Date   

Re: Does a low SWR mean your antenna is a great performer?

WK9M
 

Sounds good Allan; the actual loss depends on transmission line quality and frequency then as we chatted on the phone when I was by Ralph's earlier.  i.e the losses would be much greater with a long run at 440MHz and 3:1 as it bounces back and forth.  Maybe we should just superconducting coax and then the answer is always 100%?  Ok so maybe not practical on that one.  :)

I found the actual article on voltage, VSWR, and surge suppressors that I had talked about during the presentation if anyone is interested.  The formula is (2) on page 4 of this document for the techies in the club:
http://www.arrl.org/files/file/QEX_Next_Issue/2016/July-August/Hinkle.pdf

Vpk=sqrt(100*PWR*SWR)

So on a 100W signal into 50 ohms at 1:1, the common Ohm's law formula states 70.7V (P=(V^2)/R); solving for V.

At 3:1, the voltage isn't 70.7*3=210.9V but 173.2V...a little less than 3X as you noted.

With 1.5kW, it's an amazing 671V.  So that's why you always tune high power.

'73
Randy

On 9/22/2020 2:29 PM, John Haskell via groups.io wrote:
Randy,

Thanks for your thoughts.  Good point on the peak voltage being higher with a non-perfect match.

The  4-11-25 "rule" works well if the line is very lossy.

I must say though that the 4-11-25 "rule" doesn't quite cut it for low loss transmission lines.

For example, consider a lossless line with a 2:1 SWR.  What percentage of the transmitter's power is radiated?  Answer:  All the power is radiated [not 90%].

What about with a 10:1 SWR?  The loss is again zero!   All the power is radiated.  Think open wire or ribbon line.  This is an important concept.  Even with a high SWR,  100% of the power is radiated.

What really happens is the reflected power is re-reflected at the transmitter [near 100% of it] and is not lost to dissipation in the transmitter.  The reflected power, when it reaches the transmitter, is reflected back in the forward direction where much will be radiated when it again reaches the antenna.  Eventually all the power is radiated in spite of an SWR greater than 1 except for the portion dissipated in the transmission line.  Just think of the energy ping-ponging back and forth with some being radiated when the energy hits the antenna each time.

When some line loss is present the reflected power does suffer some loss in the transmission line on the way back and forward, and that is what the additional loss beyond the SWR 1:1 case represents.  As long as the line has, say, less than a dB or two of loss the additional loss caused by SWR can pretty much be ignored.

73,
Allan


Re: Does a low SWR mean your antenna is a great performer?

John Haskell <jasm2213@...>
 

Randy,

Thanks for your thoughts.  Good point on the peak voltage being higher with a non-perfect match.

The  4-11-25 "rule" works well if the line is very lossy.

I must say though that the 4-11-25 "rule" doesn't quite cut it for low loss transmission lines.

For example, consider a lossless line with a 2:1 SWR.  What percentage of the transmitter's power is radiated?  Answer:  All the power is radiated [not 90%].

What about with a 10:1 SWR?  The loss is again zero!   All the power is radiated.  Think open wire or ribbon line.  This is an important concept.  Even with a high SWR,  100% of the power is radiated.

What really happens is the reflected power is re-reflected at the transmitter [near 100% of it] and is not lost to dissipation in the transmitter.  The reflected power, when it reaches the transmitter, is reflected back in the forward direction where much will be radiated when it again reaches the antenna.  Eventually all the power is radiated in spite of an SWR greater than 1 except for the portion dissipated in the transmission line.  Just think of the energy ping-ponging back and forth with some being radiated when the energy hits the antenna each time.

When some line loss is present the reflected power does suffer some loss in the transmission line on the way back and forward, and that is what the additional loss beyond the SWR 1:1 case represents.  As long as the line has, say, less than a dB or two of loss the additional loss caused by SWR can pretty much be ignored.

73,
Allan


Re: IRS Determination Letter

Brad (the Voice of the Village) Berger
 

Congratulations David and thank you for getting this 501 (c)(3) together. Not only did you do an outstanding job, but you are now officially our club attorney.

The Hon. David F. Andrews Esq.
Now about that speeding ticket I got...


Brad B.


