Broadband HF Dipoles In Use By FLEX-6000 Owners ?

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  • Updated 4 years ago
With The FLEX-6000 Radios having the ability to simultaneously display virtually the entire HF spectrum it would seem desirable to have an antenna which provides a reasonable impedance match over the entire range (without frequency sensitive tuning).

(In my situation a basic dipole or vertical antenna are the only reasonable choices so I am restricting my considerations to those types.)

I have some knowledge of the literature covering the resistively terminated antenna types popularized over the past 30 - 50 years but would appreciate feedback from actual users of these antennas. (I'm aware of the 'fan-dipole' broadbanding technique but don't believe that it's practical in my situation.)

The two dipole style resistively terminated antennas that immediately come-to-mind are the folded-dipole (both 2 and 3 wire) and the 'Australian Dipole' (the first I heard of it was years ago in 'Ham Radio' when Bill Orr, W6SAI, mentioned it in his column).

Just today I came across a reference to the 'Robinson-Barnes HF Broadband Antenna' but when I go to the manufacturer's Web Site (Bushcomm HF Antennas in Bayswater, Western Australia) their folded-dipole style antennas (they make some other types) look to me like terminated folded-dipoles (they use stainless-steel for the antenna wires and I'm reminded of the old Barker & Williamson broadband terminated folded-dipole of years past) and not something 'different'.

Are there members who have experience with resistively terminated dipole type antennas ? If so I'd like to hear from you - your experiences and opinions.

Thanks;

Paul, WB5AGF
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Paul, WB5AGF

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Posted 4 years ago

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Chris Tate - N6WM, Elmer

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Paul I spoke briefly with Gerald in Visalia on the the issue regarding Flex friendly antennas that would truly allow broad banded slice availlability and performance for the Flex.  The most amazing of radios are only as good as their antennas. This could be an important topic for the brain trust.   My first thoughts revolve around Log Periodic beams...  And a search for a lightweight one would probably be worth checking out.  That being the issue, they are heavy (logs of aluminum) and expensive.
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kr4k

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Can recommend the Tennadyne T8 as an excellent HLPA for use with the 6700.

73/gus
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Chris Tate - N6WM, Elmer

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Thats a mighty looking beast but I am sure it works great.
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kr4k

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I operate three of the Bushcomm antennas with the 6700:
BBA-100Ce
BBA-600Ve
BBA-1kDe

I use it on ham, MARS, and WH2XOO experimental license frequencies, 2.2 MHz to 27 MHz. I also operate these on 160M because they are the long versions.

The antennas often get reports "best signal on the band".

Have had one of the Bushcomm antennas up for 11 years. The only notice of weathering is on the fiberglass spreaders, and those are only a little fuzzy.

The Robinson-Barnes HF Broadband Antenna is a terminated 3-wire antenna. For details on the theory and NEC modeling results, recommend Cebik's article "Notes on Wide-band Multi-Wire Folded-Dipoles".

Array Solutions used to sell a similar antenna:
http://www.arraysolutions.com/Products/AS-BB-XXSeries.htm

There are other commercial versions of the RB 3-wire:
http://www.moonraker.com.au/#!hf-antennas/c1byd
http://www.lencom.com.au/index.php/products/hf-base-antennas/3-wire-folded-dipole-antennas

Have used the B&W two-wire versions, and the Bushcomm antennas are much better.

73/gus  KR4K
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Chris Tate - N6WM, Elmer

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BTW I experimented on those resistive terminated folded dipoles many years ago when I was just starting out.  They work ok on the upper bands..  the have low SWR on the low bands but so does a dummy load.. and these are pretty close to that.    
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EA4GLI - 8P9EH - Salvador

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Have you considered a HexBeam?
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Chris Tate - N6WM, Elmer

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another choice on my short list perhaps for a residential station.  At my hilltop contest station a hex beam may last an afternoon or so before it becomes one with the hill..  
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kr4k

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I have documented that the Bushcomm antennas perform just as Cebik describes in his article. The low frequency knee on mine is about 100 kHz lower than he predicted. I have the center up 48 ft. with ends at about 30 ft.

