Re: Step attenuator for QRP transmitter to TinySA
I have two Kay 475 attenuators. They have a series of toggle switches. You can switch in 0 to 110 dB attenuation in 0.5 dB steps. The ones I have cover 0 to 1.0 GHz. They are high-quality and worth the money. They show up often on eBay.
Zack
I have a Kay Model 520 (Kay #80138) 0 - 10 scale rotary attenuator that I would like to use to allow me to test 100 Milliwatt to 5 Watt QRP transmitters using my TinySA, but I have not been able to find a spec sheet on the attenuator, so I don't know how many watts input it can handle and how much attenuation it will provide.
I, of course, do not want to overload the attenuator and/or the TinySA if I try to test my 5 watt QRP rig.? Anyone have any ideas?
EuGene, KA5NLY
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Re: Step attenuator for QRP transmitter to TinySA
This might have been mentioned, but I just built this $25 step attenuator kit for TinySA experiments- nice quality and works well
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Re: Step attenuator for QRP transmitter to TinySA
You can also use switches and a PCB is not absolutely needed  and the inside  The copper/PCB ground planes combined with the 0805 resistors makes it flat within 1dB up to 500MHz and max practical attenuation is 55dB ( 5+10+20+20)? In the shown attenuator there is one additional 20dB stage totalling 75dB but that is too much in this construction. --
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: Step attenuator for QRP transmitter to TinySA
Shameless plug:
Hope it is still possible to order PCBs from JLCPCB.
The power rating is probably about 1/4W for 1206 resistors, so you need a high power fixed attenuator in front of this one.
73, Mike AF7KR
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Re: Step attenuator for QRP transmitter to TinySA
can you share?
Tom Sides ?KI7FTK
skype: Thomas Sides 4243 e. st Charles ave Phx AZ 85042
Excellent explanation Jim.
In my early military career in electronics, we were given a hand out that clearly explained the dB in all of its forms, it was a great tool, but we were supposed to hand it back in at the end of the course... they ended up one short, that was over 40 years ago.... I still have it.
John VE7KKQ
On Fri, Feb 12, 2021 at 2:33 PM Jim Allyn - N7JA < jim@...> wrote: On Thu, Feb 11, 2021 at 06:43 PM, bigusmith wrote:
I am not used to dealing with RF output power in Decibels instead of watts
Get used to it, you'll find dB very useful.? There are lots of things in radio - and pretty much any kind of electronics - that aren't convenient to measure in watts.? If your transmitter puts out 100 watts, and you run it into a linear amplifier that puts out 1000 watts, I suppose you could say the gain of the amplifier is 900 watts, but then what if you only ran 50 watts into the amplifier?? You can't say the gain is 900 watts, therefor the output will be 950 watts, it just ain't so.? But if we say the gain of the amplifier is 10 log(1000 watts/100 watts) = 10 dB, we have something we can work with. 10 dB is a power gain of 10 times, so our amplifier will put out 500 watts with 50 watts in.
And what is the sensitivity of your receiver in watts?? Well, if you ran any amount of watts into your receiver, all you'd get out of it is smoke.? Watts doesn't work here.? So we measure receiver sensitivity in dBm -? that is, dB relative to one milliwatt.? A typical receiver might have a sensitivity of -120dBm.? If we put a 30 dB attenuator in line, the combination now has a sensitivity of -90 dBm.? Suppose you have a receiver with a sensitivity of -120 dBm at your house, and there's a transmitter up on a nearby hill, what is the path loss in watts?? Doesn't make sense. However, you could say that the path loss is 100 dB, that's a number that would make sense.?? Then if you had a 10 watt (+40 dBm) transmitter up on the hill, you could calculate that the power at your receiver is (40 dBm - 100 dB path loss) = -60 dBm, and your receiver would hear that just fine.
So, there are lots of things that aren't measured or expressed well in watts, but if we use dB (or dBm) can easily be measured or expressed.? And that's why so many things in electronics are expressed in dB, or in dB relative to some value.
If you're wondering why the B in dB is capitalized, it's because the "Bel" was named after Alexander Graham Bell, and Bell being a proper name, we capitalize it.? We should also capitalize Volts, Watts, Ohms - all come from somebody's name -? and a bunch of others, but we get sloppy and often don't bother.
