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KB1SG's Rhombic Emails
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This is a page of rhombic-related emails sent to KB1SG. It was written by Ian W. Cummings, KB1SG, and is displayed here with his permission.

Rhombic Antenna Email

Over the years I have received email related to various aspects of rhombic antenna use, design and construction. Many are first-hand accounts of rhombic "lore." I've cut and pasted from my email as I have received each item. Hopefully the reader will find this information interesting. I have left the authors off as email addresses tend to mutate over time.

Email:

Really enjoyed your web page on rhombics. I have traveled to Point Reyes many times to gaze at the rhombics at both the AT&T and MCI (old RCA) stations out there. I have also seen the Cape Cod station you write about in Chatam. I have built small rhombics to receive Los Angeles FM (broadcast band) radio stations in San Diego with some luck, but I have been limited by the amount of real estate I have had to work with, and by the hills around my home.

Once I ran 1300 feet of coax up a hillside near my home to four "quad" stacked log periodic antennas pointed to Los Angeles. I put a pre-amp by the antennas that was powered via dc over the coax. I still had a problem reaching over a hill but before the set up was destroyed by some kids I had intermittantly received an FM broadcast station in Vancover B.C. ! (We have this ducting effect here at certain times of the year).

Someday I would like to build my dream "double parallelogram rhombic" based on that RCA 144 mHz design adapted for the FM broadcast band.

Bard-Alan Finlan

I was rooting around on the Internet this morning and came across a reference to your rhombic web pages which I found quite interesting. I don't even remember now where I found the reference, but thought I'd drop you a note with some thoughts and information from my personal experience.

The best reference on Rhombics that I've ever come across is Edmund Laport's "Radio Antenna Engineering", published by Mcgraw-Hill in 1952. Laport was primarily a long wire man (to include rhombics, v-beams, etc) and was RCA's expert on transoceanic and global HF communications in the hey-day of such operations. He died 10 or 15 years ago. He was never a ham, but his passing was mentioned in QST at the time.

I am now retired from the US Naval reserves, and first came across a reference to Laport's work in 1978 when I went to do my annual two week active duty at Cheltenham, MD, just outside of Washington, DC. I knew nothing about the place, and arrived well after dark. Being an old (did I really say old??) antenna guy, I was pretty excited to see all the antennas, mostly rhombics, all over the place when I got up the next morning. Cheltenham had been the receiver site for NAVCOMMSTA Washington, DC (callsign NSS) until it was deactivated. The transmitter site was near Annapolis, MD, with phone lines linking the two sites.

The first day I was at Cheltenham, I began asking around about a ham station, and quickly got access to the club station, K3NSS (or W3NSS, I forget.) Since the NAVCOMMSTA was deactivated as an HF site, the ham station had access to most of the antennas on the site. On the wall was a large drawing of the site with the location and information on the many and various antennas. There were as I recall, 60 some odd rhombics, three or four fixed vertical log periodics, and a few others, including sector sleeves, fish bones, and so on. In the two weeks I was there, I walked all over the site looking at antennas and taking pictures.

One antenna on the site map was listed as a "Laport Rhombic", which from looking at it, was some type of stacked array of two rhombics. I did a lot of operating while there, and one night got to talking to a guy on the air in Puerto Rico (I think) who had helped build the Cheltenham antenna farm, and had a lot of information on the place. The antenna feedlines were all buried coax. This was similar in electrical size to the old RG-17 if you're familiar with that stuff. It also had a protective outer shell of wrapped hemp or jute, making the overall outer dimension about 1.5 or 2 inches. Most of the rhombics had feed lines going to each apex, all coming into the ham shack to one big patch panel. At the antenna, the coax went as far as the base of each apex pole, where there was a broadband balun, with open wire feeders going up the pole to the antenna feedpoint. The balun was in a metal case, and was most certainly not a ferite balun, but likely an air wound balun, much like the one the Heathkit sold back in the 60's. According to this guy, this was one of the first large scale uses of buried coaxial feedline at a NAVCOMMSTA. He also said that the "Laport rhombic" was designed to cut down on the multiple sidelobes that all rhombics (actually all long wires) have. This was verified later when I located a copy of Laport's 1952 book. I don't have that book handy, but if you have a copy of the 2nd edition of Johnson and Jasik, refer to Figure 11-9b for a sketch of this antenna. Laport, by the way, wrote this chapter on long wire antennas in Johnson and Jasik. If you want a copy of this chapter, I can send it to you.