Re: Does a low SWR mean your antenna is a great performer?

WK9M
 

Yes I think that a presentation would be a great idea--TLARC is looking for new presentations.  I myself put in memory the 4-11-25% rule.  i.e. 1.5:1 is 4% loss, 2:1 is 11% loss, and 3:1 is 25% loss.  I found a document online that confirms my memory is correct:
http://www.packetradio.com/pdfzips/SWRvsPowerNwatts.pdf

And as you point out, 2:1 is a .5 dB loss.  Even 3:1 is only a 1/5 of an S-unit (1.25dB loss); I'd say that a computer can hear that difference but probably not a human.

Many modern radios will start cutting power back at even moderate VSWR levels.  So as you say, watch the power out.  Both of my Kenwood HF radios are picky on 6m for example.

VSWR can have a bad effect on surge arrestors if you happen to buy a low power one and operate it with high VSWR.  (3:1 is literally 3x the voltage).  But I doubt any of us would do that, at least on purpose.  I went over that in my surge presentation about a year ago.

'73,
Randy

On 9/21/2020 12:48 PM, John Haskell via groups.io wrote:
What George quoted from ham.stackexchange is correct.

To take it a bit further, SWR can be pretty much ignored.  If your solid state transmitter functions with normal output power versus shutting down, then SWR really does not matter much for most installations.  This is particularly true at HF where cable loss is minimal.  At UHF and with a long transmission line SWR can cause unacceptable losses.  

Here are a couple of examples of SWR versus loss using inexpensive RG-58.

Assume 7MHz and 75 feet of RG-58.  The cable loss is .9dB with a SWR of 1.

But what if the SWR is 2:1?  The extra loss due to this SWR is .2dB, e.g., negligible.


For a mobile set up on 442.1MHz..   Many people go nuts with low loss cables.  Not me. I use RG-58 in the car.  Here is why.  For 442MHz, 10feet of cable, and a 2:1 SWR, the additional loss due to the 2:1 SWR versus a perfect match is .2dB.  I do not believe you will notice that extra loss.


I have been considering putting a transmission line/SWR presentation together for TLARC in hopes of dispelling some of the common myths.  If there is interest let me know.  Maybe that will get me off my butt.

73, K1AT


IRS determination letter

David Andrews
 

Folks,

 

I am pleased to share with you the attached correspondence from the Internal Revenue Service officially designating TLARC as a 501(c)3 organization. This culminates the efforts of the past many months, including becoming a Tennessee Non-Profit Corporation, revising our organizing documents, and providing multiple submittals as part of the IRS exempt application.

 

Respectfully,

 

David Andrews N1ESK, Secretary


Re: Does a low SWR mean your antenna is a great performer?

John Haskell <jasm2213@...>
 

What George quoted from ham.stackexchange is correct.

To take it a bit further, SWR can be pretty much ignored.  If your solid state transmitter functions with normal output power versus shutting down, then SWR really does not matter much for most installations.  This is particularly true at HF where cable loss is minimal.  At UHF and with a long transmission line SWR can cause unacceptable losses.  

Here are a couple of examples of SWR versus loss using inexpensive RG-58.

Assume 7MHz and 75 feet of RG-58.  The cable loss is .9dB with a SWR of 1.

But what if the SWR is 2:1?  The extra loss due to this SWR is .2dB, e.g., negligible.


For a mobile set up on 442.1MHz..   Many people go nuts with low loss cables.  Not me. I use RG-58 in the car.  Here is why.  For 442MHz, 10feet of cable, and a 2:1 SWR, the additional loss due to the 2:1 SWR versus a perfect match is .2dB.  I do not believe you will notice that extra loss.


I have been considering putting a transmission line/SWR presentation together for TLARC in hopes of dispelling some of the common myths.  If there is interest let me know.  Maybe that will get me off my butt.

73, K1AT


Does a low SWR mean your antenna is a great performer?

George N2APB
 

FYI … I was recently in a roundtable on 75M and a perennial topic was discussed at some length ... "If my antenna has an SWR of 1:1 is it a great performer?"

 

The answer is simple ("not necessarily") but the reasoning is summarized well in the following post from the ham.stackexchange list.