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Re: New FW released: Level inc/dec keys now work with external amp setting
On Sat, Feb 13, 2021 at 05:26 AM, hwalker wrote:
Doesn't look like v1.1-86 made it to the download directory.
Should be now ? --
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: New FW released: Level inc/dec keys now work with external amp setting
On Sat, Feb 13, 2021 at 04:23 AM, Erik Kaashoek wrote:
New FW release
Version V1.1-86
Changes:
- Level inc/dec keys now work correctly when an External AMp setting is active
?
Erik, ? ?Doesn't look like v1.1-86 made it to the download directory. Herb
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Re: Metal case for TinySA
Many thanks. Also got some good photos and comments from Clyde which were helpful.
I've opened the SA now so all is now clear (and it is still working !!!!). I have to say that normally I'm the type of guy that has to see under the bonnet when I'm buying a new car at the showroom, usually with a view to how I'm going to fix it when it goes wrong later!
Regards
Nigel
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New FW released: Level inc/dec keys now work with external amp setting
New FW release Version V1.1-86 Changes: - Level inc/dec keys now work correctly when an External AMp setting is active
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For more info on the tinySA go to https://tinysa.org/wiki/
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Re: Metal case for TinySA
Nigel yes, yes,and yes lol.
I have temporarily attached 2 small strips of plastic on either side of the jog wheel to protect it. I used ultra thin clear double side tape to do it , it is strong and stable. My final goal it to fabricate a piece of delrin or metal with a slit in it for the switch and attach it with a couple of countersunk 1mm screws from the inside. That will be for my second TinySA that I ordered and? the arrival of the second case.
John
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Re: Step attenuator for QRP transmitter to TinySA
This is a great thread, thanks for sharing. I have a cheap 70w amp kit, and before using it I wanted to test the spurious transmissions etc. It looks like I'll need a 50db tap and then a lower power 20 or 30db inline attenuator to the tinySA. I already have a 300w dummy load. The math short cuts also help as well :)
Heath
On Fri, Feb 12, 2021 at 2:33 PM Jim Allyn - N7JA < jim@...> wrote: On Thu, Feb 11, 2021 at 06:43 PM, bigusmith wrote:
I am not used to dealing with RF output power in Decibels instead of watts
Get used to it, you'll find dB very useful.? There are lots of things in radio - and pretty much any kind of electronics - that aren't convenient to measure in watts.? If your transmitter puts out 100 watts, and you run it into a linear amplifier that puts out 1000 watts, I suppose you could say the gain of the amplifier is 900 watts, but then what if you only ran 50 watts into the amplifier?? You can't say the gain is 900 watts, therefor the output will be 950 watts, it just ain't so.? But if we say the gain of the amplifier is 10 log(1000 watts/100 watts) = 10 dB, we have something we can work with. 10 dB is a power gain of 10 times, so our amplifier will put out 500 watts with 50 watts in.
And what is the sensitivity of your receiver in watts?? Well, if you ran any amount of watts into your receiver, all you'd get out of it is smoke.? Watts doesn't work here.? So we measure receiver sensitivity in dBm -? that is, dB relative to one milliwatt.? A typical receiver might have a sensitivity of -120dBm.? If we put a 30 dB attenuator in line, the combination now has a sensitivity of -90 dBm.? Suppose you have a receiver with a sensitivity of -120 dBm at your house, and there's a transmitter up on a nearby hill, what is the path loss in watts?? Doesn't make sense. However, you could say that the path loss is 100 dB, that's a number that would make sense.?? Then if you had a 10 watt (+40 dBm) transmitter up on the hill, you could calculate that the power at your receiver is (40 dBm - 100 dB path loss) = -60 dBm, and your receiver would hear that just fine.
So, there are lots of things that aren't measured or expressed well in watts, but if we use dB (or dBm) can easily be measured or expressed.? And that's why so many things in electronics are expressed in dB, or in dB relative to some value.
If you're wondering why the B in dB is capitalized, it's because the "Bel" was named after Alexander Graham Bell, and Bell being a proper name, we capitalize it.? We should also capitalize Volts, Watts, Ohms - all come from somebody's name -? and a bunch of others, but we get sloppy and often don't bother.