Since the feedline from both rhombic apexes came into the shack, in order to terminate the unfed end for uni-directional operation, I simply patched a Heath cantenna into that end. One day when I was there, the guy who was the custodian of the ham station saw me doing that and asked why. I replied that it had to be terminated, to which he replied that I didn't need to do that since it was already terminated "in the balun." No amount of arguing was going to convince him that this was incorrect, and that a transformer (which a balun is) will only reflect the impedance seen on one side to the other, and that with an open circuit on one side, the rhombic was NOT terminated. Oh, well.

Somewhere in my files, I have a Navy design book on rhombics. This may very well be a Navy'ized version of the War Department document (TM11-2611) that you mentioned. Whenever I can find it, I'll check and see. If you want a copy, I can make one for you.

Another story on Don Wallace. I was homeported in Long Beach, CA in the Navy from late 1970 till mid-1972. During this time, I ran the ham club on the Naval Station in my free time, and being single, spent a lot of time there operating. We had a pretty good station: a Collins S-line, Henry 2K, and a Mosely Classic-36 antenna at about 100 feet. In short, we put out a pretty good signal.

When I started working my forst DX, and operated my first DX contest from there, I found out that the big game amongst Southern California hams, was to try and beat out Don in the DX pile ups. I quickly found out that sometimes I could, and sometimes I couldn't. Probably about 50-50. I never got out to see his site at Palos Verdes, but heard all about it, and had correspondence with him once in the early 80's.

You mentioned "reentrant" terminations for rhombics. I can't find anything on this in any of my references either, but the reentrant term is used in microwave (klystrons and magnetrons) devices to refer to one type or another of coaxial line or cavity resonator. Perhaps in rhombic usage they used some type of resonant terminator?? I'll keep looking.

Brad Bradfield, PE W5CGH Systems Engineer (ex WB0CGH) Raytheon Systems Company

The Silver Springs Radio Club in Ocala, Fl used a 1000 foot 3-wire curtan rhombic for phone patching durning dersert storm. In a three month period we ran more than 9,000 phone patches. We are in the process of moving the MARS station at present and will have two Rhombics one for Europe and one for Korea. Attached is a diagram of the ANT design we use..

73's Ernie K4OSM club home page http://pig.net/~ssrc

...I was stumbling around the net looking for any mentions of Press Wireless, and somehow Altavista flagged your Rhombic Page up. ..I twa s real pleasure to read your writings about famous users of rhombics. My own involvement was at the AT&T Overseas Radio plant with receivers and control at Ft. Lauderdale FL and transmitters about 11 miles south at Ojus, FL. "Fort Lauderdale Overseas," as it was called in AT&T parlance, began in the late 1930's when one radioman from NY was sent to Hialeah, FL (now a northwestern suburb of Miami) to operate a single radiotelephone curcuit to Nassau from Miami. From that start, which was on rented space in the front porch of Tropical Radiotelegraph, AT&T evolved perhaps the only place in which Ma Bell ever ranted real estate from someone else. TRT remained the landlord and even built the newer, bigger buildings at Ft. Lauderdale and Ojus. In fact, the entire Ojus plant was operated by TRT personnel for AT&T, in addition to TRT's own transmiters there. Up at Ft. Lauderdale, the building had a partition down the middle with TRT and AT&T occupying separate premises.

...Ft. Lauderdale was also the home of AT&T's smallest but busiest shore phone station, WOM. I did a lot of time on the WOM watch, as it mushroomed from dormancy to the shore telephone station that waked AT&T up to the potential of what AT&T called "High Seas Radio."

