Re: Jacks T41 Board Sets Available
I¡¯ve been following Jack Purdum¡¯s T41 SDR project on his group. Looks like they have a few board sets left for sale from their group buy activities. You can get them from K9HZ. Eight boards for $6.15 plus shipping.
MRM
--
¡_. _._
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Does anyone have the KD8CEC 5 inch nextion files?
looking to upgrade my uBITX with the KD8CEC software, and all works well on the smaller Nextion, but want to upgrade it to the 5 inch display,
and I need the file.
thanks
N2AIE
Vince
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I totally agree with Stephen and like the #HASHTAG idea.? I own 6 uBitx (2 v4, 1 v5, and 3 v6) and have an sBitx.
73
Evan
AC9TU
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Owning three uBITX's (two v6's and one v5) with a sBITX kit due next week, I would prefer that there be just one group, the BITX20, for all of them.
BUT?if we could all religiously apply appropriate #HASHTAGS to our original posts, we would make the group much more useful.
Looking at the #HASHTAG option, I just learned that I can choose to filter out or be alerted for a post with a certain #HASHTAG! That way, I can filter out posts that don't interest me and focus on those pertinent to my units.
Unfortunately, I haven't figured out how to put a #HASHTAG on a reply to an exisitng post yet ... but when I do, I will.
--
Stephen, KO4CVU
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Re: Amplifier output calculations (was sBitx antenna-first warning)
Ashar,
That is not the output impedance of the amplifier, nor is it the
effective load on the power supply.
Almost all RF power amplifiers are specified for a 50 ohm load.? 40
watts to a 50 ohm load gives an output voltage of SQR(Pout*Rload) =
44.7Vrms = 63.2Vpeak and output current of SQR(Pout/Rload) =
0.89Arms = 1.26Apeak.? This clearly is going through a transformer
if the PA power source is 12V.? Assuming that this is the design
maximum output power, in a push-pull class B amplifier (necessary
for SSB) of perfect efficiency (no loss in the device
on-resistance), the voltage must be transformed from 12V to 63.2V
> turns ratio of 1:5.26 (the actual transformer would be half of
this ratio due to the 2 push-pull legs.? If a single device is used
it gets even more complicated as it has to effectively drive both
halves of the output from one half-phase).? This means the device
current will be 0.89Arms X 5.26 = 4.71Arms.? The input power will be
12VDC (the full source voltage) x 4.71Arms (the effective source
current) = 56.5W.? Effective load on the power supply looks like
12V/0.89A = 13.4 ohms.? Since the output power is 40W, this means
the device dissipation ideally would be 16.5W.? Translated to the
resistive equivalent, this would look like a 63.2Vrms (not a
coincidence the same as the peak output voltage) x 0.89Arms = 56.5W
source through an output impedance of ((Vsource/Voutput) - 1) x 50
ohms = 20.7 ohms.? The actual output impedance of an amplifier is
much more complicated than this, due to the device intrinsic
resistances, transformer inefficiencies and any slump in the power
supply.? If there is any negative feedback around the output stage
(for parasitic suppression or gain flattening), this further reduces
the effective output impedance (note that audio amplifiers use very
heavy negative feedback and have nearly zero output impedance).
If we now output only 10 watts from this same stage, the output
voltage and current are each reduced by half. 10 watts to a 50 ohm
load gives an output voltage of SQR(Pout*Rload) = 22.4Vrms =
31.6Vpeak and output current of SQR(Pout/Rload) = 0.45Arms =
0.63Apeak.? The device current will be 0.45Arms X 5.26 = 2.35Arms.?
The input power will be 12VDC x 2.35Arms = 28.3W.? Note that the
output power went down by a factor of 4 but the input power only by
2 (same voltage, half the current).? Effective load on the power
supply is 12V/0.45A = 26.8 ohms.? Since the output power is 10W,
this means the device dissipation ideally would be 18.3W.?
Translated to the resistive equivalent, this would look like a
63.2Vrms (yes, the same as before - somebody has to drop the voltage
across it) x 0.45Arms = 28.3W source through an output impedance of
91.1 ohms.? Again, the actual effective output impedance may be very
different from this.
