitters operate on CB channel 23 - 27.255 MHz. [parts list: http://support.radioshack.com/support_phones/doc52/52327.htm]
Another option would be to acquire an old R/C transmitter (which, of course, would drastically reduce both my required power to run the transmitter and the actual transmitted power itself).
I have a bag of 26-27 MHz crystals for the following frequencies:
26.540 MHz
26.670 MHz
26.740 MHz
26.995 MHz [RC Brown/Channel 3A]
27.090 MHz
27.125 MHz [Channel 14]
27.140 MHz [I have 3 of these!]
27.195 MHz [RC Green/Channel 19A]
27.220 MHz [Right between channels 21 and 22]
27.225 MHz [Channel 22]
27.255 MHz [Channel 23] - also the default frequency for RadioShack pager transmitters
27.270 MHz [Right between channels 26 and 27]
27.320 MHz [Right between channels 31 and 32]
27.545 MHz
27.675 MHz
27.725 MHz
27.775 MHz
If you take the in-band [26.965-27.405] frequencies out of the question, that leaves 26.540 MHz, 26.670 MHz, 26.740 MHz, 27.545 MHz, 27.675 MHz, 27.725 MHz and 27.775 MHz. 27.090 MHz is too close to 27.095 MHz (another R/C channel), as is the case with 27.140 MHz (too close to 27.145 MHz, not only heavily used for R/C purposes but also wireless computer mice, etc). 27.225 MHz is a heavily used frequency locally and I fear using it (or 27.220 MHz) would result in somebody DFing me pretty quickly.
In a perfect world, I'd have somebody build me a dozen or so transmitters that I could place throughout the city I live in various places using various frequencies and various output power levels/antennas.
eBay has various other frequencies (usually sold in pairs for transmit/receive, the "receive crystal" being tuned to 455 kHz below the indicate frequency - so a crystal set for 26.995 MHz contains a 26.995 MHz crystal and a 26.540 MHz crystal).
Anybody have any thoughts on this? The 4-watt RadioShack pager transmitters are available for cheap-ish on eBay and can apparently easily be re-crystalled. Dropping the power down to 1-2 watts or should be easy enough as well. While a secondhand R/C transmitter would certainly be cheaper, it wouldn't give me nearly as much TX power.