These antennas are not dummy loads - any more than many claim of HLPA antennas vs yagi antennas.  If you need a broadband HF antenna without a tuner, I can recommend the 3-wire RB antennas after many years use.

73/gus
Dr. Gus Lott, KR4K
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Steve N4LQ

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Gus
How is the 3rd wire connected? 
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kr4k

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Above is from Cebik's article. I add the Bushcomm OFO kit which allows you to place the BALUN at the ground. The OFO kit also significantly improves NVIS performance.

My BBA-100Ce antenna have been through at least two severe thunderstorms where winds exceeded 80 mph, toppling about 18 oak trees, and a hail storm that totaled our Airstream trailer. They are commercial grade, wind rated to 130 mph, and are built like tanks - just like the 6700 design!

Recommend reading the eHam.com reviews and Cebik's article.

The Bushcomm RB antennas and the Tennadyne T8 HLPA make using the 6700 so easy, allowing for excellent broad spectrum pan adapter views. They simplify remote 6700 operation, and antennas like this add 6700 use options like ALE and broadband waveforms. For my 6700 use, they are worth the small performance degradation compared to a dipole.
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Chris Tate - N6WM, Elmer

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Hi Gus.  I agree that they definitely work..but performance is definitely relative.

 I think the one I worked with was a B & W and in fact I am aware they use these in some military applications.. or at least used to.  Not for everyone however.  My requirements are a bit less modest at a competitive station at 2000 ft, it needs to be rotatable,  handle 120 mph winds, have measurable gain and handle full legal limit power.
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kr4k

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Rotatable? Recommend Tennadyne T14.10-30HD and two BBA-1kDe. Or you could get the 19-element 1005-CA from arraysolutions.com, which weighs at 2100 lb., rated to 25 kW:
http://www.usantennaproducts.com/pdf/lp1001_1002_1005data_sheet.pdf

73/gus
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Barry Kanne

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Hi Paul:

I have been using a B&W folded dipole, model BWD-90, that covers down to 160 meters.  It has supported my 3000 and now my 6500 with excellent results.  It is no longer available via normal ham channels as B&W have seemed to drop out of the amateur market in favor of the much higher priced government market.  But, if you come across one, I am sure you will enjoy its performance.

Mine is strung between 2 tall pine trees with a heavy duty screen door spring on each end where the support cable (aircraft cable) is connected to the tree trunk.  That way as the trees sway in a wind, the antenna remains protected against undue strain and the springs take up the slack.

I also have a 4 element beam for 10-20 and appreciate the additional gain it provides, but for general use, the folded dipole is my primary antenna.

73,
Barry in Atlanta
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Dale KB5VE

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I have run a Tenadyne t6 and it is unreal with the pan adapter on the 6000 series, I talked to a ham running a 6500 with a cobra antenna,
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Steve N4LQ

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This version is interesting. Read toward the bottom. He claims a length of 122' instead of the usual 90' puts the low current point at the resistor on harmonic related bands. Interesting. 
http://www.b-squareengineering.com/TerminatedFoldedDipole.htm

73 Steve N4LQ --- Tilted but not Terminated
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k3Tim

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Good find Steve!   Their comments seem to be spot-on.  

I had a B&W TFT long ago and it seemed to do fine under certain conditions.  Mine wasn't at the proper height.

Tim
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KD8TVB

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I run an inverted V OCF dipole for 10-80M, center is at 30 ft, ends at 9 ft... amazed how well this antenna works
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Ken - NM9P, Elmer

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I also run a home built Offset Fed Dipole, cut for 160 Meters.... About 90 ft. on the short leg and about 180 ft. on the long leg. Use a good 4:1 current balance at the center. Elevation is about 38 ft. at the feed point, and about 18 ft. on the ends with two left-hand bends on the long end to make it fit my yard. It works well on all bands except 15 meters. I still use the tuner to tweak it.
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Peter K1PGV, Elmer

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Another OCF user/lover here, about 40' up.  I'm using the Buckmaster one... perf just as Ken describes: works well except on 15 meters.