...At its peak, AT&T's Ft. Lauderdale operation ran about 30 HF transmitters, mostly 4-channel ISB, using rhombics on bearings ranging from 240 degrees aimed at El Salvador in Central America around to 67 degrees, which was an antenna placed for ship service.

...AT&T broke most of the rules about rhombic design, simply building the antennas on commonly available telephone poles, which made the height about 60 feet. The rhombics at Ft. Latuderdale were short, as well. Thus, the main lobe was certainly much broader and higher than ideal conditions would achoeve. Fortunately for us, most of our paths were single hop to the Caribbean Rim, so the high angle didn't matter a lot. What with 10 kW PEP into the antenna, we exchanged pretty blitering hot signals with our correspondents most of the time. Nighttime hours down on 4 or 5 mHz, of course, suffered a lot of absorption, but in daylight, with largely north/south paths, things were by and large rather easy. Our overall circuit quality and reliability was much higher than either NY or SF, with their multihop E/W paths.

...A comment about your remarks on paralelling rhombics: I learned from a BBC engineer that they ran 300 kW into two paralled rhombics off the Caribbean island of Antigua to Cuba, broadcasting on 11775 kHz in the mornings to blanket Castro. All I can say is that hog put in a huge signal where I was in Florida, and its sidelobes made for a very stroing signal over most all the Eastern US at places I tuned it in as an SWL. Imagine what the ERP in its main lobe must have been!

...And, of course, AT&T's fabled MUSA (Multiple Unit Steerable Antenna), so widely bragged on by Bell Labs, was an inline array of rhombics, built to slightly different vertical angles, to effect space diversity and varying vertical reception angles from England in the days of HF transatlantic radio telephony. My recall of it was that its row of rhombics ran several miles in length at Netcong, NJ, one of AT&T's two NY receiving plants.

..Hope you found some enjoyment in all this. I sure found enjoyment in reading your page. I hope you keep it there for a long time ti come. I want to get back to it again from time to time!

Don Kimberlin

I did build a Laport Rhombic back in the 80's for 2M. I certainly did get 20+db out of it (crude measurements, can't give precise gain figure.) I see you refered to another commercial SW program for rhombic analysis. I wonder if that program would address the Laport design or not. I am curious if the 27db gain figure has been reconfirmed or not for that design. I do have a copy of Laport's original article.

I am thinking about trying again with a Laport Rhombic, except applied to 6M for EME use. I have been thinking of other variations to squeeze out all the gain I can as it does make it easier for an EME QSO. I have made some 2M EME QSOs so I do have some experience with that mode.

Thanks in advance for your comments.

de Dave, N7DB (CN85)

I just discovered your page whild doing some research on the Web. A number of years ago our technical library was involved in the disposition of some old books. During the 'purge' of the library I happened upon a copy of the classic A. E. Harper, "Rhombic Antenna Design", CY 1941 and as printed on WWII paper and printing. This copy was originaly part of the old Ft. Monmouth, NJ Tech. Library and later the library was transfered here to Ft. Huachuca, AZ. The copy of "Rhombic Antenna Design" is in my library at work. Need less to say the copy of the handbook is a real treasure for me. I also still have a set of Rhombic calculators (Circular Slide Rule versions) in the office file cabinet.

If you ever need some reprints (Xerox) of the book I can provide them.

