Hi nanovnauser;
A couple of more or less encouraging comments for you. Your VNA antenna measurement results indicate the following:
1) You did well... You are using the VNA and interpreting the results correctly in the context that you have described for its use. You clearly have done a fine job matching your antenna. It looks spot on and well matched.
2) Anything that gets you on the air is a good antenna, and I applaud your effort in that regard. 20 dB below 100W puts your EIRP (very isotropic in your case BTW) at the 1W level. Time of day (interpret this as night), prevailing ionospheric conditions, and persistence can render you surprise and enlightenment. WAS has been achieved at considerably lower power levels on 80 meters, and I have personally copied a 10 mW beacon at 340 mil on 80 meters, so I'm not going to rag on your antenna. I rag on those who whine about HOA's and the like for keeping them from operating. Do a Google Earth fly over of N2PK's QTH... He manages to keep the hostile HOA police in the dark. Then take a look at his DXCC record on 160 meters, and his position on the honor roll. I've tuned up the metal roof of a brick storage building in order to QNI into our 80 meter net. The Tx performance was awesome... but whoa!!! Definitely not as desirable as a Beverage on Rx.
3) Maybe this is obvious to everybody, but I'll comment on the array of VNA photo's you attached. The Smith Chart pretty much tells the whole story, and all that follow are simply different ways of displaying exactly the same information. VNA's measure reflection coefficient; the displays are simply computational results of the same measurement.
Bottom line... I'm convinced of your ability and knowledge of using a VNA to correctly and accurately tune antennas. Getting yours tuned precisely where you wanted it is certainly a bigger challenge than tuning up a cook book design. Try getting on the air an hour or so after dusk... and especially on weekends.... when hams actually make their presence known. Try answering a few of the stronger CQ's. You may be surprised at the gems that are borne out enthusiastic dumpster diving. LOL!
--
73
Gary, N3GO
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Re: Analysing Input Impedance Matching Circuit for the NE602
Hi Roger,
Thanks for the suggestions, I have the attenuator shown in the picture and did wonder if I could use this but was not sure about the calibration procedure. I will try this as well, currently I have my NanoVNA connected directly to the transformer and have been testing various winding combinations to get a good match. So far I have got a 1.5 to 1 VSWR at 7.15MHz but the circuit is still on a breadboard so I expect the numbers to change a bit when I solder it up on a veroboard.
As kb1gmx mentioned above, the NE602 has a very good gain at 40m and I am sure that what I have now would work quite well but I am quite curious if I can make a really good match now I have a VNA to work with. The other radios I have built for 40 and 20 meters have all been quite successful and I did not have a VNA for these - now I do have one I am finding it very interesting to experiment and really see what the changes I make actually do.
I have had a look around for the BN73-202 binocular cores you mentioned and have found them at the same place I buy my FT37-43 cores - I will order a few of these and try them out - hopefully they will arrive in a day or so.
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On Tue, Mar 10, 2020 at 02:55 PM, Dragan Milivojevic wrote:
Any plans to release a review of the prototype unit that you got?
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Erik has experience his own VNA design and provided Gabriel with helpful suggestions during her SAA-2 design. I have not seen any issue reports from him to Gabriel regarding his pre-production unit, so I assume that it is performing up to its advertised specifications. That is encouraging to members of this group who value Erik's technical insight.
- Herb
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Looks like an interesting way to get on 80 meters which is not something
everyone has the airspace to do. If you want to play with it try moving
the two whips away from each other with a copper pipe in the middle. Even
four feet will make a difference as that is where this antenna needs to
radiate the most.
NE7LS
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On Tue, Mar 10, 2020, 8:15 AM <nanovnauser@...> wrote: I know its narrow band but just its for a spot frequency of 3.775Mhz,heres
some more pics of it and screen shots of it on my foxdelta analyser.also a
couple of pics of my verticle.73
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Hello Herb,
thanks for the reply. I was thinking that the designer probably designed V2 with a specific model of battery in mind, and could maybe provide a hint. (if he's reading this)
For me, the Nano is primarily a portable field instrument, with emphasis on being completely self-contained, so a battery is a high priority.
The standards supplied with the old nano are not bad - I checked them on a HP analyzer, and up to 3GHz they are very good. Of course, I could just have had luck, and other sellers sell crappy ones.
RG174 is more of a problem, but if you don't chase tenths of a decibel, such short pieces are quite "usable" up to 3.
