Popular Antenna SWR measurements...

[Macavity]

Aside from (visible spectra) Spectroscopy, I had neglected to look HERE! 😉
So much interesting stuff...

A long forgotten (SWL only!) amateur radio interest back in late 60s / early
70's rekindled (I thank @wxsatuser for much of that)! Recently I bought a
*budget* "NanoVNA"  thingie and I'm now measuring *random* "wires". 😄

SWR curves for the "white stick" X30 (blue) and X777 (orange) antennae! 🙃

Basically, I'm just EXPLORING the general VHF/UHF spectrum for *anything* interesting! 🥳
I have an N-type (coax) "Antenna Swith"to quickly "flip" between my various antennas...
Using SDRPlay / RSP1A Combo for my "studies". Checking out various Signal strength?!?

To expore HIGHER frequencies. I've just bought a SIRIO SD3000N *DISCONE* Antenna...
Discone Antennae have no gain (As you know? LOL). But the original (with added whip!):

The WHIP seems to add an extra low SWR resonance at 180MHz? I suspect I might just
remove the "whip" (as DO most Discone users?!?) This looks to have potential > 300MHz? 🤔



Thinking of trying out a "general coverage" G8FEK LNA (BBA3-SNA) to "help out" a bit? 😺

P.S. Having quite a lot of SWL fun re. FT8 Hams at *minimal* strength (Ta, wxsatuser!)
Perhaps a gateway to higher and greater things: Satellites... True Radio Astronomy etc.
Recently found a LADDER-SAFE (user-friendly!) PRO *antenna installer* to help me too! 😎

Edited February 11, 2020 by Macavity

[The Admiral]

3 hours ago, Macavity said:

budget* "NanoVNA

Hmm, didn't know such a cheap antenna analyser existed! I might investigate purchasing one. I too was a SWL as a lad in short trousers, many centuries ago when proper electronics had valves and HTs that could kill, but could afford very little then. Visiting the field of meteor detection as rekindled a mildly renewed interest. Thanks for the post.

Ian

Edited February 11, 2020 by The Admiral

[Macavity]

I see the EXACT one I bought off Ebay is no longer available. But they are FUN thing to have!
They are fairly "generic"... They seem to work...  You don't have to "re-mortgage" for a VNA? 😛

https://youtu.be/y3kdaJ7JdOg

Many more examples of the description / PC software / user guides etc. available on t'internet...

 

Edited February 11, 2020 by Macavity

[Carbon Brush]

Almost on topic.

A couple of months back I lent my old 3D printer to the Finningley radio club.
It has since made a couple of dozen protection cases/sleeves for the nanoVNA.

Obviously popular devices.

David.

[wxsatuser]

Been meaning to get one myself but I have an MFJ antenna analyser plus three Daiwa SWR/power meters that cover 1.8MHz to 2.4GHz.

[Macavity]

1 hour ago, wxsatuser said:

... but I have an MFJ antenna analyser plus three Daiwa SWR/power meters that cover 1.8MHz to 2.4GHz.

Kewl! 😎

FWIW: Thinking about VNA PLOTS has taught me a LOT about Antenna theory though? 😺
See "Smith Charts" too! Was also pleased  to find that the (my) popular Diamond X30 DID
actually resonate on 2m (1/2th wavelength) plus 70 cm (2x 5/8 Wavelength)! Hey the X777
"Aircraft Bander" is pretty much tuned to a "central" 124MHz and 300MHz "Military" Band?
(Heheh: "Don't tell 'em, Pike re. listening to Aircraft bands!) -- But a useful test of SDRs! 🙃

For general "scanning" I have found that having BOTH the Amateur band AND Aircraft band
antennae is useful +  judicious use of SDRPlay/SDRUno/RSP1A MW/FM and/or DAB filters!