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Re: Step attenuator for QRP transmitter to TinySA
Excellent explanation Jim.
In my early military career in electronics, we were given a hand out that clearly explained the dB in all of its forms, it was a great tool, but we were supposed to hand it back in at the end of the course... they ended up one short, that was over 40 years ago.... I still have it.
John VE7KKQ
On Fri, Feb 12, 2021 at 2:33 PM Jim Allyn - N7JA < jim@...> wrote: On Thu, Feb 11, 2021 at 06:43 PM, bigusmith wrote:
I am not used to dealing with RF output power in Decibels instead of watts
Get used to it, you'll find dB very useful.? There are lots of things in radio - and pretty much any kind of electronics - that aren't convenient to measure in watts.? If your transmitter puts out 100 watts, and you run it into a linear amplifier that puts out 1000 watts, I suppose you could say the gain of the amplifier is 900 watts, but then what if you only ran 50 watts into the amplifier?? You can't say the gain is 900 watts, therefor the output will be 950 watts, it just ain't so.? But if we say the gain of the amplifier is 10 log(1000 watts/100 watts) = 10 dB, we have something we can work with. 10 dB is a power gain of 10 times, so our amplifier will put out 500 watts with 50 watts in.
And what is the sensitivity of your receiver in watts?? Well, if you ran any amount of watts into your receiver, all you'd get out of it is smoke.? Watts doesn't work here.? So we measure receiver sensitivity in dBm -? that is, dB relative to one milliwatt.? A typical receiver might have a sensitivity of -120dBm.? If we put a 30 dB attenuator in line, the combination now has a sensitivity of -90 dBm.? Suppose you have a receiver with a sensitivity of -120 dBm at your house, and there's a transmitter up on a nearby hill, what is the path loss in watts?? Doesn't make sense. However, you could say that the path loss is 100 dB, that's a number that would make sense.?? Then if you had a 10 watt (+40 dBm) transmitter up on the hill, you could calculate that the power at your receiver is (40 dBm - 100 dB path loss) = -60 dBm, and your receiver would hear that just fine.
So, there are lots of things that aren't measured or expressed well in watts, but if we use dB (or dBm) can easily be measured or expressed.? And that's why so many things in electronics are expressed in dB, or in dB relative to some value.
If you're wondering why the B in dB is capitalized, it's because the "Bel" was named after Alexander Graham Bell, and Bell being a proper name, we capitalize it.? We should also capitalize Volts, Watts, Ohms - all come from somebody's name -? and a bunch of others, but we get sloppy and often don't bother.
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Re: Step attenuator for QRP transmitter to TinySA
Thanks Jim, a lot of good points in your reply.
On 12/02/2021 22:17, Jim Allyn - N7JA
wrote:
toggle quoted message
Show quoted text
On Thu, Feb 11, 2021 at 06:43 PM, bigusmith wrote:
I am not used to dealing with RF output power in
Decibels instead of watts
Get used to it, you'll find dB very useful.? There are lots of
things in radio - and pretty much any kind of electronics - that
aren't convenient to measure in watts.? If your transmitter puts
out 100 watts, and you run it into a linear amplifier that puts
out 1000 watts, I suppose you could say the gain of the amplifier
is 900 watts, but then what if you only ran 50 watts into the
amplifier?? You can't say the gain is 900 watts, therefor the
output will be 950 watts, it just ain't so.? But if we say the
gain of the amplifier is 10 log(1000 watts/100 watts) = 10 dB, we
have something we can work with. 10 dB is a power gain of 10
times, so our amplifier will put out 500 watts with 50 watts in.
And what is the sensitivity of your receiver in watts?? Well, if
you ran any amount of watts into your receiver, all you'd get out
of it is smoke.? Watts doesn't work here.? So we measure receiver
sensitivity in dBm -? that is, dB relative to one milliwatt.? A
typical receiver might have a sensitivity of -120dBm.? If we put a
30 dB attenuator in line, the combination now has a sensitivity of
-90 dBm.? Suppose you have a receiver with a sensitivity of -120
dBm at your house, and there's a transmitter up on a nearby hill,
what is the path loss in watts?? Doesn't make sense. However, you
could say that the path loss is 100 dB, that's a number that would
make sense.?? Then if you had a 10 watt (+40 dBm) transmitter up
on the hill, you could calculate that the power at your receiver
is (40 dBm - 100 dB path loss) = -60 dBm, and your receiver would
hear that just fine.
