Any experiences  tuning rhombic  antenna ?

As the little  said - is anybody here, on this forum, who  would / could share  ACTUAL experience fine tuning rhombic antenna?
Please - ACTUAL experience fine tuning rhomibc antenna

not "goolgle it "
not '"it is too big..."
not " I can make DXCC in 24 hours with my 5 over 5 over 5 Yagi..."
no  "what's rhombic antenna?"
no  "try such and such forum"

Thanks

73 AA7EJ

Ahoj Václave (or hello Ann???)

If you ask in this way, most probably nobody will answer you.

It is unclear, if you need a method how to work with NanoVna or have a
troubles with the rhombic antenna.

BR,

OK1VAW, Vojtech.

Dne 27.11.2022 v 23:07 Anne Ranch napsal(a):
> Any experiences  tuning rhombic  antenna ?
>
> As the little  said - is anybody here, on this forum, who  would /
> could share  ACTUAL experience fine tuning rhombic antenna?
> Please - ACTUAL experience fine tuning rhomibc antenna
>
> not "goolgle it "
> not '"it is too big..."
> not " I can make DXCC in 24 hours with my 5 over 5 over 5 Yagi..."
> no  "what's rhombic antenna?"
> no  "try such and such forum"
>
> Thanks
>
> 73 AA7EJ
>
>

--
zdraví,
Vojtěch.

Zasadni otazka = jak to naladit.  Kdyz chci kolem 433 MHz a ma 6 "elementu" na strane.

I just realized  - this forum  post approval is very slow and may reject my reply entirely if in Czech language .

I have  the 433MHz rhombic  connected. to nanoVNA.

I am trying to *determine its resonant frequency* by just looking for minimal SWR.

So far I found one near 1.8MHz and around 250MHz .

The antenna has 6 (six) full wavelength "elemets" ( on each side ) = estimated / desired frequency 433MHz.

For time being the far end is open.

*What would; be a best guesstimate of fundamental  resonant frequency of this setup ?
*
>From that I can calculate the 433MHz actual frequency.

I am NOT paying attention to any other measured values -
I just need the ( minimal ) SWR  to determine the resonant frequency in 70 cm band.

Rombic antennas are inherently broadband and terminated. They should not
require tuning.

On Mon, Nov 28, 2022 at 12:22 AM Anne Ranch <anneranch2442@gmail.com> wrote:

> Any experiences tuning rhombic antenna ?
>
> As the little said - is anybody here, on this forum, who would / could
> share ACTUAL experience fine tuning rhombic antenna?
> Please - ACTUAL experience fine tuning rhomibc antenna
>
> not "goolgle it "
> not '"it is too big..."
> not " I can make DXCC in 24 hours with my 5 over 5 over 5 Yagi..."
> no "what's rhombic antenna?"
> no "try such and such forum"
>
> Thanks
>
> 73 AA7EJ
>
>
>
>
>

And when terminated…unidirectional.

> On Dec 12, 2022, at 23:15, Bob W0EG <morrisnc7@gmail.com> wrote:
>
> 
> Rombic antennas are inherently broadband and terminated. They should not require tuning.
>
>> On Mon, Nov 28, 2022 at 12:22 AM Anne Ranch <anneranch2442@gmail.com> wrote:
>> Any experiences tuning rhombic antenna ?
>>
>> As the little said - is anybody here, on this forum, who would / could share ACTUAL experience fine tuning rhombic antenna?
>> Please - ACTUAL experience fine tuning rhomibc antenna
>>
>> not "goolgle it "
>> not '"it is too big..."
>> not " I can make DXCC in 24 hours with my 5 over 5 over 5 Yagi..."
>> no "what's rhombic antenna?"
>> no "try such and such forum"
>>
>> Thanks
>>
>> 73 AA7EJ
>>
>>
>
>

Anne,

As Bob said, rhombic antennas tend to be terminated structures, and
inherently broadband. However using one at VHF/UHF is different to their
use at HF.

I was involved during the mid-1970's in some of the first 2m EME QSOs
made from the UK using amateur-owned equipment. We used a 50
wavelength/leg rhombic. It worked well. However, after some thought, we
decided not to terminate the far end of the antenna, reasoning that the
energy reflected from the far end would be attenuated to such an extent
that the it would not be effective, and the use of a resistive
termination would simply result in an unwanted complication.

