Antenna for cordless phone

You seem to be obsessed with the legality of installing a little antenna that radiates less than 1 W . If the law hasn't change we are allowed to transmit using any frequency , provide the power is less than a certain value. If you interfere with any service and some one complains, you may be asked to change the operating conditions.

Don I repeat my last suggestion The best is probably a vertical whip like the one you show, designed to operating at your frequency. The standard impedance of an antennae designed to be connected to a cable have usually an operating impedance of 50 Ohms at that frequency. Make the cable (the one recommended by the antenna manufacturer) as short as possible and if practical move the main unit closer to the antenna. You may find a reasonable improvement just by moving the antenna out of the building Regards

John

Not obsessed. Just alerting the OP to federal law. :) If he chooses to break the law, those same laws provide for fines and arrest of the equipment (in rem arrest), and the FCC can also refer cases to the Justice Department for further prosecution. Monetary fines for something like this can range from a few thousand, to ten thousand dollars or more. See generally, FCC Rules 47CFR1.80 Those are the facts.

Now, does the FCC catch a lot of folks hacking illegal antennas into their cordless phones? No. But you might be suprised at just how many violations are issued each year by the FCC's Enforcement Division. I have personally been on a couple equipment witch hunts (for interference) with the Miami and Denver field agents. The outcomes are rarely pretty in the cases which I'm typically involved in (the high profile ones). The average homeowner can expect a Citation (no money fine) for a first offense, but things can get nasty if they're uncorporative, etc..., or if the Agent (for whatever reason) feels justified in pursing the matter more aggressively.

Plus, in my former career (a post you may have missed?) it should be painfully obvious why I recoil when I hear that people want to hack into their consumer electonics. You would not believe the headaches this can cause for licensed radio services!!

But to your facts, For most unlicened devices like cordless phone and the like, they'll be registered under Part-15 rules. (47CFR15) Those rules will provide field strength limits (not transmitter power output restrictions). Therefore, antennas matter greatly! The allowable field varies by frequency, according to a chart in FCC Rules part 15.209 Before leaving this topic, you should be aware that just because you might feel Part-15 devices are low power, that DOES NOT mean they are incapable of causing harmful interference. Far from it.

For example, did you know a typical CDMA or GSM cell phone (operating at its lower power output of ~ -50dBm) actually radiates LESS power than the maximum permissible under Part-15 Rules for unlicensed devices? In other words, something that's unlicensed (and lower power) actually puts out MORE power than your cell phone -- which is very much a licensed service (FCC Part 22, 24 or 27) And note also that Part-15 Low Power does not restrict operation in the Cellular / PCS bands. Think about that next time you drop a call. It may just be your neighbor hacked in an antenna on his cordless phone (or garage door opener, or blender, or TV or god knows what!)

This is one of hundreds of examples I could give to you. So yeah, you might say I'm "obsessed" -- but I am absolutely correct, and this history books are filled with examples of horrendous interference cause by well-intentioned folks just like the OP.!!

Specific to this exact situation, here is the precise rule the OP would be violating:

Sec. 15.203 Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device.

The use of a permanently attached antenna or of an antenna that uses a unique coupling to the intentional radiator shall be considered sufficient to comply with the provisions of this section. The manufacturer may design the unit so that a broken antenna can be replaced by the user, but the use of a standard antenna jack or electrical connector is prohibited. This requirement does not apply to carrier current devices or to devices operated under the provisions of Sec. 15.211, Sec. 15.213, Sec. 15.217, Sec. 15.219, or Sec. 15.221. Further, this requirement does not apply to intentional radiators that must be professionally installed, such as perimeter protection systems and some field disturbance sensors, or to other intentional radiators which, in accordance with Sec. 15.31(d), must be measured at the installation site. However, the installer shall be responsible for ensuring that the proper antenna is employed so that the limits in this part are not exceeded.

Enjoy.

-mpm

[attributions elided]

Understood. I believe you can get more *gain* from a directional antenna?

OK, ejicate me on antenna geometries.

What *physical* characteristics of an antenna correspond to "whatever" electrical characteristics?

E.g., what difference (?) do the little radial spikes make to the antenna's behavior? Why the little coil instead of just lengthening the antenna? etc. (sorry, my "pure EE" coursework is *so* far behind me that I have forgotten more of it than I ever *knew*!)

For example, the "dual band cell phone" antenna that I have looks similar to the one I referenced (URL) above. But, *without* the radial spokes and *with* a cylindrical "blob" up near the top of the whip.

