Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- BITX20
- Messages
Search
|
Re: sBitx antenna-first warning
Pierre FK8IH
Thanks Ashhar for this post. I shall now use this?in my QRP station (Hermes Lite 2 with Alexloop magnetic loop antenna, which shows SWR values largely over 40:1 to the tranceiver when tuning the loop (fortunately the LDMOS power amplifier can accept SWR>65:1 but I prefer to be cautious. This tuning-indicator brings the SWR seen by the tranceiver below 2:1 when tuning the antenna, as you say in your post. I continue to watch the development of your sBitx, wich looks like a wonder and shall decide later to buy one. 73 - Pierre - FK8IH |
|
Re: The Daylight Again - An All analog radio
Ken, The radio is all point-to-point soldering and large sized components. The performance will suffer it built on a single pcb.? I guess someone can try it. The radio needs improvements, it needs cw to be added, the t/r is primitive and can be bettered too. - f On Thu, Aug 4, 2022, 9:43 AM Ken N2VIP <ken@...> wrote:
|
|
Re: The Daylight Again - An All analog radio
¿ªÔÆÌåÓýWhat a neat little radio, thanks for sharing.Something like that, if it could be kitted out at $50 or so would make a great club project, but kiting up such a project is way beyond my skill set. I know you're not offering it as a kit, just dreaming - thanks again for sharing your projects! Ken, N2VIP On Aug 3, 2022, at 22:56, Ashhar Farhan <farhanbox@...> wrote:
|
|
Re: uBITX SWR Tolerance
#ubitxv6
WOW, Never ran that much thru rg6u quad shield. have run consistantly 150 watts thru it when i owned a QRO rig. good for you. I buy mine thru either walmart or homedepot or menards depending on when they have a sale. i buy the twist on connections . I dont like the crimps since they are prone to sharp edges if crimped wrong and be a point of possible interference? and moisture.I also seal mine with a caulking friendly to the coax. The 1:5 on my ubitxs are no problem either . All my rigs have rg6u quad shield from start to finish and i have rg6u jumpers with twist on connectors for testing ,etc.What i dont spend on the rg8x,i can splurge on good f to pl259 fittings,and extra cable in case i have a blowout or something else.All my feeds are buried ,run thru 1/2" pvc so if i need to replace a feedline,just tie onto it with new cable and pull. WOW Again on the 800 watts thru it 73 David ac9xh good thru hamcall.net,qrzcq.com and FCC
On Wednesday, August 3, 2022 at 02:16:44 PM EDT, Aaron K5ATG via groups.io <k5atg@...> wrote:
"I also use the quad shield with good results up to about the 800watt level"? WOW I consider 20 watts to be high power lol -- '72 Aaron K5ATG
|
|
Anybody have vector graphic versions of kd8cec nextion screens?
Looking to create a consistent set of nextion screens at their native resolution. ?Anybody have a set of drawings in a vector graphics form that can be resized for each platform? ?Only seen bitmapped versions that were optimized by individuals for each platform.?
|
|
Re: A uBITX Woodie
#ubitxv6
On 8/3/2022 13:10, Aaron K5ATG via groups.io wrote:
Although I might be able to put the Voyager plaque and put some clothes on the man and lady so my 19 year old son doesn't destroy it for displaying hard-core pornography (He is Autistic with Aspbergers and considers people holding hands to be hard-core porn.)I prefer the attached version. We meatbags had our chance... -- Tom Sevart N2UHC St. Paul, KS |
|
Re: sBitx antenna-first warning
Here is one of many posts from Allison that are worth reviewing,
toggle quoted message
Show quoted text
mentions the 6m 225W power amp she built using 4+4 IRF510's in push-pull. The whole thread is worth a read. ??/g/BITX20/message/22597 She has been contributing to the forum for some time now: ??/g/BITX20/message/14514 ??/g/BITX20/message/869 Just plugging a new fet into the sBitx likely won't solve anything. The circuit around it should be designed specifically for that part for good performance. Jerry, KE7ER On Wed, Aug 3, 2022 at 10:14 AM, Jerry Gaffke wrote: The IRF510 can work dependably, Allison reports years of success with HF amps at 40W push-pull, |
|
Re: sBitx antenna-first warning
¿ªÔÆÌåÓýand here is where bias and standby current (class A A/B C) comes into play :-) dg9bfc sigi Am 03.08.2022 um 15:07 schrieb Max via
groups.io:
|
|
Re: uBITX SWR Tolerance
#ubitxv6
"I also use the quad shield with good results up to about the 800watt level"?