As the input impedance of the antenna was an unknown, we fed the antenna
with a short length (c.5m?) of home-made open-wire line with a
characteristic impedance of maybe 200-300ohms and used a stub tuner and
balun to empirically establish an impedance match to the 50ohm
equipment. It would have been good to have had access to a VNA at that
time  to set-up the stub tuner.

From our results, both with echo tests, and QSOs we were able to
establish that the beamwidth was of the right order. We were also able
to make a number of 'first' QSOs.

73

Chris G4DGU

On 12/12/2022 22:08, Bob W0EG wrote:

> Rombic  antennas are inherently broadband and terminated.  They should
> not require tuning.
>
> On Mon, Nov 28, 2022 at 12:22 AM Anne Ranch <anneranch2442@gmail.com>
> wrote:
>
> Any experiences  tuning rhombic  antenna ?
>
> As the little  said - is anybody here, on this forum, who would /
> could share  ACTUAL experience fine tuning rhombic antenna?
> Please - ACTUAL experience fine tuning rhomibc antenna
>
> not "goolgle it "
> not '"it is too big..."
> not " I can make DXCC in 24 hours with my 5 over 5 over 5 Yagi..."
> no  "what's rhombic antenna?"
> no  "try such and such forum"
>
> Thanks
>
> 73 AA7EJ
>
>

Rombic antennas are inherently broadband and terminated. They should not
require tuning.

...and some "opinions" also state that they are receiving antennas (only )
That may be because they have been mostly used as directional , receiving
antennas .

...and another resource saiz that they are useful for "40 to 300 MHz
"....

I am planning to use it as a transmitting antenna , hence I want it to be
resonant - if nothing else just for simplicity for matching purposes.

I am beginning to think of it as

serially connected full wavelength radiators

and as soon as I get NEC modelling software running I 'll give it a try

Strictly speaking, SWR does not indicate the resonant frequency(s) of an antenna, rather It is determined by the frequencies of the zero crossings of the impedance phase plot.

73
Dave VE3TLY

Rombic antennas have been used for decades as transmitting antennas for
high powered shortwave (HF) stations. When terminated, they are highly
directional. For HF, the takeoff angle is a function of the antenna's
height above ground in wavelengths. Amatures use them as broadband
antennas. They don't require "tuning" as they are not resonate (just like
a long wire), but they do often require "impedance matching" to be driven
from 50 Ohm sources. Note that an "antenna tuner" is actually an adjustable
impedance matching network.

On Tue, Dec 13, 2022 at 8:14 AM Anne Ranch <anneranch2442@gmail.com> wrote:

> Rombic antennas are inherently broadband and terminated. They should not
> require tuning.
>
> ...and some "opinions" also state that they are receiving antennas (only )
> That may be because they have been mostly used as directional , receiving
> antennas .
>
> ...and another resource saiz that they are useful for "40 to 300 MHz
> "....
>
> I am planning to use it as a transmitting antenna , hence I want it to be
> resonant - if nothing else just for simplicity for matching purposes.
>
> I am beginning to think of it as
>
> serially connected full wavelength radiators
>
> and as soon as I get NEC modelling software running I 'll give it a try
>
>
>

Thanks Chis
finally making some progress collecting others' experience .
You are absolutely right as far as "lack of real knowledge" as far as
impedance goes.
Yes - here I am half a century later and still in the dark...
I probably did not say - but my goal is meteor scatter...
got to go - got "honey do ..." ( she needs orange juice for some
christmas cookies ...)

Check the ARRL Antenna book:  Rhombic atntennas are broadband and bi-directional - not resonant at one fundamental frequency.

OK, finally getting somewhere....
I wish I could post a picture / screenshot of the actual display.
In the meantime
S11 VSWR and S11 Return loss are identical
and |S11| looks more like a return loss.


In general these curves are showing the antenna being "too short " - for
desired frequency of 433 MHz. Not sure if it matters - for now.



PS
I AM NOT GOING TO GET INTO DISCUSSION ABOUT SWR AND RESONANCE .
In my opinion that belongs to the same category as discussion about
"counterpoise" and "the missing part of vertical ".