(I assume the grey/aluminum stuff beneath the "spokes" is part of a mast assembly and not germane to the actual antenna's design?)

From what I've stumbled across, the "dual bands" are somewhere in the high 800's and again in the 1900MHz region. Is this governed solely by the physical geometry of the antenna? I.e., if I "snip a bit off", can something that works in the "high 800's" be coerced to perform adequately in the "low

900's" band? Or, are other magic incantations required?

(If push comes to shove, i can live *without* the added coverage area for my cordless phone -- or buy the *right* antenna. Instead, I am trying to learn something, here... E.g., I will eventually like to get rid of this and add broader area coverage for my wifi... learn now, do later!)

Yes. Match the output impedance of the source to the load.

*That* much I remember! :>

I can get damn near any cable I might need. The "dual band" antenna has a length of (where's my magnifying glass?) coax -- seems to be labeled "NFC 200 COAXIAL CABLE" but that is pure speculation as only the bottom 50% of the print is legible (small diameter cable so the printwheel probably didn't maintain contact with it).

E.g., I know I have RG6, 9, 58, 59 out in the garage. Probably some other scraps, too.

The antenna is "dual band". It is intended for a cell phone. My problem is my *cordless* phone (NOT a cell phone) operates

900+ (I think 906-926 or something like that... I think I posted it here somewhere) so I am questioning "how close is close enough"?

I think that is the problem. Consider the diagram, again. A line from the X to the upper left corner passes through lots of "stuff" (houses). And, since it is uphill, I may even be in the shadow of the *ground* between that corner and the base (i.e., the ground may not be monotonic increase in elevation)

Repeaters are not an option. :>

I guess I should:

- drag the base up to the roof some evening (go snow blind up there during the day!). I already have a phone line up there ( Though I didn't expect to use it thusly!)

- figure out *where* (exactly) the dead spots are

If the dead spots remain (or, don't significantly improve), then there's no practical solution. return (0).

- repeat this with the base back inside to have limits on the types of performance I can expect -- best + worst.

- then experiment with different antenna types and see how close to "best" and "worst" I end up?

- then, see how far *into* the house i can pull the antenna while still maintaining the coverage. (ideally, I would like to locate it "in* the ceiling so it isn't exposed to weather and is less of a lightning bug)

Is there any harm in trying the "cell phone" antenna?

Thx,

--don

No, I was trying to describe the type of connector on the antenna that I am "questioning" -- without KNOWING the proper names for the various RF plumbing! :>

I figured most folks have seen a linksys router (with removable antennae) so could relate to that example.

The phone's base unit is something like a "reverse TNC" (??) so I can't mate the antenna to the base unit "as is".

The information "mpm" posted below is very correct, and in addition, it is worth noting that the FCC Enforcement Branch is entirely self funded.

Tom

Not obsessed. Just alerting the OP to federal law. :) If he chooses to break the law, those same laws provide for fines and arrest of the equipment (in rem arrest), and the FCC can also refer cases to the Justice Department for further prosecution. Monetary fines for something like this can range from a few thousand, to ten thousand dollars or more. See generally, FCC Rules 47CFR1.80 Those are the facts.

Now, does the FCC catch a lot of folks hacking illegal antennas into their cordless phones? No. But you might be suprised at just how many violations are issued each year by the FCC's Enforcement Division. I have personally been on a couple equipment witch hunts (for interference) with the Miami and Denver field agents. The outcomes are rarely pretty in the cases which I'm typically involved in (the high profile ones). The average homeowner can expect a Citation (no money fine) for a first offense, but things can get nasty if they're uncorporative, etc..., or if the Agent (for whatever reason) feels justified in pursing the matter more aggressively.

Plus, in my former career (a post you may have missed?) it should be painfully obvious why I recoil when I hear that people want to hack into their consumer electonics. You would not believe the headaches this can cause for licensed radio services!!

But to your facts, For most unlicened devices like cordless phone and the like, they'll be registered under Part-15 rules. (47CFR15) Those rules will provide field strength limits (not transmitter power output restrictions). Therefore, antennas matter greatly! The allowable field varies by frequency, according to a chart in FCC Rules part 15.209 Before leaving this topic, you should be aware that just because you might feel Part-15 devices are low power, that DOES NOT mean they are incapable of causing harmful interference. Far from it.