However, again, the tuner/antenna system is not intended to match
the amplifier output impedance to look like 50 ohms to the
feedline.? It is to present a 50 ohm resistive load to the
amplifier.
73,
David N1HAC
On 8/3/22 10:06 AM, Ashhar Farhan via
groups.io wrote:
toggle quoted message
Show quoted text
David,
Here is the explanation as I see it.
First, the impedance. It is the ratio of voltage to
current. Let's skip RF and only consider DC, then we will
expand this to DC.?
Ex 1: Consider a 12 supply?that is delivering 40 watts of
power to a resistor across it's terminals. It's current should
be 3.3A, so that 12v x 3.3A = 40 Watts. Now, which also means
that the resistor is 12V/3.3A =? 3.6 ohms. This is also the
case of the full power of sBitx.?
Ex 2: Now, consider that we have decreased the output of
the power supply's current?only such that we are producing? 12
watts of power. The current will now be 1 A (as 12v x 1A = 12
Watts) and the load resistance required will be 12 ohms (12V /
1A). Hence, the load impedance is changed. If you still put a
3.6 ohm resistor, the voltage from the power supply will drop
down and become unregulated and unstable, the power supply is
overloaded.
Now, let's switch to an RF 'power supply', that is, a
transmitter.?
The output impedance of a power amplifier, derived from the
above explanation is given as (Vcc * Vcc)/ (2 * Po). That is,
output impedance of the power amplifier is calculated as
square of power supply voltage divided by double the output
power.
Ex 3: Consider a QRP transmitter like the BITX20 or QRP
labs QCX. The Vcc is 12v and the output power is 5 watts,
hence, the PA output impedance is (12 * 12)/ ( 2 * 5) = 14.4
ohms.?
Ex4: In the above Ex 3, now consider that you have reduced
the power to 1 watt. The Vcc is still 12V, hence, the output
impedance is (12 * 12) / (2 * 1) = 72 ohms.
In case of regular SSB transmitters, they are tuned to
match at the maximum output to protect the transistors from
excessive power remaining in the device at the peak output, it
also makes sense as for CW and other continuous carrier modes
like FT8 and RTTY, the output power doesn't vary but remains
the same as the peak ssb envelope power.
- f??
This is not correct.? The output impedance of the PA
does not change the SWR and resistance/reactance of the
tuner/antenna combination.
What one is really doing is tuning out the reactance of the
antenna and setting the load resistance to the design value
of the amplifier.? A reactive load increases the dissipation
of the PA finals.? Tuning at low power within the voltage
and dissipation limits is safe.
David N1HAC
On 8/3/22 3:44 AM, Ashhar Farhan via
wrote:
Many recommend tuning at a lower power.
This risky as well. That is because at lower power, the
output impedance of the PA will be different. Once you
are tuned at QRP level, increasing the power will result
in a mismatch again!?
- f
Unfortunatel, no. The sbitx has no way
to check the swr (yet).?
Even if it had, as we are dealing
with very high power, fiddling with the tuner for
15-20 seconds with large mismatch will send all
the 40 watts back into the PA, destroying it.
What will work is a resistive
bridge. This will dissipate most of the power in
big resistors until you are tuned up.?
You can paraellel up ten x 470 ohm
resistors of 1 watt to make each of the three legs
of the resistive divider of the swr bridge. A DPDT
switch can bypass it once you are all tuned up.
On Wed, Aug 3,
2022, 12:21 PM Trevor Stone < tstone@...>
wrote:
In the
operating manual I see the following warning:
```
# 1. Connect the Antenna first!
The antenna jack on the back must always be
connected to a properly
matched antenna with an SWR of less than 2 on the
frequencies you intend
to transmit on. This is a recommendation for all
amateur wireless radios
but more specifically the sBitx. The sBitx can put
out upto 50 watts of
power and if the antenna does not match, it can
damage the power
amplifier transistors instantaneously.