Since we seem to be allowed to discuss non-Astro (strictly) stuff: On the *HF* bands I've
been playing with varying the length of a (not very!) long wire 52' "sloper" antenna (Fed
via 4:1 UNUN). I'm now convinced even random wires can be tuned to "better" lengths...

http://hamuniverse.com/randomwireantennalengths.html

But we digress... Massively (Sorry! lol) 🥳

Edited February 11, 2020 by Macavity

[The Admiral]

8 hours ago, Macavity said:

NanoVNA"  thingie

I've just ordered one from Amazon . I shall be interested to see how the Innovantennas 3 element LFA-Q quad Yagi in my loft that I use for meteor scatter is behaving.

Ian

Edited February 11, 2020 by The Admiral

[wxsatuser]

54 minutes ago, Macavity said:

Since we seem to be allowed to discuss non-Astro (strictly) stuff: On the *HF* bands I've
been playing with varying the length of a (not very!) long wire 52' "sloper" antenna (Fed
via 4:1 UNUN). I'm now convinced even random wires can be tuned to "better" lengths...

http://hamuniverse.com/randomwireantennalengths.html

But we digress... Massively (Sorry! lol) 🥳

Have tried a few wire ants last being a multiband sloper but not to good.

Have gone back to a multiband vertical, Hustler 6 bander and have installed many wire radials.
Still need to add more radials but it works very well on all bands.

Heard in New Zealand recently running 50watts on 40metres plus most of Europe, South America, Japan and eastern USA
All the little flags with 21 on them are where my signal was heard.

[Macavity]

Great stuff @wxsatuser. Since we last spoke, I have been able to resolve
(various HF band) FT8 transmissions that make no "waterfall" trace at all! 😎

As a random thought regarding VNA, my "tuned" longwire (via 4:1 Unun)
gives great SWRs on the (traditional) HF bands: 



UNfortunately, when I add the COAX feeder: "All h*ll breaks loose" ROFL!
I suspect the Coax outer functions as a counterpose / part of the antenna?
Who Knows? I suspect that's why most HAMS favour tuned antennas!  😛

Things seem to be much easier at VHF/UHF where the feeder is "several"
wavelengths long? At the moment I am thinking of doing a survey of all
signals received locally on VHF/UHF, with the SIRIO (to 3Gz!) Discone! 😉

Looks like SUCH THINGS  are a thing of active / serious research! 😉

Who knows? Will I be the oldest ever candidate for the RAE... Will I try
do genuine "Radio Astronomy"... Or just receive satellite weather pics. 🤔

As another GENERAL question, I am thinking of adding a G8FEK BBA3
50MHz-2GHz <1dB noise LNA to my kit of parts! Is the vendor active?
Has anyone tried these LNA's (or similar)? Will a 30dB LNA completely
overload my RSP1A/SDRUno? I sense another ASTRO "Money Pit". lol 🤣

Edited February 14, 2020 by Macavity

[wxsatuser]

I'm not a fan of long wires as such, hard to fit anything very long in my garden.

If you have not try a tuned counterpoise for each band, it might do the job.

Give the RAE a go, nothing to lose, it's not that hard with a bit of swotting.
There is nothing to lose, way back in the 80s when I got interested I actually did a course at college to do the RAE.
I helped a friend, who thought he was dim get through, we spent friday evenings going over the course.

BTW my friend was'nt dim he just needed some extra help.

[Carl Reade]

22 hours ago, Macavity said:

Great stuff @wxsatuser. Since we last spoke, I have been able to resolve
(various HF band) FT8 transmissions that make no "waterfall" trace at all! 😎

As a random thought regarding VNA, my "tuned" longwire (via 4:1 Unun)
gives great SWRs on the (traditional) HF bands: 



UNfortunately, when I add the COAX feeder: "All h*ll breaks loose" ROFL!
I suspect the Coax outer functions as a counterpose / part of the antenna?
Who Knows? I suspect that's why most HAMS favour tuned antennas!  😛

Things seem to be much easier at VHF/UHF where the feeder is "several"
wavelengths long? At the moment I am thinking of doing a survey of all
signals received locally on VHF/UHF, with the SIRIO (to 3Gz!) Discone! 😉

