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Is there an alternative for the Talking House ATU. I really don’t want to spend $300 on the one from the manufacturer.
Total posts : 45366Although some will argue FCC acceptance of making and using a homebrew ATU, the remote ATU is nothing more than an adustable loading coil with a tuning meter.
The Talking House is certified for use with the Talking House ATU which can be remote located. That means you can keep the transmitter in the house and mount the ATU/ANTENNA outside legally.
If you don’t agree with that, take a look at the INFOSPOT SYSTEM which is based on the Talking House transmitter.
They advertise “Antenna System – InfOspot is the only system of its kind to allow for separation of the transmitter and antenna/tuner by way of standard coaxial cable. This permits the antenna to be mounted in an optimum location for transmission, while the control cabinet containing the transmitter and digital message player remains conveniently located for control and maintenance. The gravity-mount roof stand with mats and mast is the most popular antenna mounting option.”
They state that you can use up to 300 feet of coax antenna lead in.
Total posts : 45366InfOspot is the only system of its kind to allow for separation of the transmitter and antenna/tuner by way of standard coaxial cable.
I find that claim as curious as where on both the Procaster and Rangemaster websites describes and illustrates with graphics using a long 2 story ground wire from the ground lead..
I also find InfOspots statement curious: “(*) FCC rules do not allow the broadcast of objectionable content or the use of a frequency that causes interference to other radio stations.”
Not that I personally would ever want objectionable material aired, but my understanding is that the FCC has no rules whatsoever on what content of a part15 transmitter
All this also reminds me of a post several weeks ago concerning the Rangemaster, If you recall..
Avoiding a radiating ground
If you are connected to a ground that looks like an antenna , then you are going to get radiation from the system. Design the ground so that will not radiate, or does not function as an antenna. For example a pole grounded at the base with a short “ground lead” connected from the top of the pole to the transmitter has been shown to be a solution.
(http://www.am1000rangemaster.com/radiate.html)I had emailed Kieth that he might wish to edit that contradiction, and his reply was simply:
Sorry, I’m not getting your point
I emailed him back, emphasizing my confusion on the statement, and he replied:
FCC agents have been passing transmitters on poles after testing them for ground radiation.
Again I emailed asking him to elaborate on what he meant by “agent have been passing..”, but didn’t get a response that time.
All the certified Part 15 transmitter descriptions certainly seems to be saturated with contradictions
Total posts : 45366Keith Hamilton is not talking out both sides of his mouth. All Part 15 users have to use the “most current” findings of FCC inspectors as the measurement of how the federal government is gauging the actually use of specific transmitting systems and devices. The FCC’s opinion is the only one that counts, unless you’re ready to hire an FCC attorney.
The objectionable content rules are not specific to Part 15 devices, but are in other parts of CFR 47, the FCC rules. Part 15 deals with only the technical rules for use of low power intentional radiators and devices. Get a complaint filed against a Part 15 broadcaster for saying the seven dirty words, and I guarantee the inspector will show up. No matter what radio service you use, objectionable content will gather problems.
First, to explain. The FCC DOES NOT do the actual certification tests on commercially sold (non-kit) Part 15 transmitters. An outside laboratory does the testing required by the FCC. The results are submitted to the Commission for there approval and grant. The systems are tested, approved and a grant issued based on the actual system tested by the lab. Each Part 15 system is considered separately, not as a class of device. That is the reason for the, so-called, lack of consistency perception on the part of low power operators. In the final analysis, the way the certified unit is used in the field and it’s compliance to Part 15 technical rules, as interpreted by the FCC inspector, is what determines whether an installation passes inspection. I know it seems inconsistent, but the FCC gets to call the shots. Whining and complaining doesn’t seem to tip the scales our direction.
And finally, just because a Part 15 system is offered for commercial sale doesn’t mean that the ultimate use of the system will be considered legal or compliant. Certified Part 15 devices can be operated in non-compliance to the rules. The official term would be, “Notice of Unlicensed Operation/NOUO”. Live, operate, and learn.
Total posts : 45366InfoSpot drops this clunker right in the middle of the ad copy
Designed to operate under FCC Part 15 rules, InfOspot is capable of 100 milliwatts of output power…
How’s that again? This seller of a certified unit doesn’t even understand the rules that regulate their product – either that, or they have designed a circuit that is 100% efficient, in which case, I’ll take two!
🙂
Total posts : 45366The 3-meter Part 15 height limit counts the antenna, antenna lead-in and ground lead. After contemplating the definitions of these specific words and reading these threads for several years, I have established some specific opinions which add wording that is left unsaid in the FCC rules.
The definition of “antenna” is clear and not ambiguous, but the other two terms can be elaborated upon in discussion:
“Antenna lead-in” I take to mean AN UNSHIELDED WIRE from the transmitter to the antenna. This WILL radiate, and is therefore COUNTED in the 3-meter measurement. But a shielded coax from the transmitter to the antenna will NOT radiate, and in my book (not the FCC printed words) is NOT an “antenna lead-in.” Therefore I consider a shielded coax, known as a “transmission line,” to be 100% legal under Part 15. I think the reason 300′ is used as a limit to the ATU design is not a matter of “rules” but rather a matter of avoiding signal loss in the long coax.
“Ground lead” to me means, a wire from the transmitter ground to an earth ground. The discussion of what legitimately counts as “ground” and how it is different from a “ground lead” has been going on here for a long time, and I agree with others that whether it radiates is a major factor, but on the other hand the purpose of proper grounding is to increase the signal outreach, which means “increase the radiation,” so I use the standard that anything at ground level or below and runs parallel to the ground, IS true ground.
