Talking House ATU On Roof of House

here we go again. this is a dead horse that has been beaten over and over and over and it's time it just gets dropped and everybody just go on with life enjoying part 15 broadcasting before another aspect of the hobby gets ruined.

for now whatever the FCC thinks they are overall ignoring the issue and we should not force them to act on the issue by bringing attention to it like what happened with the ground lead issue.

DROP THE WHOLE THING

ADMIN: PLEASE CLOSE THIS THREAD

there is plenty already discussed on this topic and we should not beat this drum any further.

use the search feature. we are rehashing what has already been discussed!!!!!

"The FCC OET certification test data details using coax cable to connect the transmitter to the ATU and was accepted."

MRAM, do you have a copy of the certification lab report? There are no details available on line for the certification test for FCC ID: DLB5LTT98 (granted in 1997). Without being able to see the lab report, we can only speculate on how it may have been tested with the ATU and coax.

The FCC OET specifies that measurements are to be made in conformance with ANSI standard C63.4. For more recently certified transmitters like the Procaster, the test report is available and shows the standard test setup: insulated table 80 cm (31.5") high over a ground plane floor and 40 cm between the rear of the table and a vertical ground plane. "All interconnecting cables that hang closer than 40 cm to the ground plane shall be folded back and forth forming a bundle 30 to 40 cm long, hanging approximately in the middle between ground plane and table".

If we assume the coax was considered an "interconnecting cable", folding it to a short length would suppress most of the RF that it might radiate. Additionally, if the ATU were grounded with a wire to the ground plane, much of the remaining possible radiation from the coax would be bypassed by the ground wire. There is a valid case for saying that these connection steps effectively remove the long coax from the 3 meter requirement. Same goes for the audio and power cables. They are also fan-folded down to a shorter effective length for RF.

There is no field strength measurement required for 15.219 certification, so even if it were certified somehow with the ATU/antenna at the top of 100 ft. of coax strung vertically, it wouldn't fail due to signal strength. BUT, it would certainly fail due to the 3 meter rule.

It's a real stretch to say that because it was certified with the ATU and coax, it is therefore legal to mount the ATU on the roof. I certainly wouldn't jump to that conclusion without seeing the certification lab report!

Carl, the confusion over whether the ATU is the actual "final RF stage" has been pretty much rendered moot by the latest overhaul of the i A.M. web site. Go to http://www.iamradio.net/ and click on "Legal & FAQ" at the top, then click the "here" link in the fourth paragraph. The input power to the final RF stage transistors inside the transmitter is 92.5 mW.

They are now selling only the newest, "calibrated" version of the talking house transmitter for $249.00. They have stopped selling the older units at the $99 fire-sale price.

I think the disagreement over whether the ATIU should be considered the final RF stage stemmed from several reported measurements from users indicating that over 100 mW was measured OUT of the coax jack on the transmitter. That presumably is not possible with the new "calibrated" units and they are no longer selling the older models.

you guys are so funny.  who cares? If the fcc comes, the outcome is always different. Either "Ok, thats fine" or "Something isnt right, lets see that cert ID? Oh.. ok.. looks good. bye."

It does not matter what other people think.say.blah.

I ran one, no one came through my door with jackboots.  It got almost the same range as my amt-5k did.. just sounded tinny to me is all.

My rangemaster didnt come close to the range.  Also - no one came knocking in my door on that either..

Follow the rules to the best you can. The FCC dont expect you to calibrate the stuff perfectly, no one really cares.  Dont go blatently breaking the rules, but make sure your installation is safe - even if that means ligntning protection.  Where I am, we dont get much airborn static, so I just run the coax up to the roof, tune the atu to max, and thats it.

 The only time anyone gets into any trouble over part15 stuff, installed correctly, close to correctly, or out and out wrong, is when some tool reports you because they dont like your programming, or, in the case of Woodside High School, an engineer from a nearby commercial station heard an fm signal radiating off the campus grounds (there were running an FM-25 with the builtin telescoping antenna).  I don't care how perfect your setup is, if someone screams loud enough, you will get taken off the air.