```
Does the sBitx have the ability to tune or check
the SWR without
damaging itself, or does one need to use an
antenna analyzer before
using the radio?
I ask because most of my operation is portable, so
my SWR changes every
time I set up my station.? SWR can be high even
for an antenna of the
right length if it's deployed in a compromised
position or if I made an
error during setup (like last month when I forgot
to attach
counterpoises to an end-fed antenna :-)
Thanks,
Trevor KF0FTJ
--
=-=-=-= Trevor Stone -=- [Flwyd] -=- <tstone @
>
=-=-=-=
Computer science, eclectic philosophy, games,
wits, esoterics, odd hats
?
? ? ? ? ?Thou brazen boil-brained malt-worm!
{embrace society}? ? ? ? ? ? ? ? ? ? ? ? ?
POLAROID does it in seconds.
Calvin: The world is a complicated place, Hobbes.?
Hobbes: Whenever it
seems that way, I take a nap in a tree and wait
for dinner.
|
Re: Farhan's Analog Again The Daylight Radio
The plans are clear to me except for T1 and T2. How are the trifiliar transformers wound? How many turns on what size toroid? Are 2 and 6 really unconnected?
--
? 73
??? Bob? KD8CGH
|
Re: sBitx, customs and management fees
Ken,
In Spain, then VAT tax is 21%. 270$ x 0.21 is aprox. 53€.
DHL management cost could avoid it, but I would have to go to Madrid, do the management, lose a few hours, etc. It is the price of comfort.
The online seller should, or could, include VAT in the price (this is how AliExpress does), but that's a minor issue.
Public services must be paid.
¸é²¹³¾¨®²Ô?
|
it is possible that you might want to switch the audio output to a couple of different things..
check this out...
vince N2AIE
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Re: sBitx antenna-first warning
Most SWR meters (for the HF frequencies) don't measure SWR. They just measure how far off the antenna/coax load is from 50 ohms (reactive and resistive).
The only reason they are fixated on 50 ohms is nearly everyone uses 50 ohm coax, and it is a good idea to try to match the 50 ohm coax for minimum loss in the coax. However, the SWR measurement is usually made at the transmitter end of the cable, so the SWR across the length of the coax cable could be high. You could just be at a lucky multiple of a 1/4 wavelength that could make the impedance of the antenna/coax system (where you stuck the SWR meter) look close to 50 ohms.?
I agree, the reactance part of the load is what kills the finals. There may be, indeed, "reflected" waves. But, the reflected waves don't somehow have electrons managing to fight their way in the opposite direction to attack, pillage and lay waste to the RF finals. The "mismatch" can be reactive (look too much like an inductive or capacitive load) and cause problems with power dissipation or excessive voltage when the finals try to drive that load.?
At HF the only way to measure the actual SWR would be to do what the old timers did. Actually run a measuring device down the length of the cable (if long enough) and records the maximin and minimum readings.?
Tom, wb6b
toggle quoted message
Show quoted text
On Wed, Aug 3, 2022 at 07:11 AM, Jerry Gaffke wrote:
There is room for doubt here.
An SWR meter assumes the transmitter wants to see a 50 ohm resistive load.
A uBitx/sBitx might work a bit better into a load that is somewhat different than assumed.
Jerry,? KE7ER
Hide quoted text
?
On Wed, Aug 3, 2022 at 06:20 AM, David McGaw wrote:
This is not correct.? The output impedance of the PA does not change the SWR and resistance/reactance of the tuner/antenna combination.
What one is really doing is tuning out the reactance of the antenna and setting the load resistance to the design value of the amplifier.? A reactive load increases the dissipation of the PA finals.? Tuning at low power within the voltage and dissipation limits is safe.
David N1HAC
?
|
Re: sBitx, customs and management fees
toggle quoted message
Show quoted text
On Aug 5, 2022, at 11:36, Ian Reeve <ian.radioworkshop@...> wrote:
?
