Hi Jerry,
Those DC-paths might prevent static build-up, but that might not be sufficient if the uBitx is unconnected and static builds up on antenna and then it is connected?
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27 okt. 2020 kl. 17:01 skrev Jerry Gaffke via groups.io <jgaffke@...>:
?Evan,
You can have large static voltages build up on some antenna systems.
Could be several thousand volts.
An RF choke to ground at the antenna port should be sufficient to deal with these.
Though in Arron's case, the EFHW matchbox should be shorting that static to ground.
Here's a group on facebook actively discussing these antennas:??
? ??
And on the uBitx, L1,2,3,4 and T2 provide a DC path to ground during receive.
When transmitting, T11 of the uBitx should be a DC short to ground
through the transmit LPF inductors.
So the choke is probably not needed in this case, but the blocking caps that NC0U shows
are not a bad idea.? I'd be worried that voltages could far exceed his 25 volt cap.
And I agree with his red question mark regarding the extra cap in series with the diodes.
While we may be protected from DC, we still need to deal with?
large RF fields, such as that AM transmitter, or Arron's VHF rig.
That's where the back-to-back diodes and the incandescent bulb become important.
?
A lot of the protection schemes that work for others may not work on a uBitx.
The base-emitter junction of the 2n3904 at Q90 is likely more sensitive
to excessive voltage than the antenna port of a typical ham rig.
Jerry, KE7ER
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Re: Simple UBITX Test Set
Regarding trying to calibrate with WWV, it actually is easier if you have a second AM receiver when WWV is sending tones. You can then match the tone frequency between the uBitX and the AM receiver much easier than when zero beating as you can do that within a few cycles as opposed to losing the low frequency notes perhaps 100's of cycles before zero beat. Note, to be accurate the 2nd receiver needs to be AM, which eliminates that receiver's error which could be added to the perceived tone frequency if using SSB. That is the technique I used on mine and it is dead on frequency.
=Vic=
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Hi Aaron, Can you borrow or buy a SWR/power meter + dummy load?
If You connect the antenna port to a dummy and the radio port to the antenna and transmit on the other antenna You can see how much power is going to the dummy load (same as going to the uBitx when connected)
Is the AM transmitter active 24/7?
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26 okt. 2020 kl. 23:30 skrev Aaron K5ATG via groups.io <k5atg@...>:
?Earlier I had a uBitX that had no transmit power. It was determined by this group to be Q90 which is believed to have been blown by a nearby transmitter. I sent it to HFSignals and they tested it and verified that it was Q90.? Now I have a replacement uBitX V6 and it is doing the EXACT same thing. Here are the measurements of transmit power by each band:
80 meters- 0.13 watts
40 meters- 0.13 watts
30 meters- 0.18 watts
20 meters- 0.12 watts
17 meters- 0.16 watts
15 meters- 0.18 watts
12 meters- 0.07 watts
10 meters- 0.09 watts
Here is my complete shack set up:
Astron RS-12A Power Supply
Any Tone AU-778uv 2m/70cm FM transceiver hooked to Diamond F718A Base Station Antenna 40 feet RG8 feed point at 20 feet elevation
HFSignals uBITX V6 hooked to MFJ-1982MP 153' long endfed antenna fed with RG8 coax feed point at 9 feet elevation. On my uBitX I installed back to back 1N4148 Diodes between K1 relay pins 12 and 16 (This was supposed to protect Q90)
The separation between the feed points of both antennas is 25 feet horizontally and 10 feet vertical.?
Both antennas are grounded with a ground wire coming down from feed point to 8' ground rods driven 7' 10" into the ground.
I have an AM Broadcast transmitter about 1/2 mile from my house where I can hear it on my uBitX.
I know that there are a lot of really smart people in this group. So I would like to know what do you think that could be blowing the Q90 transistor???
I would like to find and resolve the problem so I do not have to keep replacing the transistor.?
-- '72
Aaron Scott
_._,_._,_
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Re: ?BITX ... AGC or AVC?
Loris,
I had experimented with a AGC which was very simple. Disconnect R23 and R43 from ground and introduce
a varicap which I had MV2109. A series resistor to the varicap through which you varied the capacitance
and thereby the gain. This method worked very well with both IF stages and even on the TX branch.
I wish some members would experiment on this approach.