We (U.S. Army) have taken down almost all of the Rhombic installations that were in existance. The only Rhombic that I know about at an Army installation is the old antenna at the MARS/Amateur (K2USA) station at Ft. Monmouth, NJ. I recently looked at the antenna and it is essentially inoperable because of overgrown trees, zapped Balun transformer and questionable termination R. A few years ago we took down the Rhombics that were used at Ft. Sam Houston, TX. They were Class "D" Types With AB 105 supports. These antennas were shipped to Ft. Lewis, WA to be installed at the MARS/Command Radio Station. I think that they have not been installed as yet because I surveyed the site a number of years ago to install them but no task has reached this organization for installation. Since I will be doing some work for FEMA at the new State EOC in Olympia, WA in the next few months, I will go over to Ft. Lewis and see what the disposition of these antennas are. The last site that I know about overseas that utilized Rhombic antennas, was the TX site at Pirmasens, GE. In fact, one of the antennas was a 1200 FT. job. It was used on a circuit to Tehran, Iran that we used for telephone voice and some data. The site had another large 'nested rhombic' which was used for the circuit to Asmara, Ethopia relay station. Of course, these stations and circuits have been deactivated for some time. We also had a rosette array of rhombics at Tori Station, Okinawa for some time but as with most HF stations these were deacivated about 10 years ago. Unfortunately, I was involved with the deactivations and fortunately with many installations.

Today what long haul stations are active within DoD, are primarly associated with DCS contingency and special missions (eg, Scope Command, Mystic Star). All sites have been reengineered using fixed or rotatable RLPAs and rosette arrays of Loops for RX. The Army is not envolved with long haul DCS except for the special missions that are supported out of Ft. Detrick, MD. There are some other special HF radio missions that are associated with Army SF operations supported out of Ft. Bragg and McDill AFB. Today the primary users of HF long haul are AF and Navy.

Well, your page stirred my interest memories about rhombic antennas, so I just had to reply and provide some information. Hopefully my info. is not to trivial and may be of some help in your data base and designs.

Steve Wagner

Thank's for the reply, I thought that you would be interested.

Yes, one must erect the Rhombic structure at least over 1.5 wavelength above good earth. In fact, and in practice its best to erect the antenna (average height because of sag) at increments more than 1.5 wavelength (HF ionosphericaly propogated). With a known earth constant one may calculate or just use the charts for the optimum height at a given and descrete frequency for a point-to-point radio path or circuit. Thereby optimizing the correct launch (take-off) angle for the given point-to-point radio path with respect to the number of hops required. Another consideration in height is to take advantage of some 'ground gain' if you know the ground constants at the site and where the Fresnel Zone occurrs. The old practice of a sea water shot (properly selected and used) is really true and you sure can get some amazing results at both ends of the circuit.

I think that we still have in the drawing files the construction/installation drawings for several rhombic antenna classes. There are some standard drawings for wood pole and AB 105 designs. There are also some standard construction and design data within some of the AFTO series of documents.

An interesting thing to try if you have NEC at your disposal is to try the antenna with traveling wave segments using a single wire in a resonant rhombic. I have tried it and the results showed more gain than a multi conductor rhombic structure. No much, but some more. I had always assumed as stated within the literature that multi wire rhombic types showed more gain. However, it can be assumed when using a multiwire rhombic on harmonicaly related frequencies that the structures overall gain (over more frequencies) was slightly more than the single resonant antenna structure on an optimized frequency, I think that all of this is due to the thin wire NEC conclusion and its "Q"(?).

The old LaPort rhombic thing that was in QST and HR really brings some memories. As you know the VHF version that was published was a fairly small structure and there is no way that the thing will develop 27 dBI gain with the pattern alleged. One morning when I was (as US Army, ECOM Engineering Rep.) in a staff meeting at Collins Radio, Div. J (Antennas & High Power), a very young engineering staffer came in the meeting in a very excited state and said, "I just saw an extraordinary antenna in QST", it was the LaPort thing. He was summarly 'thrashed' about it because several of the engineering staffers knew about it. It was revealed that the design (with the dimensions given) was a scam started by several graduate engineering types at the old Stanford University RF laboratory. I think Mike Stahl got "snokered' into it and sent the design to QST. This antenna has been around for a long time and a lot of people have been "scamed" by it.