Looks like SUCH THINGS  are a thing of active / serious research! 😉

Who knows? Will I be the oldest ever candidate for the RAE... Will I try
do genuine "Radio Astronomy"... Or just receive satellite weather pics. 🤔

As another GENERAL question, I am thinking of adding a G8FEK BBA3
50MHz-2GHz <1dB noise LNA to my kit of parts! Is the vendor active?
Has anyone tried these LNA's (or similar)? Will a 30dB LNA completely
overload my RSP1A/SDRUno? I sense another ASTRO "Money Pit". lol 🤣

Hi I can vouch for G8FEK LNAs. Very professional and solid. I have the 1300 -1700 and has easily allowed me to observe the hydrogen line. I would definitely add the wideband LNA to your gear if using an SDR as they are not the most sensitive devices and won't overload it at all.

Without going deep into the dark art of antenas my favourites for HF are the Cobweb or the doublet which is fed with ladder line to an MFJ tuner. 

A lot of long wire users tend to use a 9:1balun to match

Carl

[Coto]

5 hours ago, Carl Reade said:

Hi I can vouch for G8FEK LNAs.

I don't think I would vouch for them. Even though I've bought three of their LNAs, I wouldn't consider them again, because I've found many LNAs that are a better deal for money and are well-measured with vector network analyzers. G8FEK's graphs aren't very helpful, and doesn't provide many graphs (e.g. noise figure vs frequency & temperature and gain vs frequency & temperature etc.). Mini-circuits always offers all of these graphs. ZX60-P162LN+ and ZX60-P33ULN+ are definitely some high-quality LNAs mini-circuits offers, and there's many more. There's also the SPF5189Z-based LNAs, which are dramatically cheaper and are only slightly more noisy than G8FEK's radio astronomy LNA.

[Macavity]

Thanks All / both! Grist for t'mill -- I'll have a ponder anyway... 😎

For those who like to know "What others are doing"... Not a LOT in this WIND!
But still making things in anticipation of better weather (and no Covid-19)! 😼

Below shows a Coax dipole of a "Double Bazooka" type using Electrial Duct parts!
At left my Sirio 3000N Discone. At right some bits from https://www.barenco.co.uk/brackets-clamps



Ultimately all/some of this is destined for up here... 😱



(X30N + TV antenna) But not JUST at the moment! 😅

Edited February 15, 2020 by Macavity

[wxsatuser]

Coaxial dipoles are nice, simple and cheap.
Going back a bit I used to use them on 50/70MHz just strung across loft joists.
The 70MHz one allowed good contacts with 2.5watts down to Gibraltar during the summer Es season.

Here is a photo of my SWR meters and main rig Icom 7100, shack a bit messy trying to install shelves for the satellite gear.
HF is bottom one VHF on top, just visible 35Amp psu to far right.

Spent Saturday morning messing with the QO-100 receive setup.
Turned it on and the passband was really weird, thought my SDR had gone kaput then found out the passband
has been increased from 250KHz to 500KHz, teach me to keep up with the news. 😉

New 500KHz passband, centre frequency is the old band edge PSK beacon at 10489.750GHz
BTW my setup down converts from 10GHz to 144MHz and is GPS locked, very stable signal. 😀

BTW this is the QO-100 receive setup, temporary mess waiting for new shelf space.
Far left GPS reference, middle DX Patrol downconvertor, not shown modded LNB on dish an right is the SDRPlay RSP1A.