So, there are lots of things that aren't measured or expressed
well in watts, but if we use dB (or dBm) can easily be measured or
expressed.? And that's why so many things in electronics are
expressed in dB, or in dB relative to some value.
If you're wondering why the B in dB is capitalized, it's because
the "Bel" was named after Alexander Graham Bell, and Bell being a
proper name, we capitalize it.? We should also capitalize Volts,
Watts, Ohms - all come from somebody's name -? and a bunch of
others, but we get sloppy and often don't bother.
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Re: Step attenuator for QRP transmitter to TinySA
On Thu, Feb 11, 2021 at 06:43 PM, bigusmith wrote:
I am not used to dealing with RF output power in Decibels instead of watts
Get used to it, you'll find dB very useful.? There are lots of things in radio - and pretty much any kind of electronics - that aren't convenient to measure in watts.? If your transmitter puts out 100 watts, and you run it into a linear amplifier that puts out 1000 watts, I suppose you could say the gain of the amplifier is 900 watts, but then what if you only ran 50 watts into the amplifier?? You can't say the gain is 900 watts, therefor the output will be 950 watts, it just ain't so.? But if we say the gain of the amplifier is 10 log(1000 watts/100 watts) = 10 dB, we have something we can work with. 10 dB is a power gain of 10 times, so our amplifier will put out 500 watts with 50 watts in. And what is the sensitivity of your receiver in watts?? Well, if you ran any amount of watts into your receiver, all you'd get out of it is smoke.? Watts doesn't work here.? So we measure receiver sensitivity in dBm -? that is, dB relative to one milliwatt.? A typical receiver might have a sensitivity of -120dBm.? If we put a 30 dB attenuator in line, the combination now has a sensitivity of -90 dBm.? Suppose you have a receiver with a sensitivity of -120 dBm at your house, and there's a transmitter up on a nearby hill, what is the path loss in watts?? Doesn't make sense. However, you could say that the path loss is 100 dB, that's a number that would make sense.?? Then if you had a 10 watt (+40 dBm) transmitter up on the hill, you could calculate that the power at your receiver is (40 dBm - 100 dB path loss) = -60 dBm, and your receiver would hear that just fine. So, there are lots of things that aren't measured or expressed well in watts, but if we use dB (or dBm) can easily be measured or expressed.? And that's why so many things in electronics are expressed in dB, or in dB relative to some value. If you're wondering why the B in dB is capitalized, it's because the "Bel" was named after Alexander Graham Bell, and Bell being a proper name, we capitalize it.? We should also capitalize Volts, Watts, Ohms - all come from somebody's name -? and a bunch of others, but we get sloppy and often don't bother.
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Re: Step attenuator for QRP transmitter to TinySA
On 2/12/2021 1:32 PM, Rob French wrote:
One thing to be wary of with these inexpensive step attenuators is
they may not provide a 50 ohm input impedance. I bought a similar
one (different brand) on eBay and it worked fine, except that the
input impedance changed a LOT with the attenuation amount. I
finally decided that was too dangerous for use with any rig and
bought a really nice Bird 100W 30dB attenuator (only $60 on eBay)
instead, which has a perfect 50 ohm impedance and a perfect 30 dB
attenuation. That brings even a 100W (50 dBm) signal down to 0.1 W
(20 dBm), at which point you can use inexpensive fixed
attenuators. You can buy 10, 20, and 30 dB fixed attenuators that
handle < 2W for only a few bucks on Amazon. They have true 50
ohm input impedance and seem to be calibrated pretty well. So
combine a big fixed 30 dBm attenuator with a small 30 dBm
attenuator and a 100W signal is down 60 dB to -10 dBm (0.01W),
which is safe for the TinySA.
Rob
_._,_._,_
I bought a cheap step attenuator with toggle switches.? It has
a max attenuation of 92 Db.? I guess this is true--at audio.?