I got involved in an interesting simple field problem while in Hawaii some years ago. The Marine Corps at Ewa MCAS wanted a tactical radio link (30 - 50 MHz) to the training area on the 'Big" island. The wanted to use existing VRC-46 (RT-524) tactical FM radios. Of course, the existing tactical antennas (RC-292, etc) would'nt hack the path (about 130 MI.) so we had to do something extraordinary. I made a half rhombic array for them using the wire, masts, rope guys and insulators from a couple of AN/GRA-4 antenna kits. Next I went down to Honolulu Electronics to get a handfull of 2 watt carbon resistors to make a 330 ohm terminator R and some caps and inductor to make up a Pi matching network. The antenna worked well, in fact the radio link was "full quieting" for most of the time and met all expectations. Since then, we have made up several kits during "Desert Storm" and the ill fated 'Desert I" for long haul special application tactical VHF missions.

The Rhombic antenna calculators that I have, were developed during the 40's for Army use in field design of antennas. They are physicaly fairly large and made of plastic (plexiglass) and are circular slide rule style. You can calculate tilt angles for antenna wavelength (in frequency), dimensions, etc.

I don't like using Rhombics for receive applications, especially if the site is in a high ambient noise environment. This is because of the multi lobed (secondary side-lobes) pattern that this type antenna has. As related to all of this, one of the two primary attributes that is looked at during a receive site selection survey is the ambient noise and adjacent RF environment. In addition, it is recommended (and has been a general site design practice) is to split the site for seperate RX and TX function. Of course, this is obvious especially if High Power transmitters are used for the TX function. Today, all new RX site antenna designs generally use arrays of active receive loops in rosette, X or broadside/end fire configurations. These antennas are generaly used with a TX site using rotatable or fixed type LP arrays and 1 - 10/45 KW RF power. Unfortunately, almost all the long haul traffic is now over sattelite links and the HF links are now only used for contingency/backup (in the case of DoD, NASA, FAA , etc.).

Well so much for my rambling MSG and I must get back to work. I could go on-and-on but must get back to it. These are interesting antennas and I sure would like to have the real estate to do some experiments and use them on some VHF amateur applications. One of them is to put up a "big" optimized array to europe on the 6 meter amateur band.

Good luck and the best,

Steve Wagner

I recently acquired two sets of rhombic termination resistors (300 ohms)and two 50 to 600 ohm input baluns that were manufactured by Collins. There numbers are: 1) 754-9057-001 and described as "1KW Termination Kit" 2) 774-6261-001 " 3) DAA805-68-C-0020 " "Transformer, Radio Frequency /TF506/TRC-136" 4) 758-5322-001 " "50-600 ohm Balun" plus

one - 7649858-001 also labeled - 764-9604-001-D with "REV B" one - 764 9058 001 with "REV C"

Can you shed any light on these items? I am very desireous of building a rhombic and am excited about this new acquisition. They may be surplus military as I heard about a few being used in MARS stations in Nam back in 1967 when I operated the MARS station at Ft. Detrick, Md.

John Rauch, N4YXS

Was an intercept operator with the military from 1965-1968. Spent all of this time overseas. The rhombic antenna was the mainstay of our operations until the AN/FLR-9 (elephant cage) antenna was deployed.

When these small intercept stations were consolidated, the excitment and camaraderie was lost and the work became a real grind which is why I transfered to the Infantry. Lyndon Johnson's idea of top down management and bigger is better.

Have many large antenna insulators and some antenna wire I salvaged from an Army site I helped to dismantle in later years. Some of the wire and insulators I'm now using on my flattop. This is not the ordinary stuff you'd find in the QST ads.

Dave Hough, KC7DM Las Vegas

Congrats. on a fine page about rhombic antennas, my favorite HF antenna. I used them for long haul voice & data circuts to/from KSC & Ascention Island on the Eastern Test Range in the mid 1980's. Coupled with frequency diversity techniques, you can have 100% reliable HF circuts 24 hours a day, all year, all solar cycle. The TX sites had antennas with 10 db power gain and a 45 kw SSB TX feeding the antenna, that's an ERP of aprox. 450,000 watts. Not quite QRP is it!? We had similar receive antennas and Collins HF receivers slaved to an atomic frequency standard. One day I was doing a PM on a receiver & had disconnected it from the antenna multicoupler. Out of curiosity I took the Tektronix spectrum analyzer to the output of the multicoupler, tuned it to the frequency of the TX on Ascention Is. and was SHOCKED to measure .240 volts of signal! I am a Professional Broadcast Engineer & radio amateur