Peter
K1PGV
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Tom Warren

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   I built the six-band center-loaded off-center-fed dipole by Serge Stroobandt, ON4AA. It's certainly not a StepIR but works very well and frees-up the tower for VHF/UHF yagis.
                                      http://hamwaves.com/cl-ocfd/en/  
Tom - W4TMW
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Roger Rockwell/na4rr

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How about  the broadband hexagonal beam as designed by G3TXQ.  ( http://www.karinya.net/g3txq/hexbeam/broadband/ ). and shameless plug for the one I’ve been building and selling for about three years.  This is my main antenna for 6m-20m.  I usually have panadapters open on 6,m 10, and 17.  I have become one of those 6m freaks and that is where I prefer to be.  You never know when the band is going to open or from what direction.  The hex is plenty good enough to keep an eye on the band.  When it shows some promise I switch over to the 6 element quad.  I have it on a 50ft tilt over crank-up tower.  It is at 25ft 99% of the time.  Talk about becoming a lazy ham.  I just find them on the flex6700 and talk to them.  To put icing on the cake, since the tower tilts I added Al’s (NN4ZZ) http://www.nn4zz.com/HexLock.html  The only thing that is going to make heaven better is to have a zero noise level.  Did I mention that all Flex owners get a discount on the antenna.  

 

There are about 3 people making the antenna here in the states.  All are good and make a great antenna for the Flex radios.  It is also a very buildable antenna to home brew. 

 

Roger

NA4RR

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Al / NN4ZZ

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Roger's hexagonal beam is also a good choice as the second antenna for diversity reception on the 6700.  I use several antennas for 80-6 meters connected to ANT 1 on the radio that are selected by an antenna switch.  I have the hexbeam connected to ANT2.   Works well for monitoring other bands in the second panadapter as well as diversity.  

Roger's antenna is well made and works great.   Check it out here:

http://www.k4hex.com/home.asp

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com


******** hexagonal beam right outside the shack *********

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Kevin WB4AIO

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Low SWR across the spectrum and flat receive frequency response across the spectrum are not the same thing. It is the latter that would be most desirable for utrawideband spectrum display.

The B&W version of these resistor-antennas is approximately 13 dB down from a dipole on 75 meters.

I have not made tests, but it wouldn't surprise me if a simple fan dipole had flatter receive response than one of these resistor-type antennas.

The resistor-types will have spots in the spectrum where they have high loss despite a perfect match. A plain dipole or fan dipole will have spots in the spectrum where the SWR goes very high -- but may receive well on those frequencies just the same, despite the loss due to the mismatch.
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kr4k

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Cebik explains the theory that causes the low end knee effect you describe. 90 ft. versions of these terminated antennas are really for 4.5 MHz up. The BBA-100C 27m version ~ -8 dB, BBA-100Cs 20m ver ~ -15 dB, but the BBA-100Ce 57m ver < -1 dB from a dipole on 80m.

In any case, can highly recommend a 3-wire version over the 2-wire.
(Edited)
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Steve N4LQ

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This site has more info on these broadband antennas.
http://hflink.com/antenna/

Steve N4LQ
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Steve N4LQ

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Ebay is loaded with these things http://www.ebay.com/bhp/folded-dipole
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Barry N1EU

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Sure looks like $335 worth of antenna to me (duh).

Barry N1EU
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Steve N4LQ

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Here's how you justify this. 

Either pay $335 for that antenna or pay $700 for an MFJ-998 auto tuner. 
So you buy the antenna instead and pocket the $365 or put it toward an amplifier 
to make up for the lost db

The 16:1 balun is $35 from Buxcomm and those resistors total about $35 for 200 watts of dissipation. Add the wire cost and some insulators and you may hit $125 for parts. 
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Lee, Elmer

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I bought a mfj 929 off swap.qth for $100 and stuck it in a 50 cal ammo can 
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kr4k

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For a 53 m (175 ft.) 3-wire built using 3mm (0.125 in) 304, 7x19 stranded stainless wire, high power arraysolutions.com 16:1 BALUN, and heat-sinked Ohmite TA800 resistor, stainless hardware, insulators, etc, your cost will be about $600-750. Should be continuous duty, 1.5 kW.