 

I thought this would be of interest to all, but mostly for those on the HF bands where the science of homebrewing antennas is more often practiced.

 

72, George N2APB

 

======================================================

What is the relationship between SWR and receive performance?

 

If an antenna analyzer shows 1:1, does that mean it's an ideal receiver as well?

 

No.

 

Assuming we're talking about a characteristic impedance of 50 ohms, a 50 ohm resistor (otherwise known as a dummy load) will show a SWR of 1:1, although it will almost certainly perform very poorly as either a receive or transmit antenna.

 

The low SWR simply tells you that there are no impedance mismatches along the path from the transmitter (antenna analyzer in the case of your question) to the antenna feedpoint, at the current operating frequency.

 

And what about the converse, will a well performing receive antenna show a 1:1 SWR?

 

Yes and no.

 

Yes, a SWR of 1:1 means that you aren't losing signal to impedance mismatch reflections.

 

No, another issue is how efficient the antenna is at picking up the (desired) signal, preferably (especially in the case of directional antennas) while rejecting undesired signals as well. An antenna that is 5% of a full half-length dipole isn't going to pick up as much RF as the full-length dipole, let alone a full-sized directional antenna pointed in the proper direction, simply due to the much smaller physical (antenna aperture) size.

 

Generally speaking … if an antenna analyzer or (other) transmitter shows that the antenna output presents a SWR of 1:1, then what you have is probably about as good as it gets. That does not necessarily mean that what you have is a good antenna setup as exemplified by the extreme example of a dummy load.


Space Station pass @ 8:15 tonight!

George N2APB
 

David KF4DKW reports that there’s going to be a decent pass of the ISS tonight. The cross-band repeater is back on the air too. Maybe you can hear some traffic on the downlink:
Uplink Frequency: 145.990 MHz, PL 67.0 Hz
Downlink Frequency: 437.800 MHz

This time the ISS will start in the West and arc over to the NE ... all within 6 minutes!!

If you can’t get out to see it, just dial your UHF radio over to 437.800 and give a listen!

Either way, let us know what you find.

73, George N2APB


Lenoir City Street Festival

 

Come join in on the fun at the Annual Lenoir City Street Festival in beautiful downtown Lenoir City Saturday, October 10, 2020 from 10am until 2pm.

Classic/antique car show, live music, arts and crafts, vendors, children's play area and food vendors.
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG


Re: A Lot of Hams Near Me

 

No wonder I can't hear anything!! Hokie Smokes, Bullwinkle.......
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG


Brief Meeting Recap

George N2APB
 

If you missed the meeting on Wednesday, you sure missed a good one!  You can see a brief recap of the shenanigans on our TLARC home page ... https://www.tlarc.org/

 

73, George N2APB

TLARC ... https://www.tlarc.org/

 

PS:  Who was that person in the mask???

 

PPS:  Also note the latest Membership roster and the official Minutes from August.


Re: A Lot of Hams Near Me

Lou Devillon
 

WOW!


On Fri, Sep 18, 2020, 5:35 PM Juan Lopez <jloz34@...> wrote:
Plug in your callsign to see that hams that live nearby. No wonder I have so much QRM.

Sent from my Verizon, Samsung Galaxy smartphone
Get Outlook for Android


Re: A Lot of Hams Near Me

Jim Anderson <jimk0rgi@...>
 

This is very cool - thanks! FB on the QRM, I always wondered where it was all coming from. 

73, Jim - K0RGI 

On Fri, Sep 18, 2020, 5:35 PM Juan Lopez <jloz34@...> wrote:
Plug in your callsign to see that hams that live nearby. No wonder I have so much QRM.

Sent from my Verizon, Samsung Galaxy smartphone
Get Outlook for Android


A Lot of Hams Near Me

Juan Lopez
 

Plug in your callsign to see that hams that live nearby. No wonder I have so much QRM.

