Yes, I understand trying to keep the cost of components down, but after further research, and my own experiences with a few bitx products, why keep chasing down a design around a MOSFET not intended for RF and spend a few more dollars on something like the
RD16HFF1, and be rid of the seemingly constant PA problems....
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Yeah i bobbed the PAs out of all my BIT radios and use that 20W pa. ? Its got great specs and the semi-kit only cost about $20 plus shipping.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
?
Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois
?
Owner – Operator
Villa Grand Piton - J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
email:??bill@...
?
On Mar 3, 2025, at 11:37?AM, Evan Hand via groups.io <elhandjr@...> wrote:
?
Hi Mike,
?
Have you looked at the K9HZ amp that is part of the T41 project?
?
or
?
This might meet your needs.
?
You could couple it with the LPF and T/R switch the sBitx uses.
?
73
Evan
AC9TU
-- Mike - K8MCB?
|
Amazon and AliExpress sell sealed buck boost regulators from 3 Amps to 30 Amps from about $5 to $50. They are pretty much bulletproof. Output voltage is chosen by the unit selected and input is from about 5 to 50 volts. Run your zBitx from a solar panel!
Jay NM2M?
I think you'd be best served by using a regulator to turn 13.8v into 9v, rather than trying to redesign the radio to natively run on 13.8v. I imagine a suitable circuit could be installed in the 18650 battery case on the side of the zBitx case, rather than putting such a heat source inside the case.
?
Personally, I plan to use the battery powered option, but I do understand the desire to operate from a standardized 13.8v power source...
?
Ken, N2VIP
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You might want to look at some of the DROK buck converters.? I
think they have one that will do what you want, & they are
very power efficient.
Gerry Sherman
Sent by the Windows 11 Thunderbird
On 2025-03-03 22:57, Ken N2VIP wrote:
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I think you'd be best served by using a regulator to turn
13.8v into 9v, rather than trying to redesign the radio to
natively run on 13.8v. I imagine a suitable circuit could be
installed in the 18650 battery case on the side of the zBitx
case, rather than putting such a heat source inside the case.
?
Personally, I plan to use the battery powered option, but I
do understand the desire to operate from a standardized 13.8v
power source...
?
Ken, N2VIP
|
I think you'd be best served by using a regulator to turn 13.8v into 9v, rather than trying to redesign the radio to natively run on 13.8v. I imagine a suitable circuit could be installed in the 18650 battery case on the side of the zBitx case, rather than putting such a heat source inside the case.
?
Personally, I plan to use the battery powered option, but I do understand the desire to operate from a standardized 13.8v power source...
?
Ken, N2VIP
|
Hello, we haven't received any zBitx yet and I'm already thinking about modifying something.
I don't really like the fact that it goes to a maximum of 9v, and I would like to know how to modify the device to make it work at 13,8vdc like the rest of the radio devices that most of us have.
I've looked at some components in the sBitx schematic and I think they are basically the same. So, what changes? I don't want to get more power (it wouldn't be bad to get 20w ;-) ) but I want to be able to have access to all the power sources I have.
thanks... I'm anxiously awaiting my shipment from India...
Jordi
From Catalonia.
|
Okay, I'm interested. Where is the site to order from?
--
Mike - K8MCB?
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This the complete Sbitx as built,? the only 2 changes are the upgrade of the Raspberry Pi 4 from 2GB memory to 4 GB memory and the master board was upgraded to a newer model to resolve the low power on 20 meters.? The mike, power cord with Anderson power poles,
and legs to support the Sbitx ?at a good viewing angle.??
Tom Crowley KT4XN
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Hi Tom,
?
Is the case included?? Any other items that are included, like the mic and display?
?
73
Evan
AC9TU
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|
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Hi Tom,
?
Is the case included?? Any other items that are included, like the mic and display?
?
73
Evan
AC9TU
|
Zbitx :: manual Tuner procedure
Hello!
?
while waiting for my zbitx to arrive, and after reading the sbitx manual, I can’t find a reference on how to use a manual tuner in order to keep the finals safe.?
?
I have a Chinese zmatch qrp tuner, but the tune function is way off, so I use the “work” function for better results.?
what would be the best practice?
?
thabk you in advance!
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Re: sBITX 64Bit Pi Image Available
#sBitx
Here's a link to the discussion:?
It's a very simple mod. You'll need to print the holder and some jumper wires to go to the RTC header.??
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Würde mich auch interessieren. Gibt es schon irgendwelche Infos?
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Just FYI, it shows that I'm out of stock, I do have 10 more on-hand, I just need to finish assembly.? I should be able to get most of them done tonight and the stock updated shortly.