Marko Cebokli
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If you want a low cost spectrum analyzer (SA) that goes from a few kHz to 2 GHz. buy an SDRplay RSP1A SDR receiver for around $100 US. Then download the free Spectrum Analyzer program, written by a 3rd party, from the SDRplay downloads section. This program has a lot of standard SA features but you will need some good attenuators because the RSP1A needs to have a maximum signal input below 0 dBm.
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Another way to describe two 8ft whips as a dipole... A HF rubber duck antenna.
Or an Electrically small antenna (under .1 lambda , for 80m thats 8M long)
and the loading coils or matching scheme will contribute inefficiency.
Its efficiency is typically under 5% maybe worse. Also likely lower HF antennas
less that very high (at least 20M or more) is also a hit to performance as most
of the RF radiate due to ground bounce is straight UP.
Also it has a very small Aperture, so it intercepts a significantly smaller part
of the incoming signal.
NOTE: a full sized dipole at 10ft (3M) height would greatly outperform that
antenna for distances under 300miles (`500km). It can be bent to fit available
space with some reduction in performance.
Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO
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Re: Ceramic filter measurement
Hi Dave,
Those results look really nice. If you want to try a direct approach with only resistors, here is the formula -
Make a new board, using 2 SMA to PCB connectors, one for signal in (pin 1) one for signal out (pin3)
From the center pin on both SMA connectors, go though a 56 ohm R to ground.
From the same center pin node, go from each in series though a 300 ohm R to pins 1 and 3 of the filter socket. On the output (pin3) use a 10 pf cap to ground before the 300 ohm R. That's it.
This arrangement yields (close to) the proper load for both 50 ohm in and out ports, as well as 330 ohm load for the filter itself. The actual loads seen by the filter are 326.4 ohms.
You can experiment with the 10 pf cap, it is always shown in the Murata recommended test fixture. My results show it becomes less important on wide (280 kHz) filters, and more important, especially for filter top response slope and group delay "side saddles" for narrow filters (150, 180 kHz).
So, here is another circuit adjustment than can be added to an in-situ ceramic filter, in addition to output load R, to adjust response in circuit for best performance (usually lowest distortion). These adjustments are needed as not all circuits / components used in existing gear are perfect, and no one has an unlimited supply of ceramic filters.
BTW, if anyone needs 10.7 filter data, join the FMtuners group here, there is quite a bit there in the files, which go back to 2001. It probably makes no sense to re-post it all here.
Bob
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Your two EXTREMELY short whips configured as a horizontal dipole will have very high losses and low efficiency? because they are physically short. Even though the whips load the elements to achieve resonance their efficiency is going to be horrible. This is the price you pay for "convenient" short antennas at low frequencies. Remember SWR has nothing to do with how well an antenna can radiate or receive an RF signal. A 50 ohm resistor will give you a 1:1 SWR but it will be useless as an antenna.
I generated a very quick & dirty model of your antenna and for NVIS signals arriving from straight overhead the difference between a full-sized dipole and your two short whips at 12' is on the order of >20 dB. This is a huge difference so when you say it works like rubbish it is in fact working as it should.
Gedas, W8BYA EN70
Gallery at
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
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On 3/10/2020 8:54 AM, nanovnauser@... wrote: hi all i have a 80m dipole set for 3.775 Mhz,it seems to work rubbish,ive just done some adjustments,,take a look at the pics of it on the vna,does it look ok,views welcome,cheers m3vuv.ps,forgot to say its 2 80m mobile whips in a dipole config,up at about 12 feet for nvis .
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On the whip - loading coils....
The (B)and(W)ith of an antenna is determined by it's (Q)uality factor, thus of the R L and C components that make an antenna:
L by the length of the whips
C by he surface of the whips
R defined by diameter and material of the whips
The quality factor of a combination of RLC is given by this formula
Q = 1/R *SQR(L/C)??? and BW=1/Q
Just like a resonance circuit . Note that this formula is more complex if you need real values; just for understanding.
A wire antenna with infinitely? thin wire? would have only L and no C because it has no surface to create capacitance.
the quotient of L/C is very high, and the BW will be very small
To increase bandwidth, add capacitance by using thick wire or even tubes, or add a plate at the end of the wire.
Increasing R will work also, but at the cost of signal losses by dissipation.
