EMRFD Message Archive 8284

Message Date From Subject
8284 2013-02-22 21:54:56 agustintomasferra... NE602 - Calculating input bandpass filter
I intend to experiment the basics with an NE602 double balanced mixer.
Frequency of interest 10 MHz.

From all circuits I found, there are two, more or less close to what I
intend to build winding my own coils. No toroids available for the
moment.

My questions:

a) The double tuned bandpass filter in the design here
<http://www.qrp4u.de/docs/en/direkt_rx/index.htm> is symetric: the
secondaries are connected to the antenna pot and to the pins 1 & 2 of
the NE602.

How is this possible since I am designing for a yet unknown antenna
(thus unknown impedance) while having 1500 Ohms at the input of the
NE602?

b) The other design
<http://www.gqrp.com/suddenbuildingyourkitbooklet30m.pdf> (page 11)
connects the secondary to the antenna and the primary of L2 straigth to
pins 1 & 2.

How well matched is the antenna to the tank and what about the secondary
of L2 respect to the input of the NE602?

c) I believe I will end winding two similar tuned transformers adjusted
with trimmers.

Understanding that the secondaries will show an impedance proportional
to their number of turns vis a vis that of the primary, what values
should I use to calculate my coils?

d) Could I use a tap to the primary instead of a secondary to adapt
impedances?


[Non-text portions of this message have been removed]
8286 2013-02-23 03:43:28 Lasse Moell Re: NE602 - Calculating input bandpass filter
There are a number of interesting question you raise here.
Both designs seem to be non-optimized. They use a potetiometer as an
attenuator, which
here will alter load-impedance and hence the passband too!

Looking at 10MHz ham-band it seems 1500 ohm is a bit low to load the
resonator too.
Just for fun, I played with some values... and attach what I came up
with, but this too 2 minutes with no refinement.

I'm sure other will come to the rescue and show us a properly designed
filter :)

50 ohm at input and 1500 ohm at output. The input inductor is in two
parts simulating a tapped inductor.
Having bot a tapped inductor and the capacitor at output will help to
get a more symmetrical filter.

You will likely see a bit more loss, as the Q is set to 100 for
inductors and 200 for capacitors in my simulation.

/Lasse SM5GLC


On 22 feb 2013 17:39 "agustintomasferrari" <atferrari@fibertel.com.ar>
wrote:

>
>
> I intend to experiment the basics with an NE602 double balanced mixer.
> Frequency of interest 10 MHz.
>
> From all circuits I found, there are two, more or less close to what I
> intend to build winding my own coils. No toroids available for the
> moment.
>
> My questions:
>
> a) The double tuned bandpass filter in the design here
> <http://www.qrp4u.de/docs/en/direkt_rx/index.htm>> is symetric: the
> secondaries are connected to the antenna pot and to the pins 1 & 2 of
> the NE602.
>
> How is this possible since I am designing for a yet unknown antenna
> (thus unknown impedance) while having 1500 Ohms at the input of the
> NE602?
>
> b) The other design
> <http://www.gqrp.com/suddenbuildingyourkitbooklet30m.pdf>> (page 11)
> connects the secondary to the antenna and the primary of L2 straigth
> to
> pins 1 & 2.
>
> How well matched is the antenna to the tank and what about the
> secondary
> of L2 respect to the input of the NE602?
>
> c) I believe I will end winding two similar tuned transformers
> adjusted
> with trimmers.
>
> Understanding that the secondaries will show an impedance proportional
> to their number of turns vis a vis that of the primary, what values
> should I use to calculate my coils?
>
> d) Could I use a tap to the primary instead of a secondary to adapt
> impedances?
>
> [Non-text portions of this message have been removed]
>
>
>
>
>

[Non-text portions of this message have been removed]
8288 2013-02-23 03:52:07 Lasse Moell Re: NE602 - Calculating input bandpass filter
The schematic and photo is in photos album: SM5GLC.
Attaching to e-mail seems to have been dropped.

/Lasse SM5GLC


On 23 feb 2013 12:43 "Lasse Moell" <lasse.moell@webdog.se> wrote:

>
>
> There are a number of interesting question you raise here.
> Both designs seem to be non-optimized. They use a potetiometer as an
> attenuator, which
> here will alter load-impedance and hence the passband too!
>
> Looking at 10MHz ham-band it seems 1500 ohm is a bit low to load the
> resonator too.
> Just for fun, I played with some values... and attach what I came up
> with, but this too 2 minutes with no refinement.
>
> I'm sure other will come to the rescue and show us a properly designed
> filter :)
>
> 50 ohm at input and 1500 ohm at output. The input inductor is in two
> parts simulating a tapped inductor.
> Having bot a tapped inductor and the capacitor at output will help to
> get a more symmetrical filter.
>
> You will likely see a bit more loss, as the Q is set to 100 for
> inductors and 200 for capacitors in my simulation.
>
> /Lasse SM5GLC
>
>
>
8290 2013-02-23 18:10:18 Leonard Re: NE602 - Calculating input bandpass filter
Can someone that has a 602 in circuit measure the input pin 1 and 2 opencircuit voltage? They should both be the same. It's shown as "bias" but I want to know the actual value.

