Don¡¯t send me your emails
CW4EVER
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On 16 Aug 2021, at 10:10, Knud Jorgen Olsen-Jensen via groups.io <vk2kjj@...> wrote:
?Don¡¯t send me your emails
CW4EVER
On 16 Aug 2021, at 09:15, Charles KC6UFM <kc6ufm@...> wrote:
?Hi, Luciano...
I more or less (in my head) wrote off the "extra" resistance needed to make
the NanoVNA see a flat match as being to a combination of lead
resistance/reactance and operator error.
I think it's safe to assume that the transformer is actually a 49:1 ratio.
Thanks!
On Sun, Aug 15, 2021 at 3:48 PM Luciano Luciano <luciano.wdc@...>
wrote:
Hi Charles,
I get "suspicious" when I see small differences like this i.e. 50 ohm as
in this case. Assuming the black box is lossless, you should measure either
2450 or 2500 ohm if you load the other port (with coax connector, right?)
with 50 ohm... if you measure 2450 then it is a 49:1 transformer as you
correctly guessed in the first place! Of course easier to say (and write)
in theory than to actually do in practice.
Regards,
Luciano
On Sun, Aug 15, 2021, 6:15 PM Charles KC6UFM <kc6ufm@...> wrote:
Hello, All...
I recently had a need to measure an unknown matching transformer. As it
was
in a sealed enclosure with noth but the wire terminal and coax connector
exposed, and I didn't want to damage the enclosure, I pulled out my
trusty
NanoVNA.
All I knew about the "black box" was that it was used with a
10-12-15-17-20m EFHW wire antenna. That made me assume it would be
somewhere in the range of a 49:1 ratio.
I pulled out my decade resistance box and dialed in 2450 ohms (50 ohms x
49) and put that between the output wire terminal and ground. I then
connected the NanoVNA to the coax input.
I then played with the decade box until I got a flat response from the
NanoVNA and the needed resistance to get there was 2501 ohms.
Technically,
that makes the matching network about 50:1 ratio.
All of this told me what I wanted to know, but I'm wondering if there
would
be an easier, more direct way of getting there with the NanoVNA.
I'm good with the idea that I may have just stumbled onto the right
answer
in my madness.
Take Care & 73
--
de KC6UFM
Charles
--
de KC6UFM
Charles