As far as "elevation" goes - I am more concerned with the actual physical
angle of the setup.

In theory - if I hit the meteor trace "straight up " it should reflect
nearby. Hence if angled - I would expect reflection to be "nice DX" -
further away...

And I will definitely terminate it - the meteors come only from
direction....

On Tue, Dec 13, 2022 at 11:31 AM, John Galbreath wrote:

>
> Rhombic atntennas are broadband and bi-directional

OK - so why  are they  shown with sizes specified in "lambda"  ?

That statement  IS  illogical - if they are broadbanded   any SIZE WOULD WORK.

I will have to restate my original post
Any experiences tuning rhombic antenna - using NanoVNA - ?

I did not ask for resources / references .

I asked for  experiences, and so  far I have received ONE .

i do appreciate the discussion, however,
let's not dwell on opinions presented.

As a RX antenna it could be called "non resonant  / broadbanded " - so can any non-resonant  RX antenna.
As a TX antenna it has to preset reasonable load AT THE OPERATING frequency.

That can be accomplished by

matching hardware

which is easier to realize / build when one knows
WHAT values need to be matched

in other terms
if the physical properties of the radiator are known  - such as at resonance -
the matching  job is trivial.

If the radiator  is non resonant at the desired frequency - the matching job becomes less trivial.

On 12/13/22 9:06 PM, Anne Ranch wrote:
> On Tue, Dec 13, 2022 at 11:31 AM, John Galbreath wrote:
>
> Rhombic atntennas are broadband and bi-directional
>
>
> OK - so why  are they  shown with sizes specified in "lambda"  ?
>
> That statement  IS  illogical - if they are broadbanded   any SIZE WOULD
> WORK.

Unspoken is that the leg lengths are given in *approximate* lambda,
particularly in reference to things like takeoff angle and pattern.
They're a traveling wave antenna, and broadband in the sense that the
feedpoint impedance doesn't change rapidly with frequency, they don't
have a "resonance" like a dipole, nor does the radiation pattern change
quickly over a fairly wide frequency range (10s of percent).


You didn't want references, but I would suggest getting some reference
to know what to expect.

You're building a rhombic for UHF, over an artificial ground plane - so
literature on rhombics over soil probably won't be relevant. I'd model
it in NEC.

There are also vertical pointing rhombics with no ground plane. They're
used in ionosondes (because they are easy to match and cover a multi
decade frequency range). If you look for ionosonde antenna literature,
you'll probably find something.

But if you want to know what it *should* look like, then NEC is your
friend.

>
> I will have to restate my original post
>
>
> Any experiences tuning rhombic antenna - using NanoVNA - ?
>
> I did not ask for resources / references .
>
> I asked for  experiences, and so  far I have received ONE .
>
>
> i do appreciate the discussion, however,
> let's not dwell on opinions presented.
>
> As a RX antenna it could be called "non resonant  / broadbanded
> " - so can any non-resonant  RX antenna.
> As a TX antenna it has to preset reasonable load AT THE
> OPERATING frequency.
>
> That can be accomplished by
>
> matching hardware
>
> which is easier to realize / build when one knows
> WHAT values need to be matched
>
> in other terms
> if the physical properties of the radiator are known  - such as
> at resonance -
> the matching  job is trivial.
>
> If the radiator  is non resonant at the desired frequency - the
> matching job becomes less trivial.
>
>
>
>
>
>
>
>
>
>

Anne,

I vaguely remember an article about using a Rhombic for television reception. Fortunately I kept a copy in my Antenna file.

Attached is a copy article from Radio Electronics Magazine, December 1986.

I downloaded this from the WorldRadioHistory.com site which is a great resource for technical periodicals.

Hope this helps in your design.

Mike N2MS

> On 12/13/2022 5:36 PM Anne Ranch <anneranch2442@gmail.com> wrote:
>
>
> As far as "elevation" goes - I am more concerned with the actual physical angle of the setup.
>
> In theory - if I hit the meteor trace "straight up " it should reflect nearby. Hence if angled - I would expect reflection to be "nice DX" - further away...
>
> And I will definitely terminate it - the meteors come only from direction....

determined by the frequencies of the zero crossings of the impedance phase
plot.

YES !