N0NKQ, Jeff Pearce

I am fortunate to have spoken with Ed Atems (W8BX) a retired FCC Chief Field Technician, Ed spoke of knowing the inventor of the reentrant version of the rhombic, and has some understanding of its design and construction. As I understood it, the reentrant version, instead of terminating at the base of the rhombic, the wires are fed back towards the center (towards the feed point) parrallel to each other, at some unknown distance, for some unknown length (I do not know the dimentions). This somehow induces an acceptable impeedance load, and eliminates the normal termination resistance. P.S. I am grateful for all of the information provided on this website, and someday hope to fly a rhombic myself. You can contact Ed for further information if you so desire (I'm sure he wouldn't mind). 73

- __--> Scott Singelyn (N8ZPJ) <--__

I spoke with Ed this past weekend, He mentioned that the inventor has since passed away, however, Ed was able to remember that the re-entrant matching section was 600 ohm open wire feed line run from the bottom apex of the rhombic back (in the same plane as the antenna) up the center towards the feed point. This was prune and tune to resonance at the operating frequency. Ed mentioned that he would be happy to hear from you, and would try to remember what he can. (this was a long time ago). I hope this can be of help to you and others in the amateur community. 73

__--> Scott <--__

I operated and installed the W1OP/1 Field Day antennas on the old rhombic poles at the old Chopmist Hill World War II FCC monitoring site near you. We operated there from 1966-1968. I'm not sure I used good judgement climbing those old 80 foot poles, but I'm still here to talk about it! I'll never forget the swastika shaped outdoor fireplace near the old monitoring building!

My current ham station uses towers originally used to support military rhombics, the AB-105 tower. Millions of feet of this tower were built during World War II to support rhombics.

Were you aware that Samuel F B Morse's father -- Jedidiah -- was born in Woodstock, and his grandfather is buried there?

73! Frank W3LPL

I just visited your Rhombic Site again, and enjoyed reading the material you've added!

Last weekend I attended the PRA (W1OP) 75th anniversary dinner in Providence. Several of the operators at the 1968 Field Day were there, reminiscing about that very successful Field Day using the big poles originally used for Rhombics! I looked at the 1968 Field Day results (November 1968 QST) and the W1OP gang finished in first place in the 4 transmitter class! I had forgotten that detail, it was a VERY GOOD site!

I also discovered that one of the FD operators, Frank W1EYH, thought so highly of the site that he purchased a nearby property! Frank told me that the old house where the intercept operators worked has been renovated and is now quite a nice home. He has gotten to know the neighbor across the street from the site (its on Darby Rd in North Scituate), and it turns out that he has lived there for 70 years! He has many "war" stories about the occupants across the street during World War II! By the way, the State of RI owned the site until it was auctioned in the early 1970s for a mere $12,000.00! 73

Frank W3LPL

I haven't been to the Chopmist site since the last W1OP/1 Field Day there in 1968! I'd be surprised if the poles are still there! The poles could not be missed from the road. I heard that the site was sold shortly after our last FD there. The fireplace was directly behind the main building, and I suspect it was used for outdoor cookouts for the operators.

Several articles about the site appeared in the Providence Journal, circa 1945, sounds like you have found them. I'm sure some old time FCC people still have recollections about the Chopmist site.

Yes, AB-105 military tower is still available thru surplus channels. It typically sells for about $100-125 per 10 foot section depending on condition.

Here are more details about Samuel F B Morse's father and grandfather: His father, Jedidiah Morse was born in Woodstock on 23 Aug 1761 at the Morse Homestead (its current address is 43 Center School Rd). He died in New Haven on 9 Jun 1826 and is buried in the Grove Street Cemetery in New Haven. His gravestone is a beautiful 20 foot tall monument of Rhode Island white granite topped by a granite globe. Jedidiah is often recognized as "The father of American geography."