Raj
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At 28/10/2020, you wrote: On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR
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On Wed, Oct 28, 2020 at 04:06 AM, IW4AJR Loris wrote:
On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
DEAR LORIS, ???? GOOD DAY . Thank you very much for sharing such a valuable information. I will try this with certain modification and post the result. ?Thank you & Regard, ?????????????????? 73 ???????????????????? MUTHU ???????????????????? VU2LMN
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On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR
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Re: Simple UBITX Test Set
On Tue, Oct 27, 2020 at 09:55 AM, Evan Hand wrote:
For the stock uBITX Ashhar Farhan published a video on how to calibrate and set the BFO:
Interesting. Using a Chrome web browser based audio spectrum analyzer to set the filter passband based on the noise coming out of the uBitx speaker is really cool. The spectrum analyzer looks fun to play with even if you are not aligning your uBitx filter bandpass at the moment. I think I try this on some other radios, like my vintage Kenwood, to see the difference between the SSB, AM and CW filters, just of fun. Tom, wb6b
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Q90 could blow with something not much over 0.7 volts, so silicon diodes are a far better bet than
the relatively high voltage zeners.? ?This being a 50 ohm environment (like that transmitter),
diode capacitance may not necessarily be a significant issue at HF.
Jerry, KE7ER
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On Tue, Oct 27, 2020 at 08:53 PM, Bob Lunsford wrote:
Have you considered a Zener diode with calculated breakdown if it is indeed a voltage thing? I remember Heath using a 36V Zener on the power output transistor on the HW-7/-8 to avoid killing off the final output transistor in case of high SWR with an improper or nonexistent load.
?
Bob ¡ª KK5R
?
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I built the 35W 6146 single tube crystal oscillator out of the 1969 ARRL handbook as a novice. Very exciting to watch the 40W bulb light up, smell the RF burns when I put my finger near the inductor wound on a bit of broomstick for the pi network output. Them FT243 crystals could apparently handle a fair bit of current, none of them smoked. For a quick but proper dummy load to be used with the uBitx, put a couple Mouser?660-MOS3CT631R101J in parallel For an improper device, consider Joe's (WB9SBD) dummy load, using electrodes in a water bath: Joe's powerpoint presentation was awfully long, here's my Cliff Notes, dimensions judged from his photos.
Electrodes are two 12 awg copper wires (2mm diameter) 6 inches long (16cm) and about six diameters apart.? Add baking soda till it is 50 ohms, about one teaspoon (or 5 ml).? The water will boil after 50 minutes at 100 watts.? SWR of around 1.0 through 60mhz, 1.5 at 150mhz but pulling the wires somewhat out of the water can readjust for an SWR of 1.0.? Joe reports good results up to 180mhz.? Has been working well for years.
If I was somewhat older, Joe's dummy load might make me nostalgic for an old electrical lighting system:
? ??
Jerry,? KE7ER?
On Tue, Oct 27, 2020 at 08:49 PM, Bob Lunsford wrote:
The classic rational for those who say that a lamp being used as a dummy load is that it is not only not a 50 Ohm load, it is also varying resistance depending on the temperature of the lamp's filament. Also keep in mind that it was a common thing used with relative low power transmitters, the transmitter was built around tube and not a solid state amp. While I have also used a pilot lamp on a QRP transmitter I built for 7040 KHz, it was thrilling to see the low power transmitter light up even though not quite to full brilliance.
?
More nostalgia. Today, using a lamp for a load or a power indicator is definitely old school and for me, I'd now rather wait for a proper device than tempt fate and see smoke instead of merely a bright spot in the corner.
?
Bob ¡ª KK5R
?
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Have you considered a Zener diode with calculated breakdown if it is indeed a voltage thing? I remember Heath using a 36V Zener on the power output transistor on the HW-7/-8 to avoid killing off the final output transistor in case of high SWR with an improper or nonexistent load.
Bob ¡ª KK5R
On Tuesday, October 27, 2020, 8:39:00 AM EDT, Evan Hand <elhandjr@...> wrote:
Jerry,
After reading your email again, I realized that you already stated the reason for a lamp as opposed to a resistor.? Q90 failure seems to be a somewhat frequent issue.? I have responded to more than 2 people with the diode solution.? I may have been in error on that, however, I do believe that Q90 is being destroyed by high RF or static discharge.
I am going to do some more research on any commercial rigs that I can find the schematic to see how those are protected.
Thank up for the information, and I apologize for any errors on my part including not reading your email correctly.
73
Evan
AC9TU
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The classic rational for those who say that a lamp being used as a dummy load is that it is not only not a 50 Ohm load, it is also varying resistance depending on the temperature of the lamp's filament. Also keep in mind that it was a common thing used with relative low power transmitters, the transmitter was built around tube and not a solid state amp. While I have also used a pilot lamp on a QRP transmitter I built for 7040 KHz, it was thrilling to see the low power transmitter light up even though not quite to full brilliance.