As I understand it is for the UK calculated at VAT on cost and postage plus and admin fee for the courier company.The admin fee is to cover collection of and passing to hmrc with appropriate paperwork.If the item is described and marked on the
customs declaration as a kit, I thought it was VAT exempt although there is still a admin fee for the customs declaration.These charges are levied by the customs at point of entry to your country so there is plenty of scope for miscalculation.
Get
I got my sbitx today, additional 95 euro for Irish customs. Welcome to the EU.
On Fri 5 Aug 2022 at 16:42, Ken N2VIP < ken@...> wrote:
Ouch! As a US Ham I'm curious how the €53 VAT is calculated, since the stated value is, what, about €250-300?
Sadly, the €43 for "customs management" is likely a fixed paperwork fee no matter the value of the shipment.
I wonder if VAT could be pre-paid to avoid the "customs management" fee? The VAT itself is (apparently) owed & should be paid, but maybe the additional fee can be avoided?
Anyway, just curious,
Ken, N2VIP
?
Hello,
I just received my sBitx, Basic Kit. It has been accompanied by an additional payment of €53 VAT for the Treasury and €43 for DHL for customs management.
?
So the radio has been a little more expensive than expected but I am sure it will be worth the extra cost and I will enjoy it a lot.
?
Notice for European Union buyers!
?
Ramon EA4GZI
|
Re: sBitx, customs and management fees
As I understand it is for the UK calculated at VAT on cost and postage plus and admin fee for the courier company.The admin fee is to cover collection of and passing to hmrc with appropriate paperwork.If the item is described and marked on the
customs declaration as a kit, I thought it was VAT exempt although there is still a admin fee for the customs declaration.These charges are levied by the customs at point of entry to your country so there is plenty of scope for miscalculation.
Get
toggle quoted message
Show quoted text
I got my sbitx today, additional 95 euro for Irish customs. Welcome to the EU.
On Fri 5 Aug 2022 at 16:42, Ken N2VIP < ken@...> wrote:
Ouch! As a US Ham I'm curious how the €53 VAT is calculated, since the stated value is, what, about €250-300?
Sadly, the €43 for "customs management" is likely a fixed paperwork fee no matter the value of the shipment.
I wonder if VAT could be pre-paid to avoid the "customs management" fee? The VAT itself is (apparently) owed & should be paid, but maybe the additional fee can be avoided?
Anyway, just curious,
Ken, N2VIP
?
Hello,
I just received my sBitx, Basic Kit. It has been accompanied by an additional payment of €53 VAT for the Treasury and €43 for DHL for customs management.
?
So the radio has been a little more expensive than expected but I am sure it will be worth the extra cost and I will enjoy it a lot.
?
Notice for European Union buyers!
?
Ramon EA4GZI
|
Re: sBitx, customs and management fees
I got my sbitx today, additional 95 euro for Irish customs. Welcome to the EU.
On Fri 5 Aug 2022 at 16:42, Ken N2VIP < ken@...> wrote: Ouch! As a US Ham I'm curious how the €53 VAT is calculated, since the stated value is, what, about €250-300?
Sadly, the €43 for "customs management" is likely a fixed paperwork fee no matter the value of the shipment.
I wonder if VAT could be pre-paid to avoid the "customs management" fee? The VAT itself is (apparently) owed & should be paid, but maybe the additional fee can be avoided?
Anyway, just curious, Ken, N2VIP ? Hello,
I just received my sBitx, Basic Kit. It has been accompanied by an additional payment of €53 VAT for the Treasury and €43 for DHL for customs management.
?
So the radio has been a little more expensive than expected but I am sure it will be worth the extra cost and I will enjoy it a lot.
?
Notice for European Union buyers!
?
Ramon EA4GZI
|
Re: Farhan's Analog Again The Daylight Radio
I have been getting 3D prints from my local library.? They have a much better 3D printer than I have and charge by the ounce.? ?
Ben
|
Re: sBitx, customs and management fees
Ouch! As a US Ham I'm curious how the €53 VAT is calculated, since the stated value is, what, about €250-300?
Sadly, the €43 for "customs management" is likely a fixed paperwork fee no matter the value of the shipment.