That would be an ideal project to have connected to the 6700.

73/gus
(Edited)
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Steve N4LQ

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Can you be more specific on that resistor? I looked at Ohmite's docs and don't see a TA800. Would that be 800 watts? TA100 is 100 watts. 
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kr4k

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Sorry - Ohmite TAP800.
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KY6LA - Howard, Elmer

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Just to throw gasoline on the fire. Most of the time my 6700 is connected to a SteppIR MonstIR @85'

Even when tuned to say 20M I find that I still hear a lot of signals on every other band I have an Alpha Delta 160m-10M dipole and a Pixel Loop. BUT I still hear more signals on the SteppIr on all bands at the same time than any of the other antennas which makes me wonder why people seem to be so concerned about needing broadband antennas.

Likely the better performance of the tuned antenna is due to its height. 85' vs 30'.
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Paul, WB5AGF

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(My lack of response (until now) does not mean that I'm not reading everyone's comments .... I'm mulling them over.)

I've been doing some thinking .... I found KB7GF'S Shared Apex Loop (http://www.arraysolutions.com/Products/sal_array.htm) intriguing, not only because of what it does but also because it caused me to have the sudden realization that perhaps maximum power transfer is not necessarily the holy grail of antenna design .... at least insofar as HF/MW receiving antennas are concerned.

(I'm beginning to think about a 3-wire terminated folded-dipole for broadband receive and a tuned loop for transmitting in the manner of W5QJR's design.)

Everyone please keep talking.

- Paul, WB5AGF
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K4SC

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I have been using the B-Square Engineering 122' FTD for three years and have nothing but praise for its quality and performance.  Recently took it down because I've moved from South Carolina to Iowa; what was I thinking?  Am in the process of reinstalling it at my new QTH, and will be using it with the Flex 6500.  I did use it before with the Flex 3000 and an Ameritron ALS-600 solid state amplifier and no tuner.  It worked fantastic.

Currently I am working 300 miles away from home and staying in an upstairs apartment.  I have the 6500 connected to a Pixel Magnetic Loop antenna for receiving and use a 33' fiberglass kite pole with insulated wire threaded inside for transmitting utilizing the Flex's internal ATU.  Both are mounted on my fire escape railing.  The mag loop works just super with the broadband Flex.  I can get a very good signal on all bands except 10 meters and up.  You might consider one of those for a receive antenna instead.  It really cuts the noise level down but enhances the signal to noise ratio.

Chuck K4SC Red Wing Minnesota/Mount Pleasant Iowa

(Edited)
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Steve N4LQ

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I have the Pixel Loop. Don't know about the S/N ratio but signals are cut down to the point that the noise is too weak to hear (as with many signals). Personally i think that's why everyone thinks it's quieter. IMHO etc. 
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Ron

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I also have the Pixel and find it works well.  Don't forget to try turning the ANT RF Gain up to +20db.  On most bands I generally leave it there and it helps significantly.  It would be interesting to hear a consensus (likely chance...) on a broadband transmit-only antenna for MagLoop receive-only users with space restricted locations.

Ron, K2RAS
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Chuck - KJ6HT

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I am very happy with the broadband performance of my Tennadyne TD-90, folded terminated dipole. It is at least 1.9 to 1 from 1.8-30 MHz. My experience has been that it performs about the same as a dipole and is not as susceptible to man made noise. Rog at Tennadyne is a great guy and will answer any questions you have.
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Paul, WB5AGF

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Just this afternoon I was working my way through the logic of 'long' (i.e. very-long) terminated dipoles (I've been looking at the response curves that Bushcomm Antennas so kindly provides in many of their antenna brochures and Jack Belrose's (VE2CV) technical comments back in the May 1994 issue of 'QST') and also looking at 'cage dipole' characteristics.