Supposed to be good to 30 Mhz.? On checking it with a sig gen and
SDR rx it only has max of 50 Db above about an MHz.? I took it
apart.? No isolation between sections, RF connectors not even
grounded to chassis due to thick powder coating.? Pretty
hopeless.? I got one of the many pushbutton ones on Amazon, they
are rated to 3GHz and check good to 1 GHz, the most my generator
will do.? Don't know power ratings, wouldn't want to put more than
20Db into it though.
Eric WA3UYI
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Re: Step attenuator for QRP transmitter to TinySA
On Thu, Feb 11, 2021 at 08:43 PM, bigusmith wrote:
I would pay $5 0r $10 in a heartbeat for such a chart
Print one out, their are plenty of sites that have good charts. You can also save the page of a "webcalc" to your machine and use it without having internet if you want. when I first started to use "DB's" I thought I would never feel comfortable with it but with a little practice the light went off.? the more you use it the easier it will become. Also, I had very good luck with some 30db 10W DC-3G SMA attenuators from China. At $19.99 with free shipping I took a chance and found them very flat? (+- .2db) up to 3.5G.?
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Re: Level steps with attenuation dialed in
#tinysa
On Fri, Feb 12, 2021 at 09:47 AM, Roger Need wrote:
On Wed, Feb 10, 2021 at 06:08 PM, John AE5X wrote:
Hello Eric,
I noticed an issue when using the tinySA in 'Low Output' mode:
The new "level steps" (-10dB -1dB set +1dB +10dB) in the latest firmware works great until a value is put into the 'External Amp' field. I was using 41 dB of external attenuation and had -41 dialed into this field.I then tried to change the output level by selecting the -10dB step and the SA ignored the external amp value and reverted to what would be displayed with no external value dialed in.
Has anyone else found this issue?
Roger, ? ? Yes, its an issue that I'm sure Erik has on his to do list.? Step? incrementing/decrementing also doesn't work with an external amplification value entered.? Best to add any external amplification or attenuation in mentally until Erik issues a FW fix.? ? ?A work around is to do any incrementing or decrementing before entering an external amplification/ attenuation value. The FW properly corrects the output level without error in that case. Herb
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Re: Step attenuator for QRP transmitter to TinySA
One thing to be wary of with these inexpensive step attenuators is they may not provide a 50 ohm input impedance. I bought a similar one (different brand) on eBay and it worked fine, except that the input impedance changed a LOT with the attenuation amount. I finally decided that was too dangerous for use with any rig and bought a really nice Bird 100W 30dB attenuator (only $60 on eBay) instead, which has a perfect 50 ohm impedance and a perfect 30 dB attenuation. That brings even a 100W (50 dBm) signal down to 0.1 W (20 dBm), at which point you can use inexpensive fixed attenuators. You can buy 10, 20, and 30 dB fixed attenuators that handle < 2W for only a few bucks on Amazon. They have true 50 ohm input impedance and seem to be calibrated pretty well. So combine a big fixed 30 dBm attenuator with a small 30 dBm attenuator and a 100W signal is down 60 dB to -10 dBm (0.01W), which is safe for the TinySA.
Rob
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Re: Step attenuator for QRP transmitter to TinySA
Here's a link to a useful RF Power (both dBm and Watts) to voltage chart on Repeater Builders:??
It's easy to see the relationship between dBm and Watts using this chart.
There is a ton of information on the Repeater Builders website.? Look in the RF-Related Information on their website here:?http://www.repeater-builder.com/tech-info/techindex.html
Steve_WB8GRS
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Re: Level steps with attenuation dialed in
#tinysa
On Wed, Feb 10, 2021 at 06:08 PM, John AE5X wrote:
Hello Eric,
I noticed an issue when using the tinySA in 'Low Output' mode:
The new "level steps" (-10dB -1dB set +1dB +10dB) in the latest firmware works great until a value is put into the 'External Amp' field. I was using 41 dB of external attenuation and had -41 dialed into this field.I then tried to change the output level by selecting the -10dB step and the SA ignored the external amp value and reverted to what would be displayed with no external value dialed in.
Has anyone else found this issue? Roger
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Tominaz
John Cunliffe W7ZQ
Jim Allyn - N7JA
Roger Need