Total posts : 45366Carl, I have to disagree with your statement But a shielded coax from the transmitter to the antenna will NOT radiate,
In a perfectly balanced situation the current on the inner conductor of a coax will be equal and opposite to the current on the shield and the two radiation fields will cancel but this is seldom the case in practice. The reason is that the outer conductor (the shield) has additional current induced by the antenna field which upsets the ideal balance condition. Another way to view this is that the RF field is totally enclosed inside the coax but the shield is just another conductor in the RF environment. This is no different that the radiation produced by the ground lead or the audio/power feed leads.
There are techniques which can be used to minimize transmission line radiation but the results would need to be experimentally verified.
Neil
Total posts : 45366Neil, I understand what you’re saying, and I must admit I was assuming the ideal situation where the proper cancelation would occur inside the coax to prevent leakage, but I recognize your point that this may not happen with ordinary part 15 equipment.
So, how does the ATU measure up in terms of coax leakage?
And let me jump in with this simple test idea. Suppose a desired length of coax was attached to the transmitter but terminated into a 50-ohm dummy load. Would it not then be possible to obtain a clear idea of how much the coax was radiating?
Total posts : 45366Carl,
I suspected you were referencing the ideal case but wanted to add to it for the non-ideal case we usually encounter.
Terminating the coax in a 50 ohm load will present the ideal case and excepting for leakage through the shield there will be no coax radiation but this is different than when the coax is exposed to the field from the antenna so it can’t be used to assess the effect of the coax on the radiated field(s) except for the leakage.
Neil
Total posts : 45366First, to explain. The FCC DOES NOT do the actual certification tests on commercially sold (non-kit) Part 15 transmitters. An outside laboratory does the testing required by the FCC. The results are submitted to the Commission for there approval and grant.
The FCC can, and often does, request a sample.
Total posts : 45366This comment is true. However, unless the FCC requests that the OET conduct an internal test, the results (not the report) are published in the public record and the grant is made. If you go to most any AM Part 15 transmitter manufacturers site, they will publish the results and findings of the FCC. The actual report is almost never published due to patent design security and marketing protection. The FCC requests the sample so that the staff has as actual device for “possible” testing. The internal tests are often NOT done. Only in rare cases are the actual tests completed internally, with the test report still not published for public consumption.
The FCC and the OET technicians do understand that field application of the device does not ensure compliance with the rules. Certification only means that the device passes technical inspection regarding the laboratory application only.
Total posts : 45366First, here’s a comment which may help explain the so-called performance of EH and isotron antenna types:
http://www.eham.net/reviews/detail/3519Next, I want to explain the differences in the TH system as I understand it.
1) The cable used with the ATU or ‘external antenna’, is not the usual 50 ohm transmission line coax, but instead is a standard 75 ohm RG58 TV cable. IOW, impedance is different.
2) In my tests and experience, there was virtually no difference between a short length of this TV cable and one about 22 ft. long used as the line to the ATU. I.e., the antenna’s signal strength appeared the same at resonance. IOW, the cable in this case doesn’t appear to be radiating, at least not enough to make any significant difference.
Total posts : 45366The Talking House supplies RG6 which is 75 ohms but according to tel cons with them the antenna output is 50 ohms. They insist the output is 50 ohms. So there is confusion. Regardless the Talking house sells an antenna “ATU” (WHICH THEY CALL “Aux Transmitter Unit”). So yes you can remote mount the antenna (it was approved).
OTHER COMMENTS:
The Talking House is not really suitable for remote operation (outside) in my opinion. For one it’s big. Second if you power down it will boot to a default Freq (which varies between units). It would be best to make a small single Freq transmitter to put in the box out in the weather in my opinion.
If you did remote mount it your could use the built in antenna tuner. I DO, it works OK. I have no problem with it. I don’t get over 150 feet of strong signal and good to excellent quality audio. The signal drops fast after 150 feet, say weak signal range is about 300 feet. It’s also directional. Signal is strongest inside the house, which is what I want. However with wet ground I was getting out 1000-1200 feet outside range. The TH is inside, antenna is a wire hanging out the second floor window next to the vinyl siding. This is far from ideal, but the whole house is covered very nicely. I am just doing it for my self.
I am sure if I put the TH in a box on the ground outside, 9 feet copper on the tuned output, with a good ground, range would go up. Range is not critical for me. Running wires, power, audio out to the TH would be a pain. The TH is in the same room as the computer’s, streaming internet radio, sound card, audio software to improve sound quality. I use a 15 feet audio cable from the sound card to TH to avoid noise.
If you get into long coxial runs you are losing power. This means you need a stronger transmitter to get the max 100mw at the Antenna.
Then there is the ground issue as usual. That has to be short or it’s considered part of the antenna.
Total posts : 45366The FCC requests the sample so that the staff has as actual device for “possible” testing. The internal tests are often NOT done. Only in rare cases are the actual tests completed internally, with the test report still not published for public consumption.
I can say from personal experience and a few visits to the FCC Laboratory, the FCC routinly tests equipment first a quick screen for compliance inside and then outside at its open area test site.
Total posts : 45366If you get into long coxial runs you are losing power. This means you need a stronger transmitter to get the max 100mw at the Antenna.
The loss in RG6 in the AM radio band is hardly worth mentioning, even at 100 feet.
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