WOW I consider 20 watts to be high power lol -- '72 Aaron K5ATG |
|
Re: A uBITX Woodie
#ubitxv6
Alan, I like the idea of the solar system but I am also rebuilding my 12-inch Dobsonian telescope with a lot of space imagery and I think my XYL may object to more space stuff in the house. Although I might be able to put the Voyager plaque and put some clothes on the man and lady so my 19 year old son doesn't destroy it for displaying hard-core pornography (He is Autistic with Aspbergers and considers people holding hands to be hard-core porn.)?
Jim that is a cool idea. It made me start looking up old art deco radios. They knew how to make stuff look great back then. Many of today's rigs are as Bill Meara N2CQR would say, "It just does not have a soul"? -- '72 Aaron K5ATG |
|
Re: uBITX SWR Tolerance
#ubitxv6
I also use the quad shield with good results up to about the 800watt level... if everything is right (no sharp bends anywhere) it works just fine. Otherwise I have melted and spectacular flash arc through the entire cable burns through at that power level.? ?the thing with the Rg6u? is that because of the 75ohm cable, my 50ohm transmit output sees an almost exactly 1.5 : 1 swr.... which is not a problem.?? Alan? w7aln On Tue, Aug 2, 2022, 2:40 PM david todd via <ac9xh=[email protected]> wrote: I use an emtech zm-2 tuner and also a ldg z100 tuner. both seem to work 100%. |
|
Re: sBitx antenna-first warning
Got it.? I thought it might be something like that.? I have a QRPGuys Tuning Indicator that that I was using with my uBitx v6 transceiver.? It looks like the same circuit.? I'll replace the single 5.1 ohm resistors with the parallel group you suggest.? Cool, more stuff to build!
(We need help.)? Scott |
|
Re: sBitx antenna-first warning
Jack, How much voltage were you running on the drains? - f On Wed, Aug 3, 2022, 11:00 PM Jack, W8TEE via <jjpurdum=[email protected]> wrote:
|
|
Re: sBitx antenna-first warning
Jack, W8TEE
We've tested the T41 with its 510s to 40W and nothing fried. 80-40-20M all can deliver about 25W without much effort. 15M is about 20W and 10M drops to about 13W. Like I said, it is what it is... Jack, W8TEE
On Wednesday, August 3, 2022 at 01:14:06 PM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
The IRF510 can work dependably, Allison reports years of success with HF amps at 40W push-pull, surviving everything from accidental open antenna connections to dead shorts. In posts to this forum from several years ago, Allison went into plenty of detail. She even used them on 6m at several hundred watts (with bunches of them in parallel). The QSX amp from qrp-labs uses IRF510's in push-pull, does a consistent 10W from 3 to 30mhz. ?https://www.qrp-labs.com/linear.html Clean and linear even when operating from 12v, tolerates any antenna condition. A product of collaboration between Hans and Allison.? ?Cost of $26 USD for the kit, a steal. If I were building a rig like the sBitx from scratch, I would start with that amp for a PA, perhaps add PIN diode TR switching with the HV supplied by rectified RF. HFsignals could steal that PA design for the sBitx-v2, give Hans $5 for every unit if feeling guilty. Using the IRF510 for RF power amps takes careful design.? Especially heat sinking, as the IRF510 is not very good at getting heat from the die to the TO220 tab.? The IRF510 prefers more like 24vdc for higher power and reduced distortion. Improper design can blow the gate due to exceeding Vgs max spec momentarily Needs more drive than an RD16HHF1 to get similar power levels due to moderately high gate capacitance. However, Vds max is much higher for the IRF510 than it is for the RD16HHF1, so for cases of high Vds the IRF510 would survive a high SWR better than the RD16HHF1. Allison was of the opinion that moving to the RD16HHF1 on the uBitx would not help much. Reading from??https://www.vu2ese.com/index.php/2022/07/20/the-sbitx-the-sdr-for-the-homebrewer/ "The power amplifier of Figure 6 is a conventional power chain, probably a little sub-optimal. Two stages of pre-driver amplification with metal 2N2222As boost the signal level from -15 dBm to a little above 100 mW" For "sub-optimal" we could substitute "inexpensive".? One necessary change if wanting somewhat even power output all the way up to 30mhz would be an additional stage of amplification.? Gong from -15 dBm to +20 dBm (100mW) in two stages of 2N2222's is 35 dB of gain, or 17.5 dB per stage.? That's pushing it,? Though as we saw on the uBitx, optimizing a power amp is complicated, especially when doing it for a low budget product.? If NFET's seem too hard to use and just too dang complicated, an 807 or 6146 should do fine with any SWR when operating at 40W.? ?;-) Names could be shorter 80 years ago, they didn't have 10 gazillion different electronic parts to keep track of. Jerry, KE7ER On Wed, Aug 3, 2022 at 09:29 AM, Ashhar Farhan wrote:
-- Jack, W8TEE |
|
Re: sBitx antenna-first warning
The IRF510 can work dependably, Allison reports years of success with HF amps at 40W push-pull,
toggle quoted message
Show quoted text
surviving everything from accidental open antenna connections to dead shorts. In posts to this forum from several years ago, Allison went into plenty of detail. She even used them on 6m at several hundred watts (with bunches of them in parallel). The QSX amp from qrp-labs uses IRF510's in push-pull, does a consistent 10W from 3 to 30mhz. ?https://www.qrp-labs.com/linear.html Clean and linear even when operating from 12v, tolerates any antenna condition. A product of collaboration between Hans and Allison.? ?Cost of $26 USD for the kit, a steal. If I were building a rig like the sBitx from scratch, I would start with that amp for a PA, perhaps add PIN diode TR switching with the HV supplied by rectified RF. HFsignals could steal that PA design for the sBitx-v2, give Hans $5 for every unit if feeling guilty. Using the IRF510 for RF power amps takes careful design.? Especially heat sinking, as the IRF510 is not very good at getting heat from the die to the TO220 tab.? The IRF510 prefers more like 24vdc for higher power and reduced distortion. Improper design can blow the gate due to exceeding Vgs max spec momentarily Needs more drive than an RD16HHF1 to get similar power levels due to moderately high gate capacitance. However, Vds max is much higher for the IRF510 than it is for the RD16HHF1, so for cases of high Vds the IRF510 would survive a high SWR better than the RD16HHF1. Allison was of the opinion that moving to the RD16HHF1 on the uBitx would not help much. Reading from??https://www.vu2ese.com/index.php/2022/07/20/the-sbitx-the-sdr-for-the-homebrewer/ "The power amplifier of Figure 6 is a conventional power chain, probably a little sub-optimal. Two stages of pre-driver amplification with metal 2N2222As boost the signal level from -15 dBm to a little above 100 mW" For "sub-optimal" we could substitute "inexpensive".? One necessary change if wanting somewhat even power output all the way up to 30mhz would be an additional stage of amplification.? Gong from -15 dBm to +20 dBm (100mW) in two stages of 2N2222's is 35 dB of gain, or 17.5 dB per stage.? That's pushing it,? Though as we saw on the uBitx, optimizing a power amp is complicated, especially when doing it for a low budget product.? If NFET's seem too hard to use and just too dang complicated, an 807 or 6146 should do fine with any SWR when operating at 40W.? ?;-) Names could be shorter 80 years ago, they didn't have 10 gazillion different electronic parts to keep track of. Jerry, KE7ER On Wed, Aug 3, 2022 at 09:29 AM, Ashhar Farhan wrote:
|
|
Re: Can't transmit FT8
Press on the cq decode and then, F1 for "reply to cq" On Wed, Aug 3, 2022, 10:04 PM WB2OSZ <wb2osz@...> wrote: The builtin FT8 reception works great.? I'm hearing stations from around the world. |
|
Re: sBitx antenna-first warning
Interesting discussion. Just a few very quick thoughts I think that you have to consider the average of the input power to consider the input impedance of the power device as the instantaneous power varies widely under SSB conditions according to the voice characteristics, as indicated by Farhan in the examples he?gives of varying input power. Otherwise, one can say that the low pass filter will not work correctly Furthermore, I think that it is not the case that the SWR varies according to the power, but that since you have more power output, the reflected power will be greater?with a greater indication?on the SWR meter. If the LPF is designed for 50 ohms at its output end the?SWR is not going to change with power as can be seen if the TX is terminated into a suitable dummy load, but will only change with the reactance of the antenna / feeder which does not change with power. The pi network in the old valve tx's is not a good example?because it was a matching network to tune the tx and match it to the antenna.?? What you were doing was matching the tx to the antenna impedance, whatever that was, which did not change according to the power, but what was changing was the pi network impedance transformation between the antenna and the PA according to the PA input power. Just a few quick thoughts for your consideration Regards? Lawrence On Wed, Aug 3, 2022 at 5:59 PM Ashhar Farhan <farhanbox@...> wrote:
|
Aaron K5ATG
to navigate to use esc to dismiss