Gert Gremmen
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On 10-3-2020 15:57, Ronan Daly wrote: Using mobile whips it will be rubbish. Its not a dipole - its 2 loading coils
--
Independent Expert on CE marking
EMC Consultant
Electrical Safety Consultant
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Re: Dumb question: What are REAL, IMAG, and PHASE good for?
#general_vna
Well, now the answer is beyond dumb ;<))
If you put a signal on a coax, it will start traveling along, very fast but not infinity fast.
If it reaches the end of the cable there are 3 interesting cases:
1. the cable is shorted
2. the cable is open
3. that cable is characteristically terminated (most 50 or 75 Ohm)
(which is the same as if an infinitely long cable is connected to
the end)
Case 1: as the cable is shorted, the voltage at the end will be 0 all the time. So our signal arrives and gets REFLECTED and the polarity inverses.
that is where the -1 comes from.
Case 2 : as at the end of an open cable the current is always 0. So our signal arrives , gets REFLECTED and the polarity does NOT inverse.
that is where the +1 comes from
In case 3 the signal is simply dissipated in the resistor, and no reflection occurs
that is where the 0 comes from
Note that the values? -1 to +1 are_normalized_, this means that the real value of the signal is first divided by itself before being graphed.
A voltage of 800 mV will be divided by 800 to get a normalized value of 1
This explains the values in a smith graph on the horizontal axe only.
Jean-Roger: feel free to continue ?
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On 10-3-2020 16:01, F6EGK - Jean-Roger wrote: All explanations above are right. However there can be a confusion when looking at what is really displayed by the NanoVNA.
REAL and IMAG parameters are not the samething as RESISTANCE and REACTANCE parameters. REAL and IMAG apply to reflection coefficient ¦£, in its complex form (a+j.b). That's why values are always in the [-1,1] interval, without any associated unit. When REAL=-1 and IMAG=0, it is the Short circuit situation. When REAL=1 and IMAG=0, it is the Open circuit situation. When REAL=0 and IMAG=0, it is the normal Loaded (50 ohms) situation.
LINEAR is the ¦£ modulus form of combined REAL and IMAG values, and finally POLAR is the geometric representation of REAL, IMAG and PHASE values. When POLAR is displayed by the NanoVNA, and even if data values are exactly displayed as for Smith Chart, results must not be read in the same way. Have a try by displaying two CH0 traces, POLAR and SMITH.
SWR and LOGMAG (Return Loss) are derivated from ¦£ modulus (LINEAR). For educational purposes I have created an ods file (see below), showing and calculating NanoVNA parameters. You can play with it by entering values in the blue fields, and also checking what are the arithmetic relations behind the different results. Here Group Delay is not relevant as calculations are done for a discrete (CW) frequency.
A last word about the use of REAL and IMAG parameters. The following case (see attachment) is an opened coaxial cable (length 2 meters), creating a quarter wave stub (at red marker). An opened coaxial cable remains a good use case for education and increase of knowledge. On the NanoVNAsaver snapshot we see clearly that displayed values between RESISTANCE/REACTANCE and REAL/IMAG do not allow an immediate comparison. For example at red marker, R+jX or Smith Chart highlight a value of 0+j0 ohms (short circuit situation), and checking this with REAL/IMAG chart you get -1 (REAL) and 0 (IMAG) which is the same thing. Be careful with REAL and IMAG curves which follow sinus and cosinus rules, it reflects simply a monotonous variation of PHASE.
REAL is also interesting if you want to measure a coaxial cable length, thanks to advanced TDR function.
Sorry for possible english language mistakes.
73 from Jean-Roger / F6EGK
--
Independent Expert on CE marking
EMC Consultant
Electrical Safety Consultant
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I know its narrow band but just its for a spot frequency of 3.775Mhz,heres some more pics of it and screen shots of it on my foxdelta analyser.also a couple of pics of my verticle.73
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Re: Dumb question: What are REAL, IMAG, and PHASE good for?
#general_vna
All explanations above are right. However there can be a confusion when looking at what is really displayed by the NanoVNA.
REAL and IMAG parameters are not the samething as RESISTANCE and REACTANCE parameters. REAL and IMAG apply to reflection coefficient ¦£, in its complex form (a+j.b). That's why values are always in the [-1,1] interval, without any associated unit. When REAL=-1 and IMAG=0, it is the Short circuit situation. When REAL=1 and IMAG=0, it is the Open circuit situation. When REAL=0 and IMAG=0, it is the normal Loaded (50 ohms) situation.