More nostalgia. Today, using a lamp for a load or a power indicator is definitely old school and for me, I'd now rather wait for a proper device than tempt fate and see smoke instead of merely a bright spot in the corner.
Bob ¡ª KK5R
On Tuesday, October 27, 2020, 8:29:44 AM EDT, Evan Hand <elhandjr@...> wrote:
Jerry,
According to Aaron, he did install the diodes, 1n4148s, per the picture on the original post.? That was before he used the second rig, so it appears that it did not protect Q90.? I was the one who had suggested the 1n4148.
I had done more research in the past and again just yesterday.? In the material in the links that I had provided, I found the 12volt lamp to act as a power sink on high RF input.? ?The reason for the lamp, as opposed to a resistor, is that the lamp has a very low resistance at room temperature that climes quickly when heated by the input RF.? I know that I had read multiple people say that is common protection for some commercial rigs in the distant past in this group.
At this point I am waiting for Aaron to get back to us to verify that:
1 - Q90 is truly blown through voltage measurements
2 - That the power was measured on CW vs SSB
73
Evan
AC9TU
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Re: Electronic encoder (Not rotary)
Evan,
I did the test on TX and RX of the Nextion with the decoupling as done on the rotary encoder.
No luck at all.
After, in my case, I can really afford to make a power supply completely isolated from the PCB for the Nextion.?Maybe this will eliminate the noise.
I ordered quartz 11.059, that will allow me to go later in V5.
I have the impression that there is a price stop on it, (A......n, E..y) so I took the opportunity to buy 20 for 8 € at a distributor in France.
I also found a video of Lee on smeter calibration >> see the post
cdt
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Re: V6 TX on 15 and 20 meters
Ok got the wires cut to length for 15 and 20 meters. Don¡¯t see any interference.
We¡¯ll test drive it couple days see what happens.? Thanks Larry made my day. 73 KA3DFK Chuck --
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Ouch and double ouch!
Just glad to hear that everyone is OK.
let us know when you are back on radio stuff.
good luck
73
Evan
AC9TU
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If you don't see changes in uBITX freq error after you change the master cal in MM, then you need to fix the process problem first.
I just did the math, and for every 1 hz change you desire in the uBITX vfo display, you change the MM master cal by +/- 87.??
Is that coor or what?
? I have not tested or validated this notion, but it seems right based on my poor memory of what I did last year when trying to minimize my beloved uBITX freq display error via successive MM changes.
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Ouch. Power box is one thing...? But the antenna, RIP EFHW.
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Re: What a solution for Smeter?
Hello,
i have found this video for Smeter adjustment
cdt
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Ouch!
On the bright side, it's an opportunity to get those antennas configured better.? ;-)
Jerry, KE7ER
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On Tue, Oct 27, 2020 at 10:36 AM, Aaron K5ATG wrote:
We are experiencing an ice storm and it has so far done some damage to my property. The end-fed antenna is now a thing of the past.?
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Re: Simple UBITX Test Set
Evan,
Good to know.
I gave up monitoring threads about trouble with goofy calibration schemes
a year or so after posting 35235.? And repeatedly pointing to it, just search for 35235.
Given the poor internet service at this remote site and my even worse attention span,
I generally ignore youtube videos.? A few hundred bytes of ascii text is much preferred.
The kids these days!
As you can tell, it's time for my coffee.
Jerry, KE7ER
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On Tue, Oct 27, 2020 at 09:55 AM, Evan Hand wrote:
The only uBITX that I know of that does not use zero beating as the calibration process is the stock v5.? For that version, they went to the transmission of a 10MHz carrier that you were to monitor with either a counter or another radio.
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Sorry, this is off topic/ on topic, well I don't know.? I'm going to try to pay attention to this but I will not be as active for a bit. We are experiencing an ice storm and it has so far done some damage to my property. The end-fed antenna is now a thing of the past.?  In this pic you can see that my power meter and stuff has been ripped from the house from a neighbors tree. Somehow we have not lost power.?  This is pretty much what the rest of my yard looks like.? No one at my house has been hurt, everything that has been damaged will be fixed by insurance. So I will be busy for awhile.? -- '72
Aaron Scott
QRPARCI# 16443
GQRP# 16389
4SQRP # 1080
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Vic WA4THR
Raj vu2zap
Bob Lunsford
Gerard
Aaron K5ATG