Leonard
http://kc0wox.com

8291 2013-02-23 18:44:26 Jim Kortge Re: NE602 - Calculating input bandpass filter
8292 2013-02-23 21:49:49 Ashhar Farhan Re: NE602 - Calculating input bandpass filter
an olde article by joseph carr :
http://techdoc.kvindesland.no/radio/b1/20051213190607573.pdf

- farhan
8293 2013-02-24 14:58:22 Leonard Re: NE602 - Calculating input bandpass filter
Thanks. I couldn't find it in the data sheets.
Leonard

8294 2013-02-24 14:58:22 agustintomasferra... Re: NE602 - Calculating input bandpass filter
8295 2013-02-24 14:58:22 Gene Dorcas Re: NE602 - Calculating input bandpass filter
Here's another

http://schematicsforfree.com/archive/file/Radios%20
<http://schematicsforfree.com/archive/file/Radios%20&%20RF%20Circuitry/Misc/
Using%20the%20NE602%20RF%20Chip.pdf>
&%20RF%20Circuitry/Misc/Using%20the%20NE602%20RF%20Chip.pdf



Gene, W5DOR

gene@w5dor.com

www.w5dor.com





8296 2013-02-24 14:58:22 agustintomasferra... Re: NE602 - Calculating input bandpass filter
Gracias Lasse for your time and effort.

My question: why do you asume 50 Ohms at the input? All I know is that the antenna could be anything from a dipole to a long wire.

Putting this in other way: other than with an expensive antenna tunner, how could I ensure to offer 50 Ohms at the input? That attenuator (pot), is it the one doing that?

Since I intend only to receive time signals around 10 MHz, I prefer a narrowband design.

Your comments appreciated.

Tack så mycket again.


8297 2013-02-24 14:58:22 Owe Frisk SV: [emrfd] Re: NE602 - Calculating input bandpass filter
Hi,

Try to get hold of this book, HF-Technik mit dem NE602/612 by Frank Sichla,
Beam Verlag.

A book totally devoted to the NE602 with many applications witin radio.

It´s in German language but it is easy to understand the technical text

http://www.box73.de/product_info.php?products_id=1241



73

Owe, SA0ASO



Från: emrfd@yahoogroups.com [mailto:emrfd@yahoogroups.com] För Ashhar Farhan
Skickat: den 24 februari 2013 06:50
Till: emrfd@yahoogroups.com
Ämne: Re: [emrfd] Re: NE602 - Calculating input bandpass filter





an olde article by joseph carr :
http://techdoc.kvindesland.no/radio/b1/20051213190607573.pdf

- farhan



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[Non-text portions of this message have been removed]
8298 2013-02-25 00:40:06 Lasse Moell Re: NE602 - Calculating input bandpass filter
OK
as for matching antenna to filter, this is important as the filter is
designed for one specific impedance, and if you have a filter with high
impedance design and attaches a low-z system i.e. dipole, the filter
will degrade severly.

You may have a good startingpoint by just using a simple resonant
circuit, and have both a low-z link on inductor and a high-z tap on top
of resonator, choosing the correct one for load in use.

73 Lasse SM5GLC


8299 2013-02-25 07:10:05 Tim Re: NE602 - Calculating input bandpass filter
I have built many gadgets following the KD1JV plans for NE602's. 10.7MHz IF transformers figure prominently (with additional padding capacitance as necessary for 40 and 80 meters; you probably don't need any padding for 10MHz usage). 10.7MHz IF transformers are available new (KD1JV specs the Mouser 42IF222 to step up from antenna 50 ohm impedance to the NE602's input) or easily found in old FM transistor radios.

Tim N3QE

8300 2013-02-25 10:06:08 Lasse Moell 6GHz spectrum analyzer
Technology marches on... this new spectrum analyzer from Signal Hound
seems really interesting:
http://signalhound.com/BB60A.htm

The scan speed is simply staggering, up to 24 GHz/s sweep and the
ability to record 20 MHz on disk to evaluate later (think SDR).

So far the only drawback is the some what lack lustre phase noise of the
LO...

Give it a few more years and I am sure we will see plenty of instruments
with specs like this, cheaper!
Makes my desire of a HP8566/8 slightly less...

I do have the little brother SA44B, and find it a good addition to my lab. Knowing how little there has been written about it, if any have questions, I do my best to answer, from a user standpoint.

/Lasse SM5GLC
8303 2013-02-26 01:38:10 cristi preda Re: NE602 - Calculating input bandpass filter
Hello!
I think the solution you are looking for is in this link: http://www.qrp.pops.net/bp-fil.asp, with all the explanati