Then the idea occurred to me .... wondering what would happen if one were to build a long cage-dipole (to lower the 'knee' in its response, if it were a terminated antenna, below the lowest frequency one might wish to transmit on) and then run a wire through the middle of it .... with a terminating resistor in the middle.

I don't know how I was lucky enough to select the right search term but I found these articles by Martin Ehrenfried, G8JNJ, from the May & June 2014 issues of 'RadCom' .... his 'Terminated Coaxial Cage Monopole' (TC2M) Antenna ..... see : http://www.tc2m.info/TC2M%20HF%20Vertical%20G8JNJ.pdf ... is essentially 'my' (in my head) cage dipole with a terminating resistor in the middle .... the word serendipitous immediately comes to mind.

- Paul, WB5AGF
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Steve N4LQ

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One point missing in this discussion is the antenna's pattern. 
We go to great lengths (pun) to make the resistor antenna long enough so as to avoid the large loss at low frequencies but forget about the narrow lobes that may make it difficult to communicate in certain directions on the higher frequencies.
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AA0KM

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How about this vertical?..

A monster Omni..lol

Great post`s on this topic.

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Paul, WB5AGF

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Say ..... You are a trouble maker aren't you ?

My next door neighbor would throw-a-fit ....

(I especially like the DANGER RF RADIATION sign.)
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Andrew Russell

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Just what I have always wanted.
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Steve N4LQ

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Paul
A rat is smelled.
How'd they come up with zero db gain in a resistor antenna? 
My smoke and mirror detector just went off.
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Rick Hadley - W0FG

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Many years ago, Doc Braley, W0GET or Ted Hunter, W0NTI of the Eye Bank Network fame (I don't remember which)  used to have a conical monopole like that set up at their house north of Iowa City.  They both had huge signals on 3970 every evening.
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Steve N4LQ

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So the basic concept is this: 
To apply RF power to a resistor but in doing so cause radiation?
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The answer seems to be:
Use a long feedline (the antenna) to the resistor and hope it all radiates before power gets to the resistor.
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A problem is:
If the "feedline/antenna" is of low impedance the wires must be close together and it won't radiate much.
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Answer for this is:
Make the feedline high impedance so we can increase the distance between the wires. (pull them apart). 
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This produces another problem:
The RF source, feedline and resistor need to be the same impedance:
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The solution for this is:
Use a balanced transformer to increase the source impedance to that of the feedline then use a higher value resistor to match both. 
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Then we find:
The higher the frequency, the greater distance in wavelength is between the feeder wires thus the more radiation from them and the less consumed by the resistor.
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What we need is:
Some way to measure the power consumed by the resistor for any given frequency. 
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It doesn't seem too difficult:
An RF voltmeter across the resistor would tell the story but so far nobody seems to have done so.
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One idea:
Wireless telemetry  of the RF voltage via a uhf link. 
--------------------------------------------------------------------------------------------------------------------------------
Danger: The results could be depressing. 

Steve N4LQ
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k3Tim

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For the particular frequency the resistor is at zero voltage but when the VFO moves away from this, then the resistor is needed.  Check the B2E info as well as Martin's work (below). 
--...  ...--
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Paul, WB5AGF

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Steve;

I believe that your comment about making the feedline (antenna) as long as possible and then hoping that most of the RF power radiates before it gets to the terminating resistance is most probably the central idea to having a terminated antenna reasonably efficient when used for transmitting.

When I (earlier) remarked about my looking at the 'knee' in the radiation efficiency graphs in some of the Bushcomm brochures, and referencing VE2CV's 'Technical Correspondence' comments in the May 1994 'QST', that is what was in the back-of-my-mind ..... 'above' that 'knee' (i.e. at higher frequencies) the terminated antenna is getting long enough (wavelength-wise) such that more of the applied RF gets radiated (and is not used to heat up the terminating resistor).

(I noted that the Bushcomm terminated dipoles advertised as being good down to 160M appeared to have their 'loss-knee' up near 80M and so, if the real estate was available, it would seem prudent to use those antennas for 80M - 10M. If a person was determined to transmit on 160M then an even longer terminated dipole would seem called for.)