To MLR an KG8GPD,

I agree! All this stuff should not deter anyone who wants to set up a transmitter and live in the reality that the issuance rate of NOUOs for AM is negligible.

I just have an annoying personal obsession with technicalities. I just can't seem to let anecdotal misinformation pass as truth. I often think about the famous quote: "It's true because I read it on the internet". If you noticed, I don't start threads on this stuff, I just respond.

Otherwise, I agree completely that we all should just be happy, use our own judgment and promote Part 15 as much as possible. I also agree that it's not in our best interest to discuss this stuff when we know the FCC is watching.

From Rich:"Legal in the U.S. in that such hardware (but not the roof-mounted installation of the remote ATU component of that hardware) might have been granted certification under FCC §15.219, based on certification tests not conducted directly by the FCC."

From me: Rich you and I both know that the FCC Laboratory can and often does requests samples to be verified on the OATS at Columbia, MD. If the supplied test data or configuration was suspect, they would most assuredly request a sample.

Several aspects of measuring legal AM transmitter output power for Part 15 are interesting to think and talk about.

First off, why can't a mW (milliWatt) meter with power adjustment control be made part of a transmitter? Not only would this enable the operator to achieve and control proper power level, it would serve an FCC inspection by presenting a most important indication of compliance.

Given that the Rule (15.219) says, according to popular consensus, that 100mW to the input of the final RF (amplifier) stage is the official legal power limit, wouldn't it be nice to know the efficiencies of the various transmitters? In other words, wouldn't it be worthwhile to know the ACTUAL power coming from the OUTPUT of the RF amp?

It has been a major selling point that the AMT5000 is in fact a very high efficiency transmitter transferring almost a full 100mW to the output!

But what are some other output efficiencies of other transmitters?

What is one of the worst, say, 50% efficient or less? That would amount to a loss of 50mW, but it is only an academic example and perhaps not reflective of any existing transmitter.

Somebody should measure the output efficiencies of all the Part 15 AM transmitters on the market and post them here.

We could call it a "Transmitter Challenge."

Technically the power adjustment procedure with the Rangemaster is just that except one uses an external meter or LED indicator.  You simply play with the coil tap and tuning capacitor to get a match on the antenna, and then adjust the power control for the proper input power setting of 100 milliwatts. See this video:

Link for Power Table for Rangemaster: http://www.am1000rangemaster.com/pdf/1.rtf

Here are two quotes regarding use of the ATU:

December 22, 2009 - 21:05 —

The following is an e-mail received from Radio Systems, the new owner of the patent of the Talking House transmitter:

Tony:

Thanks for the call Friday. I wanted to double-check my information so I "dug" out the patent for the TH-5 transmitter and external tuning unit this weekend.

Cleverly, the patent for the TH-5 tuning unit includes wording which goes directly to the Part 15 issue. "The external ATU is the final output stage to the transmitter when selected". This patent was included in the Part 15 filing. In other words, this means the coax cable between the TH-5 and the ATU is NOT transmission line. The antenna itself is 96", so care must be made to ensure that the ground lead doesn't put the antenna system over 3 meters in length.

However, nominally the TH-5 with external ATU does, in fact, comply with Part 15.219 since the final RF stage is the ATU.

Hope that helps,

Gerrett

--------------------------------------------------
Gerrett H. A. Conover
Vice President, Radio Systems
601 Heron Drive
Logan Twp, NJ 08085
856-467-8000 Voice
856-467-3044 Fax
856-803-1060 Direct
--------------------------------------------------

Hobby Broadcaster

December 18, 2009 Update:

Some readers had questioned whether the external antenna unit / range exdender was part of the certification process and was legal for use with this transmitter. We recently confirmed with Radio Systems that the external A.T.U. was indeed part of the transmitter's certification and is accepted as part of the certification for the i A.M. Radio / Talking House AM transmitter. This information will soon be added to the i A.M. Radio web site.