His grandfather, Deacon Jedidiah Morse, was born in Woodstock on 8 July 1726 and died in Woodstock on 29 Dec 1819. He served in the Revolutionary War and is buried in Woodstock Hill Cemetery. His grave is easy to locate. 73!

Frank W3LPL

As a kid, I spent some time at AT&T's Manahakin, Ocean Gate and Lawrenceville, NJ rhombic farms and got a chance to use their rhombics on the Ham Bands. Never forgot how well they worked or ever saw anything that compared to them! Raplh Coker, the AT&T exec in charge of these sites, offered me a job working there after high school. I opted for college- which I'm sure wasn't nearly as much fun!

Look forward to new additions to your page. I've been thinking about putting one up here on my farm here in PA. 73,

Alan, W3BV

The is Edward Addy (KE0EG). I designed the rhombics for the Desert Voices Project. I still have some pictures around here of the antennas. If you want just let me know and I can dig some of them up and send them acros to you.

The antennas were a twin pair of rhombics that were roughly 450 x 275 ft, mounted on 105 ft cedar power poles, terminated with TMC terminators and fed with 7/8 in hard line into TMC broad band high power Rhombic Balluns. The antennas were also co-phasable.

We used them to reach the tactical radios of the front line forces serving in the Gulf durring operation Desert Storm/Shield.

Just let me know if you would like me to send you some of the photo's and I would be glad to dig them up, scan a couple of them and e-mail them to you. Great page by the way!!!!

Edward E. Addy The North American Center For Emergency Communications, (NACEC) Minneapolis, MN USA

Hello Ian,

Thanks for your email to RA seeking information about RA's use of rhombic aerials (antennas).

This is just a quick note to let you know that we are happy for you to include photos & text about our two rhombics. I'll put something together for you next week.

RA has two rhombics in service, both at Shepparton (Victoria) and both "home made". Our other dozen or so aerials are all commercial curtain arrays of horizontal dipoles.

The two rhombics are called "AR" (American Rhombic) and "JR" (Japanese Rhombic) which relates to their historical targets.

Both were built in the late 1970's and represent one of the higher developments of rhombic design. They have three, 25 mm wires in each leg to improve the impedance variations over their working bandwidth. AR has a natural bearing of 065 degrees and covers the range 11-22 MHz. JR has a bearing of 353 degrees and a frequency range of 9-22 MHz. Both are rated at 100 kW carrier at 100% modulation. We find them to be very useful radiators. Some people say rhombics are antennas that radiates badly in all directions, I disagree!

JR carries about fifteen hours of RA program each day to Papua New Guinea, Guam, Japan, the west Pacific and (using a minor lobe as you noted) to central Indonesia. It carries 9710, 15240 and 15415 kHz. If you can listen to 9710 kHz between 0800-1200 UT you might hear it carrying English (0800-0900 UT) and Tok Pisin (0900-1200 UT).

AR is used only on 11880 kHz 1700-2200 UT at the moment, to the central Pacific region. I shall look forward to hearing from you. Kind regards,

Nigel Holmes Transmission Manager RADIO AUSTRALIA

Yup there gone. We put them up just for service in the Gulf War. We put them up in November of 1990 and took them down in June of 1991. We handled over 5,000 phone patches and digital messages durring the time that they were up. I do not believe that we could have provided communications like we did to that part of the world without them.

I will try to locate some more photo's but here are a couple that I found on file in this computer. I can send the others a bit biger so that they will be clearer. Hope you like them.

We are currently working on an emergency communications center that will use either 4 or 8 rhombics to cover 360 deg, with the final number will depend of the realistate that we manage to access for the arrays.

Our web site is www.nacec.org if you want to know more about us.

Images to follow in this e-mail. All the best,

Edward Addy NACEC Center Minneapolis, MN USA

 
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