If we were to put up an extremely long dipole (and not worrying about the antenna pattern for now) then I believe that it would show little reflected power (regardless of frequency) because the reflected component getting back to the feedpoint would be very low compared to the applied signal. (An infinitely-long antenna should show no reflected power regardless of the applied RF frequency.)

- Paul, WB5AGF
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Doug Hall

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K3TIM, if the resistor is non-reactive then any voltage across it results in real power being dissipated, no? In this case isn't it enough to know the magnitude of the voltage?
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k3Tim

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Hi Doug,

It looks like you are correct and I am incorrect  I was thinking P = V * I and taking into account the possibility that the voltage and current are not in phase due to complex  impedance of the antenna itself, that is measuring back at the Coax end.  If one measures across the resistor only, that's different.

Checking the ARR Handbook 2014, section 2.10.7 "Reactive Power" they show a R L series network being driven by a 250V-AC 60 cycle power source.  The voltage across the L=200V and across R=150 with the current = 2 amps.  The voltage adds to 350V, more than the 250V applied due to the L.  But the power in the resistor is 300W.  V^2/R or I^2*R works either way. The Handbook says the V and I will be in phase at the resistor, at least that is the way I read it. 

Therefore measuring the V of the termination resistor and calculating V^2*R is enough to determine the real power lost in the device.  

I have to review the  Handbook and refresh my analog circuit skills!  The handbook is a great technical resource and a true bargain.

Thanks for questioning this and catching the blunder.  

My apologies to the group for causing this confusion.  

:-(   !

k3Tim
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Steve N4LQ

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Tim
Your punishment is to determine a means of measuring RF voltage while suspended 40 feet in the air and not upsetting the system with wires and equipment.
Telemetry? 
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Martin Ehrenfried

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Hi All,

The problem with most comparisons of terminated dipole antennas is that they are usually not compared like for like with similar sized antennas, the term apples and oranges spring to mind.

Folks just see the resistive load and assume the worst without bothering to quantify the losses.

Every antenna system has some losses, the trick is to know how big these losses are, where they are occurring, and if this is likely to cause a problem in the intended application. In in some cases moderate loss may not be an issue, especially if the convenience of wide frequency coverage is the main concern. Examples of which include Frequency hopping, ALE, propagation monitoring etc.

Folks may actually be surprised to discover that the distributed losses in a tuned antenna system can sometimes be greater than the power dissipated in the resistive load of a terminated antenna, but because it's not so easy to 'see' or 'feel' these distributed losses they tend to be ignored.

Many of the questions raised in this thread WRT broadband dipole type antennas, and the TC2M in particular are covered in the TC2M article which can be found at this link.

http://www.tc2m.info/TC2M%20HF%20Vertical%20G8JNJ.pdf

These include calculated gain at 20 degree elevation and measured field strength, power dissipated in the load, properties of cage antennas WRT impedance variation and and null filling etc.

The TC2M is a good omni-directional 'search' antenna (as RX S/N is generally not defined by the antenna) which can also be used for opportunistic DX chasing if required. 

However if you just want a broadband receive antenna then consider using a good (there are lots of bad ones out there) active antenna, which is what the military and professional agencies tend to use. Either a single omni for casual listening or a steerable array or phased loops for improved S/N ratios.

The bottom line is that directional gain antennas are not ideal for broadband monitoring unless you want to concentrate on just a specific region on all frequencies at the same time. In which case a log-periodic, Beverage, or terminated Vee beam my be worth considering.

Terminated antennas have their merits, but are often criticised for the wrong reasons.

Regards, 
Martin - G8JNJ 

tc2m.info@yahoo.com

www.g8jnj.net 
www.tc2m.info 
http://websdr.suws.org.uk/
(Edited)
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k3Tim

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Hey Martin,

Thanks for the insight and the link the your articles. Very nicely done and an interesting read. The vertical version of this class of antenna is very intriguing, It seems one could also make a version that is disguised as a small  "antique" Wind Mill or something similar.

Best 73's!

k3Tim / PE / MSEE / PPSEL-IIR / 2pts