For example, did you know a typical CDMA or GSM cell phone (operating at its lower power output of ~ -50dBm) actually radiates LESS power than the maximum permissible under Part-15 Rules for unlicensed devices? In other words, something that's unlicensed (and lower power) actually puts out MORE power than your cell phone -- which is very much a licensed service (FCC Part 22, 24 or 27) And note also that Part-15 Low Power does not restrict operation in the Cellular / PCS bands. Think about that next time you drop a call. It may just be your neighbor hacked in an antenna on his cordless phone (or garage door opener, or blender, or TV or god knows what!)

This is one of hundreds of examples I could give to you. So yeah, you might say I'm "obsessed" -- but I am absolutely correct, and this history books are filled with examples of horrendous interference cause by well-intentioned folks just like the OP.!!

Specific to this exact situation, here is the precise rule the OP would be violating:

Sec. 15.203 Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device.

The use of a permanently attached antenna or of an antenna that uses a unique coupling to the intentional radiator shall be considered sufficient to comply with the provisions of this section. The manufacturer may design the unit so that a broken antenna can be replaced by the user, but the use of a standard antenna jack or electrical connector is prohibited. This requirement does not apply to carrier current devices or to devices operated under the provisions of Sec. 15.211, Sec. 15.213, Sec. 15.217, Sec. 15.219, or Sec. 15.221. Further, this requirement does not apply to intentional radiators that must be professionally installed, such as perimeter protection systems and some field disturbance sensors, or to other intentional radiators which, in accordance with Sec. 15.31(d), must be measured at the installation site. However, the installer shall be responsible for ensuring that the proper antenna is employed so that the limits in this part are not exceeded.

There's usually clandestine adapters for that. Of course the FCC bristles at those ...

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

You can probably get a reverse TNC from Pasternack. (?)

...

RP-SMA is common on wireless routers. A few use standard SMA instead of the reverse-polarity version. Connector thread = 1/4"-36. See the SMA section of and the "Matable Connectors" table at the end of that page.

says, "RP-SMA connectors are widely used by Wi-Fi equipment manufacturers to comply with [FCC regulations] which are designed to make it difficult for consumers to connect antennas with gain and thereby breach compliance."

lists an SMA to RP-SMA adapter and a multiband antenna, which in turn links to various-band antennae with SMA or RP-SMA connectors.

-

Here's the link:

l

RP-TNC. In theory they're hard to find, but reality is a little different.

You need an RP-TNC connector, that's all. RP-TNC to N cables are easy to find, if not a bit pricey. Try a web search. Others should be available too.

Until the Internet, Google, and eBay became ubiquitous something around a decade ago now, I think the FCC's approach there ("use hard-to-find connectors") worked -- but it certainly won't ever again. :-)

Murray Pasternack is a well known spammer around here.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

Prezactly. These widgets are needed by the guys designing this stuff. They exist and even the FCC can't re-can them.

text -

Of

fame? I'm surprised.!!

ferent.

a

=A0They

1. Just an observation -- The FCC is not interested in canning (or re-canning) anything! It's not what they do.
2. And here's the real zinger -- Once a connector gets into the wild (i.e, becomes commonplace to the general public), the FCC will add that connector to its list of disallowed Part-15 connectors. Note however, that the FCC does not keep a list of approved Part-15 connectors - only ones they say can't be used anymore for Part-15. Furthermore, the restriction applies only at the time the device is originally certified. So, for example, a product that was certified 10 years ago can continue to use whatever connectors it might have on it, EVEN IF later on, that same connector is added to the disallowed list of connectors!! How stupid is that?

I can understand the FCC does not want to cause manufacturers to do a lot of re-work to their products. The only saving grace, maybe, is that if the device is modified in any way that requires a new Part-15 certification, then at that point, the device will have to comply with the current list of disallowed connectors.

So, where is this list of connectors you might ask? Good question. You won't find it anywhere in the Title 47CFR Part-15!! Instead, the FCC will randomly and quite infrequently update the list via a Public Notice. You pretty much have to be a search engine genius to find them.... but they are out there. I think the last one came out 2 years ago. (?)

text -

Look at the Google archive for the group. He's caused a lot of flames over the years.

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

It's easier than you think, one doesn't have to be a search engine genius. Ok, I am pretty good at finding stuff but this took less than one minute:

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Don't be an idiot. Of course, they're in the business of regulating cans.

No. The point being that the transmitter is only legal with the specified antenna. It's *supposed* to be difficult to change the antenna.

Bottom line: A distinction without a difference.

I think he meant finding the list of banned cans.