Experiment with SWR meter

[Art]

Hi Group.

I am experimenting with different VSWR meter designs. I was interested in the SWR meter circuit, which is used in the HL2. But having soldered the circuit, I discovered one problem. I do not have original N2ADR boards, but I still want to understand where the problem is.

My SWR meter diagram is attached. The differences from the original are as follows:

1. A green ferrite ring (2300 permeability) is used.

2. Resistors 18 Ohm is used with an error of 5%

At loads of 100 Ohm and 150 Ohm, there is no error. SWR is correct and the same everywhere from 160m to 10m.

But at a load of 50 Ohm, the VSWR has unevenness:

160m - 1:05

20m - 1.3

10m - 1.4

The problem is definitely not in the 50 Ohm load, since I have several of them and all have been tested with other SWR meters.

I found that VSWR unevenness occurs at points A and B. This is checked with an oscilloscope.

The problem could be:

1.With a transformer. But I have tried different transformers. I do not have a FT37-77 ring, but is it really a problem because of this?

2. My 18 ohm resistors have a 5% error. Can I fit resistors with 1% tolerance?

[Prabir Debnath]

Yes one of the issue is with the type of ferrite. Use type 43

73

Probir VU2BQF 

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[Art]

I tried to make a transformer on a ring from 43 materials. Nothing has changed. Does only FT37-77 ring work?

The ring was like that:

https://toroids.info/FT23-43.php

суббота, 12 июня 2021 г. в 06:37:24 UTC+3, Probir:

[Art]

I tried to put a capacitive divider and the unevenness disappeared. I don’t even know if I have such resistors. Thanks to all.

суббота, 12 июня 2021 г. в 09:57:04 UTC+3, Art:

[Steve Haynal]

Hi Art,

I just checked and see SWR under 1.04 across all bands. This is with Quisk and using the default HL2FilterE3 calibration table. Were you using a calibration table?

73,

Steve

kf7o

[Art]

Hi Steve.

 I used the default calibration table too. Didn't change anything in Quisk. PowerSDR and Quisk show the same. It’s very strange that this happened to me. I did a lot of experiments, and I always got the same thing. I think I should use 1% resistors and a FT37-77 ring. Perhaps just replacing the resistors would help. Since my transformer works well in a capacitive divider circuit.

воскресенье, 13 июня 2021 г. в 05:21:07 UTC+3, softerh...@gmail.com: