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Re: Non Linear Vac Cap?!

Guenter DK7KV
 

Hi,
some caps are really not nice (far from linear) in the lower region: 

Just check and compare: https://www.amstechnologies-webshop.com/media/pdf/8e/a1/a8/Vacuum-Variable-Capacitors-Jennings-Datasheets.pdf

73 guenter


Non Linear Vac Cap?!

Barry - 2E0IDE
 

Guys

I've just changed out an air cap for a vac cap and was surprised to find, unlike a very linear air cap, the vac cap is anything but linear.:-


My controller was really accurate with the air cap and a 100:1 gearbox. The vac cap has a 5:1 gearbox. At 40M the accuracy is OK but not good at all at 20M and above.

Has anyone else had similar results with a vac cap or can advide where I may be having a senior moment!


Re: Anybody have a problem with SWR tune

Leonard A. Gucciardo KD2NEN
 

Looks like that’s what I have to do with mine. I believe it is RF that is causing the issue because it is frequency dependent. I will place my couplers in an aluminum enclosure and remotely connect them. Thanks for the input I really appreciate it. Very nice job on that coupler.

Leonard A. Gucciardo
KD2NEN

On Feb 24, 2021, at 1:12 PM, Immo <dl5kb@...> wrote:

hi Lenni,
I have an iron case for for my SWR-bridges. It is close for up to 500W and there is no issue tunig up to 24Mc. I have also two capacitors tested, one butterfly-C with a 1: 100 geared stepper and another with a vac-C and a 1: 20 geared stepper. As I started my built, I had the little bridge after Kits and parts mounted only with copper-shields open in my controller case. There I had the issue, that automatic tuning was not possible over 18Mc. At least my Teensy won't work any more and I had to change it. It was to much straying HF inside the case. Today I have both bridges in a steel case and no problems any more. I use my loop inhouse, about 2 m (6ft) from my rig and the loop controller working up to 100W. The housing of the controller is made of double sided copper coated material. All sides (in- and outside) are soldered together and  grounded. The pictures show the bridge with two 8307. This one I can remove from controller and connected over cable, mount directly at the loop. Works fine!
So you have to prove your design, I believe. Good luck!
73, Immo, DL5KB
<SWR bridge in its case.JPG>
<SWR-Bridge closed.JPG>

--
LennyG KD2NEN


Re: Anybody have a problem with SWR tune

Immo, DL5KB
 

hi Lenni,
I have an iron case for for my SWR-bridges. It is close for up to 500W and there is no issue tunig up to 24Mc. I have also two capacitors tested, one butterfly-C with a 1: 100 geared stepper and another with a vac-C and a 1: 20 geared stepper. As I started my built, I had the little bridge after Kits and parts mounted only with copper-shields open in my controller case. There I had the issue, that automatic tuning was not possible over 18Mc. At least my Teensy won't work any more and I had to change it. It was to much straying HF inside the case. Today I have both bridges in a steel case and no problems any more. I use my loop inhouse, about 2 m (6ft) from my rig and the loop controller working up to 100W. The housing of the controller is made of double sided copper coated material. All sides (in- and outside) are soldered together and  grounded. The pictures show the bridge with two 8307. This one I can remove from controller and connected over cable, mount directly at the loop. Works fine!
So you have to prove your design, I believe. Good luck!
73, Immo, DL5KB


Re: Anybody have a problem with SWR tune

Leonard A. Gucciardo KD2NEN
 

I have 2 different controllers. One I made for QRP and the other I built with a high powered breune bridge coupler for 1kw. The QRP controller uses the kits and parts tandem bridge coupler for 30 watts max. They are 2 separate controllers on 2 separate magnetic loops. Both exhibit the same behavior above 14mhz. I tried to modify software changing the average over points from 32 to 320 steps because I am using 100:1 steppers in each loop. The only thing in common are the common mode chokes I used on both controllers. Here is a picture.

On Feb 24, 2021, at 6:20 AM, Immo <dl5kb@...> wrote:

hi Lenni,
do you use the same loop with both controllers? And also the same capacitor? Is it possible, that there are problems in tuning the loop >21 Mc? Backlash, endcapacity of capacitor? 
How have you shielded the swr bridge? picture? Are the wires to stepper enough blocked? is the enclosure of the controller „close“?
HF is a like a squirrel.
73, Immo, DL5KB 

--
LennyG KD2NEN


Re: Anybody have a problem with SWR tune

Immo, DL5KB
 

hi Lenni,
do you use the same loop with both controllers? And also the same capacitor? Is it possible, that there are problems in tuning the loop >21 Mc? Backlash, endcapacity of capacitor? 
How have you shielded the swr bridge? picture? Are the wires to stepper enough blocked? is the enclosure of the controller „close“?
HF is a like a squirrel.
73, Immo, DL5KB 


Re: Anybody have a problem with SWR tune

Patrick
 

Hmmm, I'm interested to know if there is a solution to the problem and being that my electronic skills are lacking I can't offer advice that's any better than I did but I am curious if someone else has some ideas on how to resolve the issue because it seems you found a bug that we should get sorted out and when i say we, I mean someone with more knowledge than I.

