开云体育

Jim,

The 56:1 can be seen at the Myantennas website.


Andy

*
*

*Here is my? "MODIFIED"? 155 FT END-FED? wire WITH?? 9:1?? UNUN (Palomar Engineering) ? and? T-network? CLC tuner in shack*

*Lowest? SWR? set to around 7100 kHz? with a RETURN LOSS? of about?? +25dB ? (plotted as a negative to match SWR graph)
*

*Set up to tune easily on the digi end of fickle forty meters - ready for the Sunday MidAtlantic NBEMS on 7068 kHz at 10 AM EST*

*Can anyone explain the crazy? PHASE? graph with the dual phase changes?
*

*de k3eui*

On 02/23/2024 7:12 AM EST Fran?ois <18471@...> wrote:

I consider a 56/1 wideband transformer to be a utopia (I could be wrong). The fact of presenting measurements by joining two transformers head to tail does not assume anything about the operation of a single transformer.

Let's push the absurd and suppose that in the boxes they are 1/1 transformers, you will always have very encouraging measurement results.
--
F1AMM
Fran?ois

R&L. USA storefront, run by hams, fast shipping, and they know what you
are talking about when you contact them.



73

-Jim
NU0C

On Thu, 22 Feb 2024 13:01:32 -0800
"Roger Jollis" <rjollis@...> wrote:

Given a choice, I would prefer to purchase on Amazon where I have a gift

card credit and where I can get the device fairly quickly.

Hi all.

I have looked for past postings for my question, but don't find a >recent< answer. So here's my situation. I have destroyed my second NanoVNA, an H4 model that I bought last July to replace my last one. This time, instead of dropping it on a concrete floor, I connected the device to my DX Commander antenna project to begin to tune it. Not realizing that the front end is susceptible to ESD damage, I didn't use an attenuator or other external protection. Apparently there was a large enough static charge in the antenna system to blow the front end of the VNA. So the S11 input is completely unresponsive and the device shows a consistent random noise readout (video attached).

While I'm tempted to buy a Rig Expert, I would miss this robust community that stands behind the NanoVNA. And I have just last week ordered a NanoVNA book from RSGB that isn't here yet. So I am once again in the market for a new H4. Since there are so many clones out there, I don't want to get burned with buying a marginal clone device. Given a choice, I would prefer to purchase on Amazon where I have a gift card credit and where I can get the device fairly quickly. But most important is to have a reliable unit. Does anybody have some recent experience with which flavor of NanoVNA to buy?

Thanks in advance.

73 de K8YX

Short vid shows the SWR function with a 50 Ohm load connected to S11. Trace: 0, Format: S11 (Refl), Stimulus: 3.0-4.5Mhz. Makes no difference when it is connected to a load. Just noise.

On Feb 22, 2024, at 4:01?PM, Roger Jollis <rjollis@...> wrote:

?Hi all.

I have looked for past postings for my question, but don't find a >recent< answer. So here's my situation. I have destroyed my second NanoVNA, an H4 model that I bought last July to replace my last one. This time, instead of dropping it on a concrete floor, I connected the device to my DX Commander antenna project to begin to tune it. Not realizing that the front end is susceptible to ESD damage, I didn't use an attenuator or other external protection. Apparently there was a large enough static charge in the antenna system to blow the front end of the VNA. So the S11 input is completely unresponsive and the device shows a consistent random noise readout (video attached).

While I'm tempted to buy a Rig Expert, I would miss this robust community that stands behind the NanoVNA. And I have just last week ordered a NanoVNA book from RSGB that isn't here yet. So I am once again in the market for a new H4. Since there are so many clones out there, I don't want to get burned with buying a marginal clone device. Given a choice, I would prefer to purchase on Amazon where I have a gift card credit and where I can get the device fairly quickly. But most important is to have a reliable unit. Does anybody have some recent experience with which flavor of NanoVNA to buy?

Thanks in advance.

73 de K8YX

Short vid shows the SWR function with a 50 Ohm load connected to S11. Trace: 0, Format: S11 (Refl), Stimulus: 3.0-4.5Mhz. Makes no difference when it is connected to a load. Just noise.





<NanoVNA H4 Noise.mp4>

Good morning Tim,
Thanks for the note about DFU driver, I didn't knew.

An interesting thing is the fact that yesterday evening I installed nanoVNA-saver on a MacBook Air (with MacBook Ports) and I obtained the same result:
- when I connect my own NanoVNA, a communication port is appearing in MacBook list, and the NanoVNA-saver could connect to the device ;
- connecting my friend's NanoVNA, the comm port does not appear and therefore, the NanoVNA-saver could NOT connect to the device.

Thinking to what you've told me (DFU mode is a completely different driver in Windows), do I have to suppose that in this particular situation, the USB port of the ST microcontroller mounted in my friend's NanoVNA could be damaged ?
However, I know that USB has only 4 wires, +/- and dataIn/dataOut. If something was faulty on the STM USB port, would it still work in DFU mode?

Thanks a lot and a nice day,
Bob

56:1? That’s kind of a weird ratio. 49:1 is easy, it’s 7:1 turns ratio (impedance goes as the square of the turns ratio). 64:1 would be 8:1 turns.

On Feb 21, 2024, at 7:47?AM, Andrew Harman<Nexus9d9@...> wrote:

?I've seen other kits which supply 130 ft with a 56:1. (and since you went with a heavy wire you are likely a little long on your trim yet) If its high enough a counterpoise isn't necessary - but grounding at entrance is recommended. (NPFA 70, article 800) The other option for a coil at the feed point is also sometimes used - but you knew that.

Andy

On Feb 21, 2024, at 7:47?AM, Andrew Harman <Nexus9d9@...> wrote:

?I've seen other kits which supply 130 ft with a 56:1. (and since you went with a heavy wire you are likely a little long on your trim yet) If its high enough a counterpoise isn't necessary - but grounding at entrance is recommended. (NPFA 70, article 800) The other option for a coil at the feed point is also sometimes used - but you knew that.

Andy