Edited February 16, 2020 by wxsatuser

[Macavity]

Great stuff, MIke. Nice "random" (they are the best!) but useful conversation. 😎

10GHz Eh? We are not worthy... etc. etc. 😅

For VHF monitoring I have (almost?) line of sight to Liverpool, Manchester &
Blackpool ATIS from this (N.Wales coast) QTH. My excuse for "checking out"
frequencies around 124 MHz! I can "cut bits off" these dipoles for "satellite". 😉

Interesting to compare my "wideband" Diamond X777 with the homebrew
COAX "Double Bazooka" (I sense a "Carry On" film influence?). As hoped, its
center 1/4 wave coax + wire 1/4 wave ends has a much bigger bandwidth! 
(Note change of scale).Though huge bandwidths may NOT be your desire... 🥳

D777 "Aircraft":



"Double Bazooka" Coax  (Note wide bandwidht plus "better" SWR!) 😛



On the SDR1A and (Excellent) SDRUno software, I had noticed a possible
drop in signal strengths??? I did a "Factory reset" and things seemed to
get better. Something got "a bit confused" with my button pushings? 🙄

AS A WEIRDER thing, some of my Aircraft frequencies are "Bang on"...
Others (as reported!) are consistent 5kHz out! As we know, you are not
(strictly) supposed to listen to A/C, but [IMO] there seems something
weird re. (publically!) QUOTED frequencies of some Aircraft / Stuff??? 🤔

The LOCAL 2m & 70cm repeaters are pretty much on expected freqs! 🙂

I have tried to do a frequency calibration? MSF(?) on 60kHz still there.
I don't SEEM able to hear WWV(?) on 2.5, 5, 10, 15, 20MHz though... 🙃

Anyway, just more *random* thoughts for the fellow users/enthusiasts!

Edited February 16, 2020 by Macavity

[The Admiral]

1 hour ago, Macavity said:

AS A WEIRDER thing, some of my Aircraft frequencies are "Bang on"...
Others (as reported!) are consistent 5kHz out!

You do seem to be well back in the SWL mould!

I presume that you are aware that last year there was a shift to 8.33kHz channel separation for aviation use, and allocated frequencies are changed. You might want to check out the current frequencies.

Ian

Edited February 16, 2020 by The Admiral

[Guest]

19 minutes ago, The Admiral said:

You do seem to be well back in the SWL mould!

I presume that you are aware that last year there was a shift to 8.33kHz channel separation for aviation use, and allocated frequencies are changed. You might want to check out the current frequencies.

Ian

They finally switched over?🤔  Wasn't that on the cards for at least the last two decades?

[The Admiral]

1 hour ago, Macavity said:

As we know, you are not (strictly) supposed to listen to A/C

I must admit this seemed a bit draconian to me, so I had to check it out. Hmm, seems that it is illegal unless you are licensed to do so. Wouldn't have believed it .

Ian

[The Admiral]

Just now, merlin100 said:

They finally switched over?🤔  Wasn't that on the cards for at least the last two decades?

I don't know how long it's been on the stocks, but it must be a huge and expensive undertaking. Our local airfield frequency has changed. Bureaucracy moves slowly!

Ian

[Macavity]

17 minutes ago, The Admiral said:

I must admit this seemed a bit draconian to me, so I had to check it out. Hmm, seems that it is illegal unless you are licensed to do so. Wouldn't have believed it .

Heheh. Well it is a bit of a weird one! But in fact, listening to almost ALL (non amateur/commercial)
stuff COULD theoretically land you in trouble! Not encourage "illegal activities" here too! Enforcing
it with the thousands of Aircraft Band enthusiasts (At airports too) would be an impossibility tho! 😛

As a teenage SWL / radio enthusiast, I was always careful not to "transmit" anything. My late DAD
worked as a GPO "Post Office" (now BT) Draughtman... Two in-law uncles... Engineer & Linesman!
Having a criminal SON might have not been a good look for our family. lol 🤣

The best advice is probably not to discuss *contents* of the transmissions? 😺

I still SWEAR some of the frequencies are a bit off, but... 🥳

Edited February 16, 2020 by Macavity

[The Admiral]

1 hour ago, Macavity said:

I was always careful not to "transmit" anything.

Wish I could say the same! Well, actually, no I don't 'cos it was fun. Remember, these were the days of Radios Caroline and Atlanta, such role models .