I do wish I could help more.

Anyone have any ideas?


Re: Anybody have a problem with SWR tune

Leonard A. Gucciardo KD2NEN
 

It does not matter if I take the SWR circuit and isolate it. Tried shielding did nothing. Loop controller functions amazing just a big annoyance.

Leonard A. Gucciardo
KD2NEN

On Feb 23, 2021, at 4:02 PM, Patrick <kd7wpq@...> wrote:

I agree, sounds like rf interference and as if further shielding is needed.
Can you get some copper plating and make a shield to cover the SWR circuit?

--
LennyG KD2NEN


Re: Anybody have a problem with SWR tune

Patrick
 

I agree, sounds like rf interference and as if further shielding is needed.
Can you get some copper plating and make a shield to cover the SWR circuit?


Anybody have a problem with SWR tune

Leonard A. Gucciardo KD2NEN
 

I have built 2 loop controllers. 1 for 1000watts and 1 for QRP. Both controllers behave the same when I go higher than 20 meters. The SWR tune starts tuning when I transmit and on the display the SWR jumps around and is not steady as well as the power meter goes into milliwatts. It is almost as if it is RF interference. If I manually request an SWR tune the loops tune up fine. If I key the mic on AM both controllers will keep on looping in and SWR tune. They tune to success pause then start tuning again. 14mhz and below are fine. It gets worse as you go higher in frequency. If I manually turn off SWR tune I can use the loop fine.
--
LennyG KD2NEN


Re: LCD-Displays, series resistor, contrast setting

sm6moj
 

Thank you. My display lighted up and I can continue working on my project.


Re: Standard Air Variable (not butterfly) for new 40m loop

Doug Wood
 
Edited

Hi Rene,
          The package has arrived . 
               Thankyou very much. It will be put to good use.

                        Doug  VE3GVW


Re: LCD-Displays, series resistor, contrast setting

Immo, DL5KB
 

hi patrick and Andrew,
the 5 ohms are only sufficient, if there is a BUILTIN SERIES RESISTOR on the display unit like shown on my photo. Think about that not all units have this resistor. You have to verify this first!
73, Immo, DL5KB


Re: LCD-Displays, series resistor, contrast setting

Patrick
 

R1 is 4.7 ohms according to the schematic. It is apparently suggested to use 10ohm but I think that is suggest if there are no other resistors in line....


Re: LCD-Displays, series resistor, contrast setting

SM6MOJ
 

If I had understood you correctly, it is R1 that can be reduced to 5 Ohm


Re: LCD-Displays, series resistor, contrast setting

Patrick
 

Good to know information!

This is all very good information and could be used to update the instructions but even so the help on this thread has been nothing but stellar!

I am thankful for the patience and help from you and the people on this message board!

Thank you for the information and thank you Johan and the other people that have responded!

OK, gotta go now, I have work to do and then later more work on my tuner!


LCD-Displays, series resistor, contrast setting

Immo, DL5KB
 

Hi all,
since some of you have had problems with their LCD-display, something good to know.

I have two new ones of LCD2004A. Both have integrated resistors for the backplane light. 
See the red circle on the photo LCD2004: there are 51ohms (signed "510" on it), will say you can use it with the 5ohms series resistor on the board without any harm to the display. The producers have learned to enhance their products.
The old one I use at my controller has no series resistor. So an additional one on the board was necessary.
So TAKE A LOOK at yours and ACT CORRESPONDENT.

Visibility: 
The contrast is set with with a small voltage at pin3 of the display unit. On our boards there is a 10k potentiometer as voltage divider which gives the possibility to find the best contrast by turning it. The aerea is very small, so turn SLOWLY. The contrast changes from "all blocks" are shown to "blank plane". You must find your individual point. Contrast also is changed by temperature, not a lot , but it does.

Hope it helps
73, Immo, DL5KB


Re: No display 2.0

Immo, DL5KB
 

hi Andrew,
you're welcome! Now that you can see something on your display, but very weak, you should try to adjust the contrast with the 10k potentiometer right in the corner of the board. Turning it VERY SLOWLY you should find a position, where the signs on the display are shown best.
73, Immo, DL5KB


Re: No display 2.0

SM6MOJ
 

Thank you for your help. There was a microscopic flashing between pins 3 and 4 which my solder pump had not removed. I needed a x10 magnifier to see it.
I can now see text (but not very bright) on the display from a pre-compiled hex file. I will now cut the trace and put the thing together again.

Andrew


Re: Test - Not working

Patrick
 

OMG THANK YOU FOR THAT SERIOUSLY IMPORTANT INFORMATION!!!
I guess I missed that was the for contrast!
I adjusted it and WAMOH! IT'S ALIVE!!!!!

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