Measuring R,X Resonant Frequency
Greetings,
I've recently completed the construction of my first 'home brew' antenna (1/4 wave vertical). A radio friend of mine suggests I should look at resonance as well as SWR.
SWR is fine, but I can't see anything online about an R/X chart (similar to that available on the RigExpert).
Can I do this on the NanoVNA V4?
Thanks
Peter M0LMG
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All,
The groups.io fee for maintaining this group has been paid. I received several donations after I sent the notice that the amount required had been reached and have refunded those donations. For those of you who donated after the required amount had been gathered, thank you for your donation and please feel free to donate next year. For those of you who donated and whose donations are went to the subscription fee, thank you as well.
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DaveD
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On 1/11/2025 7:27 AM, Dave Daniel wrote: All,
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*No more donations are needed.*
Thank you again.
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On 1/10/2025 11:06 AM, Dave Daniel wrote:
All,
It's that time of year again when we need to pay the annual $220 fee to keep the group going. The payment is due? the 18th and will be automatically paid by me.
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The screenshot function was finally solved, the reason was that there was a problem with my chip, I didn't find that the SD_CS pins were pulled low when I probed the waveform, which was very strange, and finally I used the diode function of the multimeter to measure the voltage drop between the SD_CS pins and GND, and confirmed that the SD_CS pins were damaged, because the normal IO and GND have a voltage drop of about 0.6V, and finally I replaced an IO, and the screenshot function was used normally
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Re: Nano VNA 10M Dipole Sweep
On Fri, Jan 17, 2025 at 06:40 AM, ?lvaro Felipe Hern¨¢ndez wrote:
Whenever I have made measurements to antennas I have had very different
results -even calibrating the antenna feed coaxial cable- than placing my
VNA-F with a 10 cm. patch cord directly to the antenna feed.
This happens when you have common mode issues and the outer surface of the coax shield has become part of the antenna. For example - A dipole connect to coax with out a balun will have this issue. Roger
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Re: Nano VNA 10M Dipole Sweep
If you want a precise and real
measurement you should connect the NANO-VNA as close as possible to the antenna feed
point. I have a -F and I have never encountered this problem with either a 10 m coaxial or a 40 m coaxial (3-30 MHz). I make my measurements from the station, the NanoVNA being connected to my PC. The measurements I make, by calibrating at the connection to the antenna are a priori good since this is where I insert my LC adapters. These adapters are calculated on the basis of the s1P files; I measure the components. Then I refine the settings by mounting the adapter upside down in order to find the impedance measured in the s1p. And it works. This is also the only way to integrate the coaxial sheath into the measuring device. -- F1AMM Fran?ois -----Message d'origine----- De la part de ?lvaro Felipe Hern¨¢ndez Envoy¨¦ : vendredi 17 janvier 2025 15:40
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Re: Nano VNA 10M Dipole Sweep
Whenever I have made measurements to antennas I have had very different results -even calibrating the antenna feed coaxial cable- than placing my VNA-F with a 10 cm. patch cord directly to the antenna feed. Obviously I have had to remove the antenna feed cable and calibrate the VNA with the cable stretched on the ground. If you want a precise and real measurement you should connect the NANO-VNA as close as possible to the antenna feed point.
--
ALVARO, EA8ARX
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Re: Nano VNA 10M Dipole Sweep
RE: "digging in" Old proverb: "When you're up to your ass in alligators it's hard to remember that your job was to drain the swamp!" Bill K2TNO On Thu, Jan 16, 2025 at 6:19?PM W0LEV via groups.io <davearea51a= [email protected]> wrote: The best way to conquer the "steep learning curve" is to just dig in.....
Dave - W?LEV
On Thu, Jan 16, 2025 at 6:17?PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:
On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote:
SimSmith can do all this and far more..... And.....its freeware:
Yes it can do much more and it has a steep learning curve...
Roger
--
*Dave - W?LEV*
--
Dave - W?LEV
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Re: Nano VNA 10M Dipole Sweep
The best way to conquer the "steep learning curve" is to just dig in..... Dave - W?LEV On Thu, Jan 16, 2025 at 6:17?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote:
SimSmith can do all this and far more..... And.....its freeware:
Yes it can do much more and it has a steep learning curve...