LINEAR is the ¦£ modulus form of combined REAL and IMAG values, and finally POLAR is the geometric representation of REAL, IMAG and PHASE values. When POLAR is displayed by the NanoVNA, and even if data values are exactly displayed as for Smith Chart, results must not be read in the same way. Have a try by displaying two CH0 traces, POLAR and SMITH.
SWR and LOGMAG (Return Loss) are derivated from ¦£ modulus (LINEAR). For educational purposes I have created an ods file (see below), showing and calculating NanoVNA parameters. You can play with it by entering values in the blue fields, and also checking what are the arithmetic relations behind the different results. Here Group Delay is not relevant as calculations are done for a discrete (CW) frequency.
A last word about the use of REAL and IMAG parameters. The following case (see attachment) is an opened coaxial cable (length 2 meters), creating a quarter wave stub (at red marker). An opened coaxial cable remains a good use case for education and increase of knowledge. On the NanoVNAsaver snapshot we see clearly that displayed values between RESISTANCE/REACTANCE and REAL/IMAG do not allow an immediate comparison. For example at red marker, R+jX or Smith Chart highlight a value of 0+j0 ohms (short circuit situation), and checking this with REAL/IMAG chart you get -1 (REAL) and 0 (IMAG) which is the same thing. Be careful with REAL and IMAG curves which follow sinus and cosinus rules, it reflects simply a monotonous variation of PHASE.
REAL is also interesting if you want to measure a coaxial cable length, thanks to advanced TDR function.
Sorry for possible english language mistakes.
73 from Jean-Roger / F6EGK
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Using mobile whips it will be rubbish. Its not a dipole - its 2 loading coils
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A decent spectrum analyzer would need good image frequency (and spurs) suppression. And it would need a much faster ADC because a 5 or 10 KHz bandwidth is way too low to be useful. I need a real time spectrum analyzer that can capture at least 10 MHz of spectrum at once. In essence, a spectrum analyzer is more complicated than a vna. However, they have quite some hardware in common. It is on my wish list to design a decent 6 GHz VNA/SA combi, not a cost optimized VNA "toy" like all nanoVNA versions. But the wish list grows faster than I can handle...
Reinier
Op 10-3-2020 om 15:08 schreef Larry Rothman:
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Although, thinking about this a little more - there IS alot more space for enhanced firmware on the new V2 board which uses Analog Devices freq generator chips so additional functionality -might- be able to be developed for a spectrum analyser feature using the input port.The problem is the dynamic range and how to control input levels.
What do you think, Gabriel?
It would also be nice to have an option to flip the display 180 degrees.
Cheers,Larry
On Tuesday, March 10, 2020, 9:55:20 a.m. GMT-4, Larry Rothman <nlroth@...> wrote:
Not really worth it when there are countless RTL-SDR dongle projects that allow you to do this already on the cheap.
? ? On Tuesday, March 10, 2020, 9:49:26 a.m. GMT-4, nanovnauser@... <nanovnauser@...> wrote:
is there any plans to make a spectrum analyser along the same lines as the nanovna?,seems to me it would be a winner.
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Although, thinking about this a little more - there IS alot more space for enhanced firmware on the new V2 board which uses Analog Devices freq generator chips so additional functionality -might- be able to be developed for a spectrum analyser feature using the input port.The problem is the dynamic range and how to control input levels.
What do you think, Gabriel?
It would also be nice to have an option to flip the display 180 degrees.
Cheers,Larry
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On Tuesday, March 10, 2020, 9:55:20 a.m. GMT-4, Larry Rothman <nlroth@...> wrote:
Not really worth it when there are countless RTL-SDR dongle projects that allow you to do this already on the cheap.
? ? On Tuesday, March 10, 2020, 9:49:26 a.m. GMT-4, nanovnauser@... <nanovnauser@...> wrote:?
is there any plans to make a spectrum analyser along the same lines as the nanovna?,seems to me it would be a winner.
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Not really worth it when there are countless RTL-SDR dongle projects that allow you to do this already on the cheap.
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On Tuesday, March 10, 2020, 9:49:26 a.m. GMT-4, nanovnauser@... <nanovnauser@...> wrote:
is there any plans to make a spectrum analyser along the same lines as the nanovna?,seems to me it would be a winner.
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is there any plans to make a spectrum analyser along the same lines as the nanovna?,seems to me it would be a winner.
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Roger Need
