new mini-modules: applications

[KBG Luxford]

Wayne and list members,
The AT1 step attenuator looks very interesting.  However, would we not
need an attenuator capable of 140 db or so for receiver testing?  Yes we
could cascade four of them, but this would scarcely be very cost
effective.  How about supplying the same circuit board and parts but
with a different set of resistors to enable increases in attenuation in
say, steps of 40 db, which would mean that we would only have to buy two
kits.

Best regards from Downunder
Kevin
VK3DAP / ZL2DAP
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[Geoffrey Mackenzie-Kennedy-2]

Evening Kevin,

A step attenuator capable of adding up to140db or so of loss is certainly
very useful when working with receivers, but would be quite expensive I
believe. If two step attenuators were used in cascade they would have to be
built and connected in such a way that ensures that the attenuation in any
sneak path around the attenuators at all working frequencies is >> 140db,
and that the switched pads that make up the attenuators do not talk to one
another via spurious paths.

But even with a perfect step attenuator, the crosstalk between the coax
cables connected to the attenuator must be considered. The leakage from coax
such as RG-174 or RG-58 would be enough I think to provide a significant
sneak path around a 140db attenuator, adding measurement error particularly
so if the cables are physically close to one another. Double screened coax
helps to reduce this problem. Leakage from the signal generator must also be
considered.

To get around these problems but still have a useful step attenuator for
single frequency tests, I use a compromise arrangement consisting of a 90db
step attenuator and two HP 11708A 30db fixed attenuators or pads with N
connectors, in a way slightly similar to what you are suggesting. Having a
fixed 30db pad right at the circuit / receiver under test provides a
reasonable 50 ohm source, likewise a load for the step attenuator. The
second 30db pad when used is placed at the generator's output. The step
attenuator includes five 1db steps which I find to be very useful at times.
Double screened coax all the way.

73,
Geoff
GM4ESD


----- Original Message -----
From: "kbgluxford" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Thursday, September 28, 2006 8:12 AM
Subject: [Elecraft] new mini-modules: applications

> Wayne and list members,
> The AT1 step attenuator looks very interesting.  However, would we not
> need an attenuator capable of 140 db or so for receiver testing?  Yes we
> could cascade four of them, but this would scarcely be very cost
> effective.  How about supplying the same circuit board and parts but with
> a different set of resistors to enable increases in attenuation in say,
> steps of 40 db, which would mean that we would only have to buy two kits.
>
> Best regards from Downunder
> Kevin
> VK3DAP / ZL2DAP

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[Jack Smith-6]

If you can't find suitable fixed attenuators at the local swap meet, I
can highly recommend MiniCircuit's inexpensive HAT-series (with BNC
connectors, also available with N and SMA).
http://www.minicircuits.com/dg03-152.pdf for more details. These run
$9.95 each and are real bargains. If you are serious about RF work, a  
set of these in the steps 1, 2, 3, 6 (x2), 10 (x2) and 20 dB (x2) is an
excellent investment. This will let you make up any attenuation value
from 1 dB to 78 dB in 1 dB steps. (granted, stringing all 9 attenuators
in series for 78 dB is a bit awkward, but you get the idea.)

I know Minicircuits has a UK distributor, not sure about VK-land.


Jack



Geoffrey Mackenzie-Kennedy wrote:

> Evening Kevin,
>
> A step attenuator capable of adding up to140db or so of loss is
> certainly very useful when working with receivers, but would be quite
> expensive I believe. If two step attenuators were used in cascade they
> would have to be built and connected in such a way that ensures that
> the attenuation in any sneak path around the attenuators at all
> working frequencies is >> 140db, and that the switched pads that make
> up the attenuators do not talk to one another via spurious paths.
>
> But even with a perfect step attenuator, the crosstalk between the
> coax cables connected to the attenuator must be considered. The
> leakage from coax such as RG-174 or RG-58 would be enough I think to
> provide a significant sneak path around a 140db attenuator, adding
> measurement error particularly so if the cables are physically close
> to one another. Double screened coax helps to reduce this problem.
> Leakage from the signal generator must also be considered.
>
> To get around these problems but still have a useful step attenuator
> for single frequency tests, I use a compromise arrangement consisting
> of a 90db step attenuator and two HP 11708A 30db fixed attenuators or
> pads with N connectors, in a way slightly similar to what you are
> suggesting. Having a fixed 30db pad right at the circuit / receiver
> under test provides a reasonable 50 ohm source, likewise a load for
> the step attenuator. The second 30db pad when used is placed at the
> generator's output. The step attenuator includes five 1db steps which
> I find to be very useful at times. Double screened coax all the way.
>
> 73,
> Geoff
> GM4ESD
>
>
> ----- Original Message ----- From: "kbgluxford" <[hidden email]>
> To: "Elecraft Reflector" <[hidden email]>
> Sent: Thursday, September 28, 2006 8:12 AM
> Subject: [Elecraft] new mini-modules: applications
>
>
>> Wayne and list members,
>> The AT1 step attenuator looks very interesting.  However, would we
>> not need an attenuator capable of 140 db or so for receiver testing?  
>> Yes we could cascade four of them, but this would scarcely be very
>> cost effective.  How about supplying the same circuit board and parts
>> but with a different set of resistors to enable increases in
>> attenuation in say, steps of 40 db, which would mean that we would
>> only have to buy two kits.
>>
>> Best regards from Downunder
>> Kevin
>> VK3DAP / ZL2DAP
>
>
>
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> Elecraft web page: http://www.elecraft.com
>
>

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[Geoffrey Mackenzie-Kennedy-2]

MiniCircuits had a VK-land Representative, Clarke & Severn Electronics -
Hornsby - NSW - Australia 2077   [hidden email]   tel  [phone],
but I do not know if they hold any stock.

73,
Geoff
GM4ESD

----- Original Message -----
From: "Jack Smith" <[hidden email]>
To: "Geoffrey Mackenzie-Kennedy" <[hidden email]>
Cc: "Elecraft Discussion List" <[hidden email]>
Sent: Thursday, September 28, 2006 12:43 PM
Subject: Re: [Elecraft] new mini-modules: applications

> If you can't find suitable fixed attenuators at the local swap meet, I can
> highly recommend MiniCircuit's inexpensive HAT-series (with BNC
> connectors, also available with N and SMA).
> http://www.minicircuits.com/dg03-152.pdf for more details. These run $9.95
> each and are real bargains. If you are serious about RF work, a  set of
> these in the steps 1, 2, 3, 6 (x2), 10 (x2) and 20 dB (x2) is an excellent
> investment. This will let you make up any attenuation value from 1 dB to
> 78 dB in 1 dB steps. (granted, stringing all 9 attenuators in series for
> 78 dB is a bit awkward, but you get the idea.)
>
> I know Minicircuits has a UK distributor, not sure about VK-land.
>
>
> Jack
>

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[N8LP]

Jack beat me to the punch, but Mini-Circuits is a great source for
attenuators, terminations, directional couplers, splitter/combiners
etc., all at reasonable prices. If you're building up a test bench, you
will need most of these items.

I also find their Gali series MMICs to be very good performers, easy to
apply and quite reasonably priced.

They have no problem with small orders from Hams.

Also check out RidgeEquipment.com for surplus attenuators and dummy
loads. They have excellent quality and service.

Larry N8LP


Jack Smith wrote:

> If you can't find suitable fixed attenuators at the local swap meet, I
> can highly recommend MiniCircuit's inexpensive HAT-series (with BNC
> connectors, also available with N and SMA).
> http://www.minicircuits.com/dg03-152.pdf for more details. These run
> $9.95 each and are real bargains. If you are serious about RF work, a  
> set of these in the steps 1, 2, 3, 6 (x2), 10 (x2) and 20 dB (x2) is
> an excellent investment. This will let you make up any attenuation
> value from 1 dB to 78 dB in 1 dB steps. (granted, stringing all 9
> attenuators in series for 78 dB is a bit awkward, but you get the idea.)
>
> I know Minicircuits has a UK distributor, not sure about VK-land.
>
>
> Jack
>
>
>
> Geoffrey Mackenzie-Kennedy wrote:
>> Evening Kevin,
>>
>> A step attenuator capable of adding up to140db or so of loss is
>> certainly very useful when working with receivers, but would be quite
>> expensive I believe. If two step attenuators were used in cascade
>> they would have to be built and connected in such a way that ensures
>> that the attenuation in any sneak path around the attenuators at all
>> working frequencies is >> 140db, and that the switched pads that make
>> up the attenuators do not talk to one another via spurious paths.
>>
>> But even with a perfect step attenuator, the crosstalk between the
>> coax cables connected to the attenuator must be considered. The
>> leakage from coax such as RG-174 or RG-58 would be enough I think to
>> provide a significant sneak path around a 140db attenuator, adding
>> measurement error particularly so if the cables are physically close
>> to one another. Double screened coax helps to reduce this problem.
>> Leakage from the signal generator must also be considered.
>>
>> To get around these problems but still have a useful step attenuator
>> for single frequency tests, I use a compromise arrangement consisting
>> of a 90db step attenuator and two HP 11708A 30db fixed attenuators or
>> pads with N connectors, in a way slightly similar to what you are
>> suggesting. Having a fixed 30db pad right at the circuit / receiver
>> under test provides a reasonable 50 ohm source, likewise a load for
>> the step attenuator. The second 30db pad when used is placed at the
>> generator's output. The step attenuator includes five 1db steps which
>> I find to be very useful at times. Double screened coax all the way.
>>
>> 73,
>> Geoff
>> GM4ESD
>>
>>
>> ----- Original Message ----- From: "kbgluxford" <[hidden email]>
>> To: "Elecraft Reflector" <[hidden email]>
>> Sent: Thursday, September 28, 2006 8:12 AM
>> Subject: [Elecraft] new mini-modules: applications
>>
>>
>>> Wayne and list members,
>>> The AT1 step attenuator looks very interesting.  However, would we
>>> not need an attenuator capable of 140 db or so for receiver
>>> testing?  Yes we could cascade four of them, but this would scarcely
>>> be very cost effective.  How about supplying the same circuit board
>>> and parts but with a different set of resistors to enable increases
>>> in attenuation in say, steps of 40 db, which would mean that we
>>> would only have to buy two kits.
>>>
>>> Best regards from Downunder
>>> Kevin
>>> VK3DAP / ZL2DAP
>>
>>
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
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>> http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>>
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>
>

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[Geoffrey Mackenzie-Kennedy-2]

I'll second that Larry, MiniCircuits saved me from much blood, sweat and
tears when I built my test bench!

Geoff
GM4ESD

----- Original Message -----
From: "Larry Phipps" <[hidden email]>
To: "Jack Smith" <[hidden email]>
Cc: "Geoffrey Mackenzie-Kennedy" <[hidden email]>; "Elecraft
Discussion List" <[hidden email]>
Sent: Thursday, September 28, 2006 1:42 PM
Subject: Re: [Elecraft] new mini-modules: applications

> Jack beat me to the punch, but Mini-Circuits is a great source for
> attenuators, terminations, directional couplers, splitter/combiners etc.,
> all at reasonable prices. If you're building up a test bench, you will
> need most of these items.
>
> I also find their Gali series MMICs to be very good performers, easy to
> apply and quite reasonably priced.
>
> They have no problem with small orders from Hams.
>
> Also check out RidgeEquipment.com for surplus attenuators and dummy loads.
> They have excellent quality and service.
>
> Larry N8LP
>
>

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[wayne burdick]

On Sep 28, 2006, at 3:59 AM, Geoffrey Mackenzie-Kennedy wrote:

> Evening Kevin,
>
> A step attenuator capable of adding up to 140db or so of loss is
> certainly very useful when working with receivers, but would be quite
> expensive I believe.

This is exactly why we designed the XG1 and XG2 receiver test
oscillators. Both give you a 1 microvolt +/- 1 dB signal for use in
receiver sensitivity testing. 1 microvolt is -107 dBm, and the AT1 step
attenuator could reduce the signal to around -148 dBm. Now *that's* a
weak signal  :)

73,
Wayne
N6KR

---

http://www.elecraft.com

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[Eric Swartz - WA6HHQ]

Both the XG1 and XG2 put out about -110 dBm in their 1 uV positions.
That plus -41 dB from the AT1 should be well below all HF rig noise
floors.  :-)

73, Eric  WA6HHQ


kbgluxford wrote:

> Wayne and list members,
> The AT1 step attenuator looks very interesting.  However, would we not
> need an attenuator capable of 140 db or so for receiver testing?  Yes
> we could cascade four of them, but this would scarcely be very cost
> effective.  How about supplying the same circuit board and parts but
> with a different set of resistors to enable increases in attenuation
> in say, steps of 40 db, which would mean that we would only have to
> buy two kits.
>
> Best regards from Downunder
> Kevin
> VK3DAP / ZL2DAP
> _______________________________________________
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> Post to: [hidden email]
> You must be a subscriber to post to the list.
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> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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