Re: Simple UBITX Test Set
Vic,
I assume you are matching the hetrodyne of the uBitx BFO plus the WWV carrier
against the audio tone from an AM radio also tuned to WWV.
The tones from WWV flip between 500hz and 600hz each minute, let's go with 500hz.
So you might set the uBitx frequency display to 10.000500 mhz, then adjust?
the calibration variable?si5351bx_vcoa (reloading all three Si5351 oscillators
with each adjustment) until the hetrodyne is exactly the 500hz you hear on the
AM radio.? I'm assuming the uBitx is in LSB mode for this example, with the BFO
500hz above the carrier and not below it.
This need not be stuck with WWV, could use any shortwave carrier of known frequency.
Just set the CW sidetone from the NANO to 500hz for your audio reference,
must be attenuated sufficiently.? Or a 500hz tone from your laptop or smartphone.
Another method would detect the sub-audible beat note out of the demodulator,
perhaps with a DVM.??
Jerry, KE7ER
On Wed, Oct 28, 2020 at 04:54 AM, Vic WA4THR wrote:
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=
|
A strange thing about calibration!!
Hello,
I don¡¯t know if anyone has ever put an oscilloscope on the BF part of the audio amplifier.?Example connect to hp output with sufficient level.
I notice that the calibragre gives a pure signal of sound (a little noise in fact). No oscillation.
Not to mention setting the BFO, and after validating your calibration, you need to reinitialize your Ubitx.
And this is where it becomes fun, you find your sound (Everything seems normal to you), but each time, it is in fact modulated (Like from the AM) in 16.6 Khtz.
You can¡¯t hear it. This frequency), because your ears can¡¯t hear that frequency. And if you are a little old, these are more than 20 years old ears!! LOL
You can resume your calibration in all directions, it is always the same result.
I can¡¯t explain the reason for this phenomenon. There may be a parameter to change?
It¡¯s not a nuisance for listening, but there has to be an answer.
If some one may test also to see if i have this ?
cdt
|
Re: ?BITX ... AGC or AVC?
AmatuerRadioKits sells an AGC that, per instructions, connects to the receiver input first IF at R10.? It does appear to work, though I have not done extensive testing.
I am only offering up this option to show that others have done the IF gain adjustments, though not in the 2nd IF stage as is suggested in this topic.
Here is the link to the files for the kit:
73
Evan
AC9TU
|
Re: No output power on
#v3
Dave,
No one said that it was normal.? I was just explaining that there are built-in protections of the regulator that could explain the shutdown and then restart with the display.? That is also why I said to check the 5volt devices to verify proper operation.
I did not go into the obvious "look for overheating devices" instruction.? I believe that most would know that.
I must also say that I do not appreciate the sarcasm.? I AM ALWAYS open to suggestions and improvement opportunities.? I will try to take this as one of those and be sure to include the "not normal" comment in the future.
73
Evan
AC9TU
|
Jonas,
Good point.
Might be best to have the choke in the antenna system somewhere, not in the rig.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Wed, Oct 28, 2020 at 04:58 AM, Jonas Sanamon wrote:
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?
?
|
Re: ?BITX ... AGC or AVC?
Loris is right, Raj's R23 and R43 are both on the transmit side of the uBitx bidi amps.
So perhaps not AGC for the receiver, which is what most would be interested in.
But could also work on the receive side of the bidi amps.
A clear and complete description from Raj would help others to try it,?
"introduce a varicap" is not terribly specific.
A search in the forum posts for "Raj AGC" finds no hits on this AGC scheme.
Don, ND6T, had a couple blog posts about easy hacks to implement manual RF gain
on the Bitx40, should be possible to make these work on the uBitx.
Dozens of threads in the forum on adding AGC to the Bitx40 and uBitx.
The "automatic" part of AGC may not be needed, but a simple RF gain control
to avoid receiver overload would be good.
That and back-to-back diodes in the audio chain somewhere
to prevent blown eardrums when using headphones.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Wed, Oct 28, 2020 at 06:10 AM, IW4AJR Loris wrote:
On Wed, Oct 28, 2020 at 12:31 PM, Raj vu2zap wrote:
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.
Hello Raj ...
Interesting solution, if I have some free time I could try it!
I would like to have an explanation from you:
what is the function of AGC ?transmission for uBITX? ... perhaps as a compressor instead of an external speech-processor?
Thank you, 73 Loris - IW4AJR
|
hello to all
I have a working v3? with the 3.5" Nextion display.
I would like to program the Raduino to the hex file with the S meter option.
Question:? there seem to be different files available for the needed second I2C Nano
Which file do you feel is best to use for the second Nano?
Many thanks
Richard? VA3NDO
|
Re: No output power on
#v3
Pops and smoking are a normal part of uBITX startups..
NOT!!!!!!!!!
--
73
Dave
|
Re: ?BITX ... AGC or AVC?
On Wed, Oct 28, 2020 at 12:31 PM, Raj vu2zap wrote:
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.
Hello Raj ...
Interesting solution, if I have some free time I could try it!
I would like to have an explanation from you:
what is the function of AGC ?transmission for uBITX? ... perhaps as a compressor instead of an external speech-processor?
Thank you, 73 Loris - IW4AJR
|
You have my sympathy. Ignore my previous mails on this subject, I didn¡¯t see this ¡®til now.?
toggle quoted message
Show quoted text
27 okt. 2020 kl. 18:36 skrev Aaron K5ATG via groups.io <k5atg@...>:
?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.? <20201027_101212.jpg> 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.? <20201027_101205.jpg> 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
|
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?
toggle quoted message
Show quoted text
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
|
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=
|
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?
toggle quoted message
Show quoted text
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
_._,_._,_
|
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
toggle quoted message
Show quoted text
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
|
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
|
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
|
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
|
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
toggle quoted message
Show quoted text
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
?
|
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
?
|
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
|
Gerard
_Dave_ AD0B
Vic WA4THR
Raj vu2zap
Bob Lunsford