Now is the time to scan the "RTFM" to find WHICH nanoVNA parameter is the
"impedance phase plot"

73 AA77EJ

https://ham-antennas.groups.io/g/main/topic/95409619

I am not sure if it is "legal" to post links to another resources here ..

Yes, I have another discussion going about 4NEC2  modelling...

PS I did dust-off my ARRL antenna book ....

funny - it describes  rhombic   both as resonant and non-resonant

On 12/14/22 6:18 AM, Jim Lux wrote:
> On 12/13/22 9:06 PM, Anne Ranch wrote:
>> On Tue, Dec 13, 2022 at 11:31 AM, John Galbreath wrote:
>>
>>     Rhombic atntennas are broadband and bi-directional
>>
>>
>> OK - so why  are they  shown with sizes specified in "lambda"  ?
>>
>> That statement  IS  illogical - if they are broadbanded   any SIZE
>> WOULD WORK.
>
> Unspoken is that the leg lengths are given in *approximate* lambda,
> particularly in reference to things like takeoff angle and pattern.
> They're a traveling wave antenna, and broadband in the sense that the
> feedpoint impedance doesn't change rapidly with frequency, they don't
> have a "resonance" like a dipole, nor does the radiation pattern change
> quickly over a fairly wide frequency range (10s of percent).
>
>

NEC model of unterminated single diamond rhombic, 60 degree included
angle, legs are 3.5 meters long (~ 5 lambda at 70 cm), 1mm wire radius
No ground, etc.

Z looks like about 100 to 500 ohms without termination, about 400 ohms
with a 300 ohm termination at the far end.

Not the cleanest pattern in the world, but that's what rhombics are..

This Rhombic antenna bit has been a fun read. Somehow meteor scatter came up and I'm wondering what we are discussing.

Way back in 1954 when I was first licensed this seemed to be the king of antennas. A few years later when I was in the Army Reserve we went to camp in Ft Leonard Wood, Ft Polk, La, Ft Knox, KY and these things were everywhere. All carefully surveyed for point to point communication to critical DX locations. I suspect all terminated for a single path with, I suspect, heights adjusted for take off angle matching the favored station on the other end. I ended coming home from one camp with a trunk full of foot long brown insulators about 1X2 inch cross section and lead inserts where the wire went thru at the ends. Also a bunch of heavy copperweld wire, maybe 1/8 inch dia. Heavy. The best use I ever saw for hams was W7RM (I think) west of Seattle with a massive contest station. It's been a long time, but I think he had some antenna looking right down the strait to JA, 4-1000 single band amps in a back room to keep the blower noise down, and a JA speaking operator running that band alone.

Now for the VHF frequencies...especially meteors. Your target moves...a lot.

Build one and play. That's the nice thing about these things. Like a favorite Ham of mine would say...RF got to go somewhere.

The literature of the 50s is out there. Dig thru it, have fun, and of course, let us know what you measure with modern gear. No more Lecher wires with flashlight bulbs for tuning, but that was a lot of fun. As was tuning for maximum arc with #2 lead pencils with my 50 watt rig. The pencils quickly go so hard that they wouldn't write. After all, this is a nanovna list. Thanks,

N0UU

On 12/14/22 2:50 PM, Cox wrote:
>  This Rhombic antenna bit has been a fun read.  Somehow meteor scatter
> came up and I'm wondering what we are discussing.
>
> Way back in 1954 when I was first licensed this seemed to be the king of
> antennas.

Rhombics for point to point MF and HF links were very popular. High
gain, easy to build (plant telephone poles, string wires, done) - don't
need a lot of tuning. If you were running RTTY links commercially or for
military, you were probably running rhombics.

W6AM was famous for his antenna farm of rhombics on Palos Verdes near
Los Angeles. (well, he was famous for his mobile kilowatt SSB rig too).



>
> Now for the VHF frequencies...especially meteors.  Your target moves...a
> lot.

For this application, it's vertically oriented. Also used for
ionosondes. Could be more of a sort of weird inverted V at low
frequencies, becoming more a traveling wave antenna at higher frequencies.


>
> Build one and play.  That's the nice thing about these things.  Like a
> favorite Ham of mine would say...RF got to go somewhere.

Indeed.

>