Roger
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: Nano VNA 10M Dipole Sweep
On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote:
SimSmith can do all this and far more..... And.....its freeware:
Yes it can do much more and it has a steep learning curve... Roger
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Re: Nano VNA 10M Dipole Sweep
SimSmith can do all this and far more..... And.....its freeware: And an excellent tutorial: Dave - W?LEV On Thu, Jan 16, 2025 at 5:32?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: There is an excellent free program for Windows that really helps to
understand how transmission lines work. It is called TLDetails >>
Using this program you can select from commonly available transmission
lines (RG8, RG58, twinlead etc.), set a load impedance, cable length and
frequency and then it calculates the SWR, Return Loss, impedance and plots
on a Smith Chart. Many other useful features as well. Here is an example.
-- *Dave - W?LEV* -- Dave - W?LEV
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Re: Nano VNA 10M Dipole Sweep
There is an excellent free program for Windows that really helps to understand how transmission lines work. It is called TLDetails >>
Using this program you can select from commonly available transmission lines (RG8, RG58, twinlead etc.), set a load impedance, cable length and frequency and then it calculates the SWR, Return Loss, impedance and plots on a Smith Chart. Many other useful features as well. Here is an example.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
I use the nanoVNA to get my Hallicrafters S-40B receiver on frequency for a CW net when using it with my Elmac AF-67 transmitter on CW. I could easily set the nanoVNA slightly off the CW frequency I want to receive and use it instead of the S-40B BFO.
As suggested, it would be better for that application to use the IF frequency. That would allow tuning across a band without resetting the nanoVNA.
When I am using the nanaoVNA with the S-40B just to get it rather precisely on frequency so I can then zerobeat the VFO in the AF-67 with it, I can simply set the nanoVNA on the single wire that runs from the T/R relay to the antenna terminal of the S-40B. That injects plenty of signal for the purpose.
73,
Maynard
W6PAP
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On 1/16/25 07:00, Bruce KX4AZ wrote: Appreciate all the quick replies here confirming the BFO is do-able in theory. Easiest thing for me to try first would be the Gander VOLMET station on 13270 kHz USB, during the daytime, believe they transmit at 20/50 minutes past the hour. And the beauty of that frequency is the nice round number, great for the really cheap ($25 range) receivers with the 5 kHz tuning steps. In the past I've measure the nanoVNA CW output power at around -9 dBm, plenty to work with for air coupled "injection".
Separate from this, I've used the CW output in the past to fine tune outdoor matching transformers for receive only HF antennas. I would attach a short whip antenna and place the nanoVNA close enough to get a signal at least 10 dB above the noise floor....something around 50-100 ft away, and then evaluate the S/N ratio while swapping out matching devices etc. Worked like a champ for that.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
Not as a BFO, that should work well. It does make for a good VFO going into a first mixer. getting the levels right can be challenging.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
Appreciate all the quick replies here confirming the BFO is do-able in theory. Easiest thing for me to try first would be the Gander VOLMET station on 13270 kHz USB, during the daytime, believe they transmit at 20/50 minutes past the hour. And the beauty of that frequency is the nice round number, great for the really cheap ($25 range) receivers with the 5 kHz tuning steps. In the past I've measure the nanoVNA CW output power at around -9 dBm, plenty to work with for air coupled "injection".
Separate from this, I've used the CW output in the past to fine tune outdoor matching transformers for receive only HF antennas. I would attach a short whip antenna and place the nanoVNA close enough to get a signal at least 10 dB above the noise floor....something around 50-100 ft away, and then evaluate the S/N ratio while swapping out matching devices etc. Worked like a champ for that.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
There is an article in the August, 1963 issue of Popular Electronics describing an external BFO. It attached to the receiver antenna terminal so the idea has been around 60 years at least. I would imagine any modern, stable signal source near the received frequency would work. Dave N9ZC On Thu, Jan 16, 2025, 7:17?AM G8HUL via groups.io <g8hul= [email protected]> wrote: Probably best to do it at the IF frequency rather than at RF.
73
Jeff G8HUL
________________________________________
From: [email protected] <[email protected]> on behalf of
Bruce KX4AZ <bruce@...>
Sent: 16 January 2025 13:31
To: [email protected]
Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM
only receiver?
Has anyone ever tried using the CW output feature to generate a carrier
for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only
receive AM mode signals? It seems like this should be thoretically
possible by attaching a small whip to the nanoVNA and placing it in the
vicinity of the receiver. But probably tricky to get the exact frequency
dialed in, as well as the signal strength relative to the sideband
signals. Just seems like a fun radio exercise or for an emergency need.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
Probably best to do it at the IF frequency rather than at RF. 73 Jeff G8HUL ________________________________________ From: [email protected] < [email protected]> on behalf of Bruce KX4AZ <bruce@...> Sent: 16 January 2025 13:31 To: [email protected]Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM only receiver? Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.
