An article for QST

[kl7aj]

The absolute truth.

eric

[KA4DPO]

Very well done article Eric. Besides yourself I may be one of a few hams that own and know how to use an RF ammeter.

I especially like the way that you pointed out the obsession most hams have with VSWR and the thinking that if it's not exactly 1:1 somethings terribly wrong with their antenna.

[kl7aj]

Quote[/b] (KA4DPO @ Nov. 02 2007,12:57)]Very well done article Eric. #Besides yourself I may be one of a few hams that own and know how to use an RF ammeter.

I especially like the way that you pointed out the obsession most hams have with VSWR and the thinking that if it's not exactly 1:1 somethings terribly wrong with their antenna.
A lot of hams don't realize that the VSWR on an ANTENNA itself is always INFINITE! And yet, broadcasters for decades loaded up into antennas directly. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

eric

[va7aax]

very nice article .

BTW, how do you connect an antenna to a transmitter WITHOUT a feedline? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

[kl7aj]

Quote[/b] (va7aax @ Nov. 02 2007,14:23)]very nice article .

BTW, how do you connect an antenna to a transmitter WITHOUT a feedline? # http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif
You mean like an HT with a rubber duckie?

[AG3Y]

Only thing I would change would be to change "lossiest" to "with the greatest loss" , and "lossy" to " with loss"

Syntax is important ! 73, Jim

[kl7aj]

Quote[/b] (AG3Y @ Nov. 02 2007,14:48)]Only thing I would change would be to change "lossiest" to "with the greatest loss" , and "lossy" to " with loss" # #

Syntax is important ! # #73, Jim
I'm opposed to them taxing sin! ^_^ http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[al7n]

Eric...

Very nice article indeed.

I don't have any RF ammeters at present, but I tune all my HF antennas with small incandescent lamps bridged across a few inches of each my open wire feeders to tell me when I have maximum current in the feeders, thus maximum RF output.

It's a coarse but simple method that always always works....just like the RF ammeters do. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[n0iu]

Eric,

I see that you have written several articles for various ARRL periodicals over the years. This being the case, I am surprised you violated their #1 rule. As you know, when they publish something as a feature article, they own exclusive rights to it. Their release form says, "...the material you have submitted is original, except as noted; has not been submitted or published elsewhere..."

I guess this is one for the legal scholars out there who will determine if posting to a web site constitutes being "published elsewhere".

Other than that, it is a good read!

Scott NØIU

[kl7aj]

Quote[/b] (n0iu @ Nov. 02 2007,15:33)]Eric,

I see that you have written several articles for various ARRL periodicals over the years. This being the case, I am surprised you violated their #1 rule. As you know, when they publish something as a feature article, they own exclusive rights to it. Their release form says, "...the material you have submitted is original, except as noted; has not been submitted or published elsewhere..."

I guess this is one for the legal scholars out there who will determine if posting to a web site constitutes being "published elsewhere".

Other than that, it is a good read!

Scott NØIU
Only if QRZ pays me. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[n0iu]

Well I did say if they use it as a feature article.

And this brings up another point I would like to make. (Yes, I know this is your post Eric, but I would like to hijack it for a moment)

While it is fun to post things on QRZ or eHam or some other web site, I think more people should consider writing for a "real" publication. I am not a particularly gifted author, but I have had 5 things published over the years in QST. (3 Correspondence pieces, 1 Hints & Kinks piece and 1 feature article - for which I was paid) And don't think you have to write something that is in line with ARRL policy. My last Correspondence piece pointed out some flaws in another letter they printed from an EMCOMM cheerleader.

Read this: http://www.arrl.org/qst/aguide/ and give it a try!

Scott NØIU

OK Eric, you can have your post back!

[n4bfd]

I read your letter in QST Scott, I was surprised they printed it, but it shows that they look down both sides of the barrel I guess.

[n4cd]

Several points.

"This is why the FCC has always required the Direct Power measurement technique for determining transmitted power"

That applies to commercial BC and HF stations. I'm not sure it applies to TV stations or FM stations. In those cases, it is EIRP that is regulated for determining 'transmitted power'. Your statement is too broad and I don't believe it applies to even all commercial services.

For ham radio, the FCC determines transmitted power as the output of the last transmitter stage. Period. That is measured immediately after the last TX stage before the feedline or antenna. It is forward minus reflected power. In an ideal situation (or with a 'tuner') presenting a 1:1 VSWR, you have no reflected. It is NOT measured at the antenna.