Sent from my Verizon, Samsung Galaxy smartphone
Get Outlook for Android


09-16-2020 TLARC draft minutes.pdf

David Andrews
 

Attached are the draft minutes of the September meeting. Please send any
corrections or omissions directly to me at n1esk1@charter.net. Thanks,

David N1ESK


Re: ISS sighting tonight

Brent Martin
 

On Friday, September 18, 2020, 10:37 AM, Mikeljay <k4mjf.1@...> wrote:



Tonight at 8:12 pm looks like an excellent opportunity to view the ISS as it makes its way around the globe. This pass will take it almost directly overhead (84°) and should last around 6 minutes. 
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG


ISS sighting tonight

 



Tonight at 8:12 pm looks like an excellent opportunity to view the ISS as it makes its way around the globe. This pass will take it almost directly overhead (84°) and should last around 6 minutes. 
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG


Sevierville TN Hamfest 2020

 

Just a reminder that tomorrow, Saturday, September 19, 2020, the Sevierville TN Hamfest will be going on starting at 8am.

Vendors, Clubs and let's not forget the bone yard! 

Talk in will be on the  WB4GBI 146.940, no tone

The last word that I had was masks need to be worn in the buildings but were optional in the open air areas like the bone yard. 
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG


ARRL: FCC Recent Fee Proposal Comment Suggestion

Bob Wilson-KK4XA
 

FYI

---------- Forwarded message ---------
From: Dudley Pitts <dudpit4@...>
Date: Thu, Sep 17, 2020 at 11:31 AM
Subject: ARRL: FCC Recent Fee Proposal Comment Suggestion
To: D. Pitts <dudpit4@...>


Greetings E. TN ARRL Affiliated Clubs,
I had a very informative and interesting meeting with the Tn Section Mgr. David Thomas and his entire cabinet concerning the recent FCC Amateur Radio license fee reinstatement. As you may or may not be aware, the Notice of Proposed Rulemaking (NPRM) is now accepting comments from people concerning Docket 20-270. ARRL FCC Proposed Fee article . This link will fill you in.

Apparently, there have been some comments filed by various Hams around the country that are... shall we say "less than constructive" that have been posted by various hams around the country who are very upset concerning the FCC's decision. Keep in mind that the ARRL played no part in this decision and are doing their best to communicate our concerns to the FCC as well. The license fee of $50 is a maximum amount. The FCC has not made any decision as yet what the fee amounts will be. It could very well be a smaller amount. 

The people that will be impacted the most from the change are the new amateur radio licensees. I am very concerned about this impact due to the fact it is difficult enough to get youngsters into the hobby without adding additional financial burden. Personally, I hope a "tier system" would be decided on that would give licensees under the age of 18 a reduced fee. 

Regardless of the impacts to each of us, it still is a bitter pill to swallow. However, this is a time for us to act responsibly when making our comments. We should take this opportunity for commenting seriously and provide constructive comments and suggestions highlighting our valued services during emergencies and providing free communications and training when needed. Historically, we've provided real value to our government agencies at all levels when disaster struck.  

ARRL, including myself, are asking everyone to comment but think before you write. Now is the time to show our competent best in our comments and remind the FCC of the various achievements, support, and service readiness we provide. Thanks in advance for helping our voices be heard in the best manner possible. 

Also, it would be a good time to write your TN state representatives with your concerns. For example, US Senator Marsha Blackburn has always been a strong supporter of the Amateur Radio community and remains so to this day. I recently discovered she was not aware of the fee impact to Amateur Radio at the time of the passing of the comprehensive bill package and shares our concerns. 

Thank you for your attention to this concern and I hope for the best outcome possible for Amateur Radio. We're all in this together and together we can make our voices heard. Get online and create another kind of "pile up"! 

Thank you, 73, and stay safe,
--
Dudley Pitts KM4IYQ
ARRL East TN Affiliated Club Coordinator



Virus-free. www.avast.com


--

Bob Wilson
KK4XA
Maryville, TN

--
Bob Wilson - KK4XA


TLARC meeting 9/16

 

Well..... another meeting is in the books. If you missed it, you missed a great time. Our first face to face meeting since February, when Covid disrupted our meetings. 

Smiling faces everywhere! And lots of laughter!  It was wonderful to see everyone! 

Should we have another face to face meeting, please be sure to clear your calendar so you are able to attend.

Talk to you "on the air", and I hope to see.you soon!

Be well, stay safe!
--
73,
Michael J. Foley, K4MJF
Tellico Lake Amateur Radio Club
Smoky Mountain Amateur Radio Club
470 ARG

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