Jeff - KF7YDU - duceRF
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Thanks for the link, I'll definitely consider this option!
You can buy one prebuilt. ?
--
Mike - K8MCB?
|
Yeah i bobbed the PAs out of all my BIT radios and use that 20W pa. ? Its got great specs and the semi-kit only cost about $20 plus shipping.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
toggle quoted message
Show quoted text
On Mar 3, 2025, at 11:37?AM, Evan Hand via groups.io <elhandjr@...> wrote:
? Hi Mike,
?
Have you looked at the K9HZ amp that is part of the T41 project?
?
or
?
This might meet your needs.
?
You could couple it with the LPF and T/R switch the sBitx uses.
?
73
Evan
AC9TU
|
I have a lightly used SBITX V3 for sale.? I had replaced the original board with a new one, due to the low output on 20 meters.? the new board resolved the issue.? I was able to fix the old board and built a new SBITX. Hence no need for 2.? It has been updated with JJs latest 64k version and tested.? It also has been updated with a 4GB Raspberry Pi 4.
?
I'm asking $325.00 with free shipping in the ConUS
?
Tom Crowley KT4XN
crowleytj at hotmail dot com
404.375.5578
?
|
Re: Sbitx v3 file requirement
JJ, very helpful, thanks. I have an unmodified V2 but with the bidirectional-zeners installed on the gates pf the finals. I need to check it and these instructions are helpful. (Yes I know they are not called bidirectional-zeners but I forgot their actual name so I use this functional name.)
|
Hi Mike,
?
Have you looked at the K9HZ amp that is part of the T41 project?
?
or
?
This might meet your needs.
?
You could couple it with the LPF and T/R switch the sBitx uses.
?
73
Evan
AC9TU
|
Sorry, I should have been more specific. I'm looking for data for the entire Tx chain.
--
Mike - K8MCB?
|
Does anyone know of a singular source that documents the specs, performance, etc. of the sbitx v3 PA stage? It appears to be a fairly flexible design and I was considering it as a potential candidate to put in front of a Lime sdr mini v2. There doesn't appear to be a significant support community for that particular sdr, but I certainly would like to get the most out of it that I can. As always, any input or suggestions are welcome!
--
Mike - K8MCB?
|
Re: sBITX 64Bit Pi Image Available
#sBitx
Würde mich auch interessieren. Gibt es schon irgendwelche Infos?
|
Re: How to ruggedize the sBitx V3
More power to you.
Remember in the "thermal cascade" the JUNCTION of the device is what counts.? ?Needs to stay well below 175 C at all times.? Mosfets have a problem with a localized heating effect as well that I don't well understand, has to do with local variations in sensitivity to bias.??
To get heat away from the junction there are several thermal resistors in series, and at every one, temperature is lost, keeping the junction HOT and reducing the efficiciency of moving heat OUT
Junction to tab -- this is pretty high in the TO-220 case, esp for MOSFETS that really were not built for this RF stuff.? ?Maybe 2 deg C/watt?? ? This means you CANNOT know the actual temp of the JUNCTION.
CAse to heatsink -- this is made worse by the mica (or other insulator).? ?So the heatsink is even further COOLER than the junction
heatsink to ambient room -- this is made worse by lack of air movement
Ambient room -- if the room is HOT things are even worse.
Measuring closer and closer to the junction is problematic, too!? The Drain is RF-HOT!? ?Lots of RF voltage/power there.? ?Potential for FEEDBACK if you couple something that carries RF away (wires, etc).? ?So could be a problem where the measurement....causes damage to the radio!? ? Not certain I would be so quick to put measurment devices there that go back toward the raspberry pi....
Putting a little thermistor to an external consumer temp measurement (think, the "external" probe of a consumer thermometer) next to the tab, separated by some insulating but thermally somewhat conductive glue or caulk.... then maybe making a common-mode choke ofthe sensing wire system by putting 5 or 6 turns of a coil of it over a pencil shape.... or putting some snap-on ferrites?? ?Might make this work and not CAUSE TROUBLE.? ?Dunno.? ?
Easier to measure the temp of the heat sink NEAR the mosfets, but that is considerably removed from the JUNCTION, too.? ??
It isn't a slam dunk simple project, I think. Let usknow what works!
Gordon KX4Z
I am a programmer, and the fact that the radio has a built in RPi was the point that sold it to me (together with the bands covered, features, power level, and portability). I do have an antenna tuner and analyzer, so SWR is under control.
?
Thank you for all the suggestions. I guess I should start on the thermal control side first. Replacing the mica insulator, and adding a temperature sensor, seem like easy and useful firsts.
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EB3AM Jordi
tzsantos CR7BOG
K9HZ
Bruce W4BRU
Dirk