Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Handling the nanoVNA h4
|
Hi. I have set and calibrated the nanovna and then hooked up my antenna to see the SWR graph. Let's say I have a 20m antenna attached and it shows a nice dip at 14.45Mhz to swr of 1.2. all this time of course the device has been in my hand.
Without moving my feet I put the nanoVNA on the nearby plastic chair and when I let go the dip slides left to 14.2Mhz. Is it normal to see different swr readings like this when holding or not holding the nanoVNA? Which is the correct reading? Sorry for the newb question. Appreciate any input. Edward |
|
You were part of the resonate circuit of the antenna.
toggle quoted message
Show quoted text
You were a? Counterpoise! Virtually every talkie is depending on the operators hand to be the other half of the antenna. Kent WA5VJB?? Antenna Editor CQ Magazine. On Sunday, July 9, 2023 at 03:02:27 PM CDT, Edward Stavin VE3VYT via groups.io <edwardstavin@...> wrote:
Hi. I have set and calibrated the nanovna and then hooked up my antenna to see the SWR graph.? Let's say I have a 20m antenna attached and it shows a nice dip at 14.45Mhz to swr of 1.2.? all this time of course the device has been in my hand. Without moving my feet I put the nanoVNA on the nearby plastic chair and when I let go the dip slides left to 14.2Mhz. Is it normal to see different swr readings like this when holding or not holding the nanoVNA? Which is the correct reading?? Sorry for the newb question. Appreciate any input. Edward |
|
Hi,
toggle quoted message
Show quoted text
This indicates you have become part of the antenna system... It also indicates you might consider adding a good 1:1 choke at the antenna feedpoint, and try the test again. I would guess you will see less of a slide... See: for more on how and why this works... 73, and thanks, Dave (NK7Z) ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW Division, Technical Resources On 7/9/23 13:02, Edward Stavin VE3VYT via groups.io wrote:
Hi. I have set and calibrated the nanovna and then hooked up my antenna to see the SWR graph. Let's say I have a 20m antenna attached and it shows a nice dip at 14.45Mhz to swr of 1.2. all this time of course the device has been in my hand. |
|
Totally depends on the design of your antenna.
toggle quoted message
Show quoted text
With something like a ground plane antenna, your had should do little. A Yagi antenna with a Balun, your hand should do little. HF Dipole with a Balun, your hand should do little. A long wire antenna or no Balun, yes, your hand would do quite a bit. Easy test.?? Kent On Sunday, July 9, 2023 at 03:24:32 PM CDT, Edward Stavin VE3VYT via groups.io <edwardstavin@...> wrote:
Interesting. So should I be sure to avoid contact with the nanovna while observing or tuning the antenna swr? |
|
Hi again,
toggle quoted message
Show quoted text
Once you have added the ferrite material, check by putting the nano down, and picking it up again. If the frequency still slides around try increasing the number of turns until you see no, or little, change in frequency. Once you arrive at a point where you are seeing little, or no change in frequency, it is time to tune the antenna. 73, and thanks, Dave (NK7Z) ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW Division, Technical Resources On 7/9/23 13:24, Edward Stavin VE3VYT via groups.io wrote:
Interesting. So should I be sure to avoid contact with the nanovna while observing or tuning the antenna swr? |
|
I forgot to mention, by feedpoint, I mean the point where the coax begins.
toggle quoted message
Show quoted text
If a dipole, right after the center insulator, if a vertical, right after the coax starts, and on the coax, if an antenna that has a matching transformer on it, after the matching transformer. 73, and thanks, Dave (NK7Z) ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW Division, Technical Resources On 7/9/23 13:42, Dave (NK7Z) wrote:
Hi again, |
to navigate to use esc to dismiss