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Re: Use CW output as a BFO for SSB reception on a AM only receiver?
Hi Bruce, Yes, I have done something similar using my NanoVNA SAA-2N. I set the NanaVNA to a particular CW frequency, but have only used it to test effects of using a filter or amplifier at the input of an SDR dongle. I haven't tried using it to inject a simulated BFO signal into an AM-only capable receiver to receive SSB. I'm not sure how finely one can adjust the frequency on the NanoVNA, but what you describe should be possible. You could use various lengths of wire attached to the CH0/S11 center conductor to adjust the level of coupling to achieve higher or lower levels of "injection"of the BFO signal. I remember years ago tuning an AM-only shortwave receiver to a SSB signal of interest, and using another AM-broadcast receiver right next to the primary receiver and tuning the "injection" receiver across the 530 to 1600 kHz band in hopes to generate a beat frequency. More often than not it didn't work, but I had some mixed success with that method. I just fired up the NanoVNA set to a CW frequency 315.0 MHz and looked at the signal on SDRSharp using an RTL-SDR V4 SDR dongle, and the signal looked clean and was pretty much spot-on at 315.00 MHz. Good luck with your experimentation. Good DXing. Ken -- WB?OCV ________________________________ From: [email protected] < [email protected]> on behalf of Bruce KX4AZ <bruce@...> Sent: Thursday, January 16, 2025 5:31 AM To: [email protected] < [email protected]> Subject: [nanovna-users] Use CW output as a BFO for SSB reception on a AM only receiver? Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.
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Use CW output as a BFO for SSB reception on a AM only receiver?
Has anyone ever tried using the CW output feature to generate a carrier for reception of SSB (LSB/USB) on a cheap shortwave receiver that can only receive AM mode signals? It seems like this should be thoretically possible by attaching a small whip to the nanoVNA and placing it in the vicinity of the receiver. But probably tricky to get the exact frequency dialed in, as well as the signal strength relative to the sideband signals. Just seems like a fun radio exercise or for an emergency need.
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Re: Nano VNA 10M Dipole Sweep
Why not perform an swr sweep and see where the min swr falls? The impedance will change with exact length of feedline but thr swr min. should show you where your antenna is closest to resonance.
73,
Tom, KG3V
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On January 15, 2025 8:05:36 AM "Greg Giglio" <coffeeguy2@...> wrote: Hey David,
Good morning. Everything looks pretty good, and I'm sure you've noted the points about calibrating at the antenna feedpoint. When transmitting at low power, does your radio / SWR meter indicate pretty much in line with your VNA reading?
10m is a fairly wide band, and if your reading is still inductive, you might try something like inserting a 100pf mica / ceramic cap (at least 500V rating) across the elements at the feedpoint to see if that shifts the impedance / SWR curve more to your liking.
Congrats on taking the plunge with a DIY antenna, as well as making the effort to see HOW it works...Use common-sense precautions of course to protect your equipment, but remember that if it works, just have fun with it!
73 de KN7GIG
On Wednesday, January 15, 2025 at 06:24:49 AM EST, Siegfried Jackstien via groups.io <siegfried.jackstien@...> wrote:
at best calibrate at the cable end .... then you see the impedance of the antenna alone ... not with cable (that may rotate you results in Smith)
dg9bfc Sigi
Am 15.01.2025 07:23 schrieb "Fran?ois via groups.io" <18471@...>:
I calibrated at the S1 port directly. Then I connected S1 to the feed line and subsequently
the antenna. The plane I measured would be where the feed line attaches to the radio.
** Yes, I understood what you did.
It is not a mistake. You measure the impedance of your antenna, brought
back by your cable. It is the impedance that your TX sees in transmission.
Where it is a mistake is the deduction of saying that the antenna is too
long. You could, through software like SimNEC, find (see) the calculated
impedance of the other end of the cable (antenna side). But:
- You have to know how to use SimNEC which is not obvious
- Know what you are doing
- Assume that the cable is the one you are using
- Know the exact length of the cable
Add a length of cable (Tx side) and you will see that the impedance
brought back changes
--
F1AMM
Fran?ois
-----Message d'origine-----
De la part de David Gerhart
Envoy¨¦ : mercredi 15 janvier 2025 07:12
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Roger Need
?lvaro Felipe Hern¨¢ndez
Dave Merrill
