Re: RF Power #chat


Alan de G1FXB
 

Hi Andrew,
Don't worry too much about the wire gauge being different on the rewound toroids.
The LPF's are a tame design, for repeatability.

I replied before with a link to Han's page showing example plots of selected LPF's.
30Mtrs was one of them.
I'm sure there are plots from other builders somewhere.
If you log in QRP-Labs IO groups with a web browser use the search function or have a look in 'Files' folder ?

Else the LPF is based on W3NQN / G-QRP designs. Somebody must have posted examples on the interweb...
Concentrate on getting the fundamental out, you have the gear to fine tune the cut off at a later date in any case.

It's three bit's of wire and four capacitors.
In your best Jeremy Clarkson voice,
ask your self. 'How hard can it be ?'  ;-)


Alan

On 03/09/2017 13:06, Andrew Lenton wrote:

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Alan de G1FXB via Groups.Io
Sent: 02 September 2017 21:00
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

1.      Andrew,
It's not that then....


As you have a pair of poor performing LPF's ,
You didn't wind 20M toroids for the 30M LPF & vice versa. That is a good point I will double check, I have re wound the 20M using new wire  0.36mm slightly fatter than what is supplied,16, 17 16
& I would still do the DC check on the poor performing LPF's as a quick check ? I have done the DC check, will check to see if less than 1 ohm.

2.      Have you seen some plots that other hams have done for 20 and 30 Metres?

 

BR

 

Andrew


Alan

On 02/09/2017 20:51, Andrew Lenton wrote:

Just Rechecked that post 11th Aug, the LPF was not the QRP kit version, but one I made earlier, for the Raspberry PI, which does work rather well.

 

73

 

Andrew

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Alan de G1FXB via Groups.Io
Sent: 02 September 2017 20:36
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

Andrew,

Is it the same 20M LPF, you stated on the 11th Aug had a through loss of 0.3dB ?

https://groups.io/g/QRPLabs/message/15495

If so, what is different now.
Have you DC continuity through the filter & If you push & pull on the inductor leadouts does it change?  :-[

Hopefully trying to be 'being helpful & not abrupt.'

Alan

On 02/09/2017 20:14, Andrew Lenton wrote:

10M response:

 

Low insertion loss at 10M and Good roll off for VHF FM

 

I will look into the loss at 20 M and 30 M has anyone else experienced this?

 

 

73

 

Andrew

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Andrew Lenton
Sent: 02 September 2017 19:44
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

12M LPF response:

 

S11 normalised on same scale!

 

 

73 Andrew

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Henning Weddig via Groups.Io
Sent: 02 September 2017 17:05
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

wrong calibration: the return loss (S11) never can be above 0 dB as the lpf is a passive device.

Henning DK5LV

 

Am 02.09.2017 um 16:01 schrieb Andrew Lenton:

Just Built and measured the 17M LPF J

 

Loss 0.5 dB looks like I need to rewind my 20 M coils!

 

73

 

Andrew

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Andrew Lenton
Sent: 02 September 2017 14:10
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

I have just measured the 20meter LPF, see below:  insertion loss 2.466dB !! L, I am making the 17,15,12,and 10 today so will measure each on in turn. And post for those who are interested. Maybe I am crap at winding the coils.

 

I normalised out the connection cables, which are 0.5M each.

 

So my U3S is 125mW ( adding 2.466dB) which is nearer the mark, I will check what the loss is on other LPF.

 

73

 

Andrew

 

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Andrew Lenton
Sent: 02 September 2017 12:42
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 

Thank for this: I will measure power before the filter, see if it similar to below.

 

 

73

 

Andrew

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of SM7ETW Jan
Sent: 01 September 2017 23:16
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] RF Power #chat

 


The following is my U3S without any LPF, bias adjusted to keep overtones down.
The overtone values are dB down from main carrier.

 

U3S  all values in dBm

 

 

 

 

 

Frequency kHz

Power out dBm

2nd overtone 

3rd overtone

4th overtone

5th  overtone

137

22.6

-29.1

-8.9

-36.7

-14

475

23.6

-27.6

-9.4

-33.1

-14.1

1900

23.8

-35.5

-9.66

-39.8

-18.2

3600

23.9

-36.8

-9.9

-37.5

-14.6

5300

23.6

-36.5

-9.6

-35.1

-14.6

7100

23.9

-34.3

-10.1

-32.2

-15.1

10130

23.8

-30.8

-10.2

-26.8

-15.6

14100

23.5

-25.9

-10.4

-22.5

-22.3

18100

23.4

-22.9

-10.7

-19.2

-25

21100

23.2

-20.6

-11.2

-19

-26.9

25000

23.2

-17.6

-13.0

-19.7

-39.2

28500

23.1

-15.5

-15.3

-21.6

-39.1

50100

21.3

-17.3

-36.3

-28.3

-21.3

70100

18.8

-17.8

-23.8

-24.8

-18.8

145000

10.8

-13.3

-25.8

-10.8

-10.8

200000

9.1

-9.1

-9.1

-9.1

-9.1

220000

6.2

 

 

 

 

230000

8

 

 

 

 

 

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