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Here are links to the FCC Grant of Certification and Application for Equipment Authorization:

http://heartandhoof.com/MRAUDIO/TalkingHouseForm731.pdf

http://heartandhoof.com/MRAUDIO/TalkingHouseGrant.pdf

These next two links are copies from the Talking House OET document supplied for FCC Certification which displays the FCC ID number of the Talking House transmitter system:

OET TEST Cover Page:   http://heartandhoof.com/MRAUDIO/FCC_Exhibit%205_Cover.pdf

OET TEST Paramaters:   http://heartandhoof.com/MRAUDIO/FCC_Exhibit%205_Test_Parameters.pdf

I'm not sure what else one needs to see the transmitter is certified for use with the ATU connected by coax cable.  I don't believe the manufacturer would publicly make false statements regarding proper use of the equipment.

OET test data submitted to the FCC describes the transmitter connected to the ATU with 8 meters of coaxial cable and was accepted by the FCC.

I have never questioned the certified status of the ATU approved transmitters.

My position has been that BECAUSE an ATU located FOLLOWING the RF Amp Output is considered an "RF Stage" that must mean something different than the conventional belief that the input to the final RF amp is the definition of "final RF stage" referenced in 15.219.

But PhilB has made note that the input to the final RF amp of the iAM Transmitter is set near 100mW.

All these discussions aside, I STILL CONTINUE TO FIND some kind of contradiction in the whole thing, when comparing the ATU allowance to other more ordinary applications.

However, I have become convinced that I seem to be alone in my view, and hereinafter withdraw any further comment on the subject. It's an argument on the most miniature scale.

The point I was trying to make is simply that the ATU was included in patent info provided to the FCC for certification.  It was accepted.

The copy of the OET test data supplied to the FCC for certification was provided by the manufacturer.  It clearly describes the ATU connected to the transmitter with 8 meters of coax cable.  It was accepted.

As for "conventional belief" regarding the final stage, in this case it's a moot point.  The ATU is described as such in the patent info and was accepted as such by the FCC for certification. 

Previously posted in this thread:

"PhilB has made note that the input to the final RF amp of the iAM Transmitter is set near 100mW."

Clarification:  That "input" power is not the r-f power applied to the input terminal of the final, active r-f amplifier of a Part 15 AM transmitter.  Rather it refers to the d-c power applied to the output terminal of that r-f amplifier -- whether that amplifier consists of a vacuum tube or solid-state components.

"The copy of the OET test data supplied to the FCC for certification was provided by the manufacturer.  It clearly describes the ATU connected to the transmitter with 8 meters of coax cable.  It was accepted."

Comment:  However none of the links provided by mram1500 earlier in this thread  show the physical configuration of the Talking House system components, including its external ATU and connecting coax.

If that external ATU was located a few inches or maybe a foot above the ground plane during the FCC certification tests, then radiation from unsuppressed r-f currents flowing along the outside of the coax cable shield might reasonably be unrecognized, or considered as ~tolerable both by the non-FCC contractor performing those tests and the FCC analyst(s) who reviewed them, and which led to FCC certification of that hardware.

But when that external ATU and its connected ~ 3-m whip are elevated significantly more than that above the ground plane (earth), unsuppressed radiation from the coax cable connected to that ATU can lead to effective violations of §15.219(b) -- regardless of the FCC certification that such hardware components may have.

Clarification:  That "input" power is not the r-f power applied to the input terminal of the final, active r-f amplifier of a Part 15 AM transmitter.  Rather it refers to the d-c power applied to the output terminal of that r-f amplifier -- whether that amplifier consists of a vacuum tube or solid-state components.

INPUT POWER: P=IV whether it's the collector of the a final transistor(s) or the plate of a vacuum tube(s).