The only FCC requirement that you must do is calculate the field intensity of your signal to insure you are not exceeding 'safe levels' for exposure. - other than 60M, where it is the ERP of the antenna system that is required to be calculated based upon ASSUMED losses in the transmission line, and gain of the antenna in the peak direction (if directional in any way) - so that you do not exceed 50W ERP.

For ham radio, there is NO requirement to measure direct power AT THE ANTENNA.

I agree too many worship at the alter of VSWR. Put a 80M mobile on the car. Have 2 ohms radiation resistance and a rotten ground of 48 ohms impedance, and you have a wonderful VSWR. It just doesn't radiate worth a darn. Put in a fantastic ground, say 15 ohms, typical for an 80M mobile installation - and your VSWR is high...17 ohm impedance to 50 ohms....3:1 or so. Rotten. Of course, if you match at the antenna with a small shunt coil, you'll radiate a lot more efficiently.

Too many fail to understand that.

In the case of a tuner.....

". We tune our tuner for maximum R.F. current on the OUTPUT, but see a 1.5:1 VSWR between the transmitter and the tuner. What does this mean? Assuming the VSWR meter is indeed accurate, it means that our transmitter actually has 75 ohm output impedance at that frequency. Or possibly 33.3 ohms. "

It could also be that your tuner cannot match the antenna impedance to 50 ohms resistive.....so that the match from the transceiver to tuner is not 'perfect'. Many auto tuners stop at anything under 1.5:1 or 1.3:1. There may be no combination of caps and inductors that makes the match.

I do not see how you can conclude that the transceive must be happier at 70 ohms output or 33.5 ohms output. Please explain. And please consider the case where the tuner cannot perfectly match.and thus HAS an input impedance of 33.5 ohms or 70 ohms, or 50 ohms reactive....at the best possible setting.

Or it could indicate you have ground loops in your setup.

I don't see how you can come to your conclusions on this.

[wz0o]

Great post. As an ex brodcast engineer it goes back to the basics. Good luck and thank you for your thoughts.

[W5HTW]

Quote[/b] (kl7aj @ Nov. 02 2007,15:34)]Quote[/b] (n0iu @ Nov. 02 2007,15:33)]Eric,

I see that you have written several articles for various ARRL periodicals over the years. This being the case, I am surprised you violated their #1 rule. As you know, when they publish something as a feature article, they own exclusive rights to it. Their release form says, "...the material you have submitted is original, except as noted; has not been submitted or published elsewhere..."

I guess this is one for the legal scholars out there who will determine if posting to a web site constitutes being "published elsewhere".

Other than that, it is a good read!

Scott NØIU
Only if QRZ pays me. :)
Not true. It IS published. QRZ is the publisher, in this case.

If you write anything, and post it anywhere on the web, it is published. That doesn't necessarily mean other publishers won't touch it. But if they do, they will pay you a darned site less for it!

I was a member of some writer's boards. It was amazing the number of authors who would publish an entire novel on the site and ask for comments. Then they would seek a real publisher, and learn "so solly, already published." Some of them learned, publish some excerpts, but don't publish the whole darned thing. Not only is it "already published" but for free! And for free download!

Ed

[n3ef]

Quote[/b] (n0iu @ Nov. 02 2007,18:33)]I guess this is one for the legal scholars out there who will determine if posting to a web site constitutes being "published elsewhere".
Well, this is a very gray area. Is posting an article in an internet forum the same as publishing? One thing you can do to protect yourself is to add something like this that I found in an article about copyright guidelines for posting articles on the internet. "Unpublished manuscript: For unpublished articles, label the paper with the date and with a statement that the paper has not (yet) been published. (Example: Draft version 1.3, 1/5/99. This paper has not been peer reviewed. Please do not copy or cite without author's permission.)"

#I don't think QST is concerned about your article being posted in an internet forum anyway. This line is also from their "Author's Guide", "Important! Send material to only one potential publisher at a time. It is our policy to automatically reject any submissions that have been sent simultaneously to other magazines. Multiple submissions can only lead to copyright infringement problems for publishers." I think their concerned about articles being "formally" published elsewhere, and not informally self-published in a forum, blog, personal homepage etc.

#The legal definition of publication, from the U.S. Copyright Office:

A work is unpublished at a given point in time if it does not meet the definition of “publication.” "Publication" is the distribution of copies or phonorecords of a work to the public by sale or other transfer of ownership, or by rental, lease, or lending. The offering to distribute copies or phonorecords to a group of persons for purposes of further distribution, public performance, or public display, constitutes publication. A public performance or display of a work does not of itself constitute publication. 17 U.S.C. Sec. 101

#Eric was merely soliciting for comments on his article, not selling it, transfering ownership rights, or offering to distribute it. I think adding a line to the article indicating that it is unpublished and copyrighted would be the smart thing to do.