"House of the Rising Sun" through a 6V6 audio output valve, IIRC, on medium wave. Range was pretty minimal. Wouldn't have done it these days, far too much big brother about, and of course the wavebands are so much more crowded.

Ian

Edited February 16, 2020 by The Admiral

[The Admiral]

I've now had a bit of time to try out my new nanoVNA. Nifty little gubbins isn't it? It took me a little while to get to grips with it. I'm using it with NanoVNAsaver v2.2-1 on my laptop. I tried it on my W7 PC but I don't have a virtual COM driver on that machine.

Here's what I got with my LFA-Q quad Yagi.

A bit low for the 2m band. It does have tunable elements however, should I care to go up into the loft, but it'll do fine for Graves radar on 143.05MHz.

However, over a much wider frequency span there are a large number of other resonances and things don't look quite so rosy :

I used a simple choke balun at the antenna feedpoint. How important this will be for receiving I haven't the foggiest.

Once again I thank @Macavity for the heads up on this great device.

Ian

[Macavity]

Good Stuff! Referring to "misc. stuff": Shortwave *HF* (longwire) antennae. I sense
a CHOKE on coax (tuned radials?) is the way to go? (Thanks Mike @wxsatuser!).  😎
I imagine such things (Chokes!) help *generally* when we move up to VHF / UHF?

For SWL's (me!) I begin to wonder if we need care AT ALL about SWR on HF Bands.
Would I be right thinking that it's only "signal to noise ratio" that really matters? 🤔

A WELL TUNED antenna for VHF/UHF seems "good thing"?
You can reject off-band "QRM" etc. (Remember Q-codes?)!

I did find another really good use for my MicroVNA. You can measure velocity factor
for COAX... Make Coax Antennae... Coax rejection filters? Get an SMA T-piece and use
both connectors... Plot the "S12" (whatever) throughput etc. etc.  😎

Not *everything* "Rosy" here. lol. Amazon "seduced" me into buying cheap 30dB LNA!
Soldered power leads... Dead as a Door Nail?!? No surprise? Next month, I will have the
funds to buy a decent LNA (Low Noise Amp) that actually works?  🥳

Edited February 21, 2020 by Macavity

[wxsatuser]

10 hours ago, Macavity said:

Good Stuff! Referring to "misc. stuff": Shortwave *HF* (longwire) antennae. I sense
a CHOKE on coax (tuned radials?) is the way to go? (Thanks Mike @wxsatuser!).  😎
I imagine such things (Chokes!) help *generally* when we move up to VHF / UHF?

For SWL's (me!) I begin to wonder if we need care AT ALL about SWR on HF Bands.
Would I be right thinking that it's only "signal to noise ratio" that really matters? 🤔

 

If you transmitting chokes will most likely be very useful, stops coax from radiating,
can help with TVI and RF in the shack. On VHF may help with a better antenna pattern.

As to SWR, may be not but you will want an efficient antenna and an efficient antenna may not have
1:1 SWR

If transmitting then under 2:1 is best as modern transmitters tend to limit output past 2:1.

[Macavity]

On 20/02/2020 at 15:08, The Admiral said:

I haven't the foggiest.

Reflecting on your SWR plot... I quickly learned (in practice frankly!) that
measuring SWRs, via a coax, superimposed a "sine wave" on everything!
It's "obvious", I guess! Maybe that's what you did in this instance tho'? 🤔

The TRUE reading of an antenna SWR is measured at the feed point of
the BARE antenna. Well, that's my story (now) and I'm sticking to it. lol 😛

It's "well known" that a dipole radiates at a third harmonic? 40m -> 15m.
Not sure about "quad" elements. Possibly at the second harmonic?!?! 🤔 

My "Aircraft Band" Antenna fed via 15m coax. Note the "sine waves":



I suspect "via coax" SWRs are still useful. At least you know your antenna
hasn't blown away in the WIND! lol 🤣

Edited February 22, 2020 by Macavity