I wonder if VAT could be pre-paid to avoid the "customs management" fee? The VAT itself is (apparently) owed & should be paid, but maybe the additional fee can be avoided?
Anyway, just curious, Ken, N2VIP
toggle quoted message
Show quoted text
On Aug 5, 2022, at 05:55, ramonlh@... wrote:
? Hello,
I just received my sBitx, Basic Kit. It has been accompanied by an additional payment of €53 VAT for the Treasury and €43 for DHL for customs management.
?
So the radio has been a little more expensive than expected but I am sure it will be worth the extra cost and I will enjoy it a lot.
?
Notice for European Union buyers!
?
Ramon EA4GZI
|
Re: Turn off WiFi on your sBitx
I am beginning to think that the wifi signal is injected into another place than the lm380.
I have built an external board with a lm380 and the noise was there.
I have tried placing a grounded screen between the pi and the digital board. Noise.
I have moved the pi to "official mounting" on the backside of the display. Noise.
73 de oz9ny, niels
|
A large groups.io group can get expensive (in ham radio terms), ranging from free (up to 100 users), to $20/month (up to 500 users), to $200/month (up to 1,000 users):
There is an interesting option called "subgroups" that may be worth exploring (if available in our group bitx20, I believe this group is a in a (free) service tier that is no longer offered, so what is and is not included is unclear to me.)
And note, the group started out to support the bitx20, then embraced the bitx40, then the uBitx, and now the sBitx. Once the initial flurry of activity dies down, I think the sBitx topics will moderate just like the bitx20, bitx40, and uBitx traffic did previously.
toggle quoted message
Show quoted text
On Aug 5, 2022, at 09:07, Lou KI5FTY <lscalpati@...> wrote:
? I agree - add a new group On Fri, Aug 5, 2022 at 9:05 AM Jim K5KKB Steeb < jimsteeb@...> wrote: Love this idea!!! Flip side is alot?of us will still be checking in on both Forums anyhow
On Fri, Aug 5, 2022 at 9:02 AM Gerard < kabupos@...> wrote: Good morning,
I was absent from the forum during my vacation.
The number of topics on the Sbitx is impressive.
For an easier reading for those who are still at the Ubitx, wouldn¡¯t it be better to have a Sbitx group?
The moderator could create it and move all the Sbitx messages on it.
Have a great day.
Cdt
|
Re: The sBitx Release on www.vu2ese.com
Yep, when I try to execute using ./sbitx, I can see it's there but is crashing without the chips. Thanks!
--
Stephen, KO4CVU
|
I thought you all would be interested.? Lots of discussion of Farhan's SDR and HDR rigs.? ?Hammarlunds.? Pete's Wireless Set.? My DX-100.? 40 meter AM.??
Here it is:?
Comments welcome.? (Please put them in the box underneath the blog post).?
73? ?Bill N2CQR http://soldersmoke.blogspot.com
|
I agree - add a new group
On Fri, Aug 5, 2022 at 9:05 AM Jim K5KKB Steeb < jimsteeb@...> wrote: Love this idea!!! Flip side is alot?of us will still be checking in on both Forums anyhow
On Fri, Aug 5, 2022 at 9:02 AM Gerard < kabupos@...> wrote: Good morning,
I was absent from the forum during my vacation.
The number of topics on the Sbitx is impressive.
For an easier reading for those who are still at the Ubitx, wouldn¡¯t it be better to have a Sbitx group?
The moderator could create it and move all the Sbitx messages on it.
Have a great day.
Cdt
|
Love this idea!!! Flip side is alot?of us will still be checking in on both Forums anyhow
On Fri, Aug 5, 2022 at 9:02 AM Gerard < kabupos@...> wrote: Good morning,
I was absent from the forum during my vacation.
The number of topics on the Sbitx is impressive.
For an easier reading for those who are still at the Ubitx, wouldn¡¯t it be better to have a Sbitx group?
The moderator could create it and move all the Sbitx messages on it.
Have a great day.
Cdt
|
MadRadioModder
Vince N2AIE
David McGaw
Bob Benedict, KD8CGH
Jim K5KKB Steeb