Eric N3EF

[KB1KIX]

Quote[/b] (AG3Y @ Nov. 02 2007,17:48)]Only thing I would change would be to change "lossiest" to "with the greatest loss" , and "lossy" to " with loss"

Syntax is important ! 73, Jim
Agreed.

Other than that - great article.

I'd vote it best for the month in many issues!

And regarding the "publishing".....

I doubt many would consider this published.

I for one would think of it as more peer review.

Jonathan

[WA9SVD]

I would think the QST Editor(s) would be the ones to make the final decision as to whether it's considered unpublished (according to their standard) or not. I hope Eric hasn't jeopardized his chance of getting into QST, as it's an excellent article.
Good luck, Eric.

[wb6bnq]

Eric,

I must disagree with the quality of the article. #It is not ready for prime time publishing.

Your writing, besides having grammatical, spelling and punctuation issues, lacks continuity due to the many diversions leading up to the main subject. #Also, while addressing the main subject, you create diversions that only cloud the issue. #One example is referencing Broadcast station requirements that have no relationship to the Amateur world nor is necessary to explain the subject matter.

Good technical writing requires addressing the subject matter at a given skill level that is consistent throughout the article. #I did not feel you handled this well at all. # It also requires the writer to treat the reader with respect and not talk down to them. #Most notably, your paragraph about getting a cup of coffee violated that premise. #You may have thought it cute, but I found it to be juvenile and does not belong in such treatises.

Unfortunately you selected a subject matter that is quite complex on many levels. #If the person making the measurement does not understand the principles involved, then they cannot interpret the results properly. #It matters not how the measurement is made, nor the equipment used. #Treating it so cavalierly, as you did, only serves to add to the confusion that already exists.

The treatise requires a proper foundation to refresh the reader on the complexities associated with the main subject matter. #You need to figure out how to touch on the necessary elements of impedance (reactance), antenna and transmission theory while explaining how the RF amp meter is going to save the day. #Admittedly this is a formidable task. #Keep in mind that you are only going to skim over the theory and you should provide additional references for further study by the reader.

In determining how best to approach this task you need to first decide what skill level you want to reach. #The lower the skill, the more explanation required to cover the subject. #Second, provide mathematical analysis so the reader can test your hypothesis. #Third, including diagrams or drawings is also very helpful, especially if addressing a low skill level. #Fourth, support key statements with annotated references listed at the end of the article.

You may find my critique objectionable, sorry, but it is factual and accurate. #With all the “Dumbing Down” of the requirements for Amateur radio, the last thing needed are less than stellar articles.


Bill.....WB6BNQ

[n4cd]

Well, it seems that MFJ has just annouced in the 2008 Catalog several RF Ammeters.

The MFJ - 836 in line coaxial RF Ammeter

The MFJ - 836 - combon RF Ammeter and SWR meter all in one.

They spout some of the same hype:

"for any given antenna always gives maximum
radiated power!
Any adjustment -- transceiver or amplifier
tuning/loading controls, antenna tuner
settings, whatever -- that increases feedline
current improves power transfer and gives
you a stronger radiated signal."

Which is partially true. If your feedline current consists of 2nd and 3rd harmonic, you may be radiating more power, but not on the desired frequency.

If you are tuning for maximum line current, and your adjustments result in gigantic ground loops in your station, you aren't radiating more power.

Yes, for a given antenna, more current delivered assuming you aren't also affecting ground loop losses, means more radiated power (from somewhere). So you can have your SWR meter and RF ammter in one box if that is what you want.

They also make clamp on and r.f. sense ammeters useful for optimizing and testing ground/elevated radial systems. (or for other testing purposes when not using coax).

There is no more reason to worship at the altar of 'r.f. ammeters' than at the altar of 'SWR'. It is just one tool.

If I were stranded on a desert island with one piece of "test equipment", that might be a Spectrum Analyzer with all the appropriate test leads, power attenuators, and directional couplers to utilize it. It would give me a good frequency indicator, power indicator, SWR measuring capability, harmonic analyzer, stability checker, etc.

However, first I'd probably elect to have a solar powered rechargeable battery Volt - Ohm - Amp - LC/Cap Meter. An r.f. ammeter isn't useful when you can't figure out why your radio is sick, or if you have continuity, or trouble shooting your generator or power distribution system.

Would you rather have an RF ammeter as your only piece of test gear?

What